dabba Posted August 13, 2023 Share Posted August 13, 2023 I have now received building regs drawings for new dwelling, Cavity wall spec, 103mm facing brick, 100mm cavity with 90mm insulation slab with 10mm residual cavity, 100mm medium density block concrete blockwork, Has anyone any advice as to which 90mm slabs are best? Link to comment Share on other sites More sharing options...
SteamyTea Posted August 13, 2023 Share Posted August 13, 2023 17 minutes ago, dabba said: Has anyone any advice as to which 90mm slabs are best? Are you having UFH? 1 Link to comment Share on other sites More sharing options...
Conor Posted August 13, 2023 Share Posted August 13, 2023 29 minutes ago, dabba said: I have now received building regs drawings for new dwelling, Cavity wall spec, 103mm facing brick, 100mm cavity with 90mm insulation slab with 10mm residual cavity, 100mm medium density block concrete blockwork, Has anyone any advice as to which 90mm slabs are best? None are adequate. I suggest I creasing cavity to 150mm and going full full, as a minimum. 1 Link to comment Share on other sites More sharing options...
crispy_wafer Posted August 13, 2023 Share Posted August 13, 2023 I think you’ll get a positive verdict if you Increase the cavity width to 200mm and fill with cavity bats, or blown beads, easier to install for your builder and probably cheaper too. Beaten to it… 1 Link to comment Share on other sites More sharing options...
dabba Posted August 13, 2023 Author Share Posted August 13, 2023 16 minutes ago, SteamyTea said: Are you having UFH? Yes planning on UFH. Link to comment Share on other sites More sharing options...
dabba Posted August 13, 2023 Author Share Posted August 13, 2023 90mm slabs would acheive 0.18 which i would imagine is pretty good, if I were to increase cavity width would that be an issue regarding lintels ect? Link to comment Share on other sites More sharing options...
SteamyTea Posted August 13, 2023 Share Posted August 13, 2023 7 minutes ago, dabba said: Yes planning on UFH. Then you need a fair amount of insulation. The reason is that the floor is going to be at about 30⁰C to achieve a room temperature of around 20⁰C. The greater the temperature difference, the more insulation you will need so that the ground below the house does not sap all the energy away, leaving little to heat the house. Generally considered that a minimum of 150mm is needed, though the more the merrier. Easy enough to do the calculations. https://www.kingspan.com/kz/en/knowledge-articles/how-to-calculate-a-u-value/ 1 Link to comment Share on other sites More sharing options...
Iceverge Posted August 13, 2023 Share Posted August 13, 2023 1 hour ago, dabba said: I have now received building regs drawings for new dwelling, Cavity wall spec, 103mm facing brick, 100mm cavity with 90mm insulation slab with 10mm residual cavity, 100mm medium density block concrete blockwork, Has anyone any advice as to which 90mm slabs are best? Groan....... The Kooltherm salesman strikes again. Go back to your architect. Get them to redraw the house with 200mm EPS in the floor or 150mm PIR minimum. Use 150mm or 200mm of EPS blown beads or Cavity wall batts in the walls. Use 400mm mineral wool or cellulose for any insulation on flat over ceilings. Kingspan Kooltherm phenolic insulation is pound for pound the most expensive insulation with the exception of Vacuum insulated panels and Aerogel. It's bordering on professional negligence when "professionals" just rubber stamp manufacturers designs without any thought to the pocket of the client. 1 Link to comment Share on other sites More sharing options...
Buzz Posted August 13, 2023 Share Posted August 13, 2023 31 minutes ago, dabba said: 90mm slabs would acheive 0.18 which i would imagine is pretty good, if I were to increase cavity width would that be an issue regarding lintels ect? No issues with lintels you can get them from local BM that will span 150mm usually in stock. We went with 150mm full fill cavity batts which gives you 0.17 . It's easier to fit correctly and cost less than PIR . 1 Link to comment Share on other sites More sharing options...
dabba Posted August 13, 2023 Author Share Posted August 13, 2023 11 minutes ago, Iceverge said: Groan....... The Kooltherm salesman strikes again. Go back to your architect. Get them to redraw the house with 200mm EPS in the floor or 150mm PIR minimum. Use 150mm or 200mm of EPS blown beads or Cavity wall batts in the walls. Use 400mm mineral wool or cellulose for any insulation on flat over ceilings. Kingspan Kooltherm phenolic insulation is pound for pound the most expensive insulation with the exception of Vacuum insulated panels and Aerogel. It's bordering on professional negligence when "professionals" just rubber stamp manufacturers designs without any thought to the pocket of the client. Link to comment Share on other sites More sharing options...
dabba Posted August 13, 2023 Author Share Posted August 13, 2023 Ground floor spec, "150mm consolidated hardcore, 50mm sand blinding, provide 100mm ST2 or Gen2 ground bearing slab, 1200mm DPM, floor to be insulated over slab and DPM with rigid thermoset insulation with glass tissue facing and thermal conductivity of 0.18" it doesn't mention the insualtion thickness, pretty sure it is 150mm. will have to look at 150mm batts or beads. Link to comment Share on other sites More sharing options...
Mr Blobby Posted August 13, 2023 Share Posted August 13, 2023 3 hours ago, dabba said: if I were to increase cavity width would that be an issue regarding lintels ect You'll will have two lintels over each opening, one on the inner leaf, one on the outer leaf, so cavity width is irrelevant. 1 Link to comment Share on other sites More sharing options...
nod Posted August 14, 2023 Share Posted August 14, 2023 I haven’t trolled through the replies But hopefully someone has pointed out that 10 cavity isn’t workable Some friends of ours had exactly the same spec and ended up reducing the cavity board and using insulated plasterboard on all exterior walls Expensive mistake 1 Link to comment Share on other sites More sharing options...
joe90 Posted August 14, 2023 Share Posted August 14, 2023 I built with 200mm cavity and full fill batt insulation, concrete lintel on internal leaf and brick arches on external (which could be another concrete lintel) dead cheap and good result. 2 Link to comment Share on other sites More sharing options...
Mr Blobby Posted August 14, 2023 Share Posted August 14, 2023 (edited) ... as well as increasing the cavity width, 200mm is very doable, don't let bricklayers install PIR insulation or it will be full of gaps. Blown bead is far easier to get right. Edited August 14, 2023 by Mr Blobby 2 Link to comment Share on other sites More sharing options...
HughF Posted August 14, 2023 Share Posted August 14, 2023 17 hours ago, Mr Blobby said: You'll will have two lintels over each opening, one on the inner leaf, one on the outer leaf, so cavity width is irrelevant. Not necessarily…. We’re at 150 cavity with IG single piece steel lintels. Negates the need for a top cavity closer and the bco was happier with this than separate concs on inner/outer. did delay the build by a week and cost me £850 in lintels though 1 Link to comment Share on other sites More sharing options...
HughF Posted August 14, 2023 Share Posted August 14, 2023 150 or 200 cavity. Full fill… forget using pir in the cavity. 1 Link to comment Share on other sites More sharing options...
Iceverge Posted August 14, 2023 Share Posted August 14, 2023 4 hours ago, HughF said: Not necessarily…. We’re at 150 cavity with IG single piece steel lintels. Negates the need for a top cavity closer and the bco was happier with this than separate concs on inner/outer. did delay the build by a week and cost me £850 in lintels though Precast concrete lintels here separate for each leaf. No need for any cavity closer although I did make OSB window boxes. Simply install the windows just inside the outer leaf. Use A/T membrane taped to the window and tape to fix it back to the inner leaf. Screw J beads into the windows and fix your plaster board reveals and heads. Blow in EPS beads. Simple. 2 Link to comment Share on other sites More sharing options...
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