Breather membrane
If unticked, i.e. a non-breather membrane is used such as felt, then a minimum 50mm vented airspace between the joists/rafters is required and so must be allowed for when selecting the thickness of insulation located between the joists/rafters.
Rafter width
Rafter depth
Rafter centres
Finish/Insulation below rafter
You can either select an insulation or enter the target U-value you want to achieve below...
Insulation between joists Isover Frame Batt 32 50mmIsover Frame Batt/Roll 32 90mmIsover Frame Batt/Roll 32 140mmIsover Frame Batt 35 90mmIsover Frame Batt 35 100mmIsover Frame Batt 35 140mmIsover Frame Batt 35 150mmIsover Frame Batt 40 140mmIsover Frame Batt 43 90mmIsover Frame Batt 43 140mmIsover Frame Roll 35 90mmIsover Frame Roll 35 100mmIsover Frame Roll 35 140mmIsover Frame Roll 40 90mmIsover Frame Roll 40 140mmIsover Metac 125mmIsover Metac 175mmIsover Metac 200mmCelotex 50mmCelotex 55mmCelotex 60mmCelotex 65mmCelotex 70mmCelotex 75mmCelotex 80mmCelotex 85mmCelotex 90mmCelotex 95mmCelotex 100mmor Target U-value W/m²k
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