Cellulose vs. Foam Insulation: What Are The Differences?

Cellulose and spray foam are popular residential insulation materials, so which one is right for you? Here's how they stack up against each other.

When insulation isn’t sufficient or working correctly, you’ll undoubtedly feel it. Insulation plays a key role in the energy efficiency of a home, helping it stay cool during the summer and warm during the winter.

Many homeowners aren’t aware of the different insulation materials on the market or which ones are best in certain situations. Two of the most popular options are cellulose and spray foam. Here we’ll explain the significant differences between cellulose and foam insulation, plus categories where one is better than the other.

Spray Foam Insulation vs. Cellulose: Efficiency (R-Value)

R-value refers to the resistance (hence the “R”) of heat transfer from hot air to cold air. Consequently, R-value represents an insulation material’s ability to resist how heat flows through it. The higher the number, the more thermal-resistant the material is, and the more effectively it insulates. On average, foam and cellulose insulation carry a 3.5 to 3.7 R-value per inch.

While their R-values are similar, spray foam also provides air sealing — another important factor in keep you warm in winter and cool in summer.

Winner: On R-value alone, it’s a tie, but spray foam’s air sealing capabilities give it the advantage.

Spray Foam Insulation vs. Cellulose: Durability

John Kane, home performance director for Allied Experts, says spray foam insulation won’t degrade over time and can last for more than 30 years. However, it can be easily broken or scratched. If you have children or pets, you need to be careful with spray foam insulation because it’s also extremely toxic.

Chemically-treated cellulose insulation can last between 20 and 30 years. However, if it gets wet, the chemicals are affected and it may not resist mold as well. You don’t need to replace it if only some parts are wet, though it will be less effective. If it has soaked up a lot of water, you might need to completely replace it.

Winner: Spray foam. It consistently lasts longer than cellulose.

Spray Foam Insulation vs. Cellulose: Cost

Kane notes that cellulose insulation typically costs between $1.63 and $2.52 per square foot for the materials and installation. Spray foam is more expensive, ranging between $3.95 and $7.20 per square foot. Aside from the material, thickness is another determining factor in the cost.

Winner: Cellulose. Spray foam is considered the more premium material, and that is reflected in the higher cost.

Spray Foam Insulation vs. Cellulose: Ease of Installation

Installing foam and cellulose insulation requires specialized equipment and training. Although installing insulation on your own saves money on labor, it’s not an easy job.

You can rent equipment like a motorized hopper to install cellulose. The task is more difficult with spray foam, which requires unique equipment and specialized training. Therefore, it’s usually best left to a professional. Installation complexity is another reason why spray foam more expensive. On the other hand, cellulose can be a DIY project with the proper planning and knowledge.

Winner: Cellulose easily wins this battle. For professionals and homeowners alike, spray foam requires much more technical knowledge and careful planning to do it right.

Spray Foam Insulation vs. Cellulose: Environmental and Fire Safety

Tom Bury, co-founder of Nu Look Home Design, says cellulose insulation is made from recycled green materials, so it’s considered one of the greenest choices. But cellulose is also treated with chemicals that make it fire-resistant. If it’s not installed correctly, or if there’s a leak, the chemicals inside it can react with moisture and produce harmful fumes.

“Cellulose by design helps water seep through it and naturally evaporate, too,” Bury says. “However, if it stays moist for a long time, the chemicals inside it can break down and produce fumes harmful to your health.”

Foam insulation is toxic if eaten, and it’s highly flammable. Luckily, you can prevent this by installing a thermal-resistant barrier. Spray foam is completely waterproof or highly water-resistant. While it does absorb some water, it eventually dries out.

Winner: Both or neither. Spray foam offers more moisture resistance but lacks the fire resistance and environmental friendliness of cellulose.

Mark Soto
Mark Soto is a freelance writer from Milwaukee, Wisconsin. He has comprehensive knowledge of home improvement projects based on his previous work. Mark comes from a family of DIYers and has worked with landscapers, plumbers, painters and other contractors. He also writes about camping and his enthusiasm for the outdoors.