SarahG Posted May 21, 2023 Share Posted May 21, 2023 Our architect has spec'd the following cavity wall insulation: 100mm. cavity with 95mm. Xtratherm Cavity Therm CT/PIR insulation plus 5mm. residual cavity Just wondering if anyone knows a good alternative. One of our potential builders seemed concerned about the price of this one, we really don't want to make the walls thicker just to fit in some cheaper insulation. So just wondering if anyone knows any suitable alternatives. One of our contractors has quoted us for Celotex Thermaclass 21 Full Fill Cavity Insulation 90mm instead, is this a good alternative? We could potential get one with a slightly lower u-value and re-run the SAP report I guess. Link to comment Share on other sites More sharing options...
Dave Jones Posted May 21, 2023 Share Posted May 21, 2023 recticell Link to comment Share on other sites More sharing options...
Iceverge Posted May 21, 2023 Share Posted May 21, 2023 Thicker walls are the only way if you want to stick to a masonry cavity wall. A 150mm cavity with full fill cavity batts like Dritherm 32 or EPS Beads would be the same U value of 0.22. PIR boards are almost impossible to fit correctly in a cavity wall, even with well intentioned builders. I wouldn't consider them on those grounds alone. Have you considered SIPs or timber frame if thickness is really such an issue? Link to comment Share on other sites More sharing options...
Johnnyt Posted May 21, 2023 Share Posted May 21, 2023 We were specced Kingspan Kooltherm k106 and used cavitytherm as the alternative. Brickies had never seen it before but said it was good to work with as it interlocks no taping and no retaining disc required, dedicated slots for wall ties. Remember to put a vertical dpc in the corners Link to comment Share on other sites More sharing options...
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