Is Foam Board a Good Insulator?

| Updated on March 21, 2024

For an extreme temperature, it is good to have a well-insulated house. It saves a lot of energy consumption by reducing the use of heating or cooling appliances throughout the year, which means you have lower energy bills.

Insulation is the process of creating a barrier between the indoor and outdoor temperatures of a house. It prevents heat from escaping or entering the house through the walls, which helps in keeping the desired temperature throughout the year. 

That is, when you insulate your house, you’re going to feel cool inside the house even if there’s scorching heat outside. Similarly, you’re going to have a warmer space inside during cold weather outside.

Hence, you have a comfortable house to live in.

You get many insulation options in the market, among which foam board insulation has gained much popularity these days. You must be wondering if foam board is a good insulator.

Well, Foam Board, also known as rigid foam, is a good insulator. It provides the best long-term solution among various other insulators found in the market. 

It is costlier as compared to the other insulators, but does the work well. You can install it by yourself as well if you are someone interested in fixing household stuff.

What is a Foam Board?

Foam Board is a rigid panel of insulation that has a high insulation value per inch of thickness. It provides good thermal resistance and helps control indoor temperature. 

It is made up of materials like polystyrene, polyisocyanurate, or polyurethane.

It is a great alternative to other regular insulations like fiberglass batt and plywood.

It is one of the few types of insulation that can be used to insulate almost any part of your home, from the roof down to the underground or the outside of the foundation. 

You can install it anywhere in your home, be it floor-ceiling or unvented low slope roofs, but if you’re planning to install it on your walls, be ready to take the drywall out.

Foam insulation is made up of materials that have water resistance which helps to maintain a water-tight seal. It can help seal the gaps and close air leaks as well.

It has a high moisture resistance which is a great fit for places like an exterior foundation, inside a basement against the foundation, and on the outside of a house. Place it wherever you like.

Foam insulation usually comes with a fire safety feature. The manufacturers add flame retardant in the material which keeps away fire or helps prevent any fire accident.  The concept of fire safety makes it feel safer for buildings and property.

Now let’s talk about heat resistance. The heat resistance of any insulating materials is measured in terms of thermal resistance or R-value.

R-value tells how capable an insulating material is to resist heat flow. The higher the r-value greater will be the insulating effectiveness.

R-value depends on the thickness and density of any insulation. The r-value increases when you install more insulation in your home. 

The effectiveness of an insulation material also depends upon various factors like how it is installed or the place it is installed. Other factors like climate also determine the effectiveness.

Foam board insulation is of a different type. Therefore, the r-value of foam insulation also differs according to its type. 

Refer to the foam board insulation r-value chart to know more.


Rigid foam can be installed with ease.

You should measure the wall area and buy the foam board as per the requirement. Make sure you have a circular saw or a utility knife to cut the panel into a proper size. It should fit perfectly in the place where you are planning to install it. Once you cut the panels, set them with screws or any adhesive. Ensure everything is nice and tight.

The better performance of the foam board depends on the right installation. Therefore, you can ask the professionals to do the task if you do not want to compromise with the output.

If you feel confident about doing it yourself, you better read the instructions properly and follow the safety measures. 

Also, just keep in mind that you should seal the gaps if you want the panels to block the vapor or moisture as well.


  • Most of the foam board insulation is water-resistant. It protects the wood sheathing from rainwater. This helps in controlling the moisture buildup, Therefore, it eliminates the chances of molding and rotting.
  • Rigid foam also acts as an air barrier. If you install it properly, it prevents air leakage.
  • The foam board has better insulation per inch of thickness as compared to other materials like plywood and fiberglass batts.


  • You should install the rigid foam insulation correctly, it might seem easy to install, but if not done properly the whole effort will get wasted.
  • Foam board insulation is comparatively expensive than other insulation materials. Adding a layer of rigid foam on top of plywood will cost you more.
  • The structural strength of rigid foam is less than other insulation materials. If you use rigid foam in place of wood sheathing, it needs additional bracing to avoid racking.

The Bottom Line

We spend a lot of time in our home, so it is crucial to have a comfortable environment, it makes you relaxed both physically and mentally. 

Temperature and humidity play a major role in making a home comfortable. Too much hot or too cold can deteriorate our health.

Therefore, it is necessary to insulate your house properly.

Foam board insulation is one of the most effective insulators that we have. 

It is not just effective, but it is also easy to install. But keep in mind that you do it properly. It’s pointless if you do not seal it properly. Even a tiny hole or gap can let in the moisture, which will condense and get stuck on the vapor barrier. Hence, you’ll end up trapping more moisture than you’ll block with it.

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