Insulation for a 1,500 Sq Ft Attic
Free calculator with pre-filled dimensions • Updated March 2026
A 1,500 sq ft attic insulated to R-49 needs about 32 batts of insulation (48 sq ft coverage each).
Open calculator with these dimensions →Attic Insulation for a 1,500 Sq Ft Home
The attic is the most impactful place to insulate — heat rises, and an under-insulated attic can account for 25–30% of a home's heat loss. The 2021 IECC energy code recommends R-49 to R-60 for attics in most climate zones. At 1,500 square feet, blown-in insulation is the most practical method.
Options Comparison
| Type | R-49 Depth | Bags/Rolls | Cost (2026) |
|---|---|---|---|
| Blown cellulose | 14–15" | ~45 bags | $450–$630 |
| Blown fiberglass | 16–18" | ~40 bags | $560–$720 |
| Fiberglass batts (R-38) | 12" | ~20 rolls | $800–$1,200 |
DIY blown-in: $450–$720 + free machine rental. Professional: $1,500–$2,500 installed.
Pro Tips
- Most home improvement stores loan the blowing machine free with purchase of 20+ bags. This makes DIY blown-in attic insulation one of the best energy ROI projects — typically paying for itself in 2–3 years of heating/cooling savings.
- Seal air leaks FIRST. Before adding insulation, seal gaps around plumbing pipes, electrical wires, recessed lights, and the attic hatch with caulk or expanding foam. Air leaks can reduce insulation effectiveness by 30–50%.
- Don't block soffit vents. Install rafter baffles (cardboard or foam channels) at each rafter bay along the eaves. These maintain airflow from soffit to ridge even when insulation is deep.
- R-49 vs R-60: Going from R-49 to R-60 adds $150–$300 in materials but only saves an additional 3–5% on heating costs. R-49 is the sweet spot for most homes.
Frequently Asked Questions
How much insulation for a 1,500 sq ft attic?
For R-49 with blown cellulose, you need about 45 bags (14–15 inches deep). DIY cost is $450–$630 with a free machine rental from the home improvement store. Professional installation runs $1,500–$2,500.
What R-value should attic insulation be?
R-49 to R-60 is recommended for most US climate zones per the 2021 IECC. In hot southern climates (zones 1–3), R-38 may be sufficient. Cold northern areas (zones 5–8) benefit from R-60.
Is blown-in or batts better for attics?
Blown-in is generally better for attics because it fills around obstructions (wires, pipes, trusses) and provides more uniform coverage. Batts leave gaps at every obstacle. Blown-in is also faster and cheaper for large areas.