The best attic insulation varies by circumstance. Trussed attics, wide-open attics, vaulted attics, or attics cluttered with HVAC, plumbing, and electrical require different insulation approaches.
Best Attic Insulation
- Best Overall Attic Insulation: Greenfiber Cellulose Loose Fill
- Best Batt or Blanket Insulation: Owens Corning Fiberglass Roll
- Best Spray Foam Insulation: Dow Froth Pak 650
- Best Reflective Insulation: US Energy Products Radiant Barrier
- Best Rigid Foam Insulation: Styrofoam SM 2” Scored
These are some of the best attic insulations available. One of them is almost certain to work for your situation.
Best Overall Attic Insulation: Greenfiber Cellulose Loose Fill
Cellulose loose fill blown in attic insulation has an R-value of R-3.2 to R-3.8, and settling does not affect it. It provides a complete blanket of insulation–filling around obstructions and eliminating gaps and thermal bridging. It can reduce heating and cooling costs by 20% and reduces noise by 60% when applied to walls.
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Cellulose insulation is made from 85% recycled materials and is treated with borates–making it fire and insect resistant. It’s easy to apply over existing insulation and is efficient in all climates.
From Sanctuary, one package of this cellulose insulation covers 41.25 square feet, and it’s suitable for blown-in or spray-in applications.
- R-3.7 per inch.
- Meets Class 1 fire rating.
- Simple DIY application with machine rental
- No itch formula.
- Reduce heating costs by up to 20%.
- Can be installed over existing insulation products.
- Limited lifetime warranty.
- Very dusty during installation but not dusty after installation.
Best Batt or Blanket Insulation: Owens Corning Fiberglass Roll Insulation
Fiberglass insulation is available in batts or rolls and comes in various thicknesses with R-values between R-2.2 – R-4.3 per inch. The rolls are an excellent choice for flat unobstructed attic floors since they’re easy to place and create fewer gaps.
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You should install fiberglass rolls in two layers–the second one perpendicular to the first to eliminate gapping. You can also install these rolls over existing insulation to add R-value and cover existing gaps.
While you can find fiberglass rolls in many sizes, this attic insulation from Owen Corning is 9″ thick, 15″ wide, and 25′ long. It’s easy to cut and install and increases the home’s energy efficiency.
- Less expensive than most attic insulation options.
- Recovers thickness instantly when opened.
- Can be installed over existing insulation.
- DIY-friendly installation.
- Less mess, no dust, and a fast clean-up.
- Rolls leave fewer gaps because of fewer joins than batts.
- Difficult to install in truss-built attics and/or attics with HVAC, electrical, or plumbing.
- Difficult to eliminate gaps.
- Can irritate sensitive skin.
Best Spray Foam Insulation: Dow Froth Pak 650
Considered the best attic insulation available, spray foam can go on attic floors or the undersides of roofs. It fills cracks and gaps, then expands and dries to seal air leaks. Spray foam insulation is available in open-cell (R-3.5) or closed-cell (R-7) formulations.
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Spray foam does not settle and retains its R-value regardless of temperature changes. Some foam may shrink over time, or gaps may form as wood framing expands and contracts. Spray foam is waterproof, mold, and mildew resistant. The biggest con of spray foam is its ability to release toxic chemicals while curing, but it becomes inert when cured.
The Dow Froth Pak 650 is a two-part spray foam insulation kit for DIYers. It includes two spray foam tanks, a respirator mask, goggles, and rubber gloves. One kit covers about 650 square feet.
- R-7.0 per inch.
- Cures in minutes.
- Class A flame spread rating.
- No HFCs and low odor.
- Moisture, mildew, and mold resistance.
- Available in disposable kits or refillable, returnable cylinders.
- Can be a difficult DIY project – may require professional installation.
- Most expensive attic insulation option.
Best Reflective Insulation: US Energy Products Radiant Barrier
Reflective insulation is also known as foil insulation or bubble wrap. It’s most effective on the undersides of pitched or vaulted roofs and unventilated cavity walls in hotter climates but ineffective and counterproductive in colder climates.
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Reflective insulation has little or no R-value. Its effectiveness comes from the ability to keep heat out of the attic. It must have at least one inch of air space on the warm side and should be kept dust-free for best performance.
Some manufacturers claim an R-value of up to R-21. This may be true in specialized situations.
The US Energy Products Radiant Barrier is a solid choice for reflective insulation. It features two layers of polyethylene air bubbles between two layers of metalized aluminum polyester film. It reflects up to 97% of heat and is unaffected by humidity.
- Reflects up to 97% of heat.
- Tear resistant.
- Class 1, Class A fire rating.
- 4’ x 250’ (1000 sq. ft.) rolls
- Ideal for attics.
- Counterproductive in cold climates.
Best Rigid Foam Insulation: Styrofoam SM 2” Scored
Rigid foam board insulation provides R-5.0 per inch. Installing rigid foam between vaulted roof rafters provides very good insulation. It’s also suitable for the floors of open attics. You must fill the gaps and cracks between the foam and framing with spray foam to complete the vapor barrier.
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Install foam board between the floor joists and seal the joints. If installing a second layer, it should be perpendicular to the first. Rigid foam is difficult to install and seal in attics with HVAC, electrical, and/or plumbing.
- R-5.0 per inch extruded polystyrene foam.
- Provides vapor barrier when 2” thick and gaps are sealed.
- Effective in all climates.
- Scored to snap easily at convenient sizes.
- Easy DIY product.
- Difficult to fit around obstructions.
- All gaps must be foamed to achieve a good seal.
What to Consider Before Insulating the Attic
The best attic insulation varies from home to home. Spend a few minutes inside the attic with the different insulation options in mind. Consider efficiency, the installation process, costs, and whether you should DIY or hire a professional.
Attics that are wide open with no trusses and little or no clutter to impede installation are prime candidates for almost any product. Trussed attics with lower slopes are difficult to move around in, and low-slope attics are even worse. Attics containing HVAC, electrical wiring, and/or plumbing pipes are difficult to insulate properly.
DIY or Not?
Do-it-yourself attic insulation requires patience, attention to detail, and in some cases, no claustrophobia. (Some products are dusty or toxic. Safety equipment is required.) Professional insulation contractors do a good job but cost more.
If the attic has soffit ventilation, take extra care to keep them open. Air chutes will need to be installed to allow the air to circulate. Ventilation moves air and humidity out of the attic and keeps the insulation dry.
Floor or Roof?
You can apply insulation to the floor of the attic or to a vaulted roof. Either option is acceptable, but some products only work in one location.
Add or Remove the Existing Attic Insulation
Removing the existing attic insulation is not necessary. In many cases removing insulation only adds cost, and most products can go on top of old insulation.
One exception is asbestos insulation–often vermiculite–which is benign if undisturbed. Working in the attic can stir up tiny fibers, so it’s best to have asbestos insulation removed professionally. (Some jurisdictions make professional removal and disposal mandatory.)
Insulation costs vary between $0.50 and $7.00 per square foot for material only.
How We Chose the Best Attic Insulation
To choose the best attic insulation, we took into consideration versatility, R-value per inch, cost, and ease of installation. Our best attic insulation picks are available in multiple sizes, styles, and thicknesses.
Attic construction and situations vary. For instance: fiberglass roll insulation works very well in open attics, but fiberglass batts may be a better choice for attics with trusses or mechanical services.
It may be beneficial to use two types of insulation in an attic. Such as cellulose on the floor and reflective insulation on the undersides of a vaulted roof in hotter climates.