# Double Glazing or not?



## KieranJW (19 Oct 2021)

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*Double glazing vs Single glazing.*

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KieranJW
ian33a

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11 minutes ago
Hi,
Just read your message about the glazing by a door. I was interested in the 16mm reference to the gap between panes.

I have had a couple of customers now having windows made with Single glazing. I have done a reasonable amount t of heritage repairs and have always preferred the single glazing.

In the next year or so I will be exnteding my house and when I do I would like to replace all of my existing Pvcu windows with wooden windows using linseed paint and am deliberating on single glazed vs double glazed as my main reason for doing wooden windows is that if I do them once I should not have to replace them in my lifetime whereas I notice most people are changing pvc after around 20 years due to them looking tired.

I have read that secondary glazing is better for sound insulation and the bigger the gap the better but the thermal insulation isn't as effective as argon filled etc.
This leaves me wondering if I still go ahead as I dont want the hassle of replacing failed units.

I have fitted secondary glazing for two customers in past employment but the company did it with perspex. Apparently it was effective but never found out the longer term result.

I also though that if a dessicant can somehow be fitted in the gap it should reduce the moisture issue.

I have heard of a chinese double glazing unit that can be refilled (and I assume resealed) but never found out the name.

Any advice or discussion would be appreciated.


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## Jacob (19 Oct 2021)

If you do the calcs on energy saving and add long term maintenance/replacement DG generally not cost effective.
Has benefit of sound insulation.
Trad joinery properly with linseed oil paint well maintained lasts indefinitely, 100s of years etc


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## Woody2Shoes (19 Oct 2021)

I think you'll find it difficult to meet building regs (from a U-value point of view) without double-glazed units. Any window containing a DGU should be designed so that:
- air can freely circulate around the perimeter of the unit.
- water can quickly drain out of the rebate (it will get in, the only question is how long it takes for that to happen).
- the DGU can be removed easily (precludes glazing tape IMHO).
- any sealants used are chemically compatible with the sealant used to make the DGU

I've found that DGUs can last for a long time (10+ years easily) even in south-facing situations if the above detailing is correctly dealt with.

Soundproofing is best when:
- the gap between the two panes is biggest (hence secondary glazing often works well in this case).
- the two panes are different thicknesses.
- there is sound absorbent material in the reveal between the two panes.
- care is taken sealing round the frame and the frame is of dense material.


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## Woody2Shoes (19 Oct 2021)

PS most DGU spacer strips contain dessicant as a matter of course


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## Jacob (19 Oct 2021)

Woody2Shoes said:


> ....
> 
> I've found that DGUs can last for a long time (10+ years easily) even in south-facing situations if the above detailing is correctly dealt with.
> 
> .....


But "10+ years" is a very short time. Trad joinery can last 100 years or more.
Cost of replacing DG units at 10 or even 20 year intervals is likely to exceed any heat savings many times over.


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## Jones (19 Oct 2021)

Replacement windows require building regs approval and sign off . A registered installer can self certify and just send a form in, otherwise you must pay the fee and send in before and after plans. The replacement windows must meet current u values and fire regs.
Single glazing will not meet regs, you can get an exemption for listed buildings but it's unusual. DGU manufacture is more regulated now and with proper joinery detailing unit life should exceed 20 years. I think your 100 year estimate for trad joinery windows is a bit of a Trigger's broom scenario. TRADA have a good book on modern timber windows.


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## Jacob (19 Oct 2021)

Jones said:


> .....I think your 100 year estimate for trad joinery windows is a bit of a Trigger's broom scenario. ......


No it's normal. I replaced 150 year old windows here because they hadn't been painted or maintained for 20 or more years. Made exact replicas and used all the old glass though. 
The 150 year old door needed a bit of repair but is now good for another 150, as long as it gets a bit of paint.
People take high obsolescence for normal but they don't have to.


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## Phil Pascoe (19 Oct 2021)

And I know of double glazing that's still perfectly fine after 40 years. I've replaced wooden windows that weren't ten years old. Usually if you're not doing the work yourself the money you'd save on maintenance of wooden ones over twenty years would pay for the new uPVC anyway. You'd be lucky now finding softwood that would last 150 months let alone 150 years.


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## Ollie78 (19 Oct 2021)

Jacob said:


> If you do the calcs on energy saving and add long term maintenance/replacement DG generally not cost effective.
> Has benefit of sound insulation.
> Trad joinery properly with linseed oil paint well maintained lasts indefinitely, 100s of years etc



If worried about noise, using accoustic laminate is amazingly effective even single pane, it can of course be made into DGU's as well.

Personally I think you might as well double glaze it. If you are changing the windows anyway then a large proportion of the cost is being spent on the frames and the installation itself. The actual units are not insane money and will reduce energy transfer with low e glass and the right gasses.
I love my quiet warm accoustic laminate units.
Most customers appreciate the difference pretty immediately, even slim DGU's in heritage stuff.

Just to mention, the building regs on this stuff are a shambles. If it's new build it's different to replacements, if it's heritage and listed different again.

FENSA was just invented so building inspectors didn't have to chase Everest around. 
A company cab be registered but the installers will likely be any old fella who will be self employed anyway removing all liability. When I bought my house the widows were about 5 years old installed by a big Fensa registered firm. 
The single worst job I have seen, pure cowboys.

Ollie


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## Jacob (19 Oct 2021)

Phil Pascoe said:


> And I know of double glazing that's still perfectly fine after 40 years. I've replaced wooden windows that weren't ten years old. Usually if you're not doing the work yourself the money you'd save on maintenance of wooden ones over twenty years would pay for the new uPVC anyway. You'd be lucky now finding softwood that would last 150 months let alone 150 years.


Wood has not changed but design details and paint have. Linseed oil paint is essential for longevity. Took me some time to discover this and in the early days had some embarrassing failures with trad windows + modern paints.


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## Phil Pascoe (19 Oct 2021)

It still needs maintenance. My house needed £1400 of scaffold before I even started.


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## Jacob (19 Oct 2021)

Phil Pascoe said:


> It still needs maintenance. My house needed £1400 of scaffold before I even started.


Just normal window cleaning.
Linseed oil paint lasts 7 years or so before needing a touch up. Doesn't degrade and peel like modern paints so only needs a light clean/ rub-down and paint or oil over.
Mine all need doing now, have got a scaffold tower but just waiting for my hip operation! 12 to 18 months!


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## KieranJW (19 Oct 2021)

Jacob said:


> No it's normal. I replaced 150 year old windows here because they hadn't been painted or maintained for 20 or more years. Made exact replicas and used all the old glass though.
> The 150 year old door needed a bit of repair but is now good for another 150, as long as it gets a bit of paint.
> People take high obsolescence for normal but they don't have to.



I agree as I have have often worked on Victorian windows and older with no previous repairs and often made with softwood. Only other thing than the linseed Is they often have some lead primers. But this is definitely another conversation as I am trying to change from using Sapele and utile to something native when asked for hardwood. Not sure at the minute on the best replacement.


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## KieranJW (19 Oct 2021)

Phil Pascoe said:


> And I know of double glazing that's still perfectly fine after 40 years. I've replaced wooden windows that weren't ten years old. Usually if you're not doing the work yourself the money you'd save on maintenance of wooden ones over twenty years would pay for the new uPVC anyway. You'd be lucky now finding softwood that would last 150 months let alone 150 years.




Yes I understand I'm not really trying to do it on a cost front it is more doing it once and forgetting about it other than the maintenance which with the linseed is fairly easy. I would rather refresh than replace. I did the same with our cladding took ages to strip the paint but once done and repainted it's like new its cedar so after 55 years is still top notch. Most neighbours have clad their's in pvc years ago and they are rotting away underneath now.


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## KieranJW (19 Oct 2021)

Thanks very much to all who have replied too.


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## KieranJW (19 Oct 2021)

Woody2Shoes said:


> I think you'll find it difficult to meet building regs (from a U-value point of view) without double-glazed units. Any window containing a DGU should be designed so that:
> - air can freely circulate around the perimeter of the unit.
> - water can quickly drain out of the rebate (it will get in, the only question is how long it takes for that to happen).
> - the DGU can be removed easily (precludes glazing tape IMHO).
> ...



Yes thanks, I think this is what I was trying to work out whether to make them with ease of removal for dgu or go down bullet proof method with single glazing but losing the insulation properties. Interestingly I have been asked to make some single glazed units for a new build in summer next year and I originally point red out that the plans wanted double glazing to meet the regs so they took it back to planning and now have permission for single glazed.


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## Jacob (19 Oct 2021)

'


KieranJW said:


> I agree as I have have often worked on Victorian windows and older with no previous repairs and often made with softwood. Only other thing than the linseed Is they often have some lead primers. But this is definitely another conversation as I am trying to change from using Sapele and utile to something native when asked for hardwood. Not sure at the minute on the best replacement.


Actually the interesting thing emerging is that it wasn't the lead, it was the linseed which gave the longevity.
Best window stuff is "unsorted" grade Swedish or Russian redwood. It is "sustainable" by virtue of replanting and relatively local compared to tropical hardwoods often from dubious sources
It's was just about the most common material for joinery past and present


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## Spectric (19 Oct 2021)

Jacob said:


> No it's normal. I replaced 150 year old windows here


This says that UPVC is not the best product we should be using, proper wood windows may need a little maintenance but have the greener credentials and look better than plastic. UPVC win's on cost and being well suited to the modern house builder as anyone with a goo gun can throw them in.


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## KieranJW (19 Oct 2021)

Jacob said:


> '
> 
> Actually the interesting thing emerging is that it wasn't the lead, it was the linseed which gave the longevity.
> Best window stuff is "unsorted" grade Swedish or Russian redwood. It is "sustainable" by virtue of replanting and relatively local compared to tropical hardwoods often from dubious sources
> It's was just about the most common material for joinery past and present




Thanks. I use scandinavian unsorted and tbh I only use the heart wood for exterior I try to get tighter rings too when I select. I am definitely sold on the linseed tbh and I love to bed single glazing as it seems better than beads (which I was under the impression are sacrificial)

As an extra do you know anything about linseed and charcoal mixed to be used as a preservative. I've read that its supposed to be very durable in place of charring but not found much more than that.


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## KieranJW (19 Oct 2021)

Spectric said:


> This says that UPVC is not the best product we should be using, proper wood windows may need a little maintenance but have the greener credentials and look better than plastic. UPVC win's on cost and being well suited to the modern house builder as anyone with a goo gun can throw them in.



Mate I agree. I am the only person in our street with timber cladding, timber fascia, timber door and eventually timber windows. Everyone thinks I am mad as they sit on their low maintenance green coloured outdoor carpet. I just think the timber looks nicer (it is all painted)
as you can make a neater job and they always say about it not lasting but I am pretty sure they will be replacing their stuff before I have to. 
Beseing in mind they used to use timber successfully for gutters.

I'm not against plastic products I just don't see that the argument of them lasting longer is credible.

I love the fact that there are so many different species and all with there uses.


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## Spectric (19 Oct 2021)

When I look at the Cathedral in Durham, over 800 years old and still lots of original woodwork, I know upvc will not last that long. Real wood has a look and feel that cannot be replicated, both UPVC and MDF prove that so nature knows best.


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## Woody2Shoes (19 Oct 2021)

Jacob said:


> But "10+ years" is a very short time. Trad joinery can last 100 years or more.
> Cost of replacing DG units at 10 or even 20 year intervals is likely to exceed any heat savings many times over.


I agree that - properly designed, made and maintained - conventional timber windows are great, and much better than plastic for all sorts of reasons. The only sticking point is that - in my understanding - building regs force the use of double (not single) glazing to get a suitable U-value of thermal performance. Using DG units in timber frames is what I'm assuming the OP wants to do (and/or will have to do to conform to Part L of the build Regs) and the points I was making are in that context.


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## clogs (19 Oct 2021)

what about triple glazing....?.
I believe the Skandies have been using that for years...


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## Inspector (19 Oct 2021)

My house has triple glazed, coated and gas filled PVC windows. Warm/cool and quiet, (I see clogs slipped in a mention). There is no more single glazed here, old house having added a second pane, and double glazing is used in new builds in the cheaper homes. As for longevity there are some companies making thermal break aluminium framed windows but they are harder to find and somewhat more money, not as bulky looking though so let in more light. Getting wood that is of high quality even here is difficult at best and linseed oil paint is special order from specialty companies and is two or three times as much to buy. Have no idea how long the paint will be available before being legislated out. Besides one company say they use linseed oil from Sweden. How environmentally friendly is that? 

Pete


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## KieranJW (19 Oct 2021)

Thanks for all the replies. I've come across the thermal break aluminium windows before and from memory they seemed ok I just like the look and detail of timber so am happy with the longevity of the frames it's just the double glazed units that I am erring on.

I'm just curious why you say the timber is not of good enough quality over here? Pete

Thanks Kieran


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## Jacob (19 Oct 2021)

Inspector said:


> My house has triple glazed, coated and gas filled PVC windows......


Not that cold in UK, unless the Gulf Stream stops!


> is difficult at best and linseed oil paint is special order from specialty companies and is two or three times as much to buy. Have no idea how long the paint will be available before being legislated out. ....


Why would it be legislated out? It's highly durable and relatively low carbon as less energy goes into making it - no alkyd synthesising processes, doesn't need fossil oil derived thinners etc


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## heimlaga (19 Oct 2021)

Around here the traditional type of double glazing is casement windows with the outer casement opening outwards and the inner casement opening inwards. Both casements are single glazed and together they form a double glazed unit when they sit in their own rebates in the jambs. Made from good quality pine theese windows normally last somewhere between 50 and 250 years if properly maintained all depending on how exposed the facade is to the weather. Made from oak they seem to last indefinitely.

I don't know thy Brits seem to believe that double glazing per definition must be made with those short lived sealed units.


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## John Brown (19 Oct 2021)

heimlaga said:


> Around here the traditional type of double glazing is casement windows with the outer casement opening outwards and the inner casement opening inwards. Both casements are single glazed and together they form a double glazed unit when they sit in their own rebates in the jambs. Made from good quality pine theese windows normally last somewhere between 50 and 250 years if properly maintained all depending on how exposed the facade is to the weather. Made from oak they seem to last indefinitely.
> 
> I don't know thy Brits seem to believe that double glazing per definition must be made with those short lived sealed units.


I think it's because our houses are already too small, and having inward opening casements would further reduce the space.


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## Jacob (19 Oct 2021)

heimlaga said:


> Around here the traditional type of double glazing is casement windows with the outer casement opening outwards and the inner casement opening inwards. Both casements are single glazed and together they form a double glazed unit when they sit in their own rebates in the jambs. Made from good quality pine theese windows normally last somewhere between 50 and 250 years if properly maintained all depending on how exposed the facade is to the weather. Made from oak they seem to last indefinitely.
> 
> I don't know thy Brits seem to believe that double glazing per definition must be made with those short lived sealed units.


I think it's because DG is a relative novelty still - it only got going in the 60s when plastic windows started replacing wood and never evolved far. No tradition in other words and anyway our climate is nowhere near as cold as Finland or Canada.
Would like to see photos of your in and out openers - sounds like a good idea!


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## Jacob (19 Oct 2021)

John Brown said:


> I think it's because our houses are already too small, and having inward opening casements would further reduce the space.


Inward opening common in France - made possible by having tall narrow sashes which fold back into the window reveal and hence take up no space. They have outward openers too but as solid or slatted shutters un-glazed.


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## Phil Pascoe (19 Oct 2021)

Inspector said:


> My house has triple glazed, coated and gas filled PVC windows ...


I was chatting to the fitter (an excellent self employed fitter - I have fitted windows before) who did my two front windows this summer. I commented that the payback time between A and A+ rated windows was several decades (way longer than the windows would last) on the prices I'd been quoted and he agreed, saying also that a problem with many he'd come across was that the sealed units weren't actually the rated to the level the vendors had quoted for anyway. I asked what he thought about triple glazing and he said a total, utter waste of time in this Country - the units are made to fit standard double glazing frames (4mm - 20mm -4mm) so any any possible advantage of three layers of glass is lost by the gaps being too small.


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## Phil Pascoe (19 Oct 2021)

Jacob said:


> Inward opening common in France - made possible by having tall narrow sashes which fold back into the window reveal and hence take up no space. They have outward openers too but as solid shutters not glazed.


I wonder where I live if it would make sense to have inward opening windows and outward opening doors.


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## RobinBHM (19 Oct 2021)

Double glazing is a no brainier in terms of thermal efficiency.

U values:

single glazing 4.2
good dbl glazing 1.2
triple glazing 0.7

as a comparison:
modern flat roof 0.18
cavity wall 0.24

single glazing in a modern, draught proof house will suffer condensation

The air next to a single glazed window will feel cold - as the glass face will be similar temp as outside - it will even create droughts making the effect feel greater.


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## Jacob (19 Oct 2021)

RobinBHM said:


> Double glazing is a no brainier in terms of thermal efficiency.


But not in terms of saving. Rule of thumb is that 20% of heat is lost through SG windows, halved if DG. 10% of your bill. For me about £100 p.a. DG would be a complete waste of money


https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/587337/DECC_factsheet_11.11.16_GLAZING_LOCKED.pdf




> single glazing in a modern, draught proof house will suffer condensation


Not if there is a normal (essential) level of ventilation and insulation. I've insulated all the walls with 100mm Kingspan between studs so the inside air RH is nearly always above ambient levels. I get a bit on very cold days but have a condensation drip catcher in the cills, draining to the outside. DG plastic get condensation too and often have similar detail
The whole interior is as dry as a bone usually, including bathrooms and kitchen. Bedroom windows get misty if closed on very cold nights


> The air next to a single glazed window will feel cold - as the glass face will be similar temp as outside - it will even create droughts making the effect feel greater.


True-ish, but not much of an issue and curtains fix it at night. We have close fitting roller blinds on some of them


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## Inspector (20 Oct 2021)

KieranJW said:


> I'm just curious why you say the timber is not of good enough quality over here? Pete
> Thanks Kieran



Mostly because all the good stuff, old growth, is exported. Often as logs so there isn't even the added value of cutting it. The second and third growth is okay for construction lumber. The stuff from the Northern forests is small and full of knots including the old growth. 

Pete


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## Inspector (20 Oct 2021)

Jacob said:


> Not that cold in UK, unless the Gulf Stream stops! Why would it be legislated out? It's highly durable and relatively low carbon as less energy goes into making it - no alkyd synthesising processes, doesn't need fossil oil derived thinners etc



The British climate is basically like the West Coast of Canada, where I am from. Nothing is built with single glazing there anymore unless it is a barn, garage or some other unheated building. It's all double glazing there.

Oil based paints were legislated out for the most part ages ago because of VOCs so unless there is something chemically different about the linseed oil paint I don't understand it is always going to be a niche product and the nearly $200Can/100pounds a gallon plus shipping will keep it there.

Pete


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## Inspector (20 Oct 2021)

Phil Pascoe said:


> I was chatting to the fitter (an excellent self employed fitter - I have fitted windows before) who did my two front windows this summer. I commented that the payback time between A and A+ rated windows was several decades (way longer than the windows would last) on the prices I'd been quoted and he agreed, saying also that a problem with many he'd come across was that the sealed units weren't actually the rated to the level the vendors had quoted for anyway. I asked what he thought about triple glazing and he said a total, utter waste of time in this Country - the units are made to fit standard double glazing frames (4mm - 20mm -4mm) so any any possible advantage of three layers of glass is lost by the gaps being too small.



He might say differently if it was sub zero for 4 months or more a year like it is here.  The glazing and frames are thicker accordingly. They don't use the same frame for both double and triple glazing here.

Pete


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## sometimewoodworker (20 Oct 2021)

KieranJW said:


> I have read that secondary glazing is better for sound insulation and the bigger the gap the better but the thermal insulation isn't as effective as argon filled etc.
> This leaves me wondering if I still go ahead as I dont want the hassle of replacing failed units.


I can comment on longevity sound and comfort. My windows were changed 45 years ago they are mostly aluminium thermal break units with 2 wood units.

1) Sound reduction is significant, I have a railway 30 metres from my back windows and after the IGU’s were fitted don’t notice a train going past, before a train stopped conversation.

2) longevity of IGU’s, currently at 45 years no noticeable change, will they ever (in my lifetime) need replacement? Only time will tell.

3) comfort, only an i*d*i*o*t would ever want single glazing. It’s not just the heat loss, though that makes a difference, it’s the fact that after installing IGUs there were no more cold floor level drafts during winter so the heating was turned down and it was more comfortable. Also never having condensation running down the inside of the windows.

Are IGUs a requirement for double/triple glazing? Absolutely not, as if you look at some countries you will find double and triple glazing using single sheets of glass, but you have to get the design right to allow moisture to escape and that isn’t usual or ever done in the U.K. as IGUs avoid all of that.


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## ian33a (20 Oct 2021)

Sorry - just seen this so am late to the party. I've been conversing directly with Kieran not realising this thread existed.

Most of us know that double glazing units fail because the primary and secondary seals break down over time - generally due to sunlight damage.

Triple glazing does add thermally to the mix and has that advantage but is largely, otherwise, a marketing con in the UK. It isn't that cold to need them, the units are heavy and more expensive to produce, in standard form they do not contribute that much more to noise reduction and, worst of all, they have twice as many primary and secondary seals as double glazing and are, therefore, far more prone to failure. All glazing units are ticking time bombs but triple glazed units tick rather louder than double glazed ones. The bomb simply hasn't gone off because they are relatively new.

Most people have uPVC because they are cheap to produce and install and maintenance is cheap and easy. The average person doesn't want to spend several weeks each decade up a ladder painting them or paying somebody else to do it. Wooden windows enjoy a bad press because so many of them in new builds are cheap, shoddy quality and let draughts in. Nice wooden windows look great in the right property. Aluminium windows, especially the modern ones are fantastic on account of their low profiles and look. Thermal breaks are essential though and many old aluminium windows fall down because they don't have the break and are thus inefficient and cold.

I cannot see any obvious upsides to single glazing aside from purity (which I can appreciate). Were I to move, I wouldn't entertain a house (for very long) with single glazing. Secondary glazing makes some difference but the air gaps between the panes are not thermally efficient. 16mm in air or 12mm in argon with super warm space bars is about as good as you can get.

Not that I do it now, but the business I once owned advised domestic customers and changed tens of thousands of failed glazing units in all types of frames.


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## pgrbff (20 Oct 2021)

KieranJW said:


> Your news feed
> Latest activity
> Your profile
> Your account
> ...


I seem to remember Historic Scotland looking at properly maintained timber versus PVC and I think the timber came out better. I don't think they looked at single over double-glazed. 
Back in the 90's I discovered that in Japan they were manufacturing a sealed unit that was I believe less than 10mm thick, possibly even 8mm. One pane had dimples and was sandwiched with the second pane with the tiny area between them a vacuum. It was a long time ago so I'm sure the details are wrong but it was a suitable alternative for historic buildings. It was very expensive and possibly available through Pilkington.


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## Just4Fun (20 Oct 2021)

heimlaga said:


> Around here the traditional type of double glazing is casement windows with the outer casement opening outwards and the inner casement opening inwards. Both casements are single glazed and together they form a double glazed unit when they sit in their own rebates in the jambs. Made from good quality pine theese windows normally last somewhere between 50 and 250 years if properly maintained all depending on how exposed the facade is to the weather.


That is the type of windows we have. The house was built in the 1890s. The windows are made of pine or similar soft wood and I have no reason to believe any of them have ever been replaced.

Have you any knowledge of upgrading these windows? I have toyed with the idea of making replacement (outer?) casements to house 2 glass panes instead of 1, but have not tried it.


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## Just4Fun (20 Oct 2021)

pgrbff said:


> One pane had dimples and was sandwiched with the second pane with the tiny area between them a vacuum.


I once read about doors that incorporated vacuum panels, which were claimed to offer high insulation value. My concern (apart from cost) would be how long the panels would hold the vacuum.


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## Jacob (20 Oct 2021)

Inspector said:


> ...Oil based paints were legislated out for the most part ages ago because of VOCs so unless there is something chemically different about the linseed oil paint I don't understand...


Linseed oil paints are very low on VOCs and it's one of the main selling points. It's not processed like Acrylic and other paints and involves no volatile solvents.
It is fairly expensive here but in use is amazingly economical and convenient. Also has indefinite shelf life (no solvents).


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## KieranJW (20 Oct 2021)

Phil Pascoe said:


> I wonder where I live if it would make sense to have inward opening windows and outward opening doors.



Tbh I was actually hoping to make the windows like a french window as when I lived there when my wife and i were younger i loved the fact that you could open the aperture completely I am also not against the idea of shutters but would possibly do them in the window reveals as more an extra thermal benefit in winter nights.
Will still do inward opening door though probably.


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## KieranJW (20 Oct 2021)

heimlaga said:


> Around here the traditional type of double glazing is casement windows with the outer casement opening outwards and the inner casement opening inwards. Both casements are single glazed and together they form a double glazed unit when they sit in their own rebates in the jambs. Made from good quality pine theese windows normally last somewhere between 50 and 250 years if properly maintained all depending on how exposed the facade is to the weather. Made from oak they seem to last indefinitely.
> 
> I don't know thy Brits seem to believe that double glazing per definition must be made with those short lived sealed units.



Cool this sounds similar to something I was thinking with the secondary glazing.


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## Jacob (20 Oct 2021)

KieranJW said:


> Tbh I was actually hoping to make the windows like a french window as when I lived there when my wife and i were younger i loved the fact that you could open the aperture completely I am also not against the idea of shutters but would possibly do them in the window reveals as more an extra thermal benefit in winter nights.
> Will still do inward opening door though probably.


Internal shutters a big feature of georgian and victorian sash windows. They fold back into the reveals to look like panelling. Actually a brilliant solution and utterly superior to modern DG!






Old Victorian Wooden Window Shutters Refurbished


Refurbishing shutters for large wooden window frames in a big wooden sash window by G S Haydon.




www.gshaydon.co.uk





These are typical:  The shutter leaves fold back in to the window reveal and look like panelling. The wrought iron bar is flat and hangs down behind when they are all folded back


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## KieranJW (20 Oct 2021)

Jacob said:


> Inward opening common in France - made possible by having tall narrow sashes which fold back into the window reveal and hence take up no space. They have outward openers too but as solid or slatted shutters un-glazed.


Haha sorry that's like my above reply. I had his in mind tbh just wasnt sure about shutters on the outside in terms of aesthetics. Hence the desire to do internal hidden in the reveals but this is just ideas at the minute.


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## KieranJW (20 Oct 2021)

sometimewoodworker said:


> I can comment on longevity sound and comfort. My windows were changed 45 years ago they are mostly aluminium thermal break units with 2 wood units.
> 
> 1) Sound reduction is significant, I have a railway 30 metres from my back windows and after the IGU’s were fitted don’t notice a train going past, before a train stopped conversation.
> 
> ...


Thanks for the reply I think that's effectively what I'm trying to achieve to have a well designed window to remove my concerns of the double glazed units that can break down. I agree with he thermal problems with the single glazing but know I can make these well.

I really like the idea of double glazing by virtue of 2 casements effectively I would see this as not really different to secondary glazing with then the option to close shutters for further gains. I suppose really I like making things that last my virtue of good design and well executed joints and good standards of materials and workmanship.


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## KieranJW (20 Oct 2021)

Jacob said:


> Internal shutters a big feature of georgian and victorian sash windows. They fold back into the reveals to look like panelling. Actually a brilliant solution and utterly superior to modern DG!
> 
> 
> 
> ...



I agree about the shutters I really can't see why they are not still used.


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## Jacob (20 Oct 2021)

KieranJW said:


> I agree about the shutters I really can't see why they are not still used.


Industry de-skilled.


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## RobinBHM (20 Oct 2021)

Jacob said:


> I get a bit on very cold days but have a condensation drip catcher in the cills


So condensation is a problem.



Jacob said:


> But not in terms of saving. Rule of thumb is that 20% of heat is lost through SG windows, halved if DG. 10% of your bill. For me about £100 p.a. DG would be a complete waste of money



that argument only works if the decision to replace is only based on thermal upgrade.

if somebody is replacing the windows anyway, there is virtually no difference in cost between single and double glazing…it’s pretty much irrelevant.


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## Phil Pascoe (20 Oct 2021)

Jacob said:


> But not in terms of saving. Rule of thumb is that 20% of heat is lost through SG windows, halved if DG. 10% of your bill. For me about £100 p.a. DG would be a complete waste of money



Yes. And if you calculate the annual energy cost difference between "C", "B", "A" and "A+" the difference is very small.


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## Jacob (20 Oct 2021)

RobinBHM said:


> So condensation is a problem.


No it is not a problem at all


> that argument only works if the decision to replace is only based on thermal upgrade.
> 
> if somebody is replacing the windows anyway, there is virtually no difference in cost between single and double glazing…it’s pretty much irrelevant.


Until you come to replacing failed units, then later replacing failed plastic frames.


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## Phil Pascoe (20 Oct 2021)

ian33a said:


> Secondary glazing makes some difference but the air gaps between the panes are not thermally efficient. 16mm in air or 12mm in argon with super warm space bars is about as good as you can get.


I think your figures may be out of date - my new windows have argon filled 4mm - 20mm - 4mm panels, which I was told is the optimum gap.


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## sometimewoodworker (20 Oct 2021)

KieranJW said:


> I really like the idea of double glazing by virtue of 2 casements effectively I would see this as not really different to secondary glazing with then the option to close shutters for further gains. I suppose really I like making things that last my virtue of good design and well executed joints and good standards of materials and workmanship.


My opinion on that system is that it’s far more complex than is needed. If you research the design requirements for good non sealed units you have almost the complete benefits of IGUs while using 2 panes and can easily use different thicknesses to help with sound control and you only need a single casement. If you want to add on shutters you can sill do that.


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## Droogs (20 Oct 2021)

KieranJW said:


> I agree about the shutters I really can't see why they are not still used.


standard Edinburgh window in old stock builds is single pane sash with internal raised panel shutters. Most of those that have been replaced with DGU still retain the internal shutter as they are expected to be there in older houses. We kept ours when we fitted DG and they are used on very cold nights to keep the heat in. Our shutters are either original (1850's) or at most inter-war replacements as they are old slow growth Scots pine. The density certainly makes a difference. The DG has made a massive difference to quality of life in the flat, no more frost or fractal ice leafs on the inside of the window, calm and quiet (don't even hear the beep of the bin lorry). The central heating is usualy only used for about an hour in winter before going to bed and that is it. Before fitting the DG and the CH, which have been done only in the last 4 years, we only had a wood stove in the livingroom and an immersion heater for hot water and the original windows as well. The difference DG makes to the livability of a home is massive especially if the home is old pre war stock.

The biggest problem now is I usually go out the close(common stairwell) with the dog in evening and I'm just in a T-shirt to find it blowing a gale and cold and being very surprised.


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## Jacob (20 Oct 2021)

Droogs said:


> standard Edinburgh window in old stock builds is single pane sash with internal raised panel shutters. Most of those that have been replaced with DGU still retain the internal shutter as they are expected to be there in older houses. We kept ours when we fitted DG and they are used on very cold nights to keep the heat in. Our shutters are either original (1850's) or at most inter-war replacements as they are old slow growth Scots pine. The density certainly makes a difference. The DG has made a massive difference to quality of life in the flat, no more frost or fractal ice leafs on the inside of the window, calm and quiet (don't even hear the beep of the bin lorry). The central heating is usualy only used for about an hour in winter before going to bed and that is it. Before fitting the DG and the CH, which have been done only in the last 4 years, we only had a wood stove in the livingroom and an immersion heater for hot water and the original windows as well. The difference DG makes to the livability of a home is massive especially if the home is old pre war stock.
> 
> The biggest problem now is I usually go out the close(common stairwell) with the dog in evening and I'm just in a T-shirt to find it blowing a gale and cold and being very surprised.


I renovated some vertical sliding shutters some years ago. They didn't know they were there at first and were puzzled by the unused sash pulleys. The shutters dropped into a pocket behind the panelling and the lid closed looked like a normal window cill. They were quite big and dropped below floor level in their boxes.
Re condensation - there's a good argument for saying that it's better to have it on your sash windows rather than on the walls. It drains off and drips away through meeting rail gap and at the bottom sash. You can sometimes see icicles forming outside where it drips. So the single glazed window acts as a de-humidifier.
Also brilliant for draught control and I think Florence Nightingale noted these features and highly recommended them for health reasons


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## Phil Pascoe (20 Oct 2021)

I commented after fitting my d/g patio doors that the first thing I noticed was the noise reduction - The chap I bought them from said that's the first thing most people say.


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## Jacob (20 Oct 2021)

Phil Pascoe said:


> I commented after fitting my d/g patio doors that the first thing I noticed was the noise reduction - The chap I bought them from said that's the first thing most people say.


Well yes it's probably the single most useful thing about DG, if you live in a noisy area that is, or work in a noisy workshop.


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## RobinBHM (20 Oct 2021)

Phil Pascoe said:


> Yes. And if you calculate the annual energy cost difference between "C", "B", "A" and "A+" the difference is very small.



window energy ratings are somewhat of a marketing ploy.

the only difference between a B rating and an A rating is low iron glass.

what does that do? - it’s clearer, so allows more sunlight in, that raises little g value - which is to do with solar gain. Solar gain is pretty useless as we need heating on in the evening in the winter.


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## spanner48 (20 Oct 2021)

One solution to your problem may be a new technique: VACUUM INSULATED GLAZING, or VIG. It's two sheets of - typically 4mm - glass, with a 0.3mm gap between them, pumped out to a vacuum. The two panes are kept apart by tiny 'pills' of transparent glass frit placed every inch, in a square pattern. You get an 8.3mm pane that is as thermally effective as wide double - or even triple - glazing. And it is also as effective a sound barrier as triple. 

ADVANTAGES

• It fits almost everywhere in place of standard - typically 6mm - glass. No need to modify casements; just reduce the putty by 2mm

• It is no heavier than standard 8mm single pane

• Except under the minutest inspection, it is indistinguishable from single glazing

• Installation is easier. The edges are sealed with fused glass frit, so no need to worry about ventilation and drainage around the panel - as with conventional DGUs

• Durability is better than - particularly - narrow-gap DGUs. These have gained an evil reputation for failing after only a few years, due to the uneven heating and cooling of the outer and inner panes shearing the perimeter bond. By contrast, VIG units are routinely guaranteed for 20, 25 or 40 years. Experience so far is that failures are rare.

DISADVANTAGES

• It's not cheap. Typically at least 50% more than conventional DGUs, on an area basis

• Minimum panel size for pricing is 0.7 m^2. So redoing mock-Georgian sashes is either very expensive, or involves milling the muntins' fronts back, putting a single pane over all, and adding astragals

• They have to be ordered, individually, from the Far East [Korea, Japan, Taiwan, China]. So delivery is slow

• The UK glazing trade hasn't heard of it, and is reluctant to work with VIG. I know of only ONE experienced installer south of Coventry . . . . 

For brands, see Pilkington 'Spacia'; Landglass 'LandVac'; 'Guardian'; Asahi 'Fineo' etc.

I've used it, once. The results - so far - have been good.


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## Doug71 (20 Oct 2021)

Does the Spacia glass still have the little cover cap on it? I have customers moan about the stamp to show that glass is toughened so don't know what they would think to the little cap on each pane.


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## KieranJW (20 Oct 2021)

sometimewoodworker said:


> My opinion on that system is that it’s far more complex than is needed. If you research the design requirements for good non sealed units you have almost the complete benefits of IGUs while using 2 panes and can easily use different thicknesses to help with sound control and you only need a single casement. If you want to add on shutters you can sill do that.


 Thanks that is something I originally muted but then I was persuaded out of it by fellow tradesmen! My reasoning was that you needed a good hermetic seal and possibly dessicant other than that it was just my own thoughts really.
Where should I be looking for this information? Have you a source?


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## KieranJW (20 Oct 2021)

Jacob said:


> I renovated some vertical sliding shutters some years ago. They didn't know they were there at first and were puzzled by the unused sash pulleys. The shutters dropped into a pocket behind the panelling and the lid closed looked like a normal window cill. They were quite big and dropped below floor level in their boxes.
> Re condensation - there's a good argument for saying that it's better to have it on your sash windows rather than on the walls. It drains off and drips away through meeting rail gap and at the bottom sash. You can sometimes see icicles forming outside where it drips. So the single glazed window acts as a de-humidifier.
> Also brilliant for draught control and I think Florence Nightingale noted these features and highly recommended them for health reasons


Thanks I've seen shutters like that before.


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## KieranJW (20 Oct 2021)

spanner48 said:


> One solution to your problem may be a new technique: VACUUM INSULATED GLAZING, or VIG. It's two sheets of - typically 4mm - glass, with a 0.3mm gap between them, pumped out to a vacuum. The two panes are kept apart by tiny 'pills' of transparent glass frit placed every inch, in a square pattern. You get an 8.3mm pane that is as thermally effective as wide double - or even triple - glazing. And it is also as effective a sound barrier as triple.
> 
> ADVANTAGES
> 
> ...



Wow sounds really good. I will look into it. I have used histoglass a couple of times in the past when fitting with a colleague. I personally havent had a comeback yet but he had two enormous projects where a majority of the units failed. He followed all the guidance from the supplier and is extremely good at what he does so this has put me.off using them at all.


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## ian33a (20 Oct 2021)

Phil Pascoe said:


> I think your figures may be out of date - my new windows have argon filled 4mm - 20mm - 4mm panels, which I was told is the optimum gap.



Not sure about that Phil - there are plenty of papers on the internet stating that 12mm is optimal for argon. At one time, and I'm not saying that you were seduced by the salesman, the "bigger is better" approach was sold. I stand by 12mm as the optimal gap. Not that I'm suggesting you need to order a thermal vest and mittens for the coming winter as the difference wont be that noticeable. 

Up to a point you can have a bigger spacing but you quickly reach a point where convection of air/argon/whatever becomes a problem. The tumbling of the content between the panes causes a cold outer surface (1/2) to migrate through to the inner surfaces (3/4) by way of convection and causes condensation and/or cooling in the room. A low E coating on surface 3, to some degree, mitigates the temperature drop and keeps surface 4 warmer and this, in turn, reduces internal condensation.

You will be fine with a 20mm gap, but 12mm is generally considered optimal.


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## sometimewoodworker (20 Oct 2021)

Jacob said:


> Re condensation - there's a good argument for saying that it's better to have it on your sash windows rather than on the walls.


condensation is not inevitable. If your walls don’t get cold enough you will not have condensation on windows or walls. That rather kills that argument, doesn’t it?


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## ian33a (20 Oct 2021)

sometimewoodworker said:


> condensation is not inevitable. If your walls don’t get cold enough you will not have condensation on windows or walls. That rather kills that argument, doesn’t it?



Agreed. Equally, if you properly ventilate a room, you wont get condensation either


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## sometimewoodworker (20 Oct 2021)

KieranJW said:


> Thanks that is something I originally muted but then I was persuaded out of it by fellow tradesmen! My reasoning was that you needed a good hermetic seal and possibly dessicant other than that it was just my own thoughts really.
> Where should I be looking for this information? Have you a source?


Sorry no, but if you research places like the Nordic countries. Also the information I recall did not have hermetic seals or desiccant. It relied on the correct design of ventilation between the glass and allowed moisture to escape.

nowadays the technology may have disappeared due to the ease and ubiquitous availability of IGUs so you may need to do historical research.

I am sure that the systems existed, maybe still do. However the information I read was years ago and I have no idea were I read it, possibly in one of the woodworking magazines.


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## sometimewoodworker (20 Oct 2021)

ian33a said:


> Agreed. Equally, if you properly ventilate a room, you wont get condensation either


It’s actually reasonably easy to know how to avoid condensation.

Keep all surfaces above the dew point of the air in a room. 

Now the ways to do that are many and various but the principle is science (physics) 101


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## ian33a (20 Oct 2021)

sometimewoodworker said:


> It’s actually reasonably easy to know how to avoid condensation.
> 
> Keep all surfaces above the dew point of the air in a room.
> 
> Now the ways to do that are many and various but the principle is science (physics) 101



Totally agree, I have lost count of the number of times I have explained dew point and condensation to customers who seem to think that hermetically sealing their properties is the way to go. I even prepared a PowerPoint slide to try to explain it to them. Sadly, too many of them had a closed mind set.


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## Phil Pascoe (20 Oct 2021)

ian33a said:


> You will be fine with a 20mm gap, but 12mm is generally considered optimal.


Interesting. 
The 28mm double glazed window is currently marketed as the best option around. That is a combination of a 20mm air gap plus the glazing (2x4mm) .................... a quote from a random site, although another states that 12mm is the optimum. 
The (quite large) firm I bought from has all their panels made with 20mm gaps unless otherwise specified - I can't imagine they would do it without reason as for one it would make the frame sections heavier and therefore more expensive.


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## Phil Pascoe (20 Oct 2021)

ian33a said:


> Totally agree, I have lost count of the number of times I have explained dew point and condensation to customers who seem to think that hermetically sealing their properties is the way to go. I even prepared a PowerPoint slide to try to explain it to them. Sadly, too many of them had a closed mind set.


We used to drive past an estate agent's window with a sign saying "We can cure your condensation problems for just £499" I used to say to my wife if they bought me a couple of pints I'd tell them how - open their ****ing windows.


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## ian33a (20 Oct 2021)

Phil Pascoe said:


> Interesting.
> The 28mm double glazed window is currently marketed as the best option around. That is a combination of a 20mm air gap plus the glazing (2x4mm) .................... a quote from a random site, although another states that 12mm is the optimum.
> The (quite large) firm I bought from has all their panels made with 20mm gaps unless otherwise specified - I can't imagine they would do it without reason as for one it would make the frame sections heavier and therefore more expensive.



It was along the lines of what I thought Phil TBH. So many companies have massive manufacturing runs done in the same way that they have always done it. The economies of scale give them a better price point and then its a marketing exercise to sell a suitable benefit to customers. Standardising on certain sizes and styles makes sundries such as packers, window furniture and seals inventories smaller (and thus running costs cheaper) and fitters don't end up making as many mistakes.

When we had our windows changed 10 years ago we were sold a whole host of stuff based upon what the salesman (company owner) told us. At the time it all made sense. A couple of years later and we started a glazing repair company and my engineering background caused me to research very heavily (that, and the need to pay the mortgage!). I discovered that so much of what I was told was misinformation or semi rot. I don't blame the salesman, I think he did what he thought was right. Trouble is, the industry is riddled with myth and bad practise.


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## Jacob (20 Oct 2021)

sometimewoodworker said:


> condensation is not inevitable.


In certain conditions it is highly probable


> If your walls don’t get cold enough you will not have condensation on windows or walls. That rather kills that argument, doesn’t it?


Er..no?
If your walls aren't as cold as your windows you will get condensation on the windows, if conditions are right for condensation.


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## Jacob (20 Oct 2021)

sometimewoodworker said:


> It’s actually reasonably easy to know how to avoid condensation.
> 
> Keep all surfaces above the dew point of the air in a room.
> 
> Now the ways to do that are many and various but the principle is science (physics) 101


Not even science is just logic.  Keep all surfaces above dew point i.e. the temperature at which condensation will form. But not actually any help.
Frinstance if you boil a kettle the dew point temperature falls even as the temperature in the room rises.

Dessicants in DG unit are pointless - if the thing leaks it will slightly delay the point where you get condensation within, but won't stop it.


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## RobinBHM (20 Oct 2021)

Phil Pascoe said:


> The 28mm double glazed window is currently marketed as the best option around. That is a combination of a 20mm air gap plus the glazing (2x4mm) .................... a quote from a random site, although another states that 12mm is the optimum



above a 16mm air gap, the air inside starts to circulate by convection so 20mm and over doesnt improve u values -although I think argon with a 20mm air gap is about the sweet spot -pretty much all Upvc is 20mm air gap these days, most timber is 24mm.


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## RobinBHM (20 Oct 2021)

Jacob said:


> Dessicants in DG unit are pointless - if the thing leaks it will slightly delay the point where you get condensation within, but won't stop it



its purpose is to remove residual moisture trapped into the unit during manufacture.


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## RobinBHM (20 Oct 2021)

Jacob said:


> Keep all surfaces above dew point i.e. the temperature at which condensation will form


pretty difficult with just 4mm glass between the outside world and the inside

glass is only about 5x less conductive than steel


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## Jacob (20 Oct 2021)

RobinBHM said:


> pretty difficult with just 4mm glass between the outside world and the inside
> 
> glass is only about 5x less conductive than steel


Well it's a mystery to me that we don't have a condensation problem here, single glazed throughout some of it down to 3mm!
Sometimes see the odd patch on a cold morning but it's gone by the time I've made a cup of tea.
I did design in a drainage system with a drip catch runnel draining to the outside but it doesn't seem necessary - except for the odd very cold morning when it gets a little puddle briefly.


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## mikej460 (20 Oct 2021)

KieranJW said:


> Thanks for the reply I think that's effectively what I'm trying to achieve to have a well designed window to remove my concerns of the double glazed units that can break down. I agree with he thermal problems with the single glazing but know I can make these well.
> 
> I really like the idea of double glazing by virtue of 2 casements effectively I would see this as not really different to secondary glazing with then the option to close shutters for further gains. I suppose really I like making things that last my virtue of good design and well executed joints and good standards of materials and workmanship.


I may have misunderstood what you are saying here Kieran but just to re-iterate that if you are fitting new frames you can't fit single glazing. Unless you are Fensa registered you must notify Building Control. I would advise against not doing this as a nosey neighbour could dob you in (I speak from bitter and ultimately expensive experience here) the rules are explained here Building Regulations | Doors and windows | Planning Portal 

Our 19th century community pub (owned by the village) needs new front windows and the local company we have asked in to quote are recommending replacing the frames with Accoya Wooden windows, external wooden doors, timber windows, window frames (accoya.com) fitted with 12mm DG heritage glass. The existing frames are softwood and despite shelling out for rot to be replaced over the years they now need replacing; also the singe glazing causes really bad condensation in winter.


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## Doug71 (20 Oct 2021)

The weight of the gas dictates the best size of the cavity in double glazing, as Robin says if the cavity is too big you get the convection current effect. 

According to the charts from my supplier (using planitherm total glass) the optimum cavity for air is 16mm or 18mm, the U value actually increases once you get a 20mm cavity.

Using Argon the U value doesn't improve once you get above a 14mm cavity.

It doesn't list Krypton but I believe you need a thinner cavity for that as it's heavier.


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## Doug71 (20 Oct 2021)

Talking air circulating by convection I have 17 Heritage style rooflights in my house and almost every dg pane has blown in them.

I think the problem is that the sash part is metal and there is no thermal break in it, you can feel it gets really cold. There are two rooflights over my bed, at first I thought there was a draught coming through them but have realised it is just the heavier cold air (caused by the cold metal) falling on to me which feels like a draught. 

Don't know why anyone would want single glazing these days, I remember ice on the inside of my bedroom window when I was a kid


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## Jacob (20 Oct 2021)

Doug71 said:


> .....
> 
> Don't know why anyone would want single glazing these days, I remember ice on the inside of my bedroom window when I was a kid


You've said it yourself - 17 blown DG panes. It's common. Everybody thinks they are just an isolated unlucky incident but it is widespread, DG is not cost effective.


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## Doug71 (20 Oct 2021)

Jacob said:


> You've said it yourself - 17 blown DG panes. It's common. Everybody thinks they are just an isolated unlucky incident but it is widespread, DG is not cost effective.



Actually closer to 34 blown panes as there are two in each rooflight 

I would say the problem is the bad design of the rooflights, I made all the windows and doors for my house which went in at the same time as the rooflights (about 15 years ago) and none of the units in those have failed yet.


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## Jacob (20 Oct 2021)

Doug71 said:


> Actually closer to 34 blown panes as there are two in each rooflight
> 
> I would say the problem is the bad design of the rooflights, I made all the windows and doors for my house which went in at the same time as the rooflights (about 15 years ago) and none of the units in those have failed yet.


Have had Velux skylights in the past. They were good. Still occasionally got condensation and even ice in a very cold weather but very well designed to drain off condensation. "Heritage" version - paint the outside frame installation black?


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## ian33a (20 Oct 2021)

Doug71 said:


> Talking air circulating by convection I have 17 Heritage style rooflights in my house and almost every dg pane has blown in them.
> 
> I think the problem is that the sash part is metal and there is no thermal break in it, you can feel it gets really cold. There are two rooflights over my bed, at first I thought there was a draught coming through them but have realised it is just the heavier cold air (caused by the cold metal) falling on to me which feels like a draught.
> 
> Don't know why anyone would want single glazing these days, I remember ice on the inside of my bedroom window when I was a kid



if these panes are angled toward direct sunlight they will suffer more thermal and uv stress than units which face away. Repeated heating and cooling of the units causes a breakdown in the primary and secondary seals around the unit edges and once there is a hole, even a small one, the two panes in the DGU act like a bellows, drawing moist air in during the winter months and causing misting and dry air in during the summer months often causing the units to appear to have fixed themselves. But they haven’t.

as a rule of thumb, units facing toward direct sunlight, on average, will fail within 12 years. Units which never see sunlight can last a lot longer. I’ve seen units which are approaching 40 years of age. all of this assumes that the units were correctly installed in the first place. Before I retired we changed, on average, about 1500 failed glazing units per year. Even so, I still would not have single glazing in my house!


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## mikej460 (20 Oct 2021)

Jacob said:


> You've said it yourself - 17 blown DG panes. It's common. Everybody thinks they are just an isolated unlucky incident but it is widespread, DG is not cost effective.


I'm thinking no science or clear advantages of DG will ever convince you Jacob, but we had all the rotten SG windows replaced with uPVC DG units in our house in 2008. The front is south facing with 6 windows, a lot of the other windows facing east so also get the heat of the sun for a large part of the day. Before we did this our oil bill was scary and yet the house was only just bearable in winter. Since then not one pane has failed and our heating bill has reduced substantially; the whole house is comfortable and quieter. My only regret is not replacing them with wooden frames as uPVC was considerably cheaper at the time when we had other costly projects to do, but despite having cottage style panes it just doesn't look right to me. My only other point that no-one else has raised is the value it adds to your house, single glazing only devalues your house and makes it less attractive to buyers.


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## Phil Pascoe (20 Oct 2021)

My only other point that no-one else has raised is the value it adds to your house, single glazing only devalues your house and makes it less attractive to buyers ... 

It doesn't actually. If you speak to estate agents they'll tell D/G adds nothing because people expect it, but single glazing on the other hand does devalue it.


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## johnnyb (20 Oct 2021)

that's a bit false as the most attractive (and expensive) houses nearly always have single glazing. I work at a beautiful huge victorian house and every single window( 40 or more) is now plastic. the devaluation must be enormous. just imagine the cost to reinstate the sash windows as the boxes will have been decorated over.


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## johnnyb (20 Oct 2021)

what I will say is upvc windows in modern house have little variety maybe a colour comes in and another fades.white seems universal though. 
but the frames and the details are the same. I had an "architect" do me drawings and I wanted a dwarf wall with stone cill with sliding sashes. he couldn't do it because his drawing package only had sliding sash with a panel below(??). the endless variety of wooden windows and the minds that designed them is now just a fantasy.
I'm neither pro nor anti dg but I fail to see why this is a matter of legislation when some one can go and buy a huge gas guzzler if they want and can afford to feed it.


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## mikej460 (20 Oct 2021)

Phil Pascoe said:


> My only other point that no-one else has raised is the value it adds to your house, single glazing only devalues your house and makes it less attractive to buyers ...
> 
> It doesn't actually. If you speak to estate agents they'll tell D/G adds nothing because people expect it, but single glazing on the other hand does devalue it.


That was my point, just unclearly stated...


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## mikej460 (20 Oct 2021)

johnnyb said:


> that's a bit false as the most attractive (and expensive) houses nearly always have single glazing. I work at a beautiful huge victorian house and every single window( 40 or more) is now plastic. the devaluation must be enormous. just imagine the cost to reinstate the sash windows as the boxes will have been decorated over.


I agree with you but it does depend on what a prospective buyer really values, some people think uPVC is attractive or at least more functional, less maintenance etc.


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## mikej460 (20 Oct 2021)

I've noticed that painting uPVC is possible now and diy sheds are now selling uPVC paint. Just out of interest has anyone tried it?


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## johnnyb (20 Oct 2021)

I'm a member of a Facebook group called spraying makes sense. most of those make there living spraying upvc. the best paint is seemingly 2k. zinnser make a single pack all surface paint that's OK.the biggest job is removing the silicone.


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## mikej460 (20 Oct 2021)

johnnyb said:


> I'm a member of a Facebook group called spraying makes sense. most of those make there living spraying upvc. the best paint is seemingly 2k. zinnser make a single pack all surface paint that's OK.the biggest job is removing the silicone.


So roughly how much does it cost to have say a 4ft x 3ft double opener spray painted?


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## Jacob (20 Oct 2021)

I spent a good deal of time doing nothing but repairing/restoring sash windows and other period joinery. However doubtful the client by the end of the job they were always really pleased. They add enormous value to a period property - even quite ordinary Victorian terraces.
Nothing more tedious than streets with house after house with all the class removed and crude plastic windows all around.


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## Jacob (20 Oct 2021)

Phil Pascoe said:


> My only other point that no-one else has raised is the value it adds to your house, single glazing only devalues your house and makes it less attractive to buyers ...
> 
> It doesn't actually. If you speak to estate agents they'll tell D/G adds nothing because people expect it, but single glazing on the other hand does devalue it.


A lot of buyers are looking for period quality. It's increasingly valuable. You don't know what you've got til it's gone


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## Jacob (20 Oct 2021)

mikej460 said:


> ..... My only other point that no-one else has raised is the value it adds to your house, single glazing only devalues your house and makes it less attractive to buyers.


To some buyers maybe but certainly not all. Especially if you are looking at 15 year old plastic or dismal brown DG hardwood past its best.


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## mikej460 (20 Oct 2021)

Jacob said:


> To some buyers maybe but certainly not all. Especially if you are looking at 15 year old plastic or dismal brown DG hardwood past its best.


I agree as the old conservatory on our house was one such dismal brown monstrosity and to add to its horror a polycarbonate roof. It was the first thing we changed after we bought it...yet I still got £100 for it on eBay!


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## Jacob (20 Oct 2021)

mikej460 said:


> I agree as the old conservatory on our house was one such dismal brown monstrosity and to add to its horror a polycarbonate roof. It was the first thing we changed after we bought it...yet I still got £100 for it on eBay!



I got given a brown monstrosity earlier this year. Luckily it was single glazed and I've recycled most of it into cold frames, firewood, etc.
Most of the wood was garbage but you can find some nice pieces in cr*p modern joinery which have got there by mistake - it's worth having a good look.
And horticultural glass is a good substitute for period glass - it often has a similar ripple - I've just put two pieces in the doors of a Victorian school cupboard I'm tidying up. All nice pitch pine which was under thick white gloss on old varnish like bonfire toffee.


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## baldkev (20 Oct 2021)

I got partway through page 2 and noticed there's 6 pages!

So i skipped 4 and a half

I have timber windows and dgu's in a house approximately 13 years old. The dgu's have just started to mist up ( most of them ) 

The windows however are utter rubbish! They have been painted twice since new and the windows on the most exposed face of the house still swell up. One major fubar from the manufacturer is that they used the foam glazing tape both inside and out, leading to the foam breaking down, the windows taking on water and the fixed sashes going mouldy!! I went round with silicone and carefully gunned it all in, which reduced our issues, but our neighbours properties, most of which have never had the woodwork painted, are falling apart.

I'll be replacing our windows, and, most likely, with a matching style in plastic.

I dont believe timber quality is the same as it was, its now grown and harvested quickly, processed as fast as they dare. Its also true that a lot of people dont keep on top of maintenance, which is half the problem


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## Sandyn (20 Oct 2021)

Jacob said:


> I get a bit on very cold days but have a condensation drip catcher in the cills, draining to the outside.


Would like to know how you do that? I was just thinking of doing something similar.


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## sometimewoodworker (21 Oct 2021)

Jacob said:


> Not even science is just logic.  Keep all surfaces above dew point i.e. the temperature at which condensation will form. But not actually any help.
> Frinstance if you boil a kettle the dew point temperature falls even as the temperature in the room rises.


humm. It is Physics, just because you consider it to be logic doesn’t stop it being science.

You are interpreting keep ‘all surfaces above the dew point‘ wrongly to be “keep them just above the dew point”. Of course you need to keep the humidity low enough and ventilation/circulation good enough so that normal activities like cooking and people breathing don’t cross the dew point for a considerable time. 

While dropping under the dew point may instantly start dew forming (it probably won’t) a rise above it with reasonable circulation will evaporate a tiny amount before it becomes noticeable.



Jacob said:


> In certain conditions it is highly probable



Of course it is. That is why you design to avoid those conditions.



Jacob said:


> If your walls aren't as cold as your windows you will get condensation on the windows, if conditions are right for condensation


Of course they will. That is why you design to avoid those conditions.




Jacob said:


> Well it's a mystery to me that we don't have a condensation problem here, single glazed throughout some of it down to 3mm!
> Sometimes see the odd patch on a cold morning but it's gone by the time I've made a cup of tea.



It however isn’t a mystery but physics. The humidity in your house is low enough that the air circulation/ventilation will evaporate the condensation.


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## KieranJW (21 Oct 2021)

Jacob said:


> Not even science is just logic.  Keep all surfaces above dew point i.e. the temperature at which condensation will form. But not actually any help.
> Frinstance if you boil a kettle the dew point temperature falls even as the temperature in the room rises.
> 
> Dessicants in DG unit are pointless - if the thing leaks it will slightly delay the point where you get condensation within, but won't stop it.


Yeah sorry the idea of dessicant was to remove any moisture originally trapped inbetween when sealed. I thought the spacer bars have a dessicant in the for similar reason.


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## KieranJW (21 Oct 2021)

mikej460 said:


> I may have misunderstood what you are saying here Kieran but just to re-iterate that if you are fitting new frames you can't fit single glazing. Unless you are Fensa registered you must notify Building Control. I would advise against not doing this as a nosey neighbour could dob you in (I speak from bitter and ultimately expensive experience here) the rules are explained here Building Regulations | Doors and windows | Planning Portal
> 
> Our 19th century community pub (owned by the village) needs new front windows and the local company we have asked in to quote are recommending replacing the frames with Accoya Wooden windows, external wooden doors, timber windows, window frames (accoya.com) fitted with 12mm DG heritage glass. The existing frames are softwood and despite shelling out for rot to be replaced over the years they now need replacing; also the singe glazing causes really bad condensation in winter.



Thanks I have a customer.er who has managed to get permission for single glazing on a new property despite the original plans being for double glazing. I am more interested in having double glazing in some form if I can reduce/eliminate the failures I see with double glazed units. I will incorporate easier maintenance or replacement options I to the design I have been really pleased with all the relies and has given me a lot of food for thought. The main reason for the single glazing mention is that I know there is very little to go wrong but if I can achieve the same with double glazing in whatever form then I would go for that.

Be careful with the 12mm stuff as it can be prone to failure. I agree with Jacob on the linseed so if I was you I would look at that as a paint system I do quite a number of repairs on old windows and a properly executed repair should last and all joints or spliced should be design to shed water should any glue fail. As many people have said about the double glazing industry being full of misinformation ; this definitely applies to woodworking and heritage work. It is difficult to sift through marketing claims or old accepted methods that have come into general practice to only decades later realise how erroneous the advice was. 

I often think that we have lost a lot of knowledge around effective building as when you think older methods all used more natural products effectively so that when no longer used could be repurposed if necessary. Stone and lime could be reused, linseed nourished and protected timber, turpentine would work as a pesticide, cob was an effective insulator both against heat and cold. Stockholm tar as a preservative. Interestingly they also often had many other uses too. These seem to have a much more circular life cycle so the waste either rotted down or could be reused. The problem I have found is that it is now actually quite hard to get a good education in these methods.

I am hoping that accoya proves to be as good as is claimed as we have fitted some doors and windows for a customer who had decided that it was the way to go and it hasn't proven to be as stable as is claimed. We didn't manufacture them and the dont seem to be a problem but they are definitely not quite as good as the marketing claims. I suppose I struggle with the idea of taking poor timber and treating it. I think better to get good timber and further improve it.

So, if you can see, I like to do things properly with-in the knowledge that I have at the time. If I am proven to be mistaken in the long term I can accept that as long as I had tried to fully understand what I am doing.


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## Phil Pascoe (21 Oct 2021)

Jacob said:


> A lot of buyers are looking for period quality. It's increasingly valuable. You don't know what you've got til it's gone


I lived on a half a mile long street of very nice Victorian Houses for 20+ years - in that time vitually every house had the wooden windows removed and replaced with uPVC (one or two with aluminium). Increasingly valuable? I would seriously query that in an average Victorian house. Most had windows changed immediately upon changing hands.


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## Phil Pascoe (21 Oct 2021)

Stockholm tar as a preservative? The only thing I knew it preserved is hen's arrrrses.


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## johnnyb (21 Oct 2021)

I've no idea on cost. but a single window I reckon 1/2 day.


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## johnnyb (21 Oct 2021)

Stockholm tar was the only preservative available for ships ropes for centuries. I think they use it to keep flies off hens buttocks.


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## Jacob (21 Oct 2021)

baldkev said:


> ....
> 
> I dont believe timber quality is the same as it was, its now grown and harvested quickly, processed as fast as they dare. Its also true that a lot of people dont keep on top of maintenance, which is half the problem


It's not the timber it's the design details and cr*p modern paint. And the DG inits would have failed anyway.


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## Jacob (21 Oct 2021)

Woke this morning with condensation on most of my windows.  
You get it most this time of year - equinoctial changes of warm damp air suddenly being cooled surfaces as nights grow longer. Less so as winter advances as the absolute humidity levels fall.
Is this a problem?
No, it's a solution - windows working as de-humidifiers resulting in a dry house. It will all be gone as the day warms up and any great surplus will drip into the condensation catching cilll design and be drained off to the outside. This was one of the great strengths of the traditional sash.


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## Jacob (21 Oct 2021)

[


Sandyn said:


> Would like to know how you do that? I was just thinking of doing something similar.


It used to be common in public buildings like churches, chapels, meeting rooms. There'd be a little gutter in the cill formed one way or another and drained to the outside. In my building (ex chapel) the gutter was a little groove in the stone cill at base of each window, like a drip groove, full width, with 1/2" lead pipe connected at the middle, working as a drain. Just 6" pipe length to the outside with 1/2" an inch visible which you'd hardly notice.
Very simple, very effective. It would have been essential on a cold day if 300 people had been in, all belting out "Rock of Ages" at the tops of their voices.
I've replaced the windows with replicas and instead of using the stone runnel have incorporated a wooden one with 10mm copper pipe taking the water off. Can be seen dripping outside and on very cold days with little icicles.
If you look around old buildings you often see these details but the use has been forgotten and they may be sealed up, painted over, etc.
Sash windows wouldn't need this as they drain through the meeting rail gap or the bottom sash to bottom staff bead gap. Sometimes you encounter a beefed up bottom staff bead with a bevel which is intended as a drip catcher and also as a draught redirector when the window is open just half an inch or so


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## Jacob (21 Oct 2021)

Phil Pascoe said:


> .... You'd be lucky now finding softwood that would last 150 months let alone 150 years.


It's not the wood's fault its the design/details and cr*p modern paint.


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## Doug71 (21 Oct 2021)

@KieranJW I would be surprised if a new build could have single glazing. 

You said in an earlier post they went back to planning and got the DG changed to SG. Planning and building control are very different, In the past I have had unhappy people bring me windows to alter because planning said they could have them but the windows haven't complied with building regs for escape or toughened glazing etc. 

Sorry if I'm stating the obvious but might be worth checking.


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## Phil Pascoe (21 Oct 2021)

johnnyb said:


> Stockholm tar was the only preservative available for ships ropes for centuries. I think they use it to keep flies off hens buttocks.


It helps prevent other hens feather pecking. Once they draw blood they will likely carry on until they eviscerate the victim.


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## Ollie78 (21 Oct 2021)

Doug71 said:


> Does the Spacia glass still have the little cover cap on it? I have customers moan about the stamp to show that glass is toughened so don't know what they would think to the little cap on each pane.


Have them do what's called a furniture stamp it's tiny and sits under the sightline.

I am interested in the vacuum units, I have seen them being advertised but never seen one in real life.

Can't understand why anyone would get single glazing on purpose, even taking the trouble to go and get permission for it !
I often make double glazed stuff for old buildings, you can't tell until you get right next to them.

A note on the seals breaking down, I use hybrid polymer with full encapsulation of the units. Bedding and facing them, it looks just like a traditional putty line. This method is pretty reliable and I think better than beading, which is more likely to allow water and air to get in contact with the edge of the units over time.

This is an interesting thread about all the different glazing solutions.
If money was no object I think I would get the Internorm timber and aluminium ones with blinds built in to the units and the extra openable third glazing layer.
Properly engineered stuff, and toasty warm.

Given gas prices have gone mental I think any reduction in energy loss will pay for itself even quicker now.

Ollie


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## GregW (21 Oct 2021)

clogs said:


> what about triple glazing....?.
> I believe the Skandies have been using that for years...



It’s good for temperature below -20. Tested, customer not seen big difference in temperature resistance in that climate, however he told that lorries can be heard from direction of double glazing, not from direction of triple glazed main road.


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## Sandyn (21 Oct 2021)

Jacob said:


> If you look around old buildings you often see these details but the use has been forgotten and they may be sealed up, painted over, etc.


Now that you describe how it's done, I have seen that. It helps when it's designed in when the building was constructed. I thought you had devised a cunning method of doing it on a more modern build. I was trying to think of a reliable way of doing it.


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## Jacob (21 Oct 2021)

Sandyn said:


> .... I thought you had devised a cunning method of doing it on a more modern build. ....


I have, but it's not very cunning. I'll do a photo later


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## Phil Pascoe (21 Oct 2021)

GregW said:


> It’s good for temperature below -20. Tested, customer not seen big difference in temperature resistance in that climate, however he told that lorries can be heard from direction of double glazing, not from direction of triple glazed main road.


The experienced fitter who put in my windows said if you buy triple glazing in this Country you've been conned. The frames will be for 28mm panels and therefore the gaps will be too small.


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## ian33a (21 Oct 2021)

Phil Pascoe said:


> The experienced fitter who put in my windows said if you buy triple glazing in this Country you've been conned. The frames will be for 28mm panels and therefore the gaps will be too small.



Not totally true , but largely so:

For triple glazing to be close to effective with an argon fill you will need 4-12-4-12-4 = 36mm. 28mm panels, I agree, are not effective. 36mm is the installation that we have in our house.

These were purchased before I became interested in glazing technology and we were sold this on the basis that it would reduce road traffic noise substantially and be much more efficient.

Since having these fitted and learning a huge amount , I have always said to customers who have expressed an interest in having their panes "upgraded to triple" (or, as I originally accidentally typed "tripe"!) that triple glazing in the UK is more of a marketing exercise than a real benefit. Here's why: firstly, the temperatures in the UK barely justify the need. Secondly, the overall unit sizes needs to be substantial to maintain decent U and this is almost never possible with an existing 4-20-4 make up. Thirdly, triple glazing doesn't substantially reduce noise but acoustic glass is what should be fitted to do the job properly and, finally (the big one), having been called out to replace misted up panes, triple glazed windows double the risk of a given pane failing because they come with two sets of seals and not one. From an installation/repair perspective, triple glazed units weigh 50% more than their double glazed half brothers and with large picture windows and even with smaller units, they can be really heavy!

Triple glazed units don't cost a whole lot more than double glazed units at wholesale price. The biggest cost is in the frames, fitting, commissions and contribution to the company operating expense. Consequently, the concept can be sold as a major (marketing) advantage while the cost increase is minimal. ... but people get sucked it. If I had my time again, I'd do my best to not have triple glazed units.


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## TominDales (21 Oct 2021)

Jacob said:


> If you do the calcs on energy saving and add long term maintenance/replacement DG generally not cost effective.
> Has benefit of sound insulation.
> Trad joinery properly with linseed oil paint well maintained lasts indefinitely, 100s of years etc


Glad to hear. We have regency sash windows, very thin wood, but with shutters that can close at night. They are in a need of a good coat of paint - I've not done it for 10 years upstairs as they are high up and was wondering about DG give the need for netzero.
The windows are a feature of our house, very large, give lots of light and the glass bows out - vauxhaul glass. Looking at old photos I'd estimate they are 100+ years old. thre are 18 of them, 4'' by 8'' and one is rotten, I probably need to get painting give what you have just said, or I'll be in trouble - its took me two summers last time! Probably need to get a specialist decorator in this time.
Not sure how to source the wood for the rotten frame. The original is a strong pine very straight and strong, can you get old pitch pine these days?. the shutters are amazing, very thin panels that are straight and true 8'' by 8'' sections, quite probably original from the 1800s


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## sometimewoodworker (21 Oct 2021)

ian33a said:


> For triple glazing to be close to effective with an argon fill you will need 4-12-4-12-4 = 36mm. 28mm panels, I agree, are not effective. 36mm is the installation that we have in our house.


That may work for heat insulation but is not as effective for sound insulation as say 4-12-3-12-5. All the glass being the same thickness is far less good that having different thicknesses as sound transmission is cut at different frequencies using different glass thickness.

We have managed a 24db + reduction by using good frames laminated glass on the outside (for security) and a different inner pane thickness.

I don’t have data on how the sound reduction would be changed if the laminated panes were also different thickness


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## ian33a (21 Oct 2021)

sometimewoodworker said:


> That may work for heat insulation but is not as effective for sound insulation as say 4-12-3-12-5. All the glass being the same thickness is far less good that having different thicknesses as sound transmission is cut at different frequencies using different glass thickness.
> 
> We have managed a 24db + reduction by using good frames laminated glass on the outside (for security) and a different inner pane thickness.
> 
> I don’t have data on how the sound reduction would be changed if the laminated panes were also different thickness



Exactly (I agree totally with you - acoustic glass mentioned in a previous post by me) , I was told that this make up would work by the salesman but later discovered that it isn't especially effective from a sound insulation perspective. Acoustic glass would have been the right way to go but the glass thicknesses would need to have been tuned to the noise that I would like to have eliminated. I have seen websites which provide examples of thicknesses to tune out, for example, road or train or aircraft noise. Generally what works for one, doesn't necessarily work well for another.


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## TominDales (21 Oct 2021)

Jacob said:


> '
> 
> Actually the interesting thing emerging is that it wasn't the lead, it was the linseed which gave the longevity.
> Best window stuff is "unsorted" grade Swedish or Russian redwood. It is "sustainable" by virtue of replanting and relatively local compared to tropical hardwoods often from dubious sources
> It's was just about the most common material for joinery past and present


I think this answers my previous question. Can you get a slow grown type of pine these days? I replaced the wood on our garden gate and garage doors that is probably only 20 years old as it was like balsa and rotted right through. Whereas the original house casements and wood supporting the cast iron gutters is still sound after 200 years.


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## Jacob (21 Oct 2021)

TominDales said:


> I think this answers my previous question. Can you get a slow grown type of pine these days? I replaced the wood on our garden gate and garage doors that is probably only 20 years old as it was like balsa and rotted right through. Whereas the original house casements and wood supporting the cast iron gutters is still sound after 200 years.


People blame the wood but its design and finish which are the problem. 
Slowest growth is from further north and used to be named "Kara Sea pine", "Archangel pine" etc . "Unsorted" grade Swedish or Russian redwood are just as good as they were but you can't get the very wide boards which would have been from virgin forest.


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## Phil Pascoe (21 Oct 2021)

TominDales said:


> I replaced the wood on our garden gate and garage doors that is probably only 20 years old as it was like balsa and rotted right through. Whereas the original house casements and wood supporting the cast iron gutters is still sound after 200 years.


I stripped 100 years of paint from my fascias, drilling out all the old broken ironmongery (scores of pieces), filling the holes, soaking with cuprinol etc. The wood was fine except for the one piece I replaced ........... which was the one piece that had already been replaced. Twenty five years ago and it's still fine. One lesson I did learn (fortunately before I did that job) was not to sand the wood to too fine a finish, especially if it's never going to be looked at closely. I did these with forty grit and slightly rounded all the corners - the paint adheres so much better.


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## Woody2Shoes (21 Oct 2021)

Jacob said:


> Inward opening common in France - made possible by having tall narrow sashes which fold back into the window reveal and hence take up no space. They have outward openers too but as solid or slatted shutters un-glazed.


I think inward opening is mandatory in parts of Germany and Switzerland - so people can regularly clean their own windows (don't want anyone making the place look untidy do we?!)...


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## Richard_C (21 Oct 2021)

There's a lot of good points in this thread, but what about saleability?

We all have to sell up one day, or our heirs/executors do, or worse the local authority of you are intestate and have care bills.

When you sell, it's reasonable to assume that the buyer, valuer and surveyor they engage won't have the nuanced understanding like the people commenting here, they will just tick a box that says "DG - no" and advise buyer to negotiate the price down or look elsewhere.

At almost 70 I am realistic : I will be selling up my slightly too large and awkward house in about 10 years time *. Any work I do now has that in mind, conventional, good quality, easy care and saleable. (I'm not cynical, I'm not saying do it cheap but make it last 12 years si it's someone else's problem). Were I 35 and content to live where I do for a long time I might take different decisions.

So the DG or not question has a non technical, aesthetic, human, dimension. Only you can answer that bit.

* keep an eye on market place for lathe, Bandsaw and pillar drill sometime around 2030.


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## Jacob (21 Oct 2021)

Richard_C said:


> .......
> 
> When you sell, it's reasonable to assume that the buyer, valuer and surveyor they engage won't have the nuanced understanding like the people commenting here, they will just tick a box that says "DG - no" and advise buyer to negotiate the price down or look elsewhere.
> .......


You get the buyers to match. 
Period detail is a big seller with some people and in general adds value.
I never ran out of work when I was doing sashes etc and got some very nice jobs. My various moves went well too with original or replica sashes. 
It's a particular market and there are a lot of punters, believe me!


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## Phil Pascoe (21 Oct 2021)

Around me two very nice streets (the two nicest in the town, one of which I lived on) were considered years ago for making into conservation areas. There was a mad rush to install uPVC before it happened (ultimately it didn't, they realised too many properties had already been changed). Most of the Victorian box frame windows had already been replaced by post WW2 joinery that was crepe anyway, and of the hundreds of people I spoke to over twenty+ years no one was remotely interested in originality, they were interested only in the practicalities.


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## ian33a (21 Oct 2021)

Phil Pascoe said:


> Around me two very nice streets (the two nicest in the town, one of which I lived on) were considered years ago for making into conservation areas. There was a mad rush to install uPVC before it happened (ultimately it didn't, they realised too many properties had already been changed). Most of the Victorian box frame windows had already been replaced by post WW2 joinery that was crepe anyway, and of the hundreds of people I spoke to over twenty+ years no one was remotely interested in originality, they were interested only in the practicalities.



That's it : purists will pay. Most people want practicality and wont. 

We're seriously considering moving next year. I'd *love* something original, characterful and dreamy. At my age I *need* something with kerb appeal but practical and easy and cheap to maintain.


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## TominDales (21 Oct 2021)

Phil Pascoe said:


> Around me two very nice streets (the two nicest in the town, one of which I lived on) were considered years ago for making into conservation areas. There was a mad rush to install uPVC before it happened (ultimately it didn't, they realised too many properties had already been changed). Most of the Victorian box frame windows had already been replaced by post WW2 joinery that was crepe anyway, and of the hundreds of people I spoke to over twenty+ years no one was remotely interested in originality, they were interested only in the practicalities.


Do you think that is still as-true today? Although the vast majority of people have busy lives especially trying to raise a family with modern burnt out jobs and long commutes. But there has been a huge rise in house prices over the years and a broadening of interest in property. Around us - I'm thinking Harrogate not so much Ripon the period theme seems to be the big sell. Probably still a minority, but quite a big and well healed one.


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## KieranJW (21 Oct 2021)

Phil Pascoe said:


> I lived on a half a mile long street of very nice Victorian Houses for 20+ years - in that time vitually every house had the wooden windows removed and replaced with uPVC (one or two with aluminium). Increasingly valuable? I would seriously query that in an average Victorian house. Most had windows changed immediately upon changing hands.


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## Jacob (21 Oct 2021)

ian33a said:


> That's it : purists will pay. Most people want practicality and wont.
> 
> We're seriously considering moving next year. I'd *love* something original, characterful and dreamy. At my age I *need* something with kerb appeal but practical and easy and cheap to maintain.


Well one big advantage of the trad sash is ease of maintenance - everything can be done from inside the room - sashes themselves removed for painting but that's dead easy. Probably why so many old ones are still serviceable.


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## KieranJW (21 Oct 2021)

Ollie78 said:


> Have them do what's called a furniture stamp it's tiny and sits under the sightline.
> 
> I am interested in the vacuum units, I have seen them being advertised but never seen one in real life.
> 
> ...


 Thanks Ollie, 
I too have used the polymer putty replacements too and quite like them especially if customer is using a standard paint.

I do know of a job where slim units were used and the supplier provided sovereigns silacryl to bed the units in and they failed. I have used silacryl as an acrylic caulk substitute or as a sealant but never as a bed. 

I did wonder if bedding units with the putty replacements would help if the double glazed unit seals fail as you would effectively have a secondary seal.
I like this as I think it looks better than beads on more traditional windows. 

There is a lot of food for thought.


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## Phil Pascoe (21 Oct 2021)

TominDales said:


> Do you think that is still as-true today? Although the vast majority of people have busy lives especially trying to raise a family with modern burnt out jobs and long commutes. But there has been a huge rise in house prices over the years and a broadening of interest in property. Around us - I'm thinking Harrogate not so much Ripon the period theme seems to be the big sell. Probably still a minority, but quite a big and well healed one.


I'm speaking of only 15 years ago. (A quite big and well heeled one?)


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## Phil Pascoe (21 Oct 2021)

Jacob said:


> Well one big advantage of the trad sash is ease of maintenance - everything can be done from inside the room - sashes themselves removed for painting but that's dead easy. Probably why so many old ones are still serviceable.


Yes, but it's quite labour intensive - few people want to do the job themselves. I've repaired badly damaged box frame windows that I could have made from scratch quicker. Builders and chippies around here work for £200 a day only if they're really desperate.


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## KieranJW (21 Oct 2021)

Jacob said:


> People blame the wood but its design and finish which are the problem.
> Slowest growth is from further north and used to be named "Kara Sea pine", "Archangel pine" etc . "Unsorted" grade Swedish or Russian redwood are just as good as they were but you can't get the very wide boards which would have been from virgin forest.



I tend to only use the heart wood for exterior but I'm not sure if this is necessary it just reassures me as the durability tables are always based on heartwood and not sap wood which is generally far less durable. In the past we have used douglas fir too dependant on what the original joinery looks like it is made of. I have a friend who has been using pitch pine in repairs more recently. I also know someone who never uses softwood nowadays as he does very high class work so it is always hardwoods but when he did he tended to use larch.


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## KieranJW (21 Oct 2021)

Richard_C said:


> There's a lot of good points in this thread, but what about saleability?
> 
> We all have to sell up one day, or our heirs/executors do, or worse the local authority of you are intestate and have care bills.
> 
> ...



Wise words thanks. I am 37 and we are looking at extending as we have four children in a 3 bed house. I dont particularly like the style of house but the location is spot on for how we live. The ideal would be to build a heavy timber framed autonomous house but my wife has zero interest or inclination so the only other reason to move would be a small holding or somewhere with outbuildings for a workshop but unfortunately they seem to have gone beyond our budget in the last five or so years. So based on this I want to do the best i can with what i have so as Jacob keeps saying the correct design and finish. 

Thanks to you and all others this has given me a lot to think about.


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## KieranJW (21 Oct 2021)

Phil Pascoe said:


> Around me two very nice streets (the two nicest in the town, one of which I lived on) were considered years ago for making into conservation areas. There was a mad rush to install uPVC before it happened (ultimately it didn't, they realised too many properties had already been changed). Most of the Victorian box frame windows had already been replaced by post WW2 joinery that was crepe anyway, and of the hundreds of people I spoke to over twenty+ years no one was remotely interested in originality, they were interested only in the practicalities.



Yes unfortunately that is like a majority around my way. Astro turf, block paving plastic fascia, plastic cladding, plastic doors, plastic gates, plastic porches, dry verge and now plastic home offices/bars/hottub shelters. 
Although low maintenance it seems to suck the soul out of places and then they have to replace it as it starts looking shabby.

I appreciate what they are saying but I'd rather grass on my lawn that isn't perfect but is so much more life affirming.


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## KieranJW (21 Oct 2021)

TominDales said:


> Do you think that is still as-true today? Although the vast majority of people have busy lives especially trying to raise a family with modern burnt out jobs and long commutes. But there has been a huge rise in house prices over the years and a broadening of interest in property. Around us - I'm thinking Harrogate not so much Ripon the period theme seems to be the big sell. Probably still a minority, but quite a big and well healed one.


Yes I have some customers who have the period property but didnt realise the slight adjustments that come with the quirks of a characterful house and probably in hindsight wouldn't do it again (although they stay invested) others absolutely love it and the quirks and then go about finding out more and love the attachment this gives them.

One lady had duelling stairs in their farm house and had found out where they had originally come from before they had ended up in there home and could tell me all the different additions and when.


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## Doug71 (21 Oct 2021)

Ollie78 said:


> Have them do what's called a furniture stamp it's tiny and sits under the sightline.



My usual glass supplier won't do DG units with a furniture stamp on anymore, I guess it's to do with building regs and being able to see the stamp to prove it's toughened 

They will still supply single glazing with a furniture stamp on though, can't really see the logic of it.


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## John Brown (21 Oct 2021)

KieranJW said:


> Yes unfortunately that is like a majority around my way. Astro turf, block paving plastic fascia, plastic cladding, plastic doors, plastic gates, plastic porches, dry verge and now plastic home offices/bars/hottub shelters.
> Although low maintenance it seems to suck the soul out of places and then they have to replace it as it starts looking shabby.
> 
> I appreciate what they are saying but I'd rather grass on my lawn that isn't perfect but is so much more life affirming.


And plastic picket fences come next. Already a major feature of American life.
Personally, I hate it all, but I can understand why people get sucked into plastic DG units.
We have oak frames with DG, they're not perfect, but look great (to us). Our previous house had rotting timber framed SG box sash. I would've slowly remade them all, and incorporated DG, but as I understand it, I'm not allowed to without FENSA certification. The cost if paying someone else to do it would have been sky high.


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## Phil Pascoe (21 Oct 2021)

A friend years ago was taken to court for fitting uPVC windows in a conservation area. He was told they should have been oak frames. He said he'd been a professional decorator for thirty years and had never come across an oak framed window - they insisted he was wrong. I'm 67, I've never seen an oak framed window. They don't exist here.


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## KieranJW (21 Oct 2021)

Phil Pascoe said:


> Yes, but it's quite labour intensive - few people want to do the job themselves. I've repaired badly damaged box frame windows that I could have made from scratch quicker. Builders and chippies around here work for £200 a day only if they're really desperate.



Yes I


John Brown said:


> And plastic picket fences come next. Already a major feature of American life.
> Personally, I hate it all, but I can understand why people get sucked into plastic DG units.
> We have oak frames with DG, they're not perfect, but look great (to us). Our previous house had rotting timber framed SG box sash. I would've slowly remade them all, and incorporated DG, but as I understand it, I'm not allowed to without FENSA certification. The cost if paying someone else to do it would have been sky high.



We manufacture or fit others windows and repair but are not fensa registered as I am a sole trader sometimes working as a pair with another carpenter and joiner.

I have an nvq level 3 in carpentry and joinery and an nvq level 3 in heritage carpentry and joinery. 

As far as I'm aware the fensa certification is only a way of indicating that you have windows that comply with the building regs. 

None of my previous employers were fensa registered either.


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## John Brown (21 Oct 2021)

Phil Pascoe said:


> A friend years ago was taken to court for fitting uPVC windows in a conservation area. He was told they should have been oak frames. He said he'd been a professional decorator for thirty years and had never come across an oak framed window - they insisted he was wrong. I'm 67, I've never seen an oak framed window. They don't exist here.


I have no idea what your point is.
I'm 68, and I have oak framed windows.


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## Phil Pascoe (21 Oct 2021)

Good for you. I've never seen one. Just because something might be common in one area doesn't mean they are common or necessarily desirable in another.


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## Phil Pascoe (21 Oct 2021)

KieranJW said:


> We manufacture or fit others windows and repair but are not fensa registered



You get them inspected every time I assume?


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## KieranJW (21 Oct 2021)

Phil Pascoe said:


> You get them inspected every time I assume?



If they are done as part of a conversion which is under building regs then yes. If it is a conservation repair then we replace like for like which according to the conservation officer is fine. 
If we anticipate any issues we run it past them and it is normally us who find a solution and then put it forward for their approval.


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## baldkev (21 Oct 2021)

KieranJW said:


> As far as I'm aware the fensa certification is only a way of indicating that you have windows that comply with the building regs.


And fitting is as per regs..... im a chippy, fitted loads of windows for a company i used to work for and a fair few on my own jobs. A couple of years back i was talking to a building control officer. He asked where i was working next ( it was a completion visit )
I told him about the next job and that it included a velux. He said he hadnt seen an application and got very insistant on knowing more about the job as building control have to issue a permit to replace a window if you are not registered with fensa. Failure to do so will usually throw up problems with solicitors during house sales and when you do the work, the building control officer may drop in to see it is correctly fitted ( with cavity closers etc where necessary )

Its best to notify them etc, as it's not worth the hassle of the repercussions


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## Ollie78 (22 Oct 2021)

> Thanks Ollie,
> I too have used the polymer putty replacements too and quite like them especially if customer is using a standard paint.
> 
> I do know of a job where slim units were used and the supplier provided sovereigns silacryl to bed the units in and they failed. I have used silacryl as an acrylic caulk substitute or as a sealant but never as a bed.
> ...



Worked for a firm who used the Sylacryl backing and linseed oil for face putty, absolute rubbish way to do it in my experience. Sylacril takes ages to dry as does putty, the only advantage was the putty is easier to do neatly if you dust it off properly.

Repair care Dryseal is good but silly money, Hodgesons heritage is a bit cheaper, I use mostly Timbaglaze from chemfix. I know a place that use Stixall which is only a fiver a tube. I did a test with it and it works pretty well, I guess they are all pretty similar chemically. I find them good if you need to spray finish top coat after glazing ( which I try to avoid).

Fensa is not concerned with repair or restoration work.

There is certainly not enough building inspectors to physically inspect every window that gets installed.
I think its a bit like electrical work, technically you are not even supposed to change a socket or light switch but there is a bit about being a "competent person" somewhere in there, which means you can do it as long as you aren`t a total halfwit.

Ollie


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## sometimewoodworker (22 Oct 2021)

ian33a said:


> Exactly (I agree totally with you - acoustic glass mentioned in a previous post by me) , I was told that this make up would work by the salesman but later discovered that it isn't especially effective from a sound insulation perspective. Acoustic glass would have been the right way to go but the glass thicknesses would need to have been tuned to the noise that I would like to have eliminated. I have seen websites which provide examples of thicknesses to tune out, for example, road or train or aircraft noise. Generally what works for one, doesn't necessarily work well for another.


While I don’t know about special glass like acoustic that you mention and salesmen are alway talking at BS O’Clock. There is no real need to bother with sound tuning. If you are able to get each pane a different thickness, simple physics tells you that sound that passes through one thickness easily does not pass through a different thickness as easily. So 3 different thickness gives the best reduction. The only point is how thin can you go for the centre pane in the manufacturing process without paying silly money. Laminate C4+1.52+LowEC4+Ars8+C5 got us the 24db reduction while avoiding the need for security bars.

EDIT, it turns out that laminated glass and acoustic glass are synonymous however instead of the single PVB layer we have 5 as that makes them reasonably thief resistant, they certainly work for sound reduction as I show in my video.


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## Jacob (22 Oct 2021)

sometimewoodworker said:


> While I don’t know about special glass like acoustic that you mention and salesmen are alway talking at BS O’Clock. There is no real need to bother with sound tuning. If you are able to get each pane a different thickness, simple physics tells you that sound that passes through one thickness easily does not pass through a different thickness as easily. So 3 different thickness gives the best reduction. The only point is how thin can you go for the centre pane in the manufacturing process without paying silly money. Laminate C4+1.52+LowEC4+Ars8+C5 got us the 24db reduction while avoiding the need for security bars.


Apparently it's not about thickness per se it's about resonant frequencies - what sets one pane off resonating must be out of tune with the other so that it doesn't harmonise and pick up the same frequencies.


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## sometimewoodworker (22 Oct 2021)

Jacob said:


> Apparently it's not about thickness per se it's about resonant frequencies - what sets one pane off resonating must be out of tune with the other so that it doesn't harmonise and pick up the same frequencies.


Thank you for restating my point in a different way.


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## heimlaga (22 Oct 2021)

Just4Fun said:


> That is the type of windows we have. The house was built in the 1890s. The windows are made of pine or similar soft wood and I have no reason to believe any of them have ever been replaced.
> 
> Have you any knowledge of upgrading these windows? I have toyed with the idea of making replacement (outer?) casements to house 2 glass panes instead of 1, but have not tried it.


The only upgrades that pays off economically when counting in time materials and energy costs are to install modern rubber seals on the inner casement. As inner casements were sealed with some sort of tape on the inside there were often no proper rebates for the inner casements. Proper rebates for inner casements became common around 1900 in Finland. The best way to create such a rebate to allow for properly complessed modern rubber seals is to nail a batten inside the jamb so a rebate is formed. 
If you still want to upgrade I have seen a third casement added halfways between the inner and the outer. I have also seen new inner casements with two glass panes but they were terribly clumsy and a bit on the heavy side for the hinges. 

I have seen new outer casements with two panes but they were utter failiours. As they open outwards and are opened for ventilation an outer casement with double panes must be extremely heavily built with very solid hardware to not fall apart when held open. Both wind at weight acts on them at once. They likely didn't insulate much as the space between outer and inner casement must be ventilated by gaps to the outside to avoid condensation. Everything went wrong in short....... and the thick materials looked totally out of proportion.


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## ian33a (22 Oct 2021)

sometimewoodworker said:


> While I don’t know about special glass like acoustic that you mention and salesmen are alway talking at BS O’Clock. There is no real need to bother with sound tuning. If you are able to get each pane a different thickness, simple physics tells you that sound that passes through one thickness easily does not pass through a different thickness as easily. So 3 different thickness gives the best reduction. The only point is how thin can you go for the centre pane in the manufacturing process without paying silly money. Laminate C4+1.52+LowEC4+Ars8+C5 got us the 24db reduction while avoiding the need for security bars.



As a rule of thumb, yes, different thicknesses and gaps, in combination, provide attenuation and so suppress sound transmission. It isn't, however, a one size fits all. Different locations suffer from different sources of noise. Noise is simply a range of transmitted frequencies which we find irritating. The most irritating frequencies associated with road traffic will be different to those of a passenger train or a freight train or an aircraft. This is where the tuning aspect may become important. There are loads of tuning calculators available from glass manufacturers and mathematicians which can be used to develop a glazing unit stack up which attempts to suppress general noise and which focus upon key spectral areas and, thus, tunes the unit to address certain noise problems.


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## Phil Pascoe (22 Oct 2021)

Ollie78 said:


> I think its a bit like electrical work, technically you are not even supposed to change a socket or light switch but there is a bit about being a "competent person" somewhere in there, which means you can do it as long as you aren`t a total halfwit.
> Ollie



I believe from what I've read that you are actually tested before being considered competent, although someone may prove me wrong.


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## GregW (22 Oct 2021)

Phil Pascoe said:


> The experienced fitter who put in my windows said if you buy triple glazing in this Country you've been conned. The frames will be for 28mm panels and therefore the gaps will be too small.


28mm triple ? Well, it is ridicules.
Casements min 64mm, and min 32mm triple glaze.

Like I said, HGV going next too it


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## GregW (22 Oct 2021)

Doug71 said:


> My usual glass supplier won't do DG units with a furniture stamp on anymore, I guess it's to do with building regs and being able to see the stamp to prove it's toughened
> 
> They will still supply single glazing with a furniture stamp on though, can't really see the logic of it.



CE registered manufacturing standards.


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## RobinBHM (22 Oct 2021)

John Brown said:


> I have no idea what your point is.
> I'm 68, and I have oak framed windows.


I’ve made hundreds of oak windows.


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## Jacob (22 Oct 2021)

Phil Pascoe said:


> A friend years ago was taken to court for fitting uPVC windows in a conservation area. He was told they should have been oak frames. He said he'd been a professional decorator for thirty years and had never come across an oak framed window - they insisted he was wrong. I'm 67, I've never seen an oak framed window. They don't exist here.


Nor me. Except occasionally oak cills. This is a common mistake as oak rots much worse than pine if damp and doesn't hold paint too well. In fact I've taken out oak cill windows where the pine right down to the tenons is still in good order but the oak right next to it is rotting away.
Redwood is most common with pitch pine next.


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## Jacob (22 Oct 2021)

Ollie78 said:


> Worked for a firm who used the Sylacryl backing and linseed oil for face putty, absolute rubbish way to do it in my experience. Sylacril takes ages to dry as does putty, the only advantage was the putty is easier to do neatly if you dust it off properly.
> .....


Putty is very cheap, very easy to apply and given normal maintenance (paint) can last 100+ years.
I wouldn't have thought it would work well with DG as thermal movement in a large amount of glass would dislodge the putty, but I'm just guessing.
One odd detail with linseed oil paints is that you can paint it straight on to fresh putty. Not that surprising as it's more or less the same stuff but thinner.


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## Phil Pascoe (22 Oct 2021)

RobinBHM said:


> I’ve made hundreds of oak windows.


but not exported them to Cornwall, obviously  .


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## Jacob (22 Oct 2021)

Phil Pascoe said:


> but not exported them to Cornwall, obviously  .


nor Derbyshire


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## Ollie78 (22 Oct 2021)

GregW said:


> CE registered manufacturing standards.


If they provide a letter or certificate it is acceptable, also you can take a photo before glazing it.

A bit about the qualities of the stadip or other accoustic glass, it's all about the interlayer which is preventing the transfer of sound.
There is mention above of the spacing of panes relating to different frequencies etc. This is certainly correct but I think a bit different if you have normal glass vs accoustic. I wonder if there is a different resonance calculation for each type of glass ?
I would like to try a dgu with accoustic laminate in both panes.


Ollie


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## John Brown (22 Oct 2021)

GregW said:


> 28mm triple ? Well, it is ridicules.
> Casements min 64mm, and min 32mm triple glaze.
> 
> Like I said, HGV going next too it


HGV? What's that?


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## Just4Fun (22 Oct 2021)

heimlaga said:


> The only upgrades that pays off economically when counting in time materials and energy costs are to install modern rubber seals on the inner casement.


OK, That is interesting. We have a lot of windows so whatever we do has to be economically viable



> Proper rebates for inner casements became common around 1900 in Finland. The best way to create such a rebate to allow for properly complessed modern rubber seals is to nail a batten inside the jamb so a rebate is formed.


Also interesting. Our house has jambs which the casement closes against, but whether that is original or retrofit is difficult to say given the paint now covering them.



> If you still want to upgrade I have seen a third casement added halfways between the inner and the outer.


hmmm .... I have considered that but it is not easy to add that and cope with the existing window stays etc. I will give that more thought.

Thanks for your comments. Your comments have put me off making new outer casements and pointed me to simpler solutions (battens and rubber seals). Simpler, easier and cheaper - what's not to like?


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## RobinBHM (22 Oct 2021)

Phil Pascoe said:


> but not exported them to Cornwall, obviously  .


they tend to go into barn conversions or listed period houses.


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## GregW (22 Oct 2021)

Ollie78 said:


> If they provide a letter or certificate it is acceptable, also you can take a photo before glazing it.
> 
> A bit about the qualities of the stadip or other accoustic glass, it's all about the interlayer which is preventing the transfer of sound.
> There is mention above of the spacing of panes relating to different frequencies etc. This is certainly correct but I think a bit different if you have normal glass vs accoustic. I wonder if there is a different resonance calculation for each type of glass ?
> ...



I do single glaze in 6.8mm acoustic laminate. In comparison to 4mm standard it a heaven to clients. Impossible for Grage1, and not ok without permit on significant Grate2.

Double glazing 4/16/4 is great price/quality standard.

Triple glaze 100mm frame, 64mm casements, 4/10/4/10/4 works miracles. It’s massive in comparison to 4mm glaze 80mm casement frame, and really rare due council control listings.


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## John Brown (22 Oct 2021)

RobinBHM said:


> they tend to go into barn conversions or listed period houses.


We're in a barn conversion, but the "new wing" also has oak window frames to match.


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## baldkev (22 Oct 2021)

Jacob said:


> Nor me. Except occasionally oak cills. This is a common mistake as oak rots much worse than pine if damp and doesn't hold paint too well. In fact I've taken out oak cill windows where the pine right down to the tenons is still in good order but the oak right next to it is rotting away.
> Redwood is most common with pitch pine next.



A few years ago i worked on a farmhouse with oak windows and doors. Looked great. Unfortunately one of the patio door sets never gets opened, so no-one noticed the bottom rails had swelled and were constantly wet. The doors were only about 4 years old and the bottom galf inch or so was basically mush. 
I must admit, i was extremely suprised, ive always believed oak was supposed to be great outside.


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## sometimewoodworker (23 Oct 2021)

baldkev said:


> I must admit, i was extremely suprised, ive always believed oak was supposed to be great outside.


There are very few wood speeches that will withstand that kind of condition. Sweet Chestnut is the only one that is likely to survive, that I know of. Many speeches will do OK if protected from standing in water few last with water and air contact.


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## KieranJW (24 Oct 2021)

Ollie78 said:


> Worked for a firm who used the Sylacryl backing and linseed oil for face putty, absolute rubbish way to do it in my experience. Sylacril takes ages to dry as does putty, the only advantage was the putty is easier to do neatly if you dust it off properly.
> 
> Repair care Dryseal is good but silly money, Hodgesons heritage is a bit cheaper, I use mostly Timbaglaze from chemfix. I know a place that use Stixall which is only a fiver a tube. I did a test with it and it works pretty well, I guess they are all pretty similar chemically. I find them good if you need to spray finish top coat after glazing ( which I try to avoid).
> 
> ...


Same here I used repair care but now use timbaglaze. I never used silacryl as I used that in place of acrylic caulk.


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## Jacob (24 Oct 2021)

KieranJW said:


> Same here I used repair care but now use timbaglaze. I never used silacryl as I used that in place of acrylic caulk.


I don't see putty working on DG unless it is in a massive fillet proportional to the glass thickness. Georgian windows had very thin glass down to 2 or 3mm and very tiny rebates 5 x 14mm typical. The strength of the putty fillet being roughly in proportion to the glass thickness. Thicker glass, more putty required, mainly because of the power behind thermal movement.


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## KieranJW (24 Oct 2021)

Jacob said:


> I don't see putty working on DG unless it is in a massive fillet proportional to the glass thickness. Georgian windows had very thin glass down to 2 or 3mm and very tiny rebates 5 x 14mm typical. The strength of the putty fillet being roughly in proportion to the glass thickness. Thicker glass, more putty required, mainly because of the power behind thermal movement.


Yeah sorry this is when single glazing and not using linseed paint. (Sorry I mentioned this in a previous post) 
If using linseed paint I would use linseed putty if the customer is using something else I use he polymers (I do try to convince them to use linseed and explain the benefits)


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