Browse Forums Windows & Doors 1 May 31, 2017 7:45 pm Hi Everyone, I have been checking out WERS recently and it seems that aluminum framed double glazed windows have relatively high Uw values (generally 3.0 and above). Thermally broken aluminium can get up to 2.2 Uw (but still depending on a vendor). If I want to go below 2.0 - then I have to go with either uPVC and timber, not much of the other options. Anyone can recommend a supplier of uPVC or timber double glazed windows/doors, which won't be asking for to sell a kidney in order to glaze a house (e.g. within $300-350 per sq m)? What about Deceuninck? Are they any good? Thanks Re: Double glazed windows - Uw values 4Jun 02, 2017 9:47 pm Have been researching uPVC for a while. You will need to pick a good manufacturer if you decided to use it. I'm choosing between uPVC and thermally broken aluminium. They are usually within similar price range. Suggest you go to show room to have a look at the actual products first. Once you see a few, you will notice the difference between good and bad ones. It can be quite obvious.. from personal experience. Re: Double glazed windows - Uw values 5Jun 05, 2017 11:49 am When you compare window energy performance, check that they both have the same glazing configuration, (I prefer to check the clear glass option (4/12/4), this way you are checking the true energy performance of the window, not simply the glass). My 2 cents. Our non-broken aluminium window beats many thermally broken products - i.e. have a lower U value, check these out in http://www.WERS.net (ours at Uw 3.4 is yet to be published). PVC is an efficient insulator, but it generally requires big sections with internal steel support, so a well designed aluminium window with low-E can outperform a pvc window with clear glazing. We used to supply pvc windows, but the problem I found was the coefficient of linear expansion of PVC relative to aluminium and steel was a problem for us. And if you ad in any colour the problem gets bigger. So a 2000 length of pvc will expand 6mm over 40 degrees - where does it go? They say pvc is good for BAL 29, but BAL 29 is flame contact, and although pvc does not support combustion, a flame is 700 degrees C, and pvc melts at 160 degrees C.. So glass will fall out. Ed "ECOECO" At 'EcoEco', we design windows, we design the best windows, we do it for you, so that when you’re happy we are happy. Tel. 1800 326 326 Re: Double glazed windows - Uw values 6Jun 06, 2017 3:44 pm Hi ECOECO, 3.4 is certainly lower than 5.0 of single glazing, however, is quite far from 1.8, which could be achieved with uPVC of timber. I believe something around 2.0 could be achieved with thermally broken aluminium, though. As for thermal expansion, PVC-U is 0.000600 per C, so for 40 degree difference (zero to 40) it will expand 4.8 mm on a 2 m window (2.4 mm into each side). uPVC windows are widely used in Eastern Europe where temperature differences between summer and winter can be achieving 80 degrees and there are much higher requirements towards insulation. AFAIK they just design in 5 mm gaps in all 4 directions and insulate them with foam - this pretty much sorts the problem. By the way, any specific reason why you are not doing thermally broken aluminium? After reading this forum, I have got impression that you pricing and quality is very competitive and I would be really happy to add you to my short list if you could get close to 2.0 on Uw values. Re: Double glazed windows - Uw values 7Jun 07, 2017 2:03 pm Uw Values Taking an Awning window as standard with clear glass, the Uw values are as follows...
If you are finding values lower than my examples it is because they have added an exotic glass type and all manufcaturers can do the same thing, so compare clear glazed only. Linear Expansion The problem is in the linear coefficient of expansion of uPVC, and with steel reinforcement the linear coefficient of expansion of steel in conjunction with uPVC. For example, the coefficients of linear expansion for uPVC and steel are: -
Thus uPVC expands at 5 times the rate of the steel, which is in itself a problem for the location of hardware fixing through the uPVC to the steel. But more importantly, the increased problem of the level of expansion of the uPVC over wide temperature variations found in Australia, which when coupled with the sizes of the windows in rigid walls, can affect the structural integrity of the uPVC window or sash, where the window frame components or the sash components have no room to expand. [b]According to the Australian Bureau of Statistics, the temperature range for Australian capital cities varies as follows: - [/b]
Thus there is a maximum variation of up to 52oC for all capital cities. If we look at uPVC in relation to that variation, the expansion of a the uPVC material for a fixed window or sash would be 6.66mm (52oC x 2000mm x 0.0000640/oC) = 6.66mm of expansion, whereas the steel would expand only 1.3mm (52oC x 2000mm x 0.0000126/oC). That is in normal operation over normal temperatures, sashes will bind and windows will bow if confined in a rigid wall. uPVC in Europe The difference between Europe and Australia is style, in Australia we want big windows, big openings... yes, you can build around the problem, but why, do what the Europeans do, have smaller windows. Also imagine a dark coloured uPVC in sunlight... what termperature will that reach. I don't know the results yet of using some very special glass in our window, I will publish it when I have it. We have a thermal break window, but I could not in all honesty sell something that doesn't make sense economically for our customers, when the existing window performs so well. We will design a better thermal break window over the coming year... Ed "ECOECO" At 'EcoEco', we design windows, we design the best windows, we do it for you, so that when you’re happy we are happy. Tel. 1800 326 326 I don't know them all, the first 2 top of your list are best known. Rylock is a good company, Stegbar is for sale. 4 16160 I’m in a similar position except I’m after sliding 3 stacking doors. I am on a second-story apartment of which the balcony would not adequately fit any bi-fold or… 5 16091 I am saying that double brick has similar thermal performance due to thermal mass effect. It will be still very interesting to see the state of your framing after 10-15… 10 29734 |