How much does attic insulation cost?

DIY blown-in (R-49, 1,200 sq ft attic): $600-$1,800 in materials (machine rental is free with purchase at most big box stores). Professional blown-in (R-49): $1,800-$3,600. Professional spray foam: $1,800-$4,800. Fiberglass batts (DIY, R-30): $600-$1,200. Federal tax credit: 30% of material and labor costs (25C credit). Utility rebates: $200-$500 in many areas. After incentives: $400-$2,500 for most projects. Payback: 2-5 years from energy savings (10-20% reduction in heating and cooling costs).

What is the best attic insulation?

For most homes: blown-in cellulose or blown-in fiberglass is the best choice. Cellulose has a slightly higher R-value per inch, is made from recycled material, and fills gaps well. Blown fiberglass is non-combustible and does not absorb moisture. Both are excellent. For DIY: blown-in (either type) is recommended. The machine is free to rent with purchase, and the process is straightforward. Fiberglass batts: good for new construction or attics with easy access and regular joist spacing, but they leave more gaps than blown-in. Spray foam: the premium option (best air sealing), used for cathedral ceilings or when maximum performance is needed. Not cost-effective for standard open attics.

How much insulation do I need in my attic?

The DOE recommends R-49 to R-60 for most of the U.S. (climate zones 4-8). This equals about 14-18 inches of blown fiberglass or cellulose. If your current insulation is: less than 3 inches (R-11 or less): you need a major upgrade. 3-7 inches (R-11 to R-25): you need more. 7-10 inches (R-25 to R-38): adding to reach R-49 is recommended. 12+ inches (R-38+): you are close to the recommendation; additional insulation provides diminishing returns. Measure what you have: look at the insulation depth in the attic (measure in several spots, as it can be uneven). The first few inches provide the most benefit (going from R-11 to R-38 saves much more than going from R-38 to R-60).

Should I remove old insulation before adding new?

Usually no. You can add new insulation on top of existing insulation (this is the standard practice). Exceptions: if the old insulation is water-damaged, moldy, contaminated with animal waste (rodents, bats), or is vermiculite (which may contain asbestos). In these cases: remove the old insulation before adding new (vermiculite requires professional asbestos testing and abatement). If adding blown-in over fiberglass batts: remove any vapor barrier (kraft paper facing) from the existing batts (or slash it) to prevent moisture trapping between the layers. Then blow the new insulation on top.

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Home Improvement

Attic Insulation Guide: Types, R-Values & Installation

Lumberama Editorial Team, Insulation & Energy Efficiency Specialists Jul 20, 2026 13 min read

Why Attic Insulation Matters

Heat rises. In winter, the warm air in your home rises to the ceiling and escapes through the attic (up to 25% of a home's heat loss occurs through the roof/attic). In summer, the sun heats the roof, and that heat radiates down into the living space through an under-insulated attic. Proper attic insulation is the single most impactful energy improvement for most homes. It reduces heating and cooling costs by 10-20%, improves comfort (eliminates cold spots in winter and hot rooms in summer), and prevents ice dams (in cold climates).

R-Value Requirements

R-value measures an insulation material's thermal resistance (higher = better). The Department of Energy recommends these attic R-values by climate zone: Climate zones 1-3 (southern states): R-30 to R-
6
Climate zones 4-8 (central and northern states): R-49 to R-
6
For most of the U.S. (zones 4-8): R-49 is the minimum recommended. This translates to: 13-17 inches of fiberglass batts, 14-18 inches of blown fiberglass, or 13-17 inches of blown cellulose. If your attic insulation is less than 10-12 inches: adding more will provide significant energy savings.

Types of Attic Insulation

Fiberglass batts (rolls): Pre-cut blankets of fiberglass. Available in standard widths (15 or 23 inches to fit between joists). Easy to install (lay between joists). R-value: R-3.0 to R-3.7 per inch. Cost: $0.50-$1.00 per sq ft (R-30). Pros: affordable, widely available, DIY-friendly. Cons: can leave gaps (especially around obstructions), compresses when stored on, and must be cut to fit.

Blown-in fiberglass: Loose fiberglass fibers blown into the attic with a machine. Fills gaps and irregular spaces better than batts. R-value: R-2.5 to R-3.5 per inch. Cost: $0.75-$1.50 per sq ft (R-49). The machine can be rented from big box stores (often free with purchase of insulation bags).

Blown-in cellulose: Made from recycled newspaper treated with fire retardant (borate). Blown in with a machine. R-value: R-3.2 to R-3.8 per inch. Cost: $0.80-$1.50 per sq ft (R-49). Pros: excellent at filling gaps, higher R-value per inch than blown fiberglass, and made from recycled material. Cons: can settle over time (10-20% settling, installers account for this), can absorb moisture (treated to resist mold, but prolonged moisture exposure is a concern).

Spray foam: Applied as a liquid that expands and hardens. Open-cell: R-3.6-R-3.8 per inch. Closed-cell: R-6.0-R-7.0 per inch. Used for: cathedral ceilings (where there is no attic to ventilate), and sealing the attic floor (air sealing + insulation in one step). Cost: $1.50-$4.00 per sq ft (professional only). More expensive but provides the best air sealing.

DIY Installation (Blown-In)

Blown-in insulation is the recommended DIY method for attics. Steps:
Air seal the attic floor first (this is more important than the insulation itself). Seal gaps around: plumbing and wiring penetrations (spray foam), light fixture boxes (use fire-rated foam or fire-rated recessed light covers), the attic hatch/door (weatherstrip and add insulation), HVAC duct boots, and any other penetration through the ceiling.
Install baffles (vent chutes) at the eaves to maintain soffit ventilation (staple them between the rafters at the eaves).
Mark the target insulation depth on the truss or rafter (using rulers or markers).
Rent the blowing machine (free with purchase at most big box stores).
Feed insulation bags into the machine.
Blow the insulation to the target depth, starting from the farthest point and working back to the access point.
Level as needed. Time: 4-8 hours for a typical 1,200 sq ft attic (with 2 people). Cost: $500-$1,500 in materials (blown cellulose or fiberglass).