Basement Insulation Comparison

Fiberglass Insulation

Fiberglass insulation is made from extremely fine fibers of glass. This is often installed in the form of "batts" on a basement wall, with insulation that has a cottonlike texture and is pink or yellow in color. This insulation is attached by adhesives to tall rectangular strips of paper.

Advantages:

• Fiberglass is readily available
• Inexpensive
• Can be removed & replaced

Disadvantages:

• Soaks up water and humidity like a sponge
• Low R-value per inch
• Can support mold and mildew growth

Fiberglass Insulation In Depth

Fiberglass is an inexpensive insulation material that's popular among "do-it-yourselfers" for insulating wall studs before finishing the basement. It's readily available at most hardware stores and box stores, and its lightweight, removable design makes it a popular choice.

While fiberglass insulation is excellent in above-grade spaces, it's a notoriously poor choice for basement insulation. Fiberglass can become saturated with moisture from basement flooding, water leaking through walls, and even from water vapor passing through the pores of concrete. Wet fiberglass loses much of its insular value, and as it becomes weighted down it sags, leaving gaps in the insulation at the top. Over time, wet fiberglass will support mold and mildew growth.

Open-Cell Spray Foam Insulation

This insulation forms an expanding foam as it's sprayed. Open-cell foam insulates but cannot seal out moisture.

Advantages:

• Fast installation
• Can be used around obstacles
• Foam expands to fill gaps

Disadvantages:

• Restrictively high cost
• Does not create vapor barrier
• Permanent installation - cannot easily be removed
• Low R-value per inch
• Potential for "overspray" and messy cleanup
• Final thickness of insulation is inconsistent/uneven

Open-Cell Spray Foam In Depth

Open-cell spray foam is also used for air-sealing and insulating, but it's not a good choice for basement applications. Closed-cell spray foam has a higher insulation value: about R-6 per in. compared to R-3.7 per in. for open-cell spray foam.

Also, open-cell spray foam doesn't form a moisture barrier like closed-cell foam does, so it can't seal out moisture --a valuable quality in basement and crawl space areas.

Closed-Cell Spray Foam Insulation

This insulation forms an expanding foam when sprayed. Closed-cell spray foam creates a vapor barrier as applied.

Advantages:

• Fast installation
• High R-value per inch
• Can be used around obstacles
• Foam expands to fill gaps
• Creates a vapor barrier & resists water damage

Disadvantages:

• Restrictively high cost
• Permanent installation - cannot easily be removed
• Potential for "overspray" and messy cleanup
• Final thickness of insulation is inconsistent/uneven

Closed-Cell Spray Foam In Depth

Closed-cell spray foam is often used to air-seal the basement's rim joist and other leaks that waste energy. The rim joist (aka band joist) extends around the perimeter of the house, typically resting on the mud sill or directly on top of the foundation.

Knot holes, cracks and gaps above and below the rim joist create many pathways for air to leak into a basement, but these leaks can be sealed effectively with closed-cell spray foam.

In this application, the foam's most important function is air sealing rather than insulating. This sealing work is also useful for all the holes, cracks and gaps that allow basement air to leak through the floor structure and into the living space above.

Closed-cell spray foam comes in two forms. Pressurized cans of "one-part" spray foam are available at hardware stores and home centers. But insulation contractors often use "two-part" spray foam that combines two compounds at an application nozzle.

Rigid Foam Panel Insulation

Rigid foam panels are made with foam insulation that has been shaped into stiff wall panels that are mounted on your walls or between studs. These panels typically use a closed-cell insulation design.

• High R-value per inch
• Creates a vapor barrier & resists water damage
• Can be designed with pre-installed wall studs
• Can be removed & replaced
• Lower cost
• No messy installation

Disadvantages:

• Most difficult to install around obstacles
• Cannot be used to fill voids

Rigid Foam Panel Insulation In Depth

Rigid foam panels are lightweight and easy to install. Channels can be cut by the installer to accommodate pipes, wires, and similar obstacles, while the panels can also be customized to work around more significant obstructions.

Rigid foam insulation is often combined with sections of more expensive, closed-cell spray foam, which seals small cavities and areas where it would be difficult for rigid foam paneling to be properly installed.

Rigid foam panels will create a vapor barrier on your basement walls that will keep back water, water vapor, and humidity that could otherwise build in the basement and contribute to humidity levels and, subsequently, mold.