Foam Board Insulation – A Versatile Product With Many Uses

Foam board insulation is a versatile product with many uses. It’s a useful solution below grade where you expect high soil pressures, and above ground it helps curb thermal bridging in framed walls. It also works well to keep moisture out, especially in humid locales. And it’s easy to install!

High R-Values

R values are a standard measure of how well an insulation material resists both radiated and convective heat flow. The higher the R-Value, the more efficient the product is, and the greater the energy savings it can deliver. However, it’s important to consider other properties like permeability and embodied carbon when choosing insulation products as these can vary significantly.

Foam board insulation is known for having high R-Values, ranging from R-4 to up to R-6.5 per inch of thickness. Expanded polystyrene board (EPS or beadboard) can also be manufactured with foil or plastic facings to improve its insulating performance. It is a good option for walls as it doesn’t use HCFCs and is water resistant.

EECA recommends that ceiling and underfloor insulation be a priority in new buildings, and foam is one of the most effective options available. But don’t mistake R-Values with creating an air seal. A better indicator of the effectiveness of a product is its ability to resist the flow of warm air into a home during winter and cool air out in summer.

Moisture Resistance

Modern foam board insulation is more than just a thermal insulator; it can also be used to control the flow of moisture and vapour, especially in humid climates. A quality product like Owens Corning FOAMULAR 300 extruded polystyrene insulation has a perforated laminate on both sides which reduces thermal bridging, limits condensation and moisture dispersal, and allows air to circulate effectively, all while maintaining R-Value* year after year.

Foam insulation is particularly resistant to moisture as it’s almost always closed cell. This helps prevent absorption and dispersion of moisture during construction, as well as mould growth.

It’s important to note that if the foam insulation gets wet it needs to be allowed to dry before covering with any exterior materials. If this isn’t possible, it’s a good idea to keep the insulation tarped or covered until installation. This is a good way to ensure the insulation will perform as intended. It’s also a key factor in the longevity of the insulation.

Easy to Install

Foam board insulation is easy to install, even if you’re not a skilled builder. It comes in 4-foot by 8-foot sheets that can help you quickly cover expansive walls. You can use a utility knife to cut the boards into the size you need for your home or building project.

You can also add this type of rigid foam board to concrete slabs and below-grade walls. It’s great for protecting slabs from strong soil pressures and heavy loads. It’s also an excellent choice for insulating below-grade foundations and basements.

Like other types of insulation, foil insulation should not be installed where electrical cables or light fittings penetrate the ceiling joists. This is because foil insulation can be a fire risk. If you’re using foil insulation, be sure to use nonconductive staples. You should also allow clearance around any hot flues or exhaust fans. It is important to follow the manufacturer’s installation requirements and any local building codes.


Rigid foam insulation can do so much more than just boost an insulated panel’s R-Value. It can curb thermal bridging, slow condensation and provide a barrier between the inside and outside of your home.

It can also help you build warmer, drier homes. It helps prevent a significant amount of heat loss, and can reduce your energy bill significantly.

In slabs, underfloors and green roofs, it offers a thin, lightweight layer of high thermal protection. It allows for reduced wall, ceiling or floor thickness and opens up new design possibilities while increasing energy efficiency.

In walls, it’s used in timber and steel framed applications, and under building paper in brick or stone veneer to prevent thermal shorts through the frame. In cathedral or membrane roofs, it’s placed over purlins beneath sheeting to avoid thermal bridging and condensation. It’s even used as a strengthening infill for fabricated panels and structures.

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