Best Insulation for Attics

Quick comparison

Type	R-value/inch	Best for	DIY?	Cost installed
Blown-in fiberglass	R-2.2	Most attics	✅ Easy	$1.50–$3/sq ft
Blown-in cellulose	R-3.7	Eco-conscious	✅ Easy	$1.50–$3/sq ft
Fiberglass batts	R-3.1–R-4.3	New construction	✅ Moderate	$1–$2.50/sq ft
Open-cell spray foam	R-3.7	Rafter insulation, air sealing	❌ Pro only	$1.50–$3.50/sq ft
Closed-cell spray foam	R-6.5	Roof deck (cathedral ceilings)	❌ Pro only	$4–$7/sq ft
Mineral wool batts	R-4.3	Fire resistance, sound control	✅ Moderate	$1.50–$3/sq ft

Climate zone R-value recommendations

Climate zone	States	Attic R-value
Zone 1–2	FL, HI, southern TX/AZ/CA	R-30 to R-49
Zone 3	Southern states, Pacific NW coast	R-38 to R-60
Zone 4	Mid-Atlantic, Pacific NW, transition	R-38 to R-60
Zone 5	Great Lakes, New England, interior NW	R-49 to R-60
Zone 6–8	Northern states, mountain west, Alaska	R-49 to R-60

ENERGY STAR recommends R-49 to R-60 for most of the continental US.

Best options by scenario

Best for most homeowners: blown-in fiberglass

Blown-in fiberglass is the right choice for the vast majority of attic insulation projects. It:

• Fills around joists, blocking, pipes, and wiring without gaps
• Can be installed DIY (blower free with bag purchase at Home Depot or Lowe’s)
• Qualifies for the federal 25C energy tax credit (30% credit, up to $1,200)
• Does not settle significantly (3–5% over lifetime)
• Is class 1 fire rated

Cost for 1,000 sq ft attic to R-49: ~35–40 bags × $35/bag = $1,225–$1,400 DIY

Best eco-friendly option: blown-in cellulose

Cellulose is made from 80–85% recycled newspaper and has the lowest embodied carbon of any insulation type. It achieves R-3.7/inch (vs. R-2.2 for fiberglass), so you need less material to reach the same R-value. It settles more (up to 20%) so install to labeled settled depth, not poured depth.

Best in: Cold climates (Zones 5–8) where higher R-value per inch matters.

Best for air sealing + insulation: spray foam

If your attic has significant air leaks (visible gaps around light fixtures, wiring penetrations, and plumbing stacks), spray foam addresses both air sealing and insulation in one pass. Open-cell foam is appropriate for cathedral ceilings and unvented attic assemblies. Closed-cell foam is used on the roof deck to create a conditioned attic space.

Spray foam is not DIY. Hire a certified installer.

Best budget option: fiberglass batts (new construction only)

In new construction with open, clear joist bays, fiberglass batts are the most cost-effective option. But in existing attics with obstacles, batts consistently leave gaps around every obstruction — these gaps dramatically reduce effective R-value. Use blown-in for retrofit projects.

DIY attic insulation: what to know

1. Rent the blower free at Home Depot or Lowe’s with minimum bag purchase (usually 10 bags)
2. Seal air leaks first with expanding foam and caulk before adding insulation — insulation does not stop air movement
3. Install baffles at the eaves to maintain soffit ventilation (at least 1 inch of airspace)
4. Don’t cover recessed lights unless they are rated IC-AT (insulation contact, air tight)
5. Wear protection: N100 respirator, goggles, Tyvek suit — fiberglass particles irritate lungs and skin

Cost breakdown for a 1,000 sq ft attic

To R-38 (17 inches blown-in fiberglass):

• 30 bags × $35 = $1,050 DIY
• Professionally installed: $1,500–$3,000

To R-49 (22 inches blown-in fiberglass):

• 38 bags × $35 = $1,330 DIY
• Professionally installed: $2,000–$4,000

Federal tax credit: The Inflation Reduction Act 25C credit covers 30% of material cost (not labor), up to $1,200 per year. Use IRS Form 5695.

Use the Insulation Calculator to get exact bag counts for your attic size and target R-value.