New extension wall insulation

whiskey79

Hi there,

Currently in the process of renovating bungalow and adding an extension, which is less than 40 sq metres.

Existing bungalow is built with 80mm cavity wall, which has been previously pumped with beads. Adding to this insulation by dry-lining the existing bungalow walls with 38MM insulated slabs (25MM PIR + 12.5MM plasterboard).

Extension is being built with 100MM cavity and 100MM block on both sides. I am trying to find out what is the best type of insulation for the extension...have read many threads here that suggest best to keep the insulation in one place, i.e. 100MM insulation in the cavity without any dry-lining. But since the existing cavity-pumped bungalow is being dry-lined, would it be a good option to also dry-line the extension and fill the cavity with 80MM (or 100MM) rigid insulation for example?

I am doing this work on a budget, with just the builder, so no engineer, etc to consult. Appreciate any helpful replies.

Thanks,
W79