Your roof promotes energy efficiency in your household’s living space by keeping heat out in the summer and inside during the cold winter months. High energy bills often indicate that your HVAC system is struggling to keep your home at a comfortable temperature, and roof poor insulation could be part of the problem. Our guide to the best types of roof insulation help you determine whether your home insulation needs an upgrade—and which option will work best for your needs and budget.

Note: All cost data in this article were sourced from contractor estimates used by Angi

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R-Values for Roof Insulation

A material’s R-value measures how well it resists the flow of heat. In the context of roof insulation, a higher R-value indicates better insulating abilities. Insulating your roof with materials that have high R-values helps prevent heat loss in the winter and heat gain in the summer. This translates to lower energy bills and increased comfort in your home throughout the year.

R-values are measured per inch of thickness. If a material has an R-value of R-30, then 1 inch of that insulation provides the same resistance to heat flow as 30 inches of air. You can combine insulation materials to increase R-values. If your insulation has an R-value of 10, for example, then 2 inches of that material will have an R-value of 20.

The recommended R-value for your roof depends on your location. Colder climates typically require higher R-values for optimal insulation. Check local building codes or the Energy Star website for recommendations specific to your area.

Requirements also vary by space. Attic spaces, crawl spaces, and walls have different recommended R-values.

For a visual example of how to combine different types of insulation, check out the video below. General contractor Tom Silva helps a homeowner beef up his attic insulation by adding several inches of loose cellulose, a 9.5-inch layer of fiberglass batts, plus walkable 2-inch rigid foam insulation.

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Our Top 8 Roof Insulation Types

Check out our round-up of the eight best types of roof insulation to gain a better understanding of your options for achieving optimal energy efficiency.

1. Spray Foam Insulation

Spray foam insulation is a polyurethane foam that is commonly applied to attics and walls and is available in high-, medium-, and low-density. High-density spray foam is used in roofing or on the outside of buildings because it’s rigid enough to resist wind damage. Medium- and low-density spray foams are used in walls or unvented attics. 

High- and medium-density spray foams are considered closed-cell insulation. Low-density spray foam is considered open-cell insulation, meaning it is more flexible and malleable than medium- and high-density foam. Spray foam insulation costs vary depending on the type and location.

Cost: $1–$2 per square foot

R-Value: 3.6–5.7

Pro and Cons

Pros

• Applicable for attic, roofing, or wall home improvement projects
• Features a high R-value compared to other insulation options
• Provides soundproofing and resistance to air and moisture if using open-cell foam

Cons

• Higher price point if using closed-cell foam
• Vulnerable to water absorption if using open-cell foam

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2. Structural Insulated Panels

Structural insulated panels (SIPs) are factory-produced panels of foam insulation sandwiched between two pieces of oriented strand board (OSB). SIPs are simple to install, and their R-values are less variable than other traditional forms of insulation. 

Cost: $7–$12 per square foot

R-Value: 15–67 

Pro and Cons

Pros

• Provide continuous insulation and effective thermal- and moisture-resistance
• Improve indoor air quality when airtight and properly ventilated
• Offer structural strength in addition to insulation

Cons

• Increase risk of water retention and damage if improperly installed
• Require professional installation, likely by a roofer

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3. Rigid Insulation Boards (High-Density Polyiso Cover Boards)

Rigid insulation boards are made of insulation materials pressed into foam boards. High-density polyiso cover boards are a subcategory of rigid insulation boards and are made of compressed polyisocyanurate covered by fiberglass sheets. This forms a strong, high-density insulator that increases thermal resistance by reducing heat transfer. 

Cost: $0.70–$1 per square foot

R-Value: 5–5.6

Pro and Cons

Pros

• High R-value compared to other insulation
• Increased thermal resistance
• Fire-, moisture-, and mold-resistant

Cons

• Can be vulnerable to bug infestations
• Performs less effectively in temperatures below 50 degrees Fahrenheit

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4. Fiberglass Batt Insulation

Fiberglass batts are made of small particles of glass woven into coarse fabric. They are sold and installed in sheets that insulate spaces by trapping pockets of air, which prevents heat from escaping during the winter and entering during the summer. Fiberglass batts present a DIY installation option.

Cost: $0.30–$1.50 per square foot

R-Value: 3.14–4.3

Pro and Cons

Pros

• Easy to DIY install
• Higher R-value per inch than blown-in variants of fiberglass insulation
• Offered in standardized sizes

Cons

• Can release hazardous fibers, which are dangerous to inhale if disturbed
• Thick batts limit how much you can layer (thereby limiting R-value)

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5. Loose-Fill Insulation/Blown-In Insulation

Loose-fill or blown-in insulation is typically used for attic insulation and to fill wall cavities. It can be made from fiberglass, rock wood, or cellulose. For blown-in insulation, machinery uses air pressure to force the insulation into an empty space, insulating the roof by minimizing heat transfer and trapping air. 

Cost: $1–$4 per square foot

R-Value: 2.2–4.3

Pro and Cons

Pros

• Can be installed over existing insulation to increase R-value
• Can be installed anywhere in your home that needs insulation
• Very effective when installed properly

Cons

• Can generate fiberglass fibers that are dangerous to inhale if improperly installed
• Requires professional installation due to complicated machinery and technical skill

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6. Gypsum Cover Boards

Gypsum cover boards make your roofing system more durable and help protect it from hazards such as hail, wind, and fire. They are typically part of a multistage insulation process that involves other materials. 

Cost: $0.45–$0.65 per square foot

R-Value: 0.45

Pro and Cons

Pros

• Can be used in most roofing applications
• Especially resistant to weather damage, including to hail and wind damage
• Relatively low cost compared to other insulation options

Cons

• Features a low R-value, as it’s typically used as part of a multistage insulation process
• Requires budgeting for other insulation materials

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7. Perlite Cover Boards

Perlite is a heat-treated stone insulator typically used as a cover board for other insulators. It is lightweight and pliable, which makes it useful in tight spaces that need to be filled with non-toxic insulation. 

Cost: $0.30–$0.50 per square foot

R-Value: 2.7 

Pro and Cons

Pros

• Highly fire-resistant and can be used to fireproof chimneys, rooms, and safes
• Lightweight and reduces sound transmission
• Resistant to pests and decay

Cons

• Features a lower R-value per inch than other insulators
• Loses compressive strength if exposed to water

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8. Fiber Cement Cover Boards

Fiber cement cover boards act as a face for other insulation products and are fire-, termite-, and weather-resistant. However, they have a low R-value. While they are durable and stable, they are heavy and typically demand professional installation. 

Cost: $5–$14 per square foot (installed)

R-Value: Less than 1 

Pro and Cons

Pros

• Can be combined with other insulators for increased R-value
• Resistant to pests, fire, wind, and UV rays
• Can last up to 50 years or more if properly maintained

Cons

• Has a low R-value compared to other insulators
• Requires professional installation

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How To Choose Roof Insulation for Your Home

The right roof insulation depends on which part of your household requires the installation and the recommended R-value for your climate zone and area. You must also decide whether to take a DIY approach or hire a contractor. 

Before you begin, make sure you understand all the parts of a roof and ask yourself the following questions:

• Am I insulating my roof or attic? 
• Do I have the technical knowledge to do this myself? 
• How much insulation do I need in my climate zone?
• Which materials are the most cost-efficient?

When choosing insulation, consider both the R-value of the material and the desired overall R-value for your roof. You might need a thicker layer of insulation with a lower R-value to achieve the same overall resistance to heat flow as a thinner layer of higher R-value material.

Remember that R-values are tested under ideal laboratory conditions. The actual effectiveness of your roof insulation is affected by factors like installation quality and real-world climate conditions. Hiring a contractor costs more than applying insulation yourself, but you will benefit from personalized recommendations and professional installation.

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Our Conclusion

We recommend spray foam insulation because of its relatively simple installation process, high R-value, and applicability to different climate regions. While there are other effective insulators, contractors consistently choose spray foam for these reasons.

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FAQ About Roof Insulation

What is the best insulation for a roof?

We recommend spray foam insulation for roofs because of its higher R-value, price point, and applicability to most insulation scenarios. However, different regions have different insulation needs.

What is the most cost-effective roof insulation?

The most cost-effective roof insulation is often fiberglass batt insulation due to its ease of application, competitive R-value, and price point. However, the cost-effectiveness of difference insulation materials may vary depending on the architecture of your home.

Does adding insulation to a roof make the house hotter?

No, adding insulation to a roof doesn’t make the house hotter. Insulation increases thermal resistance, reducing heat loss in the winter and heat gain in the summer. Insulation helps your house stay warm in cold temperatures but prevents it from getting hotter in the summer. 

How can you tell if your roof needs more insulation?

To tell if your roof needs more insulation, look up the recommended R-values for attics in your area and calculate the R-value of your existing insulation. If what you have isn’t up to code, consider adding or replacing the insulation. High energy bills, uneven temperatures, and moisture buildup can all be indications that your roof needs more insulation.

What is the best roof insulation for roofs in cold climates?

The best insulation for roofs in cold climates is a multilayer approach, which helps the insulation reach the recommended R-value for the area. The U.S. Department of Energy recommends R-values as high as 60 in regions such as Alaska and Northern Minnesota. Builders and homeowners may choose to use structural insulated panels, blown-in cellulose insulation, and fiberglass batt insulation to provide multiple layers of coverage.

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