bmj1 Posted June 14, 2023 Share Posted June 14, 2023 Hi wise people, Was planning to do underfloor heating with liquid screed over kooltherm phenolic insulation. Kingspan advise that this insulation should not get wet, so plastic sheet above. So how do we do the clips for underfloor heating without piercing the insulation ? Link to comment Share on other sites More sharing options...
Thorfun Posted June 14, 2023 Share Posted June 14, 2023 8 minutes ago, bmj1 said: Hi wise people, Was planning to do underfloor heating with liquid screed over kooltherm phenolic insulation. Kingspan advise that this insulation should not get wet, so plastic sheet above. So how do we do the clips for underfloor heating without piercing the insulation ? you can't! but don't worry the liquid screed won't get through the staple holes. here's a photos of ours just staple through the dpm and in to the insulation. so simple I did all ours myself with my wife on the stapler most of the time. 1 1 Link to comment Share on other sites More sharing options...
saveasteading Posted June 14, 2023 Share Posted June 14, 2023 (edited) You just pierce the membrane and insulation and don't worry about it. Pir doesn't really get wet. The membrane is to stop the wet screed flowing between joints and floating the pir. Edited June 14, 2023 by saveasteading 1 Link to comment Share on other sites More sharing options...
Canski Posted June 14, 2023 Share Posted June 14, 2023 Can you not also glue the dpm to the insulation and use self adhesive rails for the pipe work ? 1 Link to comment Share on other sites More sharing options...
bmj1 Posted June 14, 2023 Author Share Posted June 14, 2023 6 hours ago, saveasteading said: You just pierce the membrane and insulation and don't worry about it. Pir doesn't really get wet. The membrane is to stop the wet screed flowing between joints and floating the pir. Sure. Only thing is it isn't PIR, it's the phenolic product. K103 So not quite sure how it behaves ! Link to comment Share on other sites More sharing options...
Jilly Posted June 14, 2023 Share Posted June 14, 2023 We used it as above. Works fine, am really pleased with the floor's performance. 1 Link to comment Share on other sites More sharing options...
bmj1 Posted June 14, 2023 Author Share Posted June 14, 2023 Just now, Jilly said: We used it as above. Works fine, am really pleased with the floor's performance. Ok fab. Out of curiosity, how thick did you go ? Link to comment Share on other sites More sharing options...
Jilly Posted June 14, 2023 Share Posted June 14, 2023 (edited) We could only get 100mm in, which is insufficient really and why I chose to use it, hoping it would have better performance than 100mm PIR (or EPS). Incidentally, I also researched a lot before coming to a view, and decided to use slate tiles, rather than engineered wood to improve the heat transfer. I even chanced not using decoupling mats, as the plumber thought it would reduce the efficiency of the floor, which made sense to me. We used good quality expansion joints at the door thresholds and don't heat the floor over 35 degrees and I was ultra cautious about turning it on at all in the beginning. Edited June 14, 2023 by Jilly 2 Link to comment Share on other sites More sharing options...
saveasteading Posted June 14, 2023 Share Posted June 14, 2023 3 minutes ago, Jilly said: chanced not using decoupling mats, Yes...I couldn't find figures so we chanced it too. A good comparison may be carpet underlay. Unless specially made for ufh, it is a good insulator. 1 Link to comment Share on other sites More sharing options...
bmj1 Posted June 14, 2023 Author Share Posted June 14, 2023 34 minutes ago, Jilly said: We could only get 100mm in, which is insufficient really and why I chose to use it, hoping it would have better performance than 100mm PIR (or EPS). Incidentally, I also researched a lot before coming to a view, and decided to use slate tiles, rather than engineered wood to improve the heat transfer. I even chanced not using decoupling mats, as the plumber thought it would reduce the efficiency of the floor, which made sense to me. We used good quality expansion joints at the door thresholds and don't heat the floor over 35 degrees and I was ultra cautious about turning it on at all in the beginning. Insufficient in terms of sap calcs? Or the house feels cold/is costly to heat? Are you using a heat pump ? Link to comment Share on other sites More sharing options...
Thorfun Posted June 14, 2023 Share Posted June 14, 2023 4 hours ago, Canski said: Can you not also glue the dpm to the insulation and use self adhesive rails for the pipe work ? ufh click tracks are expensive, staples are cheap! 😉 1 Link to comment Share on other sites More sharing options...
Jilly Posted June 14, 2023 Share Posted June 14, 2023 48 minutes ago, bmj1 said: Insufficient in terms of sap calcs? Or the house feels cold/is costly to heat? Are you using a heat pump ? It's a conversion, so no SAP calcs, just @SteamyTea's advice that you need loads more insulation than you think under ufh. No, I think it's worked, the hose is warm and pretty cheap to heat. On LPG at the moment but 'heat pump ready'. I think the UFH egg boxes might reduce efficiency too, so we used staples. Link to comment Share on other sites More sharing options...
bmj1 Posted June 14, 2023 Author Share Posted June 14, 2023 49 minutes ago, Jilly said: It's a conversion, so no SAP calcs, just @SteamyTea's advice that you need loads more insulation than you think under ufh. No, I think it's worked, the hose is warm and pretty cheap to heat. On LPG at the moment but 'heat pump ready'. I think the UFH egg boxes might reduce efficiency too, so we used staples. What screed did you use? I'm planning 40mm liquid screed to maximise heat transfer Link to comment Share on other sites More sharing options...
Iceverge Posted June 14, 2023 Share Posted June 14, 2023 10 hours ago, bmj1 said: kooltherm phenolic insulation. How tight are you for floor buildup space ? The sums almost never make sense Vs using PIR at a fraction of the price and doubling up insulation elsewhere instead for less money overall. Link to comment Share on other sites More sharing options...
bmj1 Posted June 14, 2023 Author Share Posted June 14, 2023 24 minutes ago, Iceverge said: How tight are you for floor buildup space ? The sums almost never make sense Vs using PIR at a fraction of the price and doubling up insulation elsewhere instead for less money overall. Very tight. ~120mm total for insulation + screed (to include underfloor heating)... I managed to pick up 75mm phenolic for £20/sheet from Secondsandco (link), so I think that's the best result I can hope for given the situation. 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted June 14, 2023 Share Posted June 14, 2023 40 minutes ago, bmj1 said: What screed did you use? I'm planning 40mm liquid screed to maximise heat transfer This will give you almost "on - off" heating characteristics. Is that a choice, or a constraint? Link to comment Share on other sites More sharing options...
Nickfromwales Posted June 14, 2023 Share Posted June 14, 2023 8 minutes ago, bmj1 said: Very tight. ~120mm total for insulation + screed (to include underfloor heating)... I managed to pick up 75mm phenolic for £20/sheet from Secondsandco (link), so I think that's the best result I can hope for given the situation. Ah, OK Link to comment Share on other sites More sharing options...
bmj1 Posted June 14, 2023 Author Share Posted June 14, 2023 6 minutes ago, Nickfromwales said: This will give you almost "on - off" heating characteristics. Is that a choice, or a constraint? A constraint. But I'm ok with it. I'm planning to have each room zoned with heatmiser. Tbh - instant response sounds good to me. I'm not sure I understand why we would want to wait an hour to feel the benefit of the heating ? Link to comment Share on other sites More sharing options...
bmj1 Posted June 14, 2023 Author Share Posted June 14, 2023 11 hours ago, saveasteading said: You just pierce the membrane and insulation and don't worry about it. Pir doesn't really get wet. The membrane is to stop the wet screed flowing between joints and floating the pir. Awesome, thank you ! Link to comment Share on other sites More sharing options...
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