dewalty Posted March 4, 2023 Share Posted March 4, 2023 After some advice please. New build single floor annexe. 40sqm floor. Walls -Thermalite - 90mm pir - thermalite. Flat Roof single ply with 150mm pir Current floor build up, 150mm pir below 100mm slab. 90mm to play with between slab and final floor finish (engineered flooring 15mm) floor temp 27c. 150mm pipe spacing. Just had a visit from liquid screeder who I've used before. He has suggested 20mm pir with 50mm screed. He is saying heat up times for slab and screed etc will be excessive. Should I stay with the original plan of using slab as thermal store? And input would be gratefully received. Thanks Link to comment Share on other sites More sharing options...
Jenki Posted March 4, 2023 Share Posted March 4, 2023 This is a second post where a 20mm PIR layer has been mentioned. To me it makes no sense. UFH is a different mindset to radiators. You mentioned using the slab as a thermal mass, and I'd go this route. Put as much insulation under the the 100mm slab. Personally I'd use the slab as a final floor it's not a huge area. Look at using EPS as an alternative to PIR for cost reasons. (You will need more depth circa 300mm) Link to comment Share on other sites More sharing options...
Dave Jones Posted March 4, 2023 Share Posted March 4, 2023 putting the insulation under the conc was a mistake. you should have put it on top of it and made it 300mm EPS but you are where you are. get the pipes stapled to the conc somehow (trays ?) and screed over. Link to comment Share on other sites More sharing options...
Andehh Posted March 4, 2023 Share Posted March 4, 2023 Just to soften it a bit for OP, 150mm of PIR anywhere underneath the UFH is still very good all considering. 20mm PIR and then 50mm is not unreasonable. I'd prob go down that route I think. Quicker warm up times and will still let some warmth creep into mega store underneath. Link to comment Share on other sites More sharing options...
nod Posted March 4, 2023 Share Posted March 4, 2023 41 minutes ago, Dave Jones said: putting the insulation under the conc was a mistake. you should have put it on top of it and made it 300mm EPS but you are where you are. get the pipes stapled to the conc somehow (trays ?) and screed over. Plus 1 Probably more to do with having Somthing to clip his pipes to than warm up times Trays or 25 mil insulation will be needed Insulation would be the cheaper option Link to comment Share on other sites More sharing options...
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