Insulation & Efficiency

Thermal performance calculations are simple arithmetic wrapped around one difficult reality: the assembly you build is not the assembly you specified. Thermal bridging through studs, joists and fixings, compression of batts, and gaps at the edges all reduce real performance below the nominal figure, sometimes substantially. The tools here compute the nominal value and say plainly where the installed value will differ.

Air movement matters as much as R-value and is not measured by it. Insulation slows conduction; it does nothing about air passing through or around it, and a well-insulated wall with an interrupted air barrier can perform worse than a modest wall that is sealed. Several pages in this category exist specifically to size the air-sealing side of that pair.