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What is Foam Board Insulation? How it Works

When considering insulation, most people envision fluffy, easily compressed, or torn materials. But rigid foam board insulation is a particular type of insulation that offers superior strength and insulating qualities.

You are interested in learning more about foam board insulation since your home isn’t as pleasant as you would like it to be. 

What is Foam Board Insulation?

Rigid polystyrene, polyisocyanurate, or polyurethane panels make up foam board insulation.

If you are rebuilding and removing the drywall, you may use foam board to completely insulate any exposed hollow in your house, including the walls. It might also be inserted into the open cavities of your pole barn.

Because rigid foam board insulation is offered in various thicknesses, lengths, and facings, it may be customised to fit your project. Some varieties of foam board even include a white foil vapour barrier on both sides to prevent water from penetrating and mould forming. 

It offers a greater R-Value per inch of thickness, is moisture resistant, and is simple to work with. There are several types of foam board insulation that buyers should be aware of:

Polystyrene (EPS): The same substance that makes up your disposable coffee cup is also used to wrap delicate items safely. It is the least expensive type of foam board insulation and has an R-value of 4 per inch of thickness. Under the siding, over the foundation walls, and under the roof.

 Extruded polystyrene: Home improvement stores may find sheets of extruded polystyrene in pink or blue colours with varying thicknesses. This insulation is denser than EPS and has a higher R-Value rating of 5 per inch of thickness.

Polyiso (Polyisocyanurate): This insulating foam board is more expensive and denser. It is typically foil-faced and has an R-value of 6 per inch of thickness to reflect radiant heat.

How Does Foam Board Insulation Work?

Foam insulation board provides solid thermal resistance and reduces heat transmission via structural elements such as wood and steel studs.

Conduction is the transfer of heat across a medium, which implies that reduced heat conduction generated by foam board insulation can serve to keep your house more comfortable if appropriately placed.

Foam board insulation is an excellent option for use on an exterior foundation, within a basement against the foundation, and outside of a house beneath a house wrap due to its resilience to moisture. Due to its higher cost, foam board insulation should only be used when moisture is an issue.

Pros and Cons of Foam Board Insulation


  • Water resistance is built into rigid foam board insulation products. This can assist in reducing the amount of moisture that may accumulate in your home, lowering the risks of mould formation.
  • The most affordable foam board on the market is an expanded polystyrene board. 
  • R-values for rigid foam insulation boards are high. The R-value of any form of insulation indicates its efficiency.
    R-values per inch of thickness can range from 3.6 to 8.0 depending on the type of foam board utilised. 
  • The outside of your home is continuously sealed by rigid foam insulation, assisting in the prevention of unwelcome air leaks that can result in inefficiencies. 
  • When heat flows through more conductive materials than insulation in a home, thermal bridging occurs.


  • There is a significant return on investment if you have the money to pay for the insulation up front. Usually, the reduced utility costs and avoided moisture damage will more than offset the original expense of the supplies and installation.
  • The advantages of rigid foam board insulation are negligible without sound installation. Fortunately, it can be installed without additional tools, but it must be done correctly.
  • Insulation made on rigid foam board offers some structural support. However, it is not as robust as OSB or plywood sheathing.

BuildersInsulation Can Install Foam Board Professionally!

Rigid foam board insulation is excellent external insulation and sealant for your property. Expanded polystyrene, extruded polystyrene, and polyisocyanurate are the three types. Contractors use each in different contexts.

This sort of insulation has both advantages and disadvantages. For starters, it is incredibly efficient in preventing moisture damage, air leakage, and thermal bridging.

It is, however, more costly than other forms of insulation and is not structurally robust on its own. However, the advantages outweigh the disadvantages, and a rigid foam board installation is an ideal choice for home insulation projects.

Basements, crawl spaces, and attics benefit from rigid foam insulation. As part of our evaluation process, BuilderInsulation can recommend suitable materials and services for your home to provide the solutions you require. 

To receive a free estimate and evaluation of your home, give us a call today!

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