richo106 Posted January 30, 2022 Share Posted January 30, 2022 Hi I am in the stages of designing exactly what insulation etc I will be having in my extension/conversion. The max cavity width we can have on the extension is 100mm, I have spoken to an eco house builder and they suggested 90mm celotex thermaclass cavity insulation and then also instead of dot and dab they would use wet plaster instead to help with air tightness and thermal mass has anyone used the thermaclass insulation? is wet plaster better than dot and dab and how much more expensive is it? Thanks again Link to comment Share on other sites More sharing options...
nod Posted January 31, 2022 Share Posted January 31, 2022 D&D can be made just as airtight as wet plaster I do both and have to follow the same airtightness standard for each Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted January 31, 2022 Share Posted January 31, 2022 Don't risk dot and dab, one crack in the blockwork (which is highly likely with drying out) and you've had it. Link to comment Share on other sites More sharing options...
joe90 Posted January 31, 2022 Share Posted January 31, 2022 11 hours ago, richo106 said: The max cavity width we can have on the extension is 100mm, Why? Link to comment Share on other sites More sharing options...
richo106 Posted January 31, 2022 Author Share Posted January 31, 2022 52 minutes ago, joe90 said: Why? We are building on top our existing bungalow with 70mm cavity and the builder is going to step it out 15mm either way to create a 100mm cavity. Many Thanks 1 Link to comment Share on other sites More sharing options...
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