Thermal conductivity of different types of windows

Not sure about what you mean there.. ..but there is a definite case for having better insulation when you don't need the light.

However, it is not a huge factor either way.

Reply to
The Natural Philosopher
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We have to have the rail 3" away because the curtains are gathered +-3" at the top. You can or course use a pelmet although those have gone out of fashion. They should overlap the window boards..and fall against them.

Of course they are not hermetic seals, but they are trappers of air to a large extent..they must be or I would not see remarkable differences between windows with curtains drawn, and not.

Reply to
The Natural Philosopher

Agreed. I found te met office stats.

Fair enough. That was a stab in the dark. I reckon that £500 a window installed with frames is an average sort of figure. And the average window is about a square meter or so,

Indeed. I thought I had made that point...that unless you had reason to replace the windows anyway, it wasn't a runner. If you put very cheap modern sealing strip round and old wood casement I reckon you rep 70-80% of the benefits of DG at about 1/0th the cost or less.

If you are installing new windows, apart from a severe attack of aesthetics, there is no reason NOT to install DG, the opportunity cost is low enough.

I was really coming at this from the point of someone who might be (genuinely) concerned about energy, and cost benefit on heating, and pointing out that received wisdom is largely driven by DG marketing and lack of hard information.

I.e. my conclusins can be stated two ways

'DG windows are 2-3 times as good as single glazed'

'installing DG windows will save you at best 2% of your energy bill, (all other things being equal)'

Both are reasonably 'true' statements.

Its about 3p .. think we worked that out..thats why in the end I switched to oil burned at 50% efficiency..except where talking about CFL lamps.

The cheaper the fuel the LESS the ROI is..so I am not sure how you got more..

Yup. I never was actually talking about installing SG from new..you only do that - as we did - out of an attack of aesthetics. Double glazing cannot be incorporated into lead lights and applied 'glazing bars' looks crap. So almost certainly your SG units will be more expensive, cos they are hand made specials.

Actually, we have high quality sealed SG here, installed from new, and I have to say the noise reductions is similar. It seems to be the sealing that is the key, rather than the DG.

I am not in general trying to say what you seem to think I am..that we shouldn't be putting DG or even TG in new builds. Of course we should bne. The *opportunity* cost is low enough, and the gains significant enough..to make it worth while.

My real thrust was at those people who have bought a nice solid (literally) walled Victorian property, find it chilly, and costing a lot to make snug, and instantly go out and fit DG.

The real point is that after whacking in loft insulation and SEALING it against draughts in the loft,and putting weatherstrip on the windows and doors, the very next think is to line the walls.

And possibly the floor.

There are HUGE potential gains to be had here, from not all that much thickness of insulation. 6" of rockwool or celotex is easy to install under a suspended floor for example. 2" of celotex on the outside walls is not going to break the bank. And you could be looking at 70% or more improvement in energy and bills.

Once that is done, boiler efficiency is not so important, and there is always a moot point as to how much MORE energy the new boiler takes to make.

Attention to electrical stuff is fairly trivial in terms of planet saving. Far better gains can be had by switching off huge amounts of public lighting between say 2 am and 6 a.m. However CFL bulbs are cheap enough to pay for themselves in a few months..I use them because they don't blow up every five minutes.

Likewise teenagers who spend 10-15 minutes in the shower are not saving water or energy vis a vis a bath, either.

Reply to
The Natural Philosopher

I'll concur with the gist of this message. In our case, our (modern) house already had insulation in the cavity (and I'm not going round adding an inside skin of more insulation and plasterboard). I'd already topped up the loft insulation to about 12-14". It's a solid concrete floor. The *last* thing to do was the DG.

That was done primarily to improve comfort levels (less condensation, less draughts coming off the cold SG pane, more even temperatures) and the SG windows needed maintenance....

J
Reply to
Jonathan Tong

I think there is some confusion here btween dg and upvc. The listed problems apply to upvc, but no such issues apply to dg. Leaded windows can be dg no problem, and oak dg does not have the butt ugly factor of upvc.

NT

Reply to
meow2222

Over our patio door/window we have net curtains and double-lined thick curtains. To prevent condensation due to the 'reverse chimney effect' we also use a sammy snake across the bottom of the curtains, when drawn for the evening.

One cold night last winter,

Reply to
Frank Lee Speke-King

The Natural Philosopher wrote: ...

Typo in the above: it should say .03 not .3. The answer is still 2.4%.

Because there are three error factors increasing the ROI from the 1% you originally calculated and only one (the fuel cost) reducing it. (i) temp diff, (ii) cost of DG, (iii) you said 8% of the heat loss is through the window when you should have said 14% = 5*2.5/(3.5*25). The net effect of all these corrections makes it a 2.4% ROI as a minimum case.

In that case the benefit of DG could be even more than 16% of course.

Fair enough. If you are comparing with high quality SG which you already have and are not costing then of course the benefits of DG will be smaller.

But you said "it's very hard to see why double glazing is so insisted on". I was just trying to explain why I think it makes a lot of sense in many cases.

Yes yes, I am completely sold on all that. You are preaching to the converted. I was just talking about DG and I wanted to fix the calculation.

Alex

Reply to
Alex Selby

In which case I absolutely agree with you. If the framea are rotten and draughty, They need replacing and DG is the way yo go.

Reply to
The Natural Philosopher

They cannot. Not true lead lights anyway. The frit sealing in DG panels is about three times as wide as the lead glazing. and a 15mm wide panle looks silly anyway in a leaded light. The only recourse is to apply fake glazing bars, and they either look really odd from inside, or outside, or if applied both sized, at an angle.

and oak dg does not have the butt ugly factor of

Oak with DG is lovely, if the style suits..but as I say, if you want real leads, DG is out.

Reply to
The Natural Philosopher

Was that SG? if so and you had say -2 outside, that would put the curtains at about 4:1 better than the SG..say around 1 or 1.2 U value.

About twice as good as DG.

Reply to
The Natural Philosopher

Aluminium patio door and window frame, about 8'w x 6'h, 1" air gap between the DG panels.

Reply to
Frank Lee Speke-King

all that tells us is the design of dg you have in mind can't be done.

The ones I saw were much deeper than that and looked fine. They were hardly noticeable.

those are like serving up a wimpy in place of beef steak au poivre.

I've seen it done twice. There is no technical reason not to create real leaded dg, but obviously the design is different to the popular sealed panels, since leaded glass is not an airtight glazing surface. DG does not inherently mean sealed, unsealed dg has been around for a long time.

The thermal characteristics are not as good as the usual dg, since the lead is so conductive and not airtight.

NT

Reply to
meow2222

Sorry I meant to say that more graciously. I think you do us a service by illuminating these issues.

Alex

Reply to
Alex Selby

That is surprising..any gen on how cold it was outside?

Reply to
The Natural Philosopher

I don't do gracious meself anyway, so no problems ;)

Reply to
The Natural Philosopher

You probably know but others might not...

It's very important to NOT to just wack some insulation between the rafters or you risk a condensation problem and potential long term problems for the roof structure. Lofts are generally designed to be ventilated spaces to allow any moisture from the house to be removed.

If you want to put insulation between the rafters and seal the loft to create a semi-warm storage space then you should consider going the whole hog as you would for a loft conversion.....

Add batterns to the sides of the rafters to stop the insulation coming in contact with the underside of the tiles/sarking and provide a 50mm ventilation space. Install sufficient insulation between and below the rafters (perhaps 150-200mm thick in total), then a correctly installed vapour barrier to keep moisture away from the cold tiles/rafters. Add small vents from the inside of the loft to the outside to allow any moisture in the loft to get out. The next step would be to line with plasterboard but that would probably make it a loft conversion in the eyes of building control.

The alternative is to put insulation between the ceiling joists and retain it as a cold roof. Seal gaps between the house and loft to keep moisture out of the loft. Leave the gaps under the eaves open to ventilate the loft. Insulate the loft hatch.

Colin

and putting weatherstrip on the windows and

Reply to
CWatters

In message , at 09:34:12 on Thu, 18 Jan 2007, The Natural Philosopher remarked:

What you can do (and I have some DG patio doors, and about a third of the other windows in my house like this) is make a double glazing unit that has a traditional sheet of lead lights in between. This has the added advantage that they are easier to clean, and it looks good too!

Reply to
Roland Perry

AFAICR it was something like -5 degC.

Reply to
Frank Lee Speke-King

Fairly normal for Speke

I went to the airport there once. I think it involves John Lennon these days for some reason - goodness knows why. There were tyre marks on the top of the car factory (Ford I think it was) from the aircraft. It made Ringway look sophisticated.

Reply to
Andy Hall

That is actually a very good idea..like a triple glazed unit eh?

Reply to
The Natural Philosopher

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