1. Choose your location
Click your build location on the map to select the climate zone.
Firth’s Online R-Value Calculator uses the H1 methodology, as described in the Building Code amendment H1 Energy Efficiency Acceptable Solution H1/AS1 - 5th Edition for all housing, and buildings (up to 300m2), to recommend concrete slab foundation insulation solutions using CodeMark certified Firth products and systems (only).