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The Differences Between Polystyrene Insulation and Polyurethane

Do you want your Minneapolis or St. Paul area home to be more comfortable and less expensive to heat and cool? If so, you might be interested in the benefits of foam insulation. You have two main types to choose from: rigid foam (polystyrene) and spray foam (polyurethane).

Polystyrene and polyurethane insulation materials sound similar, but they have their differences! Learn more about your options to help you make the best choice.

If you have any additional questions, contact our team today at (763) 400-8616 or online!

What is Polystyrene Insulation?

The Rigid Foam Insulation

Rigid foam is primarily installed in unfinished walls, roofs and foundations. The dense product provides a higher R-value than other types of insulation, allowing for excellent performance with very little thickness. Installing rigid foam reduces thermal bridging, raises the R-value of a wall or roof assembly, and greatly reduces air leaks.

There are two types of polystyrene rigid foam insulation:

  • Expanded polystyrene (EPS): With an R-value of 3.6 to 4.2 per inch, EPS is an effective way to insulate a home. It’s the less expensive option of the two and is most appropriate for above-grade applications.
  • Extruded polystyrene (XPS): An impressive R-value of 5 per inch, combined with high compressive strength and water resistance, makes XPS the perfect insulation for below-grade slabs and foundation walls.

Polystyrene Insulation in Minneapolis, MN

Available in rigid foam boards made from an expansion or extrusion process, polystyrene insulation offers easy on-site installation with only simple tools required to cut it to length or fit it around obstructions. It offers excellent insulation performance because it minimizes thermal bridging in wall assemblies and offers great resistance to airflow when sealed properly. At Metro Home Insulation, we carry two types of polystyrene insulation:

  • Expanded polystyrene – Made from expanded foam beads that are molded into shape, expanded polystyrene or EPS is ideal for above-grade applications such as exterior walls and offers an R-value of 3.6 to 4.2 per inch. Material costs are about &0.31 per square foot for each inch of thickness, plus installation costs.
  • Extruded polystyrene – Made from foam that is extruded through a die, extruded polystyrene or XPS offers impressive compressive strength along with an R-value of about 5.0 per inch. Because of its strength and durability, it is ideal for insulating below slab foundations or for below-grade foundation walls. It costs about $0.47 per square foot for materials at each inch of thickness.

What is Polyurethane Insulation?

The Spray Foam Insulation

Spray foam is the best type of insulation for reducing air leaks. It foams in place, allowing you to fill every nook and cranny. This makes spray foam ideal for oddly shaped spaces and filling gaps around floor and wall penetrations. However, because spray foam must be mixed on-site and applied while wearing special protective clothing, you must leave installation to the professionals.

There are two types of polyurethane spray foam insulation:

  • Open-cell polyurethane foam: Expect an R-value of about 3.6 per inch. Open-cell foam is permeable to moisture but impermeable to air. This makes it ideal for insulating roof assemblies that need to dry inward.
  • Closed-cell polyurethane foam: Closed-cell foam offers the best R-value per thickness of any insulation, at about 6.5 per inch. It has a glue-like consistency, adding structural integrity to any wall or ceiling you apply it to. This option is pricier than open-cell foam, but because it provides better R-value per inch and also acts as a vapor retarder, it may be the better option for your situation.

Polyurethane Insulation in St. Paul, MN

Offering superior insulating and air sealing performance, polyurethane insulation is a great way to minimize heating and cooling costs in any building. It is sprayed in place by a professional, filling all voids and gaps while creating a tight vapor seal. We offer both open-cell and closed-cell polyurethane spray foam, depending on the application.

  • Open-cell spray foam – Offering excellent air sealing performance while allowing moisture to pass, open-cell spray foam is ideal for areas that see occasional moisture and can naturally air-dry, such as the underside of a roof assembly. Open cell-foam features an R-value of about 3.6 per inch, and it typically costs $0.45 to $.65 per board foot.
  • Closed-cell spray foam – Featuring impressive moisture and air resistance, as well as high insulation values, closed-cell spray foam is ideal for any area that needs high-performance, airtight insulation, including walls, ceilings, floors, garages and more. It also offers high rigidity for improved structural integrity. At an R-value of 6.0 to 6.5 per inch, with a cost of $1.00 to 1.50 per board foot, it offers tremendous value for its performance.

To learn more about insulating your Minneapolis or St. Paul home, read this article from the U.S. Department of Energy or this guide to home insulation.

Install Foam Insulation in Minneapolis-St. Paul

Although polystyrene insulation (rigid foam) is often installed during new construction, there are sometimes exceptions for retrofit projects. While this can be a difficult decision, the team at Metro Home Insulation & Waterproofing is able to help you with any of your questions!

For help choosing between polystyrene rigid foam and polyurethane spray foam, and then installing the insulation, contact Metro Home Insulation & Waterproofing either online or by calling (763) 400-8616.

Products We Install

We install blown and batt fiberglass in homes and buildings.


Environmentally friendly and effective, cellulose works well in homes and buildings.

Spray Foam

Our team installs energy-efficient spray foam insulation to keep homes and buildings more comfortable.


Help prevent mold and moisture infiltration in homes you build with our waterproofing services.

Insulation Removal

Metro Home Insulation provides home insulation removal services.

Air Sealing

We include air sealing in our insulation projects to help maximize your energy efficiency.

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