Jan. 06, 2025
How To Choose Roof Insulation for Your Home
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How To Choose Roof Insulation for Your Home
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Stephanie Minasian-KoncewiczStephanie is an experienced digital content strategist and producer with a background in journalism. She covered education and local government as a news reporter before transitioning to digital media, with content highlights including video production for DIY projects and the creation of data visua&#;
See full bioYour 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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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.
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.
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
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
Higher price point if using closed-cell foam
Vulnerable to water absorption if using open-cell foam
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
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
Increase risk of water retention and damage if improperly installed
Require professional installation, likely by a roofer
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
High R-value compared to other insulation
Increased thermal resistance
Fire-, moisture-, and mold-resistant
Can be vulnerable to bug infestations
Performs less effectively in temperatures below 50 degrees Fahrenheit
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
Easy to DIY install
Higher R-value per inch than blown-in variants of fiberglass insulation
Offered in standardized sizes
Can release hazardous fibers, which are dangerous to inhale if disturbed
Thick batts limit how much you can layer (thereby limiting R-value)
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
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
Can generate fiberglass fibers that are dangerous to inhale if improperly installed
Requires professional installation due to complicated machinery and technical skill
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
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
Features a low R-value, as it&#;s typically used as part of a multistage insulation process
Goto Langfang Clear Chemical to know more.
Featured content:Requires budgeting for other insulation materials
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
Highly fire-resistant and can be used to fireproof chimneys, rooms, and safes
Lightweight and reduces sound transmission
Resistant to pests and decay
Features a lower R-value per inch than other insulators
Loses compressive strength if exposed to water
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
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
Has a low R-value compared to other insulators
Requires professional installation
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.
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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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.
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.
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.
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.
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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One of the most important factors in selecting the optimum flat or low-slope commercial roof insulation is designing to the desired thermal efficiency. R-value is a measurement to quantify the insulating properties of a building material. The highest R-value per inch is the best, and this helps determine flat roof insulation thickness for building regulations. Understanding relative R-values will help rank the comparison of various materials choices.
Let&#;s take a look at how the most common types of flat roof insulations rank according to R-value.
Phenolic foam had high reported initial R-values of up to 7.5 per inch, but this product has not been widely produced in the U.S. since the early 90s because of litigation concerning the corrosiveness and leaching acidic impact on metal decks or metal fasteners under certain conditions. Some roof assemblies, especially lightweight concrete decks, may have this insulation still installed.
Currently, a European manufacturer is marketing a reformulation for restricted building materials usage in the USA and Canada. Specifiers can decide if the benefits of a high R-value insulation will outweigh other potential concerns.
Polyurethane in sprayed-on foam is a high R-value choice for flat roof insulations. The American Chemistry Council Center for the Polyurethanes Industry reports R-values of up to 7.2 per inch. For commercial flat roofing, either 1-component or 2-component spray polyurethane foam is commonly used as well as insulated metal panels for the building envelope. Cold storage buildings with freezers or coolers often utilize polyurethane insulated metal panels.
There are several advantages to polyurethane: structural performance, dimensional stability and moisture resistance. The major benefit of spray polyurethane foam (SPF) is that it can conform to irregular surfaces on a wide variety of substrates. There is typically long-term stability of the R-value as well as high fire resistance. Polyurethane does have a narrower window of application temperature and humidity limitations in some climate conditions.
Polyisocyanurate (polyiso) is closed-cell foam bonded to various facers, such as glass or foil. The blowing agents used to manufacture the product have evolved over time to meet environmental goals. Many manufacturers certify their EPA-compliant blowing agents as not having any CFCs or HCFCs to meet zero ozone depletion potential (ODP) roof insulation standards.
The polyiso industry has established a standard called &#;LTTR&#; &#; Long Term Thermal Resistance &#; that indicates how polyiso will insulate over time; it is essentially an aged R-value.
As an example, the R-value of a foil-faced polyisocyanurate panel produced with pentane ranges from an initial R-value of 6.8 per inch to 5.7 per inch as projected over time. Polyisocyanurate foam board roof insulation is one of the best roofing insulations and is one of the top choices for very high thermal efficiency. Polyiso is available for flat roof insulation systems, and it also can be supplied as tapered insulation board for flat roofs.
Designers who pursue certifications under green building rating systems, such as LEED®v4, would want to review adding insulation to a flat roof, such as nonhalogenated polyisocyanurate roof insulation. These formulations do not have flame-retardant chemicals that may adversely affect the environment.
Polyiso is the only foam plastic insulation product for direct application to steel decks to achieve FM Approval for Class 1 Roof Systems. It is also classified by UL for direct-to-steel deck insulation under both single-ply and asphaltic roof membranes.
Polyiso roof insulation is also produced at high density to become a much-specified cover board. Cover boards protect the roof assembly from roof traffic, mechanical abuse and hail. These roof cover boards are resilient and lightweight.
The Polyisocyanurate Insulation Manufacturers Association (PIMA) does outstanding work in researching the latest trends in polyiso advances and is a great support for the insulation industry.
*Initial, not LTTR aged value, to make an effective comparison with other products
With an R-value of approximately 5 per inch, extruded polystyrene (XPS) is created utilizing an extrusion process to produce closed-cell rigid foam insulation with polystyrene polymer. Many manufacturers add a dye to the formulation to add a unique colouration, typically pink, green or blue to distinguish the product brand.
Most XPS is used for wall and below-grade applications. For commercial roofing, it is most commonly specified for Inverted Roof membrane Assembly (IRMA) or Protected Membrane Roof (PMR) systems. Extruded polystyrene is usually ranked in the middle of cost vs. R-value in terms of cost/benefit evaluation of flat roofing materials.
It is vulnerable to solvent-based adhesives and hot asphalt, and its use in PMR systems requiring ballast can make structural weight of the assembly an issue.
Expanded polystyrene (EPS) is made from the same base polystyrene resins as XPS, but the manufacturing process is different, resulting in beads that are formed and cut into different sizes and shapes or molded. High-density products have an approximate R-value of 4.6 as a relative comparison.
Contractors like to install EPS as it can be cut easily to meet site conditions, and it is lightweight. Theoretically, it has a more stable R-value over time as there are no chemical blowing agents that can outgas. There are no current studies that can confirm this attribute.
EPS has several disadvantages, however. It is combustible, will absorb water, can shrink and warp with high temperature exposure, and is not compatible with petroleum-based products, such as solvents, coatings and adhesives. In addition, foot traffic on the roof can damage the material.
The commercial roofing industry phased out rigid fiberglass two-by-four panels as single-ply roofing systems became a larger share of the market. Soft underfoot, fiberglass was not recommended for EPDM, PVC or TPO systems. Traditionally, fiberglass sheets were used as a substrate for hot roofing systems, and they had several advantages: They provided high fire resistance and flexibility, and they were chemically inert and resistant to mold growth.
There were few suppliers dedicated to market commercial roofing systems with the necessary resources to support various code testing in contemporary assemblies. Currently, fiberglass rolls can be purchased for specialized uses, such as metal building insulations. Additionally, there are formaldehyde-free mineral wool options for certain applications.
Considered a &#;low thermal insulation&#; in the manufacturing process, it is typically combined with binders and reinforcing cellulosic fibers. In production since the late s, perlite was considered the pioneer environmental flat roof insulation product due to its high recycled content of paper waste, often manufactured with used books. It is economical and has a stable R-value. High-density versions of the product can be installed over wide flutes with metal deck spans up to 2 1/2 inches. With hot roofing systems, perlite is available in a number of composite construction boards, including OSB and gypsums.
Perlite boards can rot when wet and need surface treatments or coatings to prevent excessive absorption of asphalt during installation. Again, with the advent of single-ply roofing systems and their increasing specifications, this product is losing favor as a choice in commercial roofing.
R-value is but one of many criteria in the selection of flat roofing insulations for commercial applications. Insulation is just one component in a full roofing assembly. Other determining factors can be:
For more information on roof insulation, please see our comprehensive guide to polyiso insulation.
For more information, please visit Rigid Roof Insulation.
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