Thedreamer Posted December 5, 2020 Share Posted December 5, 2020 (edited) 9 minutes ago, BartW said: Thanks. Trouble is the 32 seems to command double premium compared. I need 210m2 for external walls, and been working out price difference between TF manufacturer supplied insulation vs PIR (GA4120) vs variables of rockwool, and between PIR and dri35 there was roughly £1500 difference. Let alone, floors, internal partitions, roof, intermediate floors, inner face of external, etc. Yeah I expect that would be the case. I used a mixture in my build of PIR and glasswool. If I go could go back I would have just used glasswool. PIR really is horrible stuff. Dust in your eyes and mouth, a pain to cut and get accurate. Also if you have ever burned PIR it scarily. Edited December 5, 2020 by Thedreamer Link to comment Share on other sites More sharing options...
Oz07 Posted December 5, 2020 Share Posted December 5, 2020 @Thedreamer I've chucked air in the fire before and it just goes black, doesn't burn whatsoever. You talking about eps? Link to comment Share on other sites More sharing options...
Oz07 Posted December 5, 2020 Share Posted December 5, 2020 air/*PIR Link to comment Share on other sites More sharing options...
Thedreamer Posted December 5, 2020 Share Posted December 5, 2020 6 minutes ago, Oz07 said: air/*PIR PIR, Quinn therm in my case. I've burn some on a bonfire and it's produces a lot of heat and horrible toxic black smoke. I was glad when it was all covered up with plasterboard. Zero waste with glasswool, as you can always use bits elsewhere. Link to comment Share on other sites More sharing options...
BartW Posted December 5, 2020 Share Posted December 5, 2020 With that view in mind, what would you swap the inner PIR anti cold bridge layer with? More rockwool slab, perhaps cross layered and packed as part of the service cavity? Link to comment Share on other sites More sharing options...
JamesP Posted December 5, 2020 Share Posted December 5, 2020 I used 3 layers of Rockwool slabs, cross layered. 140mm,70mm and 50mm in the walls. Also 40mm Pavatherm on the outside of the studs. In the photo you can see the 70mm being fitted horizontally. The slabs are very manageable with zero waste. 3 Link to comment Share on other sites More sharing options...
BartW Posted December 5, 2020 Share Posted December 5, 2020 1 hour ago, JamesP said: I used 3 layers of Rockwool slabs, cross layered. 140mm,70mm and 50mm in the walls. Also 40mm Pavatherm on the outside of the studs. In the photo you can see the 70mm being fitted horizontally. The slabs are very manageable with zero sounds and looks good My target is 0.15. The plan is to get the TF company to fabricate and erect the structure, lay osb and vcl externally, and then take over from there. Would I do inner layer of earthwool, then inner vcl, then service cavity? I did a quick calculation in a piece of simple ios app, but when I add the “air” layer it reduces the U by quite a bit. All well and good, but timber battens add quite a bit being a cold bridge. see below for comment please: Link to comment Share on other sites More sharing options...
Oz07 Posted December 5, 2020 Share Posted December 5, 2020 1 hour ago, JamesP said: I used 3 layers of Rockwool slabs, cross layered. 140mm,70mm and 50mm in the walls. Also 40mm Pavatherm on the outside of the studs. In the photo you can see the 70mm being fitted horizontally. The slabs are very manageable with zero waste. interesting birds mouth detail or are they nogs between rafters? Link to comment Share on other sites More sharing options...
ADLIan Posted December 5, 2020 Share Posted December 5, 2020 Re U value. Thermal bridge in layer 5 at 15% timber will have a big impact. Resistance of 25mm airspace is wrong, should only be 0.18 (not 1.02) Link to comment Share on other sites More sharing options...
JamesP Posted December 5, 2020 Share Posted December 5, 2020 @BartW Similar build up to yours, but OSB on the inside. I have enclosed a hand drawing of the wall build up, from the outside its, Cedar Cladding Counter batten Batten Breather membrane Pavatherm 3 x Rockwool VCL OSB Batten PB @Oz07 Small birds mouth as I used 3.6m which just fitted. Floor, Wall, Roof Build up Jan 2018..pdf Link to comment Share on other sites More sharing options...
Oz07 Posted December 5, 2020 Share Posted December 5, 2020 It looks like it hooks over the inside edge of plate Link to comment Share on other sites More sharing options...
JamesP Posted December 5, 2020 Share Posted December 5, 2020 7 minutes ago, Oz07 said: It looks like it hooks over the inside edge of plate Yes it does. Link to comment Share on other sites More sharing options...
A_L Posted December 5, 2020 Share Posted December 5, 2020 (edited) 1 hour ago, BartW said: see below for comment please: as for ADLIan, only more so, there must be timber in your layers 2, 4 & 5. (or more elsewhere). I have copied your table and added 15% timber to 2, 4 & 5. Result - U value falls to 0.216 adding a cavity and brick façade reduces U to 0.205 Edited December 5, 2020 by A_L tidy up Link to comment Share on other sites More sharing options...
BartW Posted December 5, 2020 Share Posted December 5, 2020 Thanks guys. How do the TF suppliers manage to back their back up their claims as to uValue then? And is there a more accurate tool I could use to calculate my target U? (PS. mac user here). Link to comment Share on other sites More sharing options...
Thorfun Posted December 5, 2020 Share Posted December 5, 2020 31 minutes ago, BartW said: And is there a more accurate tool I could use to calculate my target U? Don’t know about more accurate but I’ve been using changeplan. https://www.changeplan.co.uk/u_value_calculator.php Link to comment Share on other sites More sharing options...
ADLIan Posted December 5, 2020 Share Posted December 5, 2020 Get the insulation manufacturer to do them. They tend to have the correct software and know the conventions that must be used Link to comment Share on other sites More sharing options...
BartW Posted December 5, 2020 Share Posted December 5, 2020 8 minutes ago, ADLIan said: Get the insulation manufacturer to do them. They tend to have the correct software and know the conventions that must be used Yes, this is on the cards, hopefully won't kick the fuss about it knowing I would want to supply my own insulation. An early comparison for our build as priced by one of the suppliers resulted in savings of nearly £4k + VAT, and that is without shopping around, or optimising the product. Kit supplier price: £8,895 + VAT. Bought individually: Link to comment Share on other sites More sharing options...
redtop Posted December 15, 2020 Share Posted December 15, 2020 On 05/12/2020 at 19:32, JamesP said: @BartW Similar build up to yours, but OSB on the inside. I have enclosed a hand drawing of the wall build up, from the outside its, Cedar Cladding Counter batten Batten Breather membrane Pavatherm 3 x Rockwool VCL OSB Batten PB @Oz07 Small birds mouth as I used 3.6m which just fitted. Floor, Wall, Roof Build up Jan 2018..pdf 237.97 kB · 9 downloads Same as mine except I used the smartply for vcl and OSB racking. 100mm rockwool and 140mm pavatherm 1 Link to comment Share on other sites More sharing options...
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