BMcN Posted March 5, 2019 Share Posted March 5, 2019 Morning, With regards to PIR insulation when placed under floor, does it matter about being foil faced? My floor will be concrete slab / DPM / 120-150mm PIR / UFH pipes / 75mm concrete screed. If the answer above is yes, is there anything I could use on top of the PIR to replicate the foil face, like an aluminium VCL like this? Thanks Link to comment Share on other sites More sharing options...
Onoff Posted March 5, 2019 Share Posted March 5, 2019 I've repaired damaged foil faced pir with heavy duty Bacofoil before. Bit of spray adhesive, job done. Link to comment Share on other sites More sharing options...
PeterW Posted March 5, 2019 Share Posted March 5, 2019 1 hour ago, BMcN said: With regards to PIR insulation when placed under floor, does it matter about being foil faced? Nope. Just put a thin plastic slip membrane between the insulation and the concrete. Link to comment Share on other sites More sharing options...
BMcN Posted March 5, 2019 Author Share Posted March 5, 2019 1 hour ago, PeterW said: Nope. Just put a thin plastic slip membrane between the insulation and the concrete. That's what I am hoping, I'd be able to reduce the cost of insulation quite a bit by going without foil. Link to comment Share on other sites More sharing options...
PeterW Posted March 5, 2019 Share Posted March 5, 2019 DPM above and below - use 25mm of EPS below the first DPM instead of sand blinding, then pack the PIR in, second DPM and job done ... Link to comment Share on other sites More sharing options...
BMcN Posted March 5, 2019 Author Share Posted March 5, 2019 What's the thinking behind the double dpm? Just to save on messing around with blinding? Link to comment Share on other sites More sharing options...
A_L Posted March 5, 2019 Share Posted March 5, 2019 17 minutes ago, BMcN said: What's the thinking behind the double dpm? Just to save on messing around with blinding? No, there is a danger that the insulation will undergo hydrolysis (breakdown to its constituent chemicals) in permanently damp/wet conditions. http://blog.celotex.co.uk/technical/what-celotex-insulation-can-be-used-in-floor-applications/ Link to comment Share on other sites More sharing options...
BMcN Posted March 5, 2019 Author Share Posted March 5, 2019 1 hour ago, A_L said: No, there is a danger that the insulation will undergo hydrolysis (breakdown to its constituent chemicals) in permanently damp/wet conditions. http://blog.celotex.co.uk/technical/what-celotex-insulation-can-be-used-in-floor-applications/ Sorry I got confused as I misread Peters post. Yes dpm then PIR then another dpm to protect from screed. Why the recommendation of 25mm eps instead of blinding? Link to comment Share on other sites More sharing options...
PeterW Posted March 5, 2019 Share Posted March 5, 2019 It’s just easier than sand blinding and protects the DPM from punctures. Link to comment Share on other sites More sharing options...
BMcN Posted March 5, 2019 Author Share Posted March 5, 2019 16 minutes ago, PeterW said: It’s just easier than sand blinding and protects the DPM from punctures. Thanks. I'll see what depth I have as the hardcore is in and compacted but I can't remember what depth I have left to the FFL. Link to comment Share on other sites More sharing options...
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