Closeup on the end grain of stacked pieces of polyiso radiant barrier foam board insulation

If your home isn’t as comfortable or cozy as you want it to be, you may want to consider foil-backed radiant barrier foam board insulation.

Besides enhancing the efficiency of the radiant barriers, foam boards also reduce strain on your HVAC system, which can lead to massive cost savings in terms of maintenance. 

This insulation can be installed easily into any open cavities in your attic—unless you want it in your walls. In that case, you must remove the drywall first. 

Why Reflective Foam Boards Are Perfect For Wall Cavities 

If your home has a cavity wall within the structure, investing in reflective foam boards will be worth your while. These walls trap cold air between the inner and outer parts of the wall. If the gaps between are empty, the wall allows more cold air to pass through than you realize.

This is what happens: With time, the wall leaves behind moisture which eventually reaches the inner part of the wall leading to dampness. Besides becoming a breeding ground for mold, the damp wall compromises the thermal performance of your whole building. Which, in turn, makes your HVAC system work overtime. The result is a cold home and a skyrocketing energy bill. 

This instance is where reflective foam boards can prove invaluable. Foam boards can be easily inserted into a cavity wall to provide another layer of insulation and protection from the elements.

Using foil-backed boards can partially fill these cavities. Just make sure they are light and thin enough to allow some free space and have sufficient U-value to do a proper job. 

Types of Foam Boards 

Foam boards are rigid insulation panels made of one of three materials. Depending on your needs, you can choose from the following to be installed:

Expanded Polystyrene (EPS)

Expanded polystyrene is what keeps your coffee warm and your takeout or delivery food piping hot before it reaches you. 

A closeup on the edge of a piece of expanded polystyrene radiant barrier foam board insulation

With an R-value of four per inch of thickness, the installation is highly efficient and is also the most cost-effective foam board insulation. The material can be installed under roofs, underneath the siding, and over foundation walls. 

Extruded Polystyrene (EXP)

Denser than EPS, extruded polystyrene foam insulation is available in varying thicknesses. It offers an R-value of five per inch of thickness. In addition, you can find extruded polystyrene in different sizes, so it can suit the cavities or space you need it for.

Sheets of foil-faced EXP installed in an attic
Courtesy of

Extruded polystyrene is available as straight foam boards and with tongue-and-groove edges for reducing airflow. This insulation is used as foundation insulation panels. 

Polyiso (Polyisocyanurate)

Compared to EPS and EXP foam boards, polyisocyanurate boards are denser and a tad bit expensive.

Sheets of polyiso foam board insulation
Courtesy of R Max

However, they also offer an impressive R-value of 6 per-inch thickness and are often available with foil-backing that reflects radiant heat. The material is used on top of house sheathing and underneath siding or attic spaces. 

Top Benefits of Foil-Backed Foam Boards 

Foam boards with reflective backing have an insulated core. This way, you get the best traits of rigid insulation boards and the reflective quality that can block radiant heat from entering your home and turning it into a furnace.

Some of the top benefits these boards offer include:

Unmatched Thermal Performance 

The combination of rigid panels and foil enhances the insulation power of these boards exponentially. The boards are impressive insulators on their own.

Depending on the type you get, they can also prevent moisture from seeping into your home.

Since mold and mildew can rot your property from the inside out, foil-backed insulating boards pay for themselves in the long run.

Besides reflecting radiant heat, these boards also retain the heat from your furnace during the winter to keep you toasty warm. In other words, foam boards with reflective backing work year-round to reduce your energy bills without compromising your comfort.

Hard Insulation Core 

With a hard insulation core, foil-backed boards can stand the test of time and changing weather conditions. The rigid code prevents the boards from sagging, bending, and breaking. Plus, with sufficient foam boards, you can strengthen your walls and your attic’s structural integrity as well. 

Easy Installation 

Foam boards are incredibly lightweight, which makes installation easy and fast. Compared to other insulating materials that can add more weight and require special tools for installation, these can be trimmed to desired lengths and shapes with a strong pair of scissors or even a sharp knife. 

Plus, it can be stuck to the walls or inside cavities in your attic with nails or adhesive. However, leave the installation to the professionals. It may look easy, but a single improperly placed foam board can ruin its insulating integrity. 

Low Maintenance and Replacement Costs 

If installed by professionals, reflective foam boards can last indefinitely. 

Once installed, this insulating option requires little to no maintenance since the material is immune to vapor, moisture, and dampness. In other words, the last thing you will have to worry about is mold or fungi growth. 

For the best results, search for foil-backed foam boards that are fire resistant and eco-friendly. 

Where To Buy Reflective Foam Boards 

You can find reflective foam boards in a range of popular home improvement stores like Amazon, Lowe’s, Menards, Walmart, and Home Depot, to name a few.

If you prefer to buy them from local contractors, first make sure they are reliable. Some may sell foam boards with prices that are higher than market value. Choose those who have decent reviews and can also install the foam boards for you. 

Top Options To Choose

Not all foam boards are the same. Some of the top options from a brand called Johns Manville include this Foil-Faced Foam Sheathing board, Foil-Faced Polyiso Foam Board Insulation, or this AP Foil-Faced Foam Sheathing.

Your choice should depend on your insulation needs and the structure of your home. A professional and experienced contractor can help you narrow down your choices. 

Bottom Line 

Radiant barrier foam boards with reflective backing are a sound investment decision. Besides reducing your energy bill, they can strengthen your home’s structural integrity and ensure your HVAC system will last long-term.

However, it would be best it you hired professionals to install them to give you peace of mind during and after installation.

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