Extension and Ag Research News


Insulate Basements to Save Money

Insulating foundations or basements can be one of the best ways to cut heating costs.

Summer is a good time to prepare to save money this winter.

“Depending on the construction of your home, one of the most cost-effective ways to save money on heating costs would be to insulate an uninsulated foundation or basement,” says Carl Pedersen, North Dakota State University Extension Service energy educator. “Many people believe that basements are supposed to be cold. That is simply not true. Basements are cold because they are either poorly insulated and not heated or both.”

The NDSU Extension Service has a new free publication, “Insulating to Reduce Heating Costs,” that can help homeowners insulate their foundation or basement, as well as other parts of the house. The publication educates homeowners on where to focus their insulation efforts, the types of insulation available, how to compare the cost of various types of insulation and how to install insulation.

The publication is available through the NDSU Agriculture Communication Distribution Center at NDSU.DistributionCenter.ndsu.edu or (701) 231-7882. It also is available online at http://www.ag.ndsu.edu/pubs/yf/home/ae1368.pdf.

While a basement need not be heated, it always should be insulated, according to Pedersen. The misconception that the foundation or ground will insulate the home is costing homeowners money.

Concrete is an extremely poor insulator. A material’s resistance to heat transfer is measured as R-value. The R-value of 10 inches of poured concrete is 1, the same as a single-glazed window. An uninsulated foundation is similar to surrounding the entire house with single-glazed windows.

Insulating an uninsulated basement wall to R-19 can save homeowners 20 percent on their annual heating bill. If the heating bill is $1,000, the added insulation could save $200 per year.

Homeowners can insulate either the outside or inside of a heated basement, Pedersen says. If finishing the basement, insulating the interior wall surfaces is the easiest. If the basement already is finished, or if the homeowner doesn’t plan to finish it, the best option is to insulate the exterior wall surface.

A basement insulated on the outside of the wall results in more heat storage than insulating on the inside. The concrete stays warmer and will release heat to the house if the home heating system temporarily fails. It also keeps the footing warm, limiting the potential for soil movement due to freezing.

If insulating the inside foundation wall, the first step is putting up vertical furring strips or 2- by 4-inch framing. Put batt, blanket or rigid insulation between the strips. Install batt or blanket insulation with vapor retarders by stapling the edges of the retarder to the front of the furring strips.

Pedersen cautions homeowners to be sure that type of insulation has a vapor retarder. Batt and blanket insulation is becoming less common in basement insulation due to moisture problems. Moisture can enter the insulation from both sides, reducing its R-value and creating the potential for mold growth. Rigid insulation is becoming the insulation of choice for basements.

Polystyrene rigid insulation is the most common basement wall insulation because of its higher R-value and better moisture resistance. Simply glue rigid insulation to the wall or attach it to furring strips and finish the wall with a 15-minute fire-rated thermal covering.

Rigid insulation is used to insulate the outside of a basement wall both above and below the ground level. Remove the soil from the outside foundation to a depth of 4 feet and glue the rigid insulation to the foundation with construction adhesive. Make sure to cover any exposed above-ground insulation to prevent degradation by the sun and other elements.

When insulating a basement, an often overlooked area is the rim joist. This is the area where the wall framing meets the foundation. Cut rigid insulation to fit these areas and caulk the seams to ensure the least amount of air infiltration possible. Cover the insulation with a 15-minute fire barrier.

Fiberglass insulation also can be used in the rim joists, but a vapor retarder must be installed to reduce moisture problems.

For more information on this or any other energy-related topic, contact Pedersen at (701) 231-5833 or carl.pedersen@ndsu.edu, or visit http://www.ndsu.edu/energy.

NDSU Agriculture Communication

Source:Carl Pedersen, (701) 231-5833, carl.pedersen@ndsu.edu
Editor:Ellen Crawford, (701) 231-5391, ellen.crawford@ndsu.edu
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