Iceverge Posted Monday at 00:36 Posted Monday at 00:36 5 hours ago, DannyT said: build houses everyday and there is no way I’d have PIR in the cavity Preach.
allthatpebbledash Posted 6 hours ago Author Posted 6 hours ago Using a dense block external leaf, and lightweight block internal seems to achieve 0.18 with 32 batts in the cavity I just seen. Are the lightweight blocks terrible as I’ve heard of them cracking and crumbling easily. Using dense blocks both leafs and 32 batts gives 0.19 which is so close. Would it not be possible to do this and say increase u-value of floor or roofs? Or windows? Anything to compensate for such a small nominal. It’ll allow for using the much cheaper and better dense blocks for walling and go with fully filled cavity mineral wool. For now taped PIR at 140mm is being planned.
Oz07 Posted 4 hours ago Posted 4 hours ago On 12/04/2026 at 20:27, DannyT said: I'm with you I've never used pir in cavities either. I've done traditional with dot and dab and got great air test score. Parge coat prior and linked to airtight membrane on ceiling. I don't see how the pir helps you with this?
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