Conduction: Heat flows from the hot part(s) of an object to the cold part(s) of the object. If objects are in contact with one another, heat will transfer from one object to the other. Conductive heat transfer happens molecule to molecule. Heat always travels from hot to cold, never from cold to hot.

Every material has a different capacity to resist conductive heat flow, which is expressed as an RSI/ R-value. Insulation works by reducing heat flow with tiny pockets of air, which are relatively poor conductors of heat.

Durability effect: Thermal conduction through framing components (i.e. thermal bridging) can create cold spots where condensation can occur resulting in the growth of mould and mildew. This can cause the premature degradation of building materials.

Comfort effect: When conductive heat loss is reduced, the house is more comfortable because envelope surface temperatures are higher and indoor temperatures are more stable. A cold wall absorbs heat from a warmer body (e.g. a person) radiating heat to the surroundings. The rate of heat transfer depends on the temperature difference between the body and the wall (i.e. a warmer wall would absorb less heat from that body).

Energy Efficiency effect: Reduced conduction, along with reduced air leakage, reduces unwanted heat loss and gain.