Insulation FAQ

Start with area and target R-value. Multiply your square footage by the R-value gap you need to close, then divide by the coverage rating on the bag. Our attic and blown-in calculators do exactly that arithmetic for you.

Attics: R-30 in the far south, R-49 through the middle of the country, R-60 from the Midwest north. Walls: R-13 to R-21 depending on framing depth. Floors over unconditioned space: R-19 to R-38.

Blown-in attic work runs roughly $1.40 to $2.70 per square foot installed. Batts in open walls are $1.20 to $2.20. Closed-cell spray foam is the expensive one at $1.00 to $1.75 per board foot installed.

Blown-in attic insulation and unfaced batts in open framing are very DIY-friendly — the machine is free with a bag minimum at most stores. Dense-pack in closed walls and large spray foam jobs are not; leave those to a contractor with the right rig.

In cold climates, yes on the warm-in-winter side. In hot-humid climates a vapor barrier on the inside can trap moisture and cause more harm than good. Air sealing matters more than vapor barriers almost everywhere.