Spray foam insulation has long been used as a common form of insulation in many commercial and industrial buildings. Its popularity in these settings is due to its many benefits, which include better energy efficiency, improved sound deadening, and enhanced fire resistance.

Spray foam insulation is an excellent choice for roofing insulation. Besides offering incredible energy savings, spray foam also creates an air-tight seal and deters mold.

There are two types of spray foam insulations: open and closed-cell. The former has an R-value of 3.8 per inch, while the latter’s R-value is up to 7 per inch.

Therefore, closed-cell spray foam is the better option if you’re looking for an insulation material with a high R-value. Here are some reasons to use spray foam insulation.

Below, we look at a few reasons to use spray foam as roof insulation. 

1. Provides High Energy Savings

Spray foam tends to create an air-tight seal around your home since it expands to fill cracks or gaps. As a result, your home’s HVAC system doesn’t have to work as hard to maintain the desired temperature.

In other words, spray foam helps you achieve better energy efficiency in your home, which leads to significant energy savings. It’s also a better option for hard-to-reach spaces than fiberglass batts requiring cutting and fitting.

2. Creates a Moisture Barrier

Moisture can be a nuisance since it leads to the growth of mold and mildew. It can also cause wood rot, which weakens the structural integrity of your home.

The problem is even worse in metal roofs due to angular junctions and corners. Complex roof designs, such as a gazebo, can be hard to insulate. Moreover, flashings move with thermal expansion and contraction, creating gaps that allow moisture to enter.

Spray foam insulation, especially closed-cell spray foam, conforms to the roof’s surface, creating a seamless moisture barrier. Thus, the spray foam helps prevent roof leaks, and water and ice dams from forming on your roof.

3. Provides Structural Strength

The high compressive strength of spray foam insulation makes it ideal for supporting the weight of a roof. It also helps to distribute the load evenly, prolonging the roof’s life.

In addition, spray foam doesn’t sag or settle over time like other insulation materials, such as fiberglass. As a result, it doesn’t leave any gaps that allow air or water to enter.

4. Deters the Growth of Mold

Mold loves damp and humid conditions, which is why it commonly grows in the attic. If left unchecked, mold growth can lead to serious health problems, such as respiratory issues.

Spray foam insulation helps deter the growth of mold by creating a moisture barrier. In addition, it’s also resistant to mold and mildew thanks to its closed-cell structure.

Besides, spray foam does not have any nutritional value for pests and rodents, nor does it provide a haven for reproduction. Thus, even though spray foam is not a pest-repellant, it can help prevent infestations. 

5. Offers Enhanced Fire Resistance

The last thing you want is for your roof to catch fire. Although spray foam is not fire resistant, you can treat it with flame retardants. These are chemicals that help slow down or prevent the spread of fire.

When applied to spray foam insulation, flame retardants create a barrier that slows the spread of fire. Thus, it gives you more time to evacuate the premises and call the fire department.

In addition, closed-cell spray foam has a higher density than open-cell spray foam.

6. Easy to Install

Yes, you must follow plenty of safety precautions when installing spray foam insulation. However, the process is relatively easy since you only need a few tools, such as a sprayer. Don’t worry about buying a sprayer since it will be included in the kit. 

Installing spray foam is also quicker than other insulation materials. For example, you merely have to spray it into place rather than cut and fit pieces of fiberglass insulation.

You can also install spray foam in hard-to-reach places, such as attics and crawl spaces. That’s because it comes in a liquid form that expands and fills the nooks and crannies.

7. Can Be Used In Any Part of the Roof

Possibly the most notable reason to use spray foam as roof insulation is that you can use it anywhere. Do you want to insulate the underside of the roof? Are you planning to insulate the top? The material is ideal for both places.

Spray foam insulation can be used in any part of the roof, including the valleys, ridges, and hips. You can also use it around chimneys, skylights, and vent pipes.

You can also apply spray foam insulation to decking under metal roof panels before installing the panels. It doesn’t create any problems and helps insulate the space between the decking and the panels.

The only time you can’t use spray foam is when there’s a danger of the insulation coming into contact with live electrical wires

If live wires are present in the area you want to insulate, it’s best to stop the project immediately and get help removing the wires from the area. Wires that are in contact with insulation can become a safety hazard.

Which Type of Spray Foam Insulation Should You Use For the Roof?

The difference between open and closed-cell spray foam is in their structure. Closed-cell spray foam has a denser structure, while open-cell spray foam has a more honeycomb-like structure.

The cells in open-cell foam are not fully encapsulated. Thus, they’re more flexible and soft. Meanwhile, the cells in closed-cell foam are fully encapsulated. As such, they’re more rigid.

The type of spray foam you use will depend on the project. If you’re insulating an existing roof, use open-cell spray foam. It is ideal for retrofitting since it does not add as much weight to the roof as closed-cell foam, which is heavier by volume. 

You can also use open-cell spray foam to insulate the underside of the roof deck, provided there’s enough headroom. The material is also perfect for filling small gaps and cracks.

On the other hand, closed-cell spray foam is ideal for new construction and roofing projects. It’s also the best choice for insulating the top of the roof since it’s more resistant to fire and pests.

Do note that closed-cell foam expands less than open-cell foam. Therefore, you should use the former when insulating tight spaces.

However, the eventual thickness of the foam will depend on how much foam you sprayed. Low-rise foam (closed cell) usually only expands 2x its original volume, but open cell expands 3x-4x. So the final thickness will be dependent on the amount of foam you apply, but you may need more open cell than closed cell to reach the same R-value.

A common concern when using spray foam for roof insulation is that the material might cause rot. Spray foam doesn’t rot your roof. However, the culprit here is water, which can seep through cracks and gaps in the roof. Thus, opt for breathable spray foam insulation to prevent this.


Evan has decades of experience as a project manager for large-scale commercial renovation home-building projects throughout the US. Currently, Evan runs a successful construction management company in Virginia.

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