Area to insulate
Attics give the biggest payback because heat rises and uninsulated attics lose tremendous energy. Walls are harder to upgrade but valuable in older homes.
Attic floor area is typically equal to the top-floor square footage. Wall area is total perimeter x wall height, minus windows and doors.
Current and target R-value
DOE recommends R-49 to R-60 for attics in most US climate zones, R-13 to R-21 for walls, and R-15 to R-25 for basement walls. Older homes may have R-11 or less in the attic.
Climate and bill
Include both winter heating and summer cooling bills. If you only have one fuel (e.g. all-electric), use that. Total annual cost matters more than monthly average.
Project cost
Typical 2026 installed costs: blown attic insulation $1-2/sq ft. Wall insulation (drill-and-fill) $1-2/sq ft. Spray foam $2-5/sq ft. Higher in expensive labor markets.
Your savings
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Savings depend heavily on your climate, fuel costs, and air sealing. Insulation works best when paired with air sealing – 30% of heat loss in older homes is through air leakage, not conduction. Federal tax credits of up to 30% (capped at $1,200/year) are available through the Energy Efficient Home Improvement Credit; check current eligibility rules before buying.