Double-glazing

[Pford75]

Given the regular comments on the forum re:uPVC and double glazing in general, I thought i'd just mention something of interest.

Before purchasing our current property, we used to live in a brand new development (not quite a Barratt box...but still fairly uninspiring). All of the houses had timber-framed double glazing.

Well, we spoke with our old neighbours at the weekend and it appears that 4 of the sealed units have all leaked and are now full of condensation! This all occurred within about a month of each other...and the property is only 6 years old. They have been advised that they will require new sealed units (one of them is a patio door)....this could be very costly. At least with my single-glazed windows, I don't have this problem.

Just think of the economic and environmental cost of replacing sealed units every 6 years!

 

[Nemesis]

I totally agree - we double glazed roof light (original type - metal) and withing 12 months it started to fail.

But no-one seems to count all these add on costs of replacement and manufacture.

 

[tony]

If the wrong type of sealant is used, this can eat into the double glazing seal to fail.

On glazing sealant should be used.

Clear silicone sealant may be cheaper but in the long run, it might not be !!.

regards

tony

 

[AMc]

One of the many architects I've interviewed for my house recently commented on our quite well made faux Georgian double glazed wooden sashes installed by the last owner...
He pointed at the original windows in the unrenovated part of the house and at the new ones and showed me the differences in the glazing bar width (substantial). Then he told me that the sealed unit manufacturers shorten the guaranties on them because the spacers in the units should be recessed enough to keep them from direct exposure to sunlight. If you do that with a multipane window you end up with glazing bars a couple of inches thick.
Sure enough the failed unit in our house is on the most exposed window and has some condensation I think the windows are about 12 years old.

The manufacturing costs will still pale in comparison with the running costs of single vs. double glazing over even 6 years. A failed sealed unit is still much more efficient than single glazing even if it's unsightly.

FWIW everywhere I've ever had single glazing I've also had condensation and usually black mould after a while so you can't win

I guess if you're forced to replace your windows then looking for long guaranties on the units is a prudent thing to do and if you don't have to then consider secondary glazing as a more maintainable solution.

 

[Nemesis]

We have single glazed windows - we have little condensation and no mould. Opening the windows slightly allows any condensation on the bathroom window to vanish rapidly. It's how sashes are designed to operate.

I think that the whole issue of how much is saved with DG is not so simple. We have small windows, and at night we close the shutters. We also have curtains. I think sensible draughtproofing measures (not cutting off all air intake) will help cut heat loss too.

I gather linseed oil makes the seals degrade too. That lets out putty, which in traditional windows is part of the way windows are glazed and affects their apperance.

Me - I'm sticking with my single glazed sashes with original cylinder glass. I think I'd rather spend my cash on other heat retaining measures.

As far as the roof light goes - I'm going to single glaze and try some form of secondary glazing.

 

[NT]

The manufacturing costs will still pale in comparison with the running costs of single vs. double glazing over even 6 years.

the figures I've seen indicate retrofit dg never pays back its cost.

A failed sealed unit is still much more efficient than single glazing even if it's unsightly.

until it goes mouldy


NT

 

[AMc]

I guess if you're forced to replace your windows then looking for long guaranties on the units is a prudent thing to do and if you don't have to then consider secondary glazing as a more maintainable solution.

I never mentioned retrofitting double glazing.

If you're forced to replace your windows then (unless you're listed) you will end up with double glazing as you'll have a tough time getting a FENSA registered installer to supply anything else or building regulations approval on single glazed replacements.

 

[Nemesis]

I wonder how many people have been prosecuted for not fitting FENSA certificated windows?

 

[AMc]

AFAIK - A FENSA registered installer can certify that replacement and new windows conform to building regulations without needing inspection by building control. A sample of their work is inspected and they have to renew their registration.
Anyone can fit windows but they should conform and be inspected by building control (or at least BC should be informed).
http://www.fensa.co.uk/what.html

Our house has had its windows replaced. There was no paperwork and no building control certificate. There is the outside chance that they don't conform and there could be a safety issue or a problem with the installation making them less efficient. We had to take the chance that they were OK.

Your biggest problem with using a non-FENSA installer will come when you try and sell the house and can't provide the papers and end up having to get a retrospective building control certificate to placate your buyer.

Your biggest danger is that the windows were fitted really badly - for example a timber load bearing lintel is replaced with some PVCu by some idiot DIY or builder - and you could end up with a major structural problem.

I guess the answer to your question will come from how many prosecutions building control have brought for fitting substandard windows.

 

[biffvernon]

Do leave FENSA out of it - that's just a trade organization that allows self-certification. The important issue is that the window conforms to Part-L so doesn't leak heat. Essentially, that means it has a U-value of less than 2.

On the cost issue you have to see the difference between money cost and energy cost. Of course, double glazing might not 'pay for itself' in a month of blue moons, but the energy saving, even when the embodied energy in the glass (and its replacement) is counted, is positive after quite a short time (depending on heating levels and weather).

On the glazing bar width issue 'a couple of inches' is a bit on the gross side. For a standard igu you need a rebate and bead of about 13mm to cover the mastic on the spacer. One each side and 6mm for the bit of wood up the middle means 32mm across for your glazing bar. Say 34mm if you leave a bit of wiggle room.

 

[Nemesis]

I wonder (rhetorically) how many sales have fallen though as the certification hasn't been available?

Not many I would imagine.

And I still wonder (rhetorically) how many prosecutions building control has brought.

 

[Flyfisher]

I guess if you're forced to replace your windows then looking for long guaranties on the units is a prudent thing to do and if you don't have to then consider secondary glazing as a more maintainable solution.

I never mentioned retrofitting double glazing.

When the HIPs shambles is finally sorted out, retrofitting failed DG will probably become a legal requirement in order to maintain your energy rating. How will anyone know? Well, it'll come up during the annual "House MOT" test that will be brought in by stealth once we've been softened up by energy certs. Plus, of course, the energy certs will be the instrument by which local councils can implement a 'green levy' component in the council tax. Of course, this will all be in the name of saving the planet and won't have anything to do with increasing taxes :roll:

Talk about the thin end of the wedge.

Your biggest problem with using a non-FENSA installer will come when you try and sell the house and can't provide the papers and end up having to get a retrospective building control certificate to placate your buyer.

I don't think you need to worry too much about this for a while - surely the windows were replaced before the recent legislation came into force :wink:

I've heard there is quite a healthy market on Ebay for red/black mains cable, for much the same reason I suspect!

 

[Nemesis]

I've heard there is quite a healthy market on Ebay for red/black mains cable, for much the same reason I suspect!

Strange you should mention that ... we seem to have quite a stash...

 

[Penners]

Given the regular comments on the forum re:uPVC and double glazing .... we spoke with our old neighbours at the weekend and it appears that 4 of the sealed units have all leaked and are now full of condensation! This all occurred within about a month of each other...and the property is only 6 years old

That's not an argument against double-glazing - it's an argument against crap double-glazing.

Double glazing and uPVC window frames are two separate arguments. The former (properly manufactured and installed) is A Good Thing. The latter is unequivocally, unarguably and definitively A Bad Thing.

 

[alice]

When my mother had the windows of her listed house replaced last October, there was no question that they had to be double glazed. That's the regulation. One back window was still original and that was restored. The front windows were taken out in the 70's and large fixed single glazed glass panels were put in and those were replaced with six panel double glazed sash windows.

She was really upset that she couldn't keep her unpaneled look and insisted they would mess up her sea views, but my husband and I talked and talked to her and in the end she was quite happy with how the historically correct (more or less) windows looked (not that she had any choice in the matter).

I certainly hope she doesn't have any fogging issues, what with all the trouble she had getting them in. My modern double glazed windows in my 10 year old house haven't fogged at all, and they survive Texas heat and exposure.

alice

 

[Nemesis]

Sorry, but there is no regulation that single glazed window in a listed building has to be replaced with double glazed.

The planning situation is quite complex, but it's not the case.

It's really a question of building by building - and how good or how bad the CO is (if there is indeed a CO, which is another vexed question).

 

[alice]

Then if there's no reg, her CO was incorrect in insisting they be double glazed, because she didn't want that at all to begin with. She was (and is) worried about the seals breaking (as others have mentioned here) and fogging up her view.

It was quite a brouhaha between her (my mother) and the CO because she didn't want the windows changed to begin with, but it was part of the grant for refurbishing the front of her building (it's a listed terrace). At one point, the windows had been delivered on site, and the CO looked them over and sent them back (which really ticked her off and added months to the project). I don't know if that was for not having double glazing or if they weren't historically correct for some other reason (I was back in the States, then). He was really picky on the width of the wood bits, so I know they were six paneled windows and not solid glass ones like she had before.

I don't know if I care to tell her she didn't need double glazing to begin with. That's a hornets nest I don't care to stir up.

alice

 

[chuckey]

We had 19 Placky double glazed windows fitted in 1985. So far 5 (out of 38) panels have failed. Four of them on a south facing window (out of 6) and now the fifth in a shaded west facing window. Oh yes and also a large timber framed pane has failed (a bit older, put in in 1982).
So I would say, big windows and windows that face south fail first, due to the thermal stresses "working" the glued seal.
I change the panels myself, I think the panels cost about £50 for 34" X 26" or there abouts.
Frank

 

[Nemesis]

No, she didn't have to have double glazing - and it's hardly historically correct, no doubt the glazing bars are far too thick in order to accommodate it.

The regulations can be waived for listed buildings. English Heritage produces guidance.

Clearly if there was a grant involved then the local authority has some control over what is put in, but I can't see why double galzing was specified.

 

[chuckey]

How did that face get there??? its meant to be 5 out of 38.
Frank