dogman Posted June 21, 2017 Share Posted June 21, 2017 Can anyone please help. The calculation of U values for triple glazing panels If you have a glazing panel, made up as 4-20-4-18-6.8, soft coat, soft coal, Lam/tuf glass with warm edge spacers and argon filled is it possible to reduce the air gap to 10mm and 10mm and still achieve the same thermal efficiency. Everything i have found on line suggests it is not possible. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted June 21, 2017 Share Posted June 21, 2017 (edited) No, I'm afraid it's not possible, or at least not without going for some really exotic product, like vacuum glazing, which will be a lot thinner (but isn't that easy to buy, and is mega expensive). The gap between the glazing is quite critical to performance - too big and circulating convection currents can develop in the gas filling the gap, too small and the conducted heat loss through the gas in the gap increases, pretty much in direct proportion to the reduction in gap width. 20mm is about the optimum gap, 16mm is just about the lowest acceptable gap for 3G, anything less than this will reduce the performance too much. Edited June 21, 2017 by JSHarris Link to comment Share on other sites More sharing options...
dogman Posted June 21, 2017 Author Share Posted June 21, 2017 @JSHarris any idea of the potential performance decrease. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted June 21, 2017 Share Posted June 21, 2017 (edited) It's not that easy to calculate, but I doubt that a 10mm gap 3G unit (if available) would be significantly better than a 20mm gap 2G unit, with the possible exception that if it had two low e panes the radiated IR loss would be lower. I'd expect a Ug value of something around 1.0 to 1.6 W/m².K, with Uw (the actual window U value) being worse, and dependent on the frame type and the ratio of glazing area to frame area. This is largely guesswork, though, as I can't quickly find any data for 10mm gap 3G glazing units. It's based on the fact that I think that Ug will probably vary in a pretty linear way in relation to gap thickness, all else being equal, so the typical 0.5 to 0.8 W/m².K Ug of a 4-20-4-20-4 unit would be around doubled if the gap was halved. Edited June 21, 2017 by JSHarris Link to comment Share on other sites More sharing options...
dogman Posted June 21, 2017 Author Share Posted June 21, 2017 Thanks @JSHarris i did find an old article on the BRE site that basically stated that a 28mm high spec double glazed unit would out perform a similar spec 3G unit. Link to comment Share on other sites More sharing options...
Dudda Posted June 21, 2017 Share Posted June 21, 2017 Why do you need the 3G glass thinner? Is it not thinner frames you should look for which are a lot easier to find? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted June 21, 2017 Share Posted June 21, 2017 (edited) 9 minutes ago, dogman said: Thanks @JSHarris i did find an old article on the BRE site that basically stated that a 28mm high spec double glazed unit would out perform a similar spec 3G unit. That sounds reasonable, as a 28mm DG unit would probably be a 4-20-4 unit, whereas a 28mm 3G unit would have to be be something like 4-8-4-8-4, which would be a fair bit worse (not even sure that such a thing is available). Edited June 21, 2017 by JSHarris Link to comment Share on other sites More sharing options...
dogman Posted June 21, 2017 Author Share Posted June 21, 2017 @Duddadon't ask. Major issues with window company. Trying to fob us off Link to comment Share on other sites More sharing options...
dogman Posted June 21, 2017 Author Share Posted June 21, 2017 i have found some info on another companies web site . 4-20-4-18-6.8 is a 0.52 centre U value going to 4-14-4-14-6.8 is a centre U value of 0.77. Link to comment Share on other sites More sharing options...
Mr Punter Posted June 21, 2017 Share Posted June 21, 2017 Maybe different gas - krypton or xenon may perform better. Link to comment Share on other sites More sharing options...
PeterW Posted June 21, 2017 Share Posted June 21, 2017 @Nick or @craig may be able to help with this as they are in the business from what I've gleaned the centre U is irrelevant as basically you can eliminate any savings with a poor edge spacer ..! 1 Link to comment Share on other sites More sharing options...
dogman Posted June 21, 2017 Author Share Posted June 21, 2017 I understand that the glazing i have has warm edge spacers made by swissspacer, argon filled and the glass is Planitherm low e soft coat according to the stickers on the glass. And above all this they are passive certified Link to comment Share on other sites More sharing options...
Jeremy Harris Posted June 21, 2017 Share Posted June 21, 2017 That sounds right, we also have Planitherm glazing units, double soft e coated internal panes and argon filled, with warm edge spacers. Our gaps are bigger though, most are 4-20-4-20-4 with the toughened stuff at the front being 4-20-4-18-6.8. How come you've ended up needing thinner glazing? Link to comment Share on other sites More sharing options...
MikeSharp01 Posted June 21, 2017 Share Posted June 21, 2017 If they are passive certified then the Uw value must be OK why do you need it thinner? Link to comment Share on other sites More sharing options...
dogman Posted June 21, 2017 Author Share Posted June 21, 2017 33 minutes ago, JSHarris said: Our gaps are bigger though, most are 4-20-4-20-4 with the toughened stuff at the front being 4-20-4-18-6.8. so are ours for every other window and door 32 minutes ago, MikeSharp01 said: If they are passive certified then the Uw value must be OK why do you need it thinner? Because they have made the three large sliding doors (3m/3m and 4.2m)that can only take 34mm units and delivered 52.8mm glazing units. Link to comment Share on other sites More sharing options...
Stones Posted June 21, 2017 Share Posted June 21, 2017 7 hours ago, JSHarris said: It's not that easy to calculate, but I doubt that a 10mm gap 3G unit (if available) would be significantly better than a 20mm gap 2G unit, with the possible exception that if it had two low e panes the radiated IR loss would be lower. I'd expect a Ug value of something around 1.0 to 1.6 W/m².K, with Uw (the actual window U value) being worse, and dependent on the frame type and the ratio of glazing area to frame area. This is largely guesswork, though, as I can't quickly find any data for 10mm gap 3G glazing units. It's based on the fact that I think that Ug will probably vary in a pretty linear way in relation to gap thickness, all else being equal, so the typical 0.5 to 0.8 W/m².K Ug of a 4-20-4-20-4 unit would be around doubled if the gap was halved. When we were sourcing our windows, Rational still sold (they perhaps still do) 3G units with smaller gaps between panes. There was very little difference performance wise between those and their 2G. I think that type of 3G had probably been their initial 3G offering, made to fit in a 2G frame. Big step up in performance / U value with their 18 - 20mm gap 3G units. Link to comment Share on other sites More sharing options...
PeterW Posted June 21, 2017 Share Posted June 21, 2017 So if you get them to use Laminated both sides with Planitherm Ultra N coatings with a 20mm krypton cavity you will have 33.5m and a Ug of 1.0W/(m².K). Change to Argon and it's 1.1W/(m².K) Thats rough and ready from the Calumen calculator from St Gobain Make it 4-10-4-10-4 with Planitherm Ultra N on panes 1 & 3 and you're at 0.8W/(m².K) Ug Have they suggested laminated or toughened ..? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted June 21, 2017 Share Posted June 21, 2017 51 minutes ago, dogman said: Because they have made the three large sliding doors (3m/3m and 4.2m)that can only take 34mm units and delivered 52.8mm glazing units. Sounds to me like this is their problem, that they have to fix. I wonder why they didn't notice that they couldn't fit a 52.8m thick glazing unit into a frame that can only take 34mm? Link to comment Share on other sites More sharing options...
dogman Posted June 21, 2017 Author Share Posted June 21, 2017 6 minutes ago, JSHarris said: Sounds to me like this is their problem, that they have to fix. I wonder why they didn't notice that they couldn't fit a 52.8m thick glazing unit into a frame that can only take 34mm? Correct They did notice but wanted to swap out glass not frames. But to be honest every single window has an issue and we have a senior manager coming out to see us as most are manufacturing issues Link to comment Share on other sites More sharing options...
Jeremy Harris Posted June 21, 2017 Share Posted June 21, 2017 (edited) 7 minutes ago, dogman said: Correct They did notice but wanted to swap out glass not frames. But to be honest every single window has an issue and we have a senior manager coming out to see us as most are manufacturing issues Sadly I think there are a fair few window manufacturers that make errors like this. We had a window delivered that was 400mm too wide, and to their credit they came back with a replacement a week later, but it shouldn't have happened in the first place, as the schedule was very clear. We also had a problem with a defective glazing unit; again they replaced it quickly, but it should have been spotted before it left the factory (it wasn't transit damage). For some reason, windows and doors seem to cause a disproportionate number of problems. I will admit to losing faith in getting the manufacturer to fix adjustment problems, after two goes at it, and spent a day adjusting all the doors myself. Not hard to do, but a bit time consuming. Worth it to get all the doors closing smoothly, with the latches operating very easily, and the tiny air leaks that were picked up on the air test fixed. I get the feeling that the big suppliers are geared up to fit loads of windows to new developments, and rush the installation work, knowing that buyers of new homes seem happy with crap............. Edited June 21, 2017 by JSHarris Link to comment Share on other sites More sharing options...
ProDave Posted June 21, 2017 Share Posted June 21, 2017 1 hour ago, dogman said: so are ours for every other window and door Because they have made the three large sliding doors (3m/3m and 4.2m)that can only take 34mm units and delivered 52.8mm glazing units. Another one agreeing this is their problem. They have not supplied what you ordered. I think I am one of many on here that had no problems with Rationel (other than one window cill that got damaged in transit and they replaced promptly) so am happy to recommend them. Link to comment Share on other sites More sharing options...
craig Posted June 21, 2017 Share Posted June 21, 2017 3 hours ago, PeterW said: @Nick or @craig may be able to help with this as they are in the business from what I've gleaned the centre U is irrelevant as basically you can eliminate any savings with a poor edge spacer ..! The spacer used is important, standard spacer warmedge for example can in the region of 0.046 psi value and a plus version 0.026 psi value. I've seen this be the difference between a pass and a fail in a Passive House. I personally wouldn't use a 20mm spacer in a glass unit unless it was absolutely necessary. In my view a triple glazed unit at 4/18/4/18/4 is optimum for a 0.52Ug. Doubled glazed 4/18/4 being optimum for a doubled glazed unit. It it becomes a little more complicated when introducing laminated glass on the external or internal pane and then boils down to the system. Some suppliers can accommodate 52mm glazing units, some can only accommodate 40mm / 44mm glazing units. However, one important factor, is a glass is only as good as the supplier of the glazing unit (which isn't necessarily the window manufacturer). I've seen brand new 3G units filled halve way up with water inside the unit. Link to comment Share on other sites More sharing options...
craig Posted June 21, 2017 Share Posted June 21, 2017 (edited) 1 hour ago, dogman said: so are ours for every other window and door Because they have made the three large sliding doors (3m/3m and 4.2m)that can only take 34mm units and delivered 52.8mm glazing units. It happens but it shouldn't, they should be fully aware. I don't know the program they use but it sounds like the unit is put into the system prepared for a specific glass size and the glass is then entered seperately. Sounds like human error to me. I've had it happen myself, when replacing a glass unit. It was 44mm, it came as 48mm resulting in the glazing beads being to big. Thankfully that's an easy fix, so is your's but a costly one to the supplier. Edited June 21, 2017 by craig Link to comment Share on other sites More sharing options...
dogman Posted June 22, 2017 Author Share Posted June 22, 2017 Has anyone on the site had an Internorm lift and sliding door fitted anywhere between 3 - 4m wide and 2.1m high. with the 54mm triple glazing with the 0.67 u value.if they have are that able to give me a ball park cost fitted. (or any other manufacturer of similar standard) Link to comment Share on other sites More sharing options...
Barney12 Posted June 22, 2017 Share Posted June 22, 2017 19 minutes ago, dogman said: Has anyone on the site had an Internorm lift and sliding door fitted anywhere between 3 - 4m wide and 2.1m high. with the 54mm triple glazing with the 0.67 u value.if they have are that able to give me a ball park cost fitted. (or any other manufacturer of similar standard) Ours is bi-parting. The price was a smidge over £6k fitted (as part of a much bigger order). I have to say it is a thing of beauty! As for the other doors well they would be if they were right 1 Link to comment Share on other sites More sharing options...
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