Insulation is a material used to reduce heat transfer between areas with different temperatures. In buildings, it slows the movement of heat through walls, roofs, and floors, helping maintain comfortable indoor temperatures while reducing heating and cooling costs. R-value is the standard measure of insulation effectiveness—the higher the R-value, the greater the insulation's resistance to heat flow.

Different insulation types have different R-values per inch of thickness. Fiberglass batts are common and affordable, blown-in options provide better coverage in existing walls, cellulose is eco-friendly and effective, rockwool is fire-resistant, and spray foam provides excellent air sealing and high R-values. The choice depends on project location, budget, climate zone, and accessibility of the space to be insulated.

Building codes require specific R-values for different climate zones and building components (attics, walls, basements). Proper installation is critical—gaps, compression, and thermal bridging can significantly reduce effectiveness. Combining insulation with air sealing creates an effective thermal envelope that maximizes energy efficiency and comfort.