Fluffing occurs when insulation is installed to a minimum thickness but not to the minimum weight requirements. The result is a less dense application of insulation that requires fewer bags. When insulation is fluffed, air passes more easily through it, leading to increased heat loss. Additionally, the fluffed loose-fill insulation eventually may settle and result in a thinner layer with a lower overall R-value.2 Fiberglass is typically more problematic with fluffing than cellulose or rock wool. The best way to verify if fluffing has occurred, either accidentally or by dishonest contractors, is to count the number of bags used during installation and compare it to the instructions and coverage charts on the bag. The manufacturer should specify the amount of insulation per square foot (or square meter) of space needed to obtain the required R-value.