Bikerz Posted December 14, 2019 Share Posted December 14, 2019 (edited) Retrofit UFH I have a new concrete slab going in, how much insulation should I be putting in if I have whatever space I want? 200mm polystyrene stuff? I will be doing a concrete 4" ontop of insulation, then pipes in/and finished off with a 50mm liquid screed on top (to tie into rest of house at same level), unless anyone disagrees? Rest of house is block and beam so will be 50-80mm PIR insulation and the 50mm liquid screed with the UFH in. The reason is half house is Timber suspended and half block and beam, so timber suspended coming out and a solid base going in. Its my 30 year home so do it right and do it once. Thanks Sheldon Edited December 14, 2019 by Bikerz Link to comment Share on other sites More sharing options...
jfb Posted December 14, 2019 Share Posted December 14, 2019 200mm minimum of EPS (polystyrene) under slab. Why not attach UFH pipes to mesh in slab then no need for screed on top? 37 minutes ago, Bikerz said: 50-80mm PIR insulation and the 50mm liquid screed with the UFH in. This seems very little insulation. Does it even meet building regs? Also 50mm screed with pipes in it seems very thin but I don't know quite what liquid screeds are capable of. I would have thought 70mm minimum screed. Link to comment Share on other sites More sharing options...
jfb Posted December 14, 2019 Share Posted December 14, 2019 Just noticed it is a retrofit so that may constrain you. Link to comment Share on other sites More sharing options...
nod Posted December 14, 2019 Share Posted December 14, 2019 50 mil screed is fine as long as it is liquid and what ever space you are left with I would fill with kingspan or celotex As long as it is double sided foil backed Link to comment Share on other sites More sharing options...
Bikerz Posted December 16, 2019 Author Share Posted December 16, 2019 Thanks guys. Yes Retrofit so no care on building regs in regard to that, only for my own efficiency to get it insulated best I can within my physical limits. On a Eco home forum I am on, they have said dont put in concrete slab as warm up times are terrible and too slow, even if you do have all that thermal mass. Liquid screeds can go as low as 40mm but I think 50mm is the safe reasonable limit without pushing it. I will make sure I get the foil both sides and use a DPM so it doesnt effect the concrete. Link to comment Share on other sites More sharing options...
Russell griffiths Posted December 16, 2019 Share Posted December 16, 2019 Concrete slabs might be slow to warm up....... but you only do this once, once it’s up to temperature it stays on until spring when you turn it off. Link to comment Share on other sites More sharing options...
SteamyTea Posted December 16, 2019 Share Posted December 16, 2019 48 minutes ago, Bikerz said: On a Eco home forum I am on, they have said dont put in concrete slab as warm up times are terrible and too slow, even if you do have all that thermal mass. Which forum is that then? The warm up times will be a function of the power delivered to the slab. Link to comment Share on other sites More sharing options...
Bikerz Posted December 16, 2019 Author Share Posted December 16, 2019 Thanks guys. Navitron Its a 1967 built detached property in Warwickshire approx 150m2 downstairs. CWI is 50mm and filled. Tripple glazed. SO not brilliant, but trying. Currently working couple but Mrs will prob be working from home soon. Going to put some solar on roof with a divert excess to Thermal Store or Unvented cylinder to stop sort cycling an oil boiler. (No gas in area) 30 year home, so do it right, do it once. Link to comment Share on other sites More sharing options...
tonyshouse Posted January 1, 2020 Share Posted January 1, 2020 200mm of eps is not too much. ? 50 or 80 of pir is woefully insufficient vaguely worried about ground gasses, including radon and clay heave, why did they use beam and block? Response times, i love slow response times, = comfortable = stays warm and stops overheating, good design is important If it was mine i would be filling under beam and block areas with eps beads, full fill, and digging deeper to include more eps under the new concrete, would miss out the screede as suggested and fix pipes mid way in the 100 concrete on A142 mesh Link to comment Share on other sites More sharing options...
Bikerz Posted January 2, 2020 Author Share Posted January 2, 2020 I didnt think you should fill under the block and beam as your just add moisture from ground into blocks, I think that is a daft idea. I understand about the 50mm being crap, but its retrofit and I know of some people without ANY and even some companies only fit 30mm! So yes 50mm not ideal but Im happy to live with as a friend has NOTHING in his on solid concrete and his is more comfortable than with rads and heating bill the same. So the solid floor your suggesting get a solid base then do what? 2 x 200mm thick EPS? Then pipes cable tied to A142 mesh and 100mm liquid screed? (I might as well have the liquid screen as rest of house having it and changing height so it all levels nicely. Im wondering about how sturdy a screed is onto on like 400mm of EPS (am I worrying unnecessary?) Cheers Link to comment Share on other sites More sharing options...
Jeremy Harris Posted January 2, 2020 Share Posted January 2, 2020 No reason not to fill under block and beam with an insulation material that is unaffected by moisture, AFAICS. Materials like bonded EPS beads blown into the cavity, or leca beads poured in, would be OK. Link to comment Share on other sites More sharing options...
Bikerz Posted January 2, 2020 Author Share Posted January 2, 2020 (edited) Thank You. I didnt realise this. I will look into doing this. I presume covering up the current air bricks too to stop the material coming out in high winds. However Id have to remove some blocks to get access between some beams maybe. Will have to see what I have once we start I guess. Edited January 2, 2020 by Bikerz Link to comment Share on other sites More sharing options...
Bikerz Posted March 9, 2020 Author Share Posted March 9, 2020 So just for others info in future. We did various levels of insulation from 165mm to 30mm with an average liquid screed of 67mm. We did not insulate under block and beam. UFH is in and commissioning on Friday so will update with results. Link to comment Share on other sites More sharing options...
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