The great 'Double Glazing Con'

[dzj]

I wonder if they had similar discussions in the late 1800s here when double glazing was becoming standard on houses.

Do you mean this type of double glazing?

 

[RogerS]

Much as it goes against the grain ( :wink: ) I am with Jacob on this one 100%

And here is the original post about the linseed oil paints. For those who are new to the forum, Mr Grimsdale is Jacob. http://www.woodworkuk.co.uk/forum/viewt ... f=7&t=1968

 

[Jonzjob]

I haven't had time to read all this thread, but I think we would be a lost cause without double glazing. This is our lounge window, 5 X 2.2 metres,



our bedroom window is 4 X 2.2 metres and the second bedroom jobbie is 3.3 X 2.2 metres. The kitchen one is only 2 X 1 metre. So triple would be nice to both keep the heat in and out, but out of the question.

Plus, in the winter, as our house faces dead south, the sun shines in through to the back of the rooms and even although our underfloor heating is set to 20º the room temps can reach up to 27º. In the summer the eves are built so that the sun doesn't shine in at all.

We also have a large open fire :shock: :shock: Lovely too on a very cold winters day, good cosy value..

 

[DennisCA]

I wonder if they had similar discussions in the late 1800s here when double glazing was becoming standard on houses.

Do you mean this type of double glazing?

No I didn't have any type in particular in mind.

 

[RogerS]

As I mentioned in the OP, John, double-glazing is beneficial in circumstances such as yours. It's when you have small windows in a property where the lunacy of the Building Regs chasing u-values down the drain becomes obvious. And, as I found out, makes diddly squat to any EPC Certificate.

 

[Beau]

It's not the DGUs that are the problem it's the way EPCs are scored that is the issue, that and the prices peddled by some national installers.

Double glazing provides a greatly increased acoustic and thermal insulation values. A standard 4mm annealed glass sheet has a u value of u/5.8. the same double glazed unit with two sheets of 4mm and a 16mm spacer with 90% argon fill gives you u/2.6. Add a low emissive coat to the DGU and this falls to u/1.2. This not only decreases heat loss from the building but also helps to improve the internal atmosphere by reducing condensation and stabilising internal relative humidity.

The acoustic performance is also marked, especially if you have two different glass thicknesses making up the DGU.

On top of that DGUs are not really that expensive. 19m2 of 4-16-4 low-e argon fill should be in the region of £600 +VAT for the units. You should make that back in gas bills in 5-7 years depending on usage. (That article is from 2005 claiming £150-200 p/a, the price of gas has gone up about 10% since then.)

As for the 5 year replacement, 5 years is the minimum guarantee provided by most unit manufacturers. However the vast majority of units last much, much longer. 15-20 years is a better estimate of average life span. The reasons units fail is also much better understood now than it was 30 years ago. Units should be drained and vented so the hot melt used in the sealing process is never sat in water either through condensation or weathering. This is why the units are sat on packers and the frames should have drain holes. That goes for uPVC frames and wooden frames. On the subject of longevity the uPVC frames also have a limited life with UV degradation. If you have wooden windows that are well maintained the cost of replacing the units ever 20 years should be easily recoverable against the rising cost of gas.

Having said all that if your sales person manages to get someone to pay £12.5k then the payback will never really appear. I did the 9 windows in our house which equal approx 13m2 for less than £2k 3 years ago but I do have trade contacts for the uPVC frames and a glass merchant that gets a lot of custom from us.

What he said.

Made a few DG windows over the years never had any complaints of failed units. Cant imagine going back to single glazing with all the condensation related problems. More inclined to look at triple glazing for any future windows I make particularly if they are north facing. In a completely uninsulated house I am sure the difference a bit of DG makes in very small but with a low U value homes the percentage difference DG makes is far greater.

 

[Jacob]

I wonder if they had similar discussions in the late 1800s here when double glazing was becoming standard on houses.

It didn't get going in the UK until quite recently. 1960s? No doubt there were all manner of earlier experiments.
Finland a lot colder than the UK so it's a different ball game altogether. But I'd expect that there was (and continues to be) lots of discussion of the other ways of keeping the heat in, such as blinds, curtains, shutters, insulation in general.

Cant imagine going back to single glazing with all the condensation related problems. More inclined to look at triple glazing for any future windows I make particularly if they are north facing. In a completely uninsulated house I am sure the difference a bit of DG makes in very small but with a low U value homes the percentage difference DG makes is far greater.

There plenty of cheaper ways of fixing condensation problems and anyway DG doesn't do it very well without other measures in place.
Yes to the percentage difference but its a fraction of a smaller bill so the actual savings total remains the same whatever condition the rest of the house. This sometimes takes some people a bit of time to get their heads around!

 

[Phil Pascoe]

People often forget where the base line is. If someone quotes say £2000 to replace your windows With DG plastic are you replacing because you have to, putting them in a new build or are you pulling out reasonable windows to do it? Insulation properties and expected energy savings are the same - e. g. you'll save 10%. 10% of what - 10% compared to an old ill fitting window? a new single glazed window? a hole in the wall? You need to be realistic. Personally, I haven't enough life left to paint windows, or enough money to pay someone to paint them every few years.

 

[Jacob]

Much as it goes against the grain ( :wink: ) I am with Jacob on this one 100%

And here is the original post about the linseed oil paints. For those who are new to the forum, Mr Grimsdale is Jacob. http://www.woodworkuk.co.uk/forum/viewt ... f=7&t=1968

Forgotten about that! I'll dig out the photos. It's an on going experiment and so far all is well on old and new work.
It's particularly good over failed paint surfaces where it seems to stop any further deterioration and at the same time stick tight to bare areas. Doesn't seem to get a mention in the literature but this can save a massive amount of work - stripping, making good etc.

 

[Lons]

He still has never fitted even one PVCu unit as he freely admits yet is such a self proclaimed authority on that subject - very strange - very Jacob :lol: (hammer)

Just for the record. I am not a double glazing fitter. My business was construction and during that time I fitted hundreds of PVCu units as part of builds and extensions plus a **** of a lot conservatories. I also have fitted many timber units including bespoke frames for grade 2 listed buildings. So I do have the experience.

I can honestly say that in 18 years I have had only 2 callbacks to PVCu (and I would know of any problems as the vast majority of my customers are local and repeat). One of those required a simple door hinge adjustment which was caused by a child using the door as a swing and took 15 minutes and the other was a broken window handle which was faulty. That never happens with traditional fittings of course, does it! :wink:

My own windows and doors I fitted 13 years ago which shocked me when I looked it up :shock: and my conservatory 15 years. Nothing wrong with any of them, and no sign of seal failure or frame degradation. They just get a fairly regular wipe over when the windows are cleaned

PVCu isn't for everyone and certainly doesn't suit most old traditional buildings. They are over hyped for sales profit and building regs are a joke driven by political compliance with Brussels. The regs really don't make sense at times and if pressed the inspectors freely admit that elements are nonsensical however they have to be complied with.
Jacob is right in that there are ways to reduce condensation and save heat, some cheap, some bloody expensive others need a major life change to how we cook, wash our clothes and take baths or showers. Maybe we should revert to the bath night in front of the fire once a week instead of a lovely steaming power shower and lose the cooker / microwave in favour of a pot over an open fire.:lol:

We all have our own ideas but they are just opinions not fact and will make our decisions on that basis. I'm very happy with mine and more importantly, so is the missus.

Anyway, I've made a decision on my free time - workshop today, golf tomorrow. \/
cheers
Bob

 

[Lons]

......
How many have you actually fitted yourself to provide you with so much enlightenment btw?
cheers
Bob

Several hundred sash windows period replica replacement and repair maintenance of several hundred more. Zero plastic windows. A couple of goes at DG in old sashes but decided it was a waste of time. And a lot of other woodworky stuff, conservation, building work and bits n bobs of furniture.
A never ending stream of enquiries ; what to do about failed DG units i.e. seals gone misted up inside and the impossibility of getting anyone to honour guarantees. They tend to imagine that they are just unlucky, not realising that it is extremely common. The ones that don't fail seem to be the lucky few.

Trad windows can last 100s of years. I'm strongly inclined to think that I wouldn't have been in business at all if it hadn't been for modern paint - stripping off the old linseed oil paint and replacing with modern is the kiss of death. Even new work suffers with modern paint. I'm about 7 years into linseed oil paints and the difference is astonishing. I wish I had known about it sooner.

The only part of that which actually answered my question was this

Zero plastic windows

:lol: :lol: :lol:

 

[Jacob]

.....
I can honestly say that in 18 years I have had only 2 callbacks to PVCu

Over the years I've had hundreds of queries about failed DG units. Maybe they simply give up on the original suppliers and go straight to the alternatives.

......
Jacob is right in that there are ways to reduce condensation and save heat, some cheap, .....

Controlled ventilation costs very little. Worst option of all is the dreadful "de-humidifier".

 

[RogerS]

There is a small joinery company that recently supplied 400 double-glazed timer windows for a construction site down South. They used the 'heritage' type spacers in the double-glazing units...ie the ones that are lower profile than normal and so let the DGU sit inside a 10mm rebate rather than deeper rebates of 15mm or more.....you know the ones, those with 6 x2 glazing bars ... :wink:

370 have failed. There's a moral there somewhere...not sure where...heritage seals maybe.

 

[DennisCA]

But I'd expect that there was (and continues to be) lots of discussion of the other ways of keeping the heat in, such as blinds, curtains, shutters, insulation in general.

For my house it was triple glazed windows, insulation 330mm thick in walls, 500mm in roof, 250mm in the floor under the concrete plate and 150mm on the sides of the plate. The ground outside the house foundation is insulated under the soil out to 1 meter to prevent the ground around the house from freezing or getting too cold, essentially the ground under the house never freezes and so doesn't have frost heaving.

We heat our house with electricity that runs a geothermal pump, our consumption during the coldest months was 700-900kWh per month, but in fairness that included my freestanding workshop and all other electrical consumption. In addition to heating that is.

 

[RogerS]

DennisCA..is your house a relatively newbuild? Does Finland have a lot of older properties (as we do over here in the UK) and if so what energy saving schemes have they adopted?

 

[DennisCA]

Most finns who live in houses live in houses built after WW2 when there was a post war boom in building.
Thicker insulation and double or triple glaze windows are the norm. Hydronic radiant heating is also the norm as opposed to forced air heating. Dunno if those are tricks but that's what's normal for most houses.

I know more details about my own house because we recently built it (2013-2014), I know my parents house build in the late 70s did not have the same type of foundation or the same level of insulation, nor insulation around the foundation. Triple glazed original windows still in place though.

The latter is something they're planning to add since I had lots of insulation left over.

 

[Lons]

There is a small joinery company that recently supplied 400 double-glazed timer windows for a construction site down South. They used the 'heritage' type spacers in the double-glazing units...ie the ones that are lower profile than normal and so let the DGU sit inside a 10mm rebate rather than deeper rebates of 15mm or more.....you know the ones, those with 6 x2 glazing bars ... :wink:

370 have failed. There's a moral there somewhere...not sure where...heritage seals maybe.

I can honestly say Roger that the only sealed units I have changed and there have been a few over the past 18 years have been fitted in timber frames. A number of reasons for failure firstly poorly fitted and sometimes wrongly sized, usually too tight. No gap at the base so the inevitable water ingress sits around the seal and the use of the wrong silicone sealant which attacks the seal.

Jacob claims

Over the years I've had hundreds of queries about failed DG units.

Unless he has a lot of very poor fitters and poor quality components around where he lives I'd suggest it's an exageration :roll:

Low profile seals are vulnerable but I'd suggest for one project to have that many failures either the manufacturers of the units or the fitters have got it badly wrong.
I fitted that type into a grade 2 listed stable build and was very careful to fit properly, 11 years down the line they're perfect and I know that 'cos I was there last weekend.

cheers
Bob

 

[Jacob]

......
Jacob claims

Over the years I've had hundreds of queries about failed DG units.

Unless he has a lot of very poor fitters and poor quality components around where he lives I'd suggest it's an exageration :roll:.....

Not at all.
Phone would go every week if not every day. I was well known as a joiner/woodworker doing repair/restoration so maybe it was people with failed units in wooden windows who would call me rather than the DG suppliers.
Dunno. No doubt about them failing all over the place though.

 

[Lons]

so maybe it was people with failed units in wooden windows who would call me rather than the DG suppliers.

At last Jacob, the truth is out and you're starting to make sense. failed sealed units in TIMBER frames has bu**er all to do with the argument and your clain that PVCu frames are ****

As I stated I've had zero failed units in PVCu frames but a number in timber frames to replace (non fitted by me), the vast majority were caused by poor original installation. The manufacture of frames and glass are seperate production procedures and whilst some of the window guys make sealed units themselves, usually in a seperate factory, the majority buy them in.
PVCu frames allow the glass to move, be ventilated and be drained so they have a much longer life, all things being equal.

cheers
Bob

 

[woodpig]

I need to replace a window and want to improve the sound insulating performance but can't get the figures for triple glazing or acoustic double glazing to see which is best.