7 Best Roof Insulation Materials (2024 Guide)

Insulating your roof is one of the most important ways to keep your home warm during the winter and cool in the summer. Good roof insulation can also lower your energy consumption, add structural support to walls and roofs, and seal gaps that reduce air leakage.

There are several factors to consider when choosing the best roof insulation for your home. This article breaks down the pros and cons of seven popular options.

What is a roof insulation R-value?

Before we get into the specifics of each roof insulation material, let’s discuss R-value. Home insulation is rated by R-value. The R-value is the insulation’s ability to resist heat that travels through it. The higher the R-value, the better the insulation’s heat resistance.

Since heat rises to the highest point in your home, keeping the heat from leaving through the roof will keep your home warm in the winter and lower your energy costs.

The U.S. Department of Energy's Energy Star program has determined the proper R-value for each part of your home’s insulation, depending on where you live. Areas with warmer climates have lower R-value requirements, while colder areas need insulation with higher R-values. Look up your region on Energy Star to determine the minimum R-value for your roof insulation.

Top roof insulation materials for homes

There are seven types of insulation commonly used in homes:

• Spray foam insulation
• Rigid foam boards
• Batt insulation
• Loose-fill or blown-in insulation
• Insulating concrete forms (ICF)
• Structural insulated panels
• Reflective system

We explain the pros, cons, and costs of each below.

1. Spray foam insulation

One of the most common and effective ways to insulate roofs is with sprayed-in-place roof foam insulation.

Spray-applied foam is highly effective for sealing all cracks and crevices, as it fully adheres to the underside of the roof deck and framing. This creates an effective barrier that reduces air leakage and fully insulates against heat loss.

Spray foam insulation yields a higher R-value than the same thickness of traditional batt insulation. There are two types of sprayed-in-place foam insulation — open-cell and closed-cell — each typically made with polyurethane:

• Open-cell foam: The cells are intentionally left open and filled with air, making the foam softer and more flexible. It’s lighter and less expensive than closed-cell foam but better suited for interior applications, like soundproofing, as it cannot absorb water.
• Closed-cell foam: The cells are completely closed and filled with a gas that expands the foam, making it more rigid and stable. It has a greater R-value and provides greater resistance against moisture and air loss, but it’s more expensive.

Average Installation Cost: $14,110 for 1,500 square feet of insulation

R-value:

• Open-cell foam R-value: 3.6 to 3.8 per inch
• Closed-cell foam R-value: 4.9 to 7 per inch

2. Rigid foam boards

Rigid insulation boards can be used anywhere in your home, from the roof and attic space down to the foundation. They’re durable, dense sheets of closed-cell foam that provide excellent thermal resistance — up to twice the resistance of other insulating materials of the same thickness.

There are three main types of rigid foam insulation boards:

• Polyiso: This foam typically comes with a foil facing that serves as a radiant barrier. It’s the most expensive of the three but also has the highest R-value.
• Extruded polystyrene (XPS): This foam is usually blue or pink and has a plastic surface. It’s water-resistant, but its main insulating material is flammable.
• Expanded polystyrene (EPS): Similar to XPS but with a lower R-value, EPS is a quality, inexpensive roof insulation option for homeowners on tighter budgets.

Average Installation Cost: $2,045 for 1,500 square feet of insulation

R-value:

• Polyiso R-value: 6.5 to 6.8 per inch
• XPS R-value: 5 per inch
• EPS R-value: 3.6 per inch

Pros and cons of rigid foam board roof insulation

3. Batt insulation

Perhaps the most common and widely available roof and attic insulation type is batt blanket insulation. It consists of flexible fibers made from fiberglass (most common), mineral wool, or cotton. 

Batts and rolls of material are available in standard widths to be applied between wall studs, attic trusses and rafters, and floor joists. They can be purchased with or without facings for application inside a wall or on an exposed area, like an attic.

Batt insulation is easy for homeowners to install themselves. It’s inexpensive compared to other insulation materials but has a lower R-value, isn’t as energy efficient, and doesn’t perform as well in colder temperatures.

Average Installation Cost: $3,074 for 1,500 square feet of insulation

R-value: 2.2 to 4.5 per inch

Pros and cons of batt insulation

4. Loose-fill insulation or blown-in insulation

This type of insulation is often blown into hard-to-reach places — like a roof or unfinished attic — through a long, flexible tube. Loose-fill insulation or blown-in insulation comes in two materials, each made from loose fibers or recycled waste:

• Cellulose insulation: The more durable option. This material doesn’t degrade or lose its R-value over time.
• Fiberglass insulation: This material typically loses R-value over time, particularly in colder climates.

The primary advantage of these materials is that they easily conform to any space without disturbing the existing structures or finishes. This makes them well-suited for retrofits or home renovations.

Average Installation Cost: $2,042 for 1,500 square feet of insulation

R-value:

• Fiberglass R-value: 2.5 to 3.5 per inch
• Cellulose R-value: 3.2 to 3.7 per inch

Pros and cons of loose-fill or blown-in insulation

5. Insulating concrete forms (ICF)

The rebar structures that hold poured concrete in place when building walls can be repurposed for insulation. Insulating concrete form (ICF) systems consist of foam boards connected to hollow insulation blocks and fastened to the rebar.

The ICF system is durable and stable, providing exterior structural support. The ICF walls provide substantial thermal resistance, with R-values up to 5 per inch. 

Average Installation Cost: $24,072 for 1,500 square feet of insulation

R-value: 5 per inch

Pros and cons of insulating concrete forms

6. Structural insulated panels (SIP)

Made of prefabricated boards with foam in between, structural insulated panels are growing in popularity. Because they’re available in different sizes and shapes, these panels can be used in various ways, such as in walls, ceilings, floors, and roofs.

The SIP system panels typically consist of a 4-inch- to 8-inch-thick foam insulation board sandwiched between two sheets of facing materials. They have excellent durability and provide higher energy efficiency (12% to 14% energy savings) than other insulating materials with high structural strength. However, they lack moisture resistance and require waterproofing material or exterior sheathing for protection.

Average Installation Cost: $17,207 for 1,500 square feet of insulation

R-value: 5 to 7.2 per inch

Pros and cons of structural insulated panels

7. Reflective insulation system (RIS)

Radiant barriers, commonly called reflective insulation systems, differ from most insulating materials. Instead of resisting heat escaping, the insulation has a unique surface that reflects warm air entering through the roof from the sun’s radiation.

RIS materials are typically installed in attic areas to reduce cooling costs. In fact, they can help homeowners save 5% to 10% on their energy bills.

Average Installation Cost: $2,076 for 1,500 square feet of insulation

R-value: 3 per inch

Pros and cons of reflective insulation systems

Comparing roof insulation materials at a glance

Here’s a snapshot to easily compare types of roof insulation:

*Costs are based on the national average to install 1,500 sq. ft. of insulation.

How to choose the right insulation for your roof

Now it’s time to determine which type of roof insulation is best for your home. Once you have located the R-value climate zone your home is in, you’ll better understand the types of insulation that are right for you.

Whether you’re planning on installing it yourself or hiring a roofing contractor, insulating your home will lower your energy bills, reduce your carbon emissions, and keep your home at a comfortable temperature year-round.

Here are things to consider when choosing a roof insulation material:

• Installation process: Certain insulations, such as spray foam, require advanced experience and special equipment to install, so they’re not ideal for the DIY route.
• R-value requirements: Regarding materials, look for insulation that meets at least the minimum R-value requirements for where you live.
• Budget: Most home improvement projects have some financial constraints. You will likely determine your insulation choice based on your budget. Batt insulation and rigid boards are quality, affordable materials.
• Energy efficiency: Insulations like SIP, ICF, and rigid boards help homeowners reduce their energy consumption (heating and cooling) by up to 20%. In some cases, the energy savings realized over the lifespan of an energy-efficient roofing insulation offset the installation cost.

Frequently asked questions

Does roof insulation make a difference?

Installing roof insulation is one of the most important ways to keep your home warm during the winter and cool in the summer. Installing insulation based on the required R-value level for your home can reduce your home’s energy consumption, add structural support to your roof, and reduce air leakage by sealing unnoticed gaps.

What roof insulation has the highest R-value?

There are several roof insulations that provide a high R-value. The insulations with the highest per-inch R-value levels are:

• Polyiso rigid boards: 6.5 to 6.8 per inch
• Structural insulated panels: 5 to 7.2 per inch
• XPS rigid boards: 5 per inch
• Insulating concrete forms: 5 per inch

Does adding roof insulation make your house hotter?

Adding roof insulation will reduce heat loss in the winter and keep your home warm. On the flip side, you can apply reflective roof insulation to reduce the heat entering your home in the summer.

How do I know if my roof needs more insulation?

One sure way to determine if your roof needs more insulation is to track whether your energy bills continually rise in colder months. This is typically a sign of heat loss through the roof or substantial air leakage. Adding insulation will provide heat resistance.

What’s the cheapest roof insulation?

The lowest-cost insulation materials are typically batt insulation and reflective insulation systems.