Don't squash the insulation as this can reduce its thermal performance by over 50%. ... Don't remove any insulation as this can reduce the thermal performance of the loft.

What happens if you squash loft insulation?

Squashed Loft Insulation results in >200% greater heat loss than designed, contributing significantly to the Performance Gap.

Is it OK to compress loft insulation?

When you compress fiber glass batt insulation, the R-value per inch goes up, but the overall R-value goes down because you have less inches or thickness of insulation. ... So, you don't get the full R-value on the label, but the insulation still works perfectly well if all you've done is compress it.