I have a deep window frame above my front door. It currently has a single glazed pane in it. I was wondering whether anyone has had any experience getting a correct sized double glazed pane made up and fitting it into the existing frame.
Are glazing companies willing to make a double glazed pane for this? And would it be cheap enough to be worthwhile. Also, would the double glazed pane fit OK into the existing pane? It is deep enough to accomodate the pane from what I can tell.
You can get sealed units made up, however there are issues with respect to getting the units to last. Apparently they will fail ( mist up) if not fitted to allow for proper ventilation around the edges. And they require deeper rebates.
Check out the following web site - they seem very knowledgeable on the forum:
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There is an "e-book" for download there, giving the ins and outs of fitting sealed units in old frames:
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meaning to try replacing one myself, but not got around to it yet...
You need to be able to accommodate a unit at least 12mm thick. Most good DG companies will supply you with a sealed unit, and they are surprisingly cheap. I recently bought 8 of them (1.5x1.2m average) at about £50 each.
The key point is that it must not end up sitting in a puddle of water in the frame. This is easily avoided through careful sealing.
We've double glazed our whole house by getting the glass company to make factory sealed units to exactly the size we specified. That's thirty five (I think) units. Spouse fitted them over a couple of years so the cost - which was VERY low - wasn't felt at all.
They've been perfect in every way. There has been absoutely no misting. They were easy to fit (he does know what he's doing but with a little care and intelligence anyone could do it - it's safer than single pane glazing). The key is accurate measuring. For the largest panes - up to 4' square - it needed two people because the units are heavy (on two ladders for 1st floor lights); for others one person inside and one outside was a help but not absolutely necessary. He did our 1st floor bedroom the week after being discharged from hospital after a hip replacement.
What I like best is that we retain the timber frames and don't have the reduced light which is inevitable with plastic frames. The relative cost was unbelievably low and we were in control at all times. The only disruption was one pane being out at any one time - at our convenience.
Are you talking about sash frames and windows here, Mary? How did you fit in the units and did you have to add to the sash weights if they were sashes?
No, sorry, I should have specified.I suppose it they had been sashes I'd have said so.
But I don't suppose he'd have been daunted by sashes and he has a collection of lead which he occasionally casts into moulds for various purposes. Working out the required added weight for the counterbalances would have been the cerebral part of the exercise.
Just in case you find that there is not enough depth for a double glazing unit, it is possible to have a stepped unit made - ie the two panes of glass are different sizes and the metal spacer is the size of the smaller pane, allowing the unit to fit a rebate meant only for single glazing, held in pace only by the larger pane.
Yes - any decent glazier will order up a double glazed panel in any size. But it can't just be fitted with putty - it needs to be fully sealed against rain and must be in a flexible seal so when the frame moves slightly it doesn't get subject to twisting, etc. The glazier will supply materials and details.
If it's in a rebate it will probably have to be enlarged. If it's got planted on beading, then this can be changed or moved.
Heat loss through windows rule of thumb is about 10%. Double glazing halves this and so saves 5% of heating component of fuel bills. Typically about £500 p.a. hence saving £25 p.a. Really not worth the bother. Higher proportion of heat lost through windows if the house is highly insulated but the small saving is the same i.e. larger % of smaller bill - still not worth it. Add in rapid obsolescence of DG units makes it very costly - they all mist up eventually. Better to increase loft insulation, reduce draughts, thicker curtains etc etc. Cheaper to install new gas condensing CH boiler will save much more. Double glazing expensive con.
There are other considerations than cost, even if your figures were universally accurate.
Not in my experience. It probably depends on the quality of the original units.
During the day?
Double glazing increases the comfort of a house, you can sit (as we do) close to uncurtained windows on the coldest of days and still be comfortable.
Down draughts from single glazed windows can be shown by holding a candle flame near to them. The candle will flicker and gutter, it won't with an efficiently double glazed window.
That depends on who does it. If you do it yourself (this IS a DIY ng) it is not expensive and you have control of the whole process.
Yes, efficient insulation and draughtproofing are very important in the whole scheme of things but you won't dissuade me about the desirability of dg.
You seem to either believe what you have no experience of or have had an unfortunate experience. It's not everyone's experience.
In 'The Which Book of Plumbing & Central Heating' the heat loss quoted for single glazed wooden windows is 5 W/sq.metre/deg C and for DG wooden or plastic windows is 2.9 ditto. This means DG saves 42% heat loss. Similar figures are quoted elsewhere, say approx 50% as a rule, of average 10% heat loss of whole house i.e. about 5% overall. If you work it out on paper every other way of reducing heat loss from simple draught measures up to replacing old boiler with modern high efficiency boiler, will cost less than whole house DG but save more or at least be more cost efficient. In other words DG is the last thing you should bother with - only after putting into place ALL the other measures especially loft insulation - and even then is not worth it unless you have money to burn. You can work it out for yourself.
Actually, one of the things I like about windows is you can sit next to them if you want to be a bit cooler but everyone else doesn't.
OTOH Jacob's calculations are on heat loss and not including getting rid of unwanted heat gain. So how much would I save, Jacob, on my summer air/con power bills if I double glazed (which I won't). Figure on air/con being 'on' for a total of about 5 months a year [June - September plus bits and pieces in other months.
In article , snipped-for-privacy@jpbutler.demon.co.uk (jacob) wrote:
From the New Statesman 6 January 2003
It's all a lot of hot air ========================= Resist double glazing salesmen, advises JEFF HOWELL. They can't save us from global warming Are you, in these midwinter bothered by double glazing salesmen? They are annoying bastards at the best of times. But they have become especially irritating since 1 April 2002, when they could start claiming that, as well as fighting global warming and stopping old people dying from hypothermia, they had the British government on their side. April Fool's Day was an appropriate date to launch the mishmash of convoluted reasoning that forms the new Part L1 of the Building Regulations for England and Wales, and which decrees that henceforth all new windows shall be double-glazed. The new rules include much genuflecting to the Kyoto Protocol, which committed western governments (though not the US, obviously) to reducing waste heat. Or "carbon emissions", as we are now supposed to call it. Other European countries have decided to crack down on carbon emissions from power stations, factories and motor vehicles, but the British government has decided that our primary source of carbon emissions is poor people heating their homes with one-bar electric fires, and that if they would all just replace their windows with new double glazing, then that should do the trick. They reached this conclusion after much unselfish committee-stage work by the British glass industry, which helpfully suggested that a thermal insulation value of two watts per square metre per degree centigrade would be about right. And now that the new building regulations have been unveiled, it must be gratifying for the glass-makers to find that the only way to achieve this new insulation value is by using sealed double-glazed units made with their own special low-emissivity ("low-e") glass. And I am sure it is nothing more than a coincidence that April saw the price of low-e glass rise by 5 per cent, followed by a further 10 per cent hike in September. Low-e glass is very clever stuff. It has a metallic coating that reflects approximately 25 per cent of escaping heat back into the room. The downside is that the metallic coating also reflects approximately 25 per cent of incoming light back outside, so that the new windows appear much darker than ordinary glass. It is a testament to the enduring scientific ignorance of the British public that they are consistently surprised by this. After all, heat and light are but a few wavelengths apart on the electromagnetic spectrum, and if you reflect one, then you are sure as hell likely to reflect the other. But the salesman didn't mention it, so the punters are puzzled. It's all done with mirrors, you see. When we say "double glazing", what we really mean is "replacement windows". Most replacement windows are sold over the phone by commission-paid salesmen, and are made from PVC-U, or uPVC as it used to be called. The "U" stands for "unplasticised", to distinguish it from plasticised PVC, which is what raincoats are made out of. But though PVC-U is not as bendy as raincoat material, it is still a bit bendy, which is why the window frames are so chunky looking. They have to be, to stop the things from flopping around when you open them. So the darkness inside homes fitted with replacement PVC-U windows is also a function of at least one-quarter of the window area being taken up with the framing material itself. Beautiful 1930s houses with delicate timber fenestration are having their windows replaced with PVC-U. They look as though their front elevations have been redrawn using a blunt pencil. And despite their chunkiness, PVC-U window frames still have to be reinforced internally with steel or aluminium alloy bars. Which creates a bit of a problem when it comes to reaching the aforementioned thermal insulation value. For, contrary to popular perception, PVC is not a particularly good insulator. Considerably less effective than wood, for example. And when you poke a bit of metal down inside it, it becomes even more likely to conduct heat out of the house; which is why owners of new double glazing are often surprised to find condensation forming on the plastic frames of their new windows. But the chief complaint of double glazed homeowners is not about insulation, it is about internal misting. Sealed glazed units are bound to mist up sooner or later, due to the irrevocable forces of nature. The sealing material that joins the two panes of glass has to be flexible, otherwise the glass would break, and physics dictates that a flexible seal will also be vapour-permeable. Sealed glazed units cope with the constant seepage of moist air by incorporating a desiccant within the perforated alloy spacer bars that run around the perimeter. Eventually, the desiccant will become saturated, and the double glazing will mist up. This is also something that the salesmen never mention. The timescale before the glazing mists up depends on the quality of the installation. Dryglazed vented units in German windows may last 30 years. Cheap back-street British units stuck in with putty have been known to fail after three months. Double glazing won't save you any money in the long run. If you take into account making the product, installing it, disposing of the old windows . . . well, it's like nuclear power; it's a net consumer of money and energy. There used to be an advert on the telly, with dear old Ted Moult saying: "You only fit double glazing once, so fit the best - fit Everest." So how come Everest is now leafleting all its customers, telling them they might wish to "upgrade" to the new standards? Jeff Howell is a bricklayer, and building columnist for the Sunday Telegraph
Dunno - you'll have to work it out for yourself! Can't say I've ever suffered from unwanted heat gain in Britain. I'd open the windows and generate a bit of through draught. The french have the answer to summer heat - high ceilings, large windows opening inwards with slatted shutters closed on the outside - bliss, who needs air conditioning?
Come to think - summer heat gain would be based on difference between reasonable room temp say 65F and high summer air temp say 85F - 20deg F difference. Not a lot compared to winter frost, say - 5F; heat loss based on temp difference of 70 deg F. Hence DG contribution summer saving less than a 3rd of winter saving on any particular day with these temperatures. It would depend on the frequency of high/low temps and the efficiency of cooling compared to heating. I'd guess cooling less efficient than heating but I don't know. Opening windows a cheaper and more pleasant option.
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