Without further ado, here are the 11 most common mistakes.
1. Not providing for good air circulation between the roof and the insulation
2. Neglecting to find out the most efficient R-value for your area and insulate accordingly
3. Installing fiberglass batting with the paper side (vapor barrier) facing toward the outside
4. Omitting a vapor barrier that prevents the accumulation of moisture between the batting and the underside of the roof
5. Puncturing the vapor barrier unnecessarily, or neglecting to puncture the vapor barrier of the top batt when installing two layers.
6. Distorting, compressing, or squeezing the fiberglass batt insulation out of shape
7. Using paper-faced batting against a heat source like chimneys, heating ducts, etc.
8. Neglecting to get into all of the small spaces and corners with the insulation
9. Covering eave vents with insulation, thereby cutting off ventilation.
10. Not ventilating properly
11. Making unnecessary trips up and down the attic stairs during installation. Assemble all tools and equipment in your work area prior to beginning the job.