Double Glazing or not?

[KieranJW]

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Double glazing vs Single glazing.

• Participants
  • KieranJW
  • ian33a
• Start date11 minutes ago

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KieranJW
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UKW Supporter
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.

 

[Jacob]

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

 

[Woody2Shoes]

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.

 

[Woody2Shoes]

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

 

[Jacob]

....

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.

 

[Jones]

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.

 

[Jacob]

.....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.

 

[Phil Pascoe]

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.

 

[Ollie78]

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

 

[Jacob]

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.

 

[Phil Pascoe]

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

 

[Jacob]

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!

 

[KieranJW]

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.

 

[KieranJW]

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.

 

[KieranJW]

Thanks very much to all who have replied too.

 

[KieranJW]

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.

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.

 

[Jacob]

'

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

 

[Spectric]

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.

 

[KieranJW]

'

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.

 

[KieranJW]

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.