The Ultimate Guide to Rigid Board Insulation

March 17, 2022

Appropriately insulating is among the most vital things that a homeowner can do to enhance the general energy efficiency of his or her home. The United States Department of Energy approximates that homeowners’ energy usage for artificially cooling and heating their homes accounts for around 50% of total energy use. Investing in more efficient heating and cooling technologies is one way to minimize your cooling and heating bills. Nonetheless, insufficient insulation in your roof, foundation, or walls will raise your energy usage, the type of heating and cooling notwithstanding.

Most homes across the country use mats or batts of soft insulation such as cellulose, natural sheep wool, and fiberglass insulation. Rigid foam insulation in building and construction is a comparatively new technology. It is easy to install, long-lasting and can improve the energy efficiency of even the leakiest homes.

What is rigid board insulation?

Rigid board insulation is made from dense, rugged sheets of certain types of foam. The commonly used foam products are polyiso, polyurethane, or polystyrene. These types of foams are "closed-cell" due to their chemical structure, instead of most insulation products that are open cells. 

Closed-cell insulation products such as the rigid board are usually more durable and robust. Moreover, they possess a higher R-value. 

Using rigid board insulation

Since rigid foam boards come as solid sheets, many homeowners can self-install them in strategic areas around their homes. After fastening the foam boards to the walls, place furring strips over the boards. These strips give a safe base for completing your basement using bamboo plywood, drywall, or other material. For structures with concrete walls in their basements, rigid board insulation will be more durable, particularly in comparison to cellulose or fiberglass insulation. 

Rigid foam board insulation is ideal for other home areas such as attics, foundation walls, roofs, and regular walls since they are moisture resistant. Nonetheless, this insulation option is generally recommended for below-grade applications like basements or external insulation.

The thickness of rigid insulation board 

Rigid foam insulation board comes in standard thicknesses of a half-inch to two inches. Homes situated in extreme climates can order thicknesses of at most six inches directly from some manufacturers. All in all, the thicker the board, the better the insulation abilities. 

Where to use rigid board Insulation

Rigid foam insulation boards can be used practically everywhere that insulation is required in homes. These boards can be used on basements, foundations, attics, regular walls, and roofs. When used above-grade, foam board insulation reduces thermal bridging, improving the home’s energy efficiency. On below-grade basements, a rigid board improves insulation while preventing moisture leaks.

Rigid board prepared from polyisocyanurate generally provides the most remarkable insulation capacity. Luckily, most rigid foam board insulation made using polyiso does not contain brominated flame-retardant chemicals, as these could be hazardous when inhaled. Nonetheless, this type of foam absorbs water, thus unsuitable for below-grade applications.

The durability of rigid board insulation 

Due to its water resistance and firmness, rigid board insulation can generally last over a century. 

The appropriate installation is key to ensuring the durability of this product. For instance, if you install a polyiso rigid board in the foundation, moister would quickly ruin the product, the same way it would ruin fiberglass batt or cellulose insulation.


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