Insulation Waste Allowance
Do not assume one fixed percentage for every insulation project. Keep the measured net area separate, then add an editable allowance for cutting and purchasing conditions.
What can increase the allowance?
Irregular shapes, repeated edge cuts, short offcuts, mixed bay sizes and damaged pieces can increase the amount of material that cannot be reused efficiently.
Package rounding is separate
After applying the allowance, divide by the exact product coverage and round up to whole packages. This can add material even when the percentage allowance is small.
Different formats behave differently
Boards, rolls and batts can create different offcut patterns. Spray-applied products should be estimated using the manufacturer's stated coverage or yield.