CADjockey Posted March 12, 2023 Share Posted March 12, 2023 Hi, further to recent post on window combined U values, I've investigated the maths to make my own calculations and it's reasonably comprehensible. I followed a short YouTube video and now have an easy to complete spreadsheet that will do the heavy lifting. The only hole I have is an understanding of how to calculate the Thermal Bridge Coefficient for the final multiplication for which they used a 0.3 value... If anyone has a guide or can tell me if 0.3 is a usable figure it would be most helpful. I'm sure the window manufacturers/suppliers can and have done all this but the fitter seems less knowledgable and as I need to be able to provide the evidence to the SAP guy in th end I thought a little knowledge would not be a bad thing. Many Thanks. Link to comment Share on other sites More sharing options...
craig Posted March 12, 2023 Share Posted March 12, 2023 You just need to give your SAP guy the performance declaration. They don’t (shouldn’t) need individual items calculated uvalue. On your sheet, you should account for the sides (jambs), top (head), cill (bottom) Uf values. Jambs and head are likely to be the same but the cill is likely to be different. You should also use the psi value for the spacer bar and that should be good enough for the Uw but in all honesty, your window supplier should be able to give you each window value calculated to ISO 10077-1. I’d be concerned if they couldn’t. Link to comment Share on other sites More sharing options...
CADjockey Posted March 13, 2023 Author Share Posted March 13, 2023 11 hours ago, craig said: I’d be concerned if they couldn’t. I'm sure they can, but thanks. Link to comment Share on other sites More sharing options...
ADLIan Posted March 13, 2023 Share Posted March 13, 2023 Window supplier need to provide test data to confirm window performance. Calculated U-values can be used but these must be done by a BFRC certified window thermal modeller. Link to comment Share on other sites More sharing options...
CADjockey Posted March 13, 2023 Author Share Posted March 13, 2023 1 hour ago, ADLIan said: Window supplier need to provide test data to confirm window performance. Calculated U-values can be used but these must be done by a BFRC certified window thermal modeller. Yup get that, I just wanted to understand how it works and it gives me some peace of mind to feel it's not just a load of smoke. I will be requesting a full calcs sheet in any event. Link to comment Share on other sites More sharing options...
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