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What Is Urethane Insulation?

By B. Turner
Updated May 16, 2024
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Urethane insulation is a building product used to prevent air transfer through the exterior walls of a home. It is comprised of polymer chains connected by organic compounds known as carbonates, or urethanes. The terms urethane and polyurethane are used interchangeably when it comes to most applications, including insulation.

There are two basic types of urethane insulation, including rigid foam boards and spray foam. Rigid boards come in a variety of sizes, and typically range from 1 to 2 inches (2.54 to 5.08 cm) in thickness. These boards are primarily used in new construction, and are installed inside of walls or around other structures in the home. Spray foam insulation is typically used in existing structures, which may lack sufficient insulation material. This product is sprayed into the wall through tiny holes, and quickly expands to fill the entire wall cavity.

This material can be used is a number of different application in the home. Rigid insulation is frequently installed on the exterior of the wall framing system, where it is sandwiched between the home's sheathing and exterior cladding layers. Sheets of rigid insulation may also be attached to the home's roof or foundation, to provide additional thermal resistance in these areas. Spray foam is installed inside the same cavity as the wall studs, with sheathing, plywood, or drywall used to form the wall's boundaries.

Urethane insulation offers several advantages over other insulating materials. Though it is slightly more expensive than traditional fiberglass batts, it is considered a superior insulator, with two to three times the thermal resistance of alternative products. The closed-cell construction of urethane foam helps to block air flow, and also keeps the material from collapsing or sagging. Sheets of the insulation take up very little space, resulting in thinner walls and more available living area. Finally, urethane insulation is difficult to ignite, and is more resistant to fire than either fiberglass or polystyrene insulation.

Despite its many benefits, there are a number of factors that must be considered when using urethane insulation. As it ages, this material experiences a condition known as thermal drift, which can lead to decreased levels of thermal resistance. Adding a foil or plastic coating to the insulation can eliminate or slow thermal drift. Urethane insulation is also susceptible to insects burrowing into the material, which reduces its effectiveness. To prevent insect damage, insulation should be treated with an insecticide, especially when installed on foundation or basement walls.

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Discussion Comments
By TreeMan — On Aug 11, 2011

Does anyone have any suggestions as to what the best insulation material is for an attic? Currently, it is unfinished and the only insulation is some fiberglass insulation that I can tell is past its prime.

The article mentions urethane insulation is usually a bit more effective than fiberglass, but is also more expensive. What kind of price difference should I expect? I would like the avoid having to hire anyone. Is there any way to install the foam insulation by yourself? I can unroll the fiberglass insulation, so maybe this would be the best route.

By Izzy78 — On Aug 11, 2011

A few years ago we had foam urethane insulation applied below our house to try to keep the house warmer in the winter. I couldn't believe the difference it made. In both the summer and winter, we have noticed that the temperature in the house is much more stable, which means the air conditioner and furnace don't have to run as much. Just from installing the insulation, we have seen a very noticeable difference in our utility bills.

By stl156 — On Aug 10, 2011

@jcraig - It sounds like the material you are describing probably is urethane insulation. When I was a kid I used to love wrestling. For some reason we had a lot of extra urethane insulation in our garage, and it was great for makeshift tables and weapons.

Has anyone here ever dealt with the spray foam that is blown into walls? We just moved into a new house and discovered that when the previous owners built on the garage, they decided not to insulate it for some reason. We would like to be able to use one of the car spaces to put our exercise equipment and some of the kids' toys, but it would just be too cold out there in the winter.

My main questions are how effective is the material compared to regular fiberglass rolls or urethane panels? Also, how much does it cost to have it installed, and how long does it take? Out of curiosity, I was also wondering how much of a pain the foam would be to work around if we ever needed to do some rewiring or other work inside the walls.

By jcraig — On Aug 09, 2011

Is urethane insulation the stuff that often comes as a yellow material with a thin shiny metal layer on the outside? It seems to fit the description in the article.

When we remodeled a home I lived in many years ago, we used this type of insulation inside the walls. Since it came in the same size as normal boards, it was easy to cut it into shape and put it inside the walls before we installed drywall. I'm not sure how it would have compared to something like fiberglass insulation, but at least I didn't have to deal with the itchiness fiberglass can cause.

Could someone explain thermal drift and how it works? Does it have something to do with the fibers breaking down, and how long will the insulation last before it starts happening? How does the foil or plastic coating stop it from happening?

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