Honest! I bought from John Knight Glass, they quoted £226 extra for a 3G over 2G in a 4 panel (3600mm x 2100mm) bi-fold.
Quite a specialist bit of glass really. I'm not surprised that the cost difference was so low. For more 'normal' windows I'd expect quite a bit more difference.
The outside pane cold enough to have condensation on the outside with a 23°C temperature difference, I doubt it. Some double-glazing is very good, uW 1.3 with PVC frames and coated glass, triple with the same specification will get you uW 1.1; better than the wall it's mounted in unless you have cavity-wall insulation, or insulation on the in/outside of the wall.
"Necessary". It depends what you're aiming at. In my case it was removing the central heating and being able to heat the whole house for the whole day by running the wood burner for a few hours in the evening. Triple glazing, wall insulation, under-floor insulation, double outside door. Of course it wasn't necessary, the alternative was cold spots in the house, condensation, a moaning wife, a 1000e gas bill and contributing to climatic change.
The way the uW values are calculated allows fair comparison of small windows, however, for big windows where losses through the frame are proportionally smaller the calculation flatters double glazing (or doesn't show how much better triple glazing is for big glass areas). For big windows it's better to look at the glass figures, typically uG 1.1 for double and uG for .7 for triple.
We get condensation on the outside of our triple glazed window with 20 degrees inside but the wall is obviously badly insulated so really need to get that sorted now.
The ski chalet we were in last week in Villeneuve had lovely wooden double glazed windows just sat in the brickwork with no mastic or mortar to fill in the gaps between the brick and wooden frame, you could see daylight around the frame. Must be a French thing.......
DG units don't fail suddenly; it's an inevitable process that takes a few years to happen. There has to be an in/out flow of air in order to accommodate changes in atmospheric pressure. Pressure increases and air comes in in tiny volumes and brings moisture. The units are built with a moisture absorber which, after some years, becomes saturated and unable to absorb any more moisture. The moisture level builds up inside the unit until it begins to condense.
Utterly wrong. Modern units will have a completely air tight seal around the edge and will, if a reasonable unit, be filled with either Argon (good) or Krypton (better) gas to prevent thermal bridging. This seal can, over time decay, but almost all units a guaranteed for 5 years with the better ones being 10 years. If you can keep water and UV light away from the butyl seal, they last longer.
UPVC is rubbish as heat insulation
That is incorrect.
Agree with this. It is possible to make a very thermally efficient window in timber using laminates including air pockets and effectively celotex, however this isn't the norm. Often modern PVC will outperform. It'll look crap though!
The outside pane cold enough to have condensation on the outside with a 23°C temperature difference, I doubt it.
We absolutely get this as a 'complaint' from customers every winter. That's with a relatively standard low E argon filled unit, in a wooden frame. It happens all the time.
That brings me onto relative 2g vs 3g performance. It is possible, with the correct layup (low E coating, potentially on both pieces of glass, Krypton gas infill and other better coatings (all brad specific names currently) get a 2g to outperform a lower spec 3g unit. But you're not comparing apples with apples. Put the same coatings on 3g, fill with the same gas, it'll outperform without any question. It will however, be more expensive, and not just because of the glass, but the sash / frame needing to accommodate a circa 45mm unit as opposed to a circa 32mm one.
If you're looking to get quotes, make sure you look really closely what exact layup of glass you're being offered, an what the u value of the finished window is. There's a massive difference, and that's before we get onto solar control, self cleaning, uv protection, laminated glass!
Trickle vents are required for new builds, or any replacement windows on older properties that already have them fitted. It's the equivalent of leaving your window open a crack so that you get a bit of air in. If you tend to keep all your door and windows shut all the time, it's a good thing as it prevents damp. I've got kids and dog who leave doors open all the time so we get plenty of fresh air in the house so when it's closed u and the heatings on, we want to heat the place and not get cool air in. Don't want them, don't like the look but have to have them. I have put them on for a new window in a garage conversion I've just finished, but as soon as it's signed off, I'll be replacing the sash with one that's not got a trickle vent in it!
Edukator, I'm not lying, I've seen it with my own eyes several times since having them installed a few months ago. At first I though I had duff units and it was moisture between the panes, but it's not, it's definately condensation on the outside pane. Underfloor heating stat set to19 degrees, -4 Degs outside.
wobbliscott, it's quite common with thermally efficient windows. Glass has come on a long way in recent years.
After a conversation with a lady who does Energy Performance Certificate testing for Your Move,said that DG and TG/3G are rated the same in their assesesments. With this in mind we chose DG for our house,went with local family firm,it's a corner house so 6 windows and a front door £3.5k all in, very pleased. Fitters were a great bunch of lads,worked fast and cleaned up when finished. I kept the brews and biccies coming so all went like clockwork. 😀
wobbliscott - MemberEdukator, I'm not lying, I've seen it with my own eyes several times since having them installed a few months ago. At first I though I had duff units and it was moisture between the panes, but it's not, it's definately condensation on the outside pane. Underfloor heating stat set to19 degrees, -4 Degs outside.
Yeah, our new (almost 1yr old) double glazing gets the fog on the outside thing on occasion. First time I saw it I thought the panels had packed up.
On the workshop patio doors, there is often condensation on the outside of the DG unit......
Edukator, I'm not lying,
I tried to stop just short of accusing you of doing so, and now I've got a whole posse after me with condensation on the outside glass. For condensation to form the glass has to be colder than the air which must also have a very high relative humidity, if the water is not from fog then as with UFOs, I'll remain skeptical till I see it with my own eyes.
Edukator, Last year I produced 11073 sashes. Every single one of those is installed in a house somewhere (UK, Italy, France, Spain, Japan, USA) This happens. Really, we have it as part of our normal 'product information' pack. I don't have any reports from Japan (in an admitidly non airtight building as it has trees growing through the roof) or Italy, but I do in Spain and a lot in the UK and US. You don't have to believe me, but you're wrong.
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For condensation to form the glass has to be colder than the air
Don't think that's right - it doesn't need to be colder, it just needs to be in contact with air that's near saturated and to provide a surface for the water to condense on.
FWIW, I also get condensation outside the double glazing on some cold days.
EDIT - I reckon Pilkington know a thing or two about glass
http://www.pilkington.com/en-gb/uk/householders/faqs/external-condensation
Saint-Gobain are pretty good with the clear stuff as well.
[url= http://uk.saint-gobain-glass.com/trade-customers/condensation-double-glazing ]http://uk.saint-gobain-glass.com/trade-customers/condensation-double-glazing[/url]
Ok, I'm wrong. I'll have to leave the shutters open on a cold damp night and try to prove it to myself.
