Attic · Wall · Air Sealing
The boring upgrade with the best ROI
Insulation rarely makes the news, but in most U.S. climates it's the single highest-ROI residential energy upgrade. The IRA 25C envelope category ($1,200/year cap) covers 30% of the cost — and most utilities run aggressive insulation rebates because they see the demand reduction directly.
Federal credit (25C)
| Measure | Cap | Requirement |
|---|---|---|
| Attic insulation | $1,200 envelope | 2021 IECC R-value criteria |
| Wall insulation | $1,200 envelope | 2021 IECC R-value |
| Rim joist / band joist | $1,200 envelope | Continuous air seal + R-value |
| Air sealing materials | $1,200 envelope | Caulks, foam, weatherstripping |
| Home energy audit | $150 | Certified BPI or RESNET inspector |
Utility rebates
Insulation is the single most-rebated category by utilities, with programs ranging $0.10-$0.50 per square foot of attic insulation, plus per-bag and percentage-of-cost programs. Most utilities also run "free home energy audits" — they send a contractor to your home, install basic measures (CFL bulbs, smart strips, weatherstripping) for free, and identify deeper retrofits.
DOE HOMES — the big stack
Insulation is the prototypical HOMES measure. A whole-home insulation + air-sealing project that hits 35% modeled savings unlocks the $4,000 HOMES rebate (or $8,000 for LMI households). HOMES is administered through your state energy office.
Climate-zone R-value floors (2021 IECC)
| Climate zone | Attic R-value | Wall R-value |
|---|---|---|
| Zones 1-2 (FL, S TX, S CA, HI) | R-30 | R-13 cavity |
| Zone 3 (most of South) | R-30 to R-49 | R-13 to R-20 |
| Zone 4 (Mid-Atlantic) | R-49 | R-20 |
| Zones 5-6 (Midwest, NE) | R-49 to R-60 | R-20 to R-25 |
| Zone 7-8 (N tier, AK) | R-60 | R-25 to R-30 |
Order of attack
- Air sealing first — fix leaks before adding insulation, otherwise heated/cooled air bypasses the insulation
- Attic insulation second — biggest single envelope opportunity in most U.S. homes
- Rim joist insulation — overlooked, large air-leak surface
- Wall insulation — only if walls are accessible (drill-and-fill blown-in for retrofits)
- Basement / crawlspace — environmental considerations and moisture management