Attic Insulation Savings Guide

The diminishing-returns curve

Heat loss is proportional to 1/R. That means each extra R-value matters less than the previous one:

• R-13 → R-19: cuts attic loss by 32%
• R-19 → R-30: cuts another 37%
• R-30 → R-49: cuts another 39%
• R-49 → R-60: cuts another 18%

So the biggest wins come from your first few inches above old insulation.

Real dollar savings

For a 1,200 sq ft attic in a 6,000 HDD climate (think Boston, Chicago, Denver), with heat at $18/MMBtu, going from R-19 to R-49:

• Heat loss before: ~7.6 MMBtu/year through the attic
• Heat loss after: ~2.9 MMBtu/year
• Savings: ~$85/year

Project cost at $1.50-$2.50/sq ft installed = $1,800-$3,000. Simple payback: 20-35 years on insulation alone. But — combine with air sealing first and the savings roughly double, dropping payback to 10-15 years.

Always air seal first

Insulation slows conductive heat loss but does nothing for air leakage. Air leaks through attic penetrations (can lights, plumbing chases, top plates, the hatch) can equal half your attic heat loss. Seal first, insulate second.

DIY vs pro

• DIY blown-in cellulose: ~$0.80-$1.20/sq ft including blower rental.
• Pro blown-in: $1.50-$2.50/sq ft.
• Pro spray foam: $4-$8/sq ft (overkill for most attic floors).

Don't forget the rebates

The federal 25C tax credit ended December 31, 2025, but many states and utilities still offer insulation rebates. Check our rebates page and DSIRE for current programs, and save your receipts.