Why must insulation fit properly in tight areas like eaves?

Insulation needs to fit properly in tight areas like eaves primarily to ensure effective R-value. R-value is a measure of insulation's ability to resist heat flow; the higher the R-value, the greater the insulating effectiveness. If insulation is not installed correctly and does not fit snugly in these areas, it can create gaps that allow air to flow in and out. This airflow can significantly reduce the overall thermal performance of the insulation, undermining its ability to keep the indoor temperature stable. Properly fitting insulation ensures that it provides the intended resistance to heat transfer, thereby enhancing energy efficiency and comfort within the living space.