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What is Foam Board Insulation and Why Do You Need It?

When and How You Might Need to Use Foam Board Insulation

Foam board insulation consists of insulation panels made from polystyrene, polyurethane, or polyisocyanurate. You can use foam boards to insulate any part of your property, including the open cavities of your pole barns. Foam board insulation is available in different lengths, thicknesses, and facings, allowing the installer to fit them in any space. The insulation comes in standard size 4X8 sheets with a thickness ranging from 1/4 inch to 2 inches. Through structural elements like steel studs and wood, foam board insulation reduces heat conduction and provides efficient thermal resistance. Foam board is an excellent alternative to fibreglass batt insulation. Foam board is easy to work with, resistant to moisture and has a high R-Value per inch.

Foam board insulation has a high moisture resistance, which makes it ideal to use in places where there is a likelihood of getting wet. It’s the ideal insulation inside your basement against the foundation, the exterior foundation, or the outside of your house beneath the house wrap. Compared to conventional batt insulation, foam board insulation is more expensive. Therefore, you should only use foam board insulation when moisture is an issue and when it’s within your budget.

The foam board is easy to use; you can use a circular saw with a masonry blade to cut it. You can score it with a utility knife and snap it the same way you would drywall. Use screws with large washers to attach the insulation. You could also attach the insulation using a special adhesive specifically made for attaching foam board insulation. You can use spray foam or caulk to attach small pieces of foam board insulation.

Pros and Cons of Foam Board Insulation

Below are some of the pros and cons of foam board insulation:


  • Due to its water resistance properties, foam board insulation reduces the growth of mould and mildew
  • Foam board insulation can create an air barrier if it’s installed properly
  • Foam board materials are long-lasting and will serve you for many years without the need for replacement


  • If they aren’t taped correctly, foam boards won’t provide airflow
  • In some instances, the air bubbles in the foam boards might accumulate moisture, which reduces their efficiency

For proper installation, you must use the foam boards precisely to ensure they fit in the target area properly. Air leakage might occur if the boards aren’t cut properly.

Different Foam Board Insulation Types

There are several foam boards insulation types:

Expanded Polystyrene

Commonly abbreviated as EPS, this material is the same as that used to make disposable coffee cups. The same material also comes in handy during packaging to prevent fragile items from breaking. This is the most affordable type of insulation, providing an R-value of 3.6 to 4 per inch of thickness. The EPS insulation can be used under roofing, beneath siding, and over foundation walls. EPS is approved for below-ground applications, ground contact and can be treated to resist insects. You should use this insulation over house wrap or alongside products that incorporate laminated factory options. EPS doesn’t hold water in the long term. It’s available in faced and unfaced designs.

Extruded Polystyrene

Extruded polystyrene (XPS) is also known as the blue or pink board, and it’s available in different thicknesses and edge profiles. This foam board insulation is denser than the EPS and has a higher R-value with a rating of 5 per inch of thickness. It can accommodate lots of applications because it’s available in different size configurations. To help limit air movement, insulation is available with tongue-and-groove or straight edges. This type of insulation is the rigid pink or blue panels found in homes. Extruded polystyrene foam board is mainly used for foundation insulation panels. This insulation is probably one of the most commonly used foam board insulation products for residential projects. This insulation is easy to use, lightweight, and reasonably priced.

Polyisocyanurate (Polyiso)

This foam board insulation is denser and more costly. It can easily reflect radiant heat because it comes in foil-faced. It comes in different thicknesses and can be used in attic spaces, underneath the siding, and over house sheathing, where its reflective properties come in handy. This insulation is mainly available in commercial establishments; more recently, it has become common in residential buildings. Its R-value ranges between 7.0 and 8.0 per inch of thickness. Due to its foil facing, this insulation is easy to seal with good quality foil-faced tapes. Polyiso is a closed-cell foam that contains low-conductivity gases in the cells.

The Pink and Blue polystyrene foam boards are distinct from the expanded polystyrene boards. The extruded polystyrene is more expensive than the expanded polystyrene insulation. The expanded polystyrene insulation of a less effective insulator and is more fragile than the extruded polystyrene.

Here are Other Foam Board Types

The blue and pink rigid foam insulation boards comprise the same material: polystyrene resin. The manufacturing process involves melting and forcing the resin through a die for the desired shape. Pink and blue boards have the same level of performance; both have an R-value of 5 per inch of thickness. The pink and blue boards are sold under different brand names.

Given that the manufacturing process, chemical composition, and insulating capabilities of the two boards are the same, what is their principal difference? The main difference between the pink and blue foam boards is that different companies manufacture them. Owen Corning manufactures the pink foam board, while Dow Chemical Co. manufactures the blue foam board. Pink foam board is marketed under different brand names, including Propink, Foamular, Insulpink, and Thermapink. The Blue foam board is marketed under the brand name Styrofoam.

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