I have glass wool ceiling batts left over, can I install them in walls?
The thermal performance of a batt is dependent on the thickness. If you have an R 3.0 batt at 175mm thickness this will not fit into a 75mm or 90mm thickness wall stud. Compression of the batt will result in loss of thermal rating and can exert undue pressure on the wall cladding.
Which type of insulation is better, the polyester or glass wool?
Insulation is rated on either its thermal or acoustic value. If a thermal batt is rated at R3.0 for example, there is no difference in performance whether it is polyester or glass wool. It is rather a personal or a financial choice.
Can I use polyester as a roofing blanket?
The polyester is not suitable as it wraps around the fixing screws required for installation.
Which foil or wrap can I use to wrap around my walls?
If you have a timber stud frame, you must use a breather foil or breathable building membrane. For a steel framed home a 6.5mm foil faced foam product with an R value of R0.2 must be used in order to satisfy the thermal bridging requirements. There are 6.5mm products in the market that do not meet these standards so choose carefully.