Fact Checked

What is Rigid Insulation?

B. Turner
B. Turner

Rigid insulation is a building material used to provide thermal resistance to walls, foundations, and roofs. It is available in formed or extruded sheets of varying sizes, which are made from polystyrene or polyurethane. This material helps to improve the energy efficiency of a home by keeping cold or hot air from penetrating the walls. The thermal resistance of rigid insulation is measured by the material's R-value. Higher R-values mean that the material is more resistant to temperature transfer, while low R-values mean that air can easily pass into or out of the home.

The use of rigid insulation in the home can dramatically improve the comfort of occupants, while helping to lower energy bills. The resulting reduction in energy use also benefits the environment, leading to fewer greenhouse gas emissions. While many types of insulation may perform this function, rigid insulation generally provides a higher thermal resistance than other materials of a similar size. Rigid panels are denser and thinner than other insulation materials, and can be installed with fewer gaps or joints, resulting in less air leakage.

Rigid insulation may be installed on roofs.
Rigid insulation may be installed on roofs.

Sheets of rigid insulation are typically installed between a home's framing members and the exterior sheathing or cladding. The panels are placed tightly together, and joints may be caulked or sealed to provide maximum thermal resistance. In situations where moisture infiltration is a possibility, the insulation may be coated with a water-resistant coating.

Rigid insulation may also be installed on roofs or foundations. Roof panels must be dense enough to walk on, and are usually installed above the roof framing, but below the roof tiles or shingles. Water-resistant rigid panels can be placed on the exterior of foundations, but it is more common to install them on the interior of basement walls, or below a ground-level floor. When installed on the exterior of the foundation, the panels can be treated with insecticides to prevent termite damage.

There are three main types of rigid insulation, and each offers its own benefits and drawbacks. Molded expanded polystyrene (MEPS) is made sheets formed from liquid polymers. This is the most affordable and most common type, of rigid panel and is often referred to as beadboard. Extruded expanded polystyrene (XEPS) is more expensive, but is also stronger and denser, making it well suited for roof installations. Polyurethane foam board is the thinnest of the three, and works best in small spaces or in homes subject to extreme temperatures.

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Discussion Comments


I have done a lot of insulation jobs and rigid insulation is really the way to go for almost any project. Roof insulation is so much easier and so much more effective when you use rigid insulation.

Rigid foam insulation is also the best option when you are installing insulation behind drywall. If you are working with experienced contractors the job can go incredibly quickly. You have to know about the various kinds of insulation types and make sure you are using the best material for the job, but once this decision has been made there is not a lot left to do.


My wife and I bought an old house a few years back that had almost no insulation in it. The original builders had installed some fiberglass insulation but they had not installed it properly and it had worn down in a lot of area. We moved in in the summer and noticed immediately that the house was always hot no matter how much we ran the AC. Also, our electrical bills were astronomical.

Eventually we hired a contractor to add new insulation. The job only took a few days and he worked at what seemed like a reasonable rate. It was only once we got our next few electrical bills that we realized what an incredible deal this was. Our costs had been cut almost in half. Over the long run we saved a lot more money than we spent to have the job done. Anyone living in an uncomfortable house should look into having it re-insulated. The benefits cannot be overstated

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    • Rigid insulation may be installed on roofs.
      By: Monkey Business
      Rigid insulation may be installed on roofs.