What happens to insulation that is compressed?

When insulation is compressed, it loses significant R-value. R-value measures the thermal resistance of insulation materials; it indicates their ability to resist heat flow. When insulation is compacted, such as when it is pushed down or squished between framing members, the air pockets within the insulation that provide insulation properties are reduced. Since it's the trapped air that helps to slow down heat flow, compressing the insulation decreases its effectiveness in insulating a space. As a result, the overall performance of the insulation diminishes, leading to a lower R-value. Maintaining the intended thickness of insulation is crucial for ensuring optimal energy efficiency and thermal performance in a building.