What is the primary effect of insulation in a building?

The primary effect of insulation in a building is to reduce heat flow. Insulation is designed to minimize the transfer of heat between the interior of a building and the outside environment. Its effectiveness is measured by its R-value, which indicates the material's resistance to heat flow; the higher the R-value, the better the insulation performs. By reducing heat loss in the winter and heat gain in the summer, insulation helps maintain a comfortable indoor temperature, contributes to energy efficiency, and lowers heating and cooling costs.

While insulation might have secondary functions, such as contributing to soundproofing or having some degree of impact on moisture control, its main purpose is effectively to slow down the movement of heat, ensuring that conditioned air remains within the living spaces of the structure. This essential function highlights why reducing heat flow is the cornerstone of insulation's role in building performance.