How much does attic insulation cost, and how much should it cost?
Short answer. Adding blown-in insulation to a typical attic commonly costs in the low thousands of dollars, while removing old insulation first, or converting to spray foam under the roof deck, costs considerably more. The price depends on attic size, the target R-value, the material, access, and prep work like air sealing and baffles.
What drives the price
- Material: blown fiberglass and cellulose are generally the most economical for open attic floors. Batts cost more in labor on irregular attics. Spray foam costs the most.
- Target depth: going from a few inches to the roughly R-49 that ENERGY STAR recommends for an uninsulated Climate Zone 3 attic takes much more material than a light top up.
- Removal: old insulation that is wet, moldy, or contaminated by rodents must be vacuumed out first, which can rival the cost of the new material.
- Air sealing: sealing top plates, light fixtures, and chases before insulating adds cost but makes the insulation far more effective.
- Baffles: rafter vents at each soffit keep the new insulation from blocking intake.
- Access: low slopes, tight trusses, and HVAC equipment in the way slow the work.
How to compare quotes
- Ask for the installed R-value and settled depth, not just the number of bags.
- Confirm air sealing and baffles are included and listed.
- Ask for a depth marker or certificate left in the attic.
- Check your electric or gas utility for rebate programs, which change from year to year.
Do the roof first if it is due
If the roof is leaking or near replacement, handle that before insulating. New insulation hides leaks and is ruined by them. See attic heat and shingles and signs you need a new roof.