Technical Papers

Rim Joist Insulation Fixes Cold and Drafty Floors

Wednesday, November 11th, 2020 by Chelsea Bowen

Older homes and new construction alike can suffer from improper insulation. A variety of techniques and insulation types like fiberglass batting and foam board are widely used in walls, attics, basements. But one area that goes overlooked in most homes is the rim joist. Crucial in preventing air leakage and protecting the overall energy efficiency of a home, insulating the rim joists is a must!

What is a rim joist?
Illustration of poorly Insulated Rim Joists

A rim joist is found at the edge of the wood floor framing system that sits atop your foundation. It is the piece of lumber that goes around the outside perimeter of the home and comes into contact with your home’s sill plate and subfloor. It’s leaky and under-insulated, allowing air from gaps in the siding to enter your home.

Why does this matter?

The lower level of your home has negative air pressure. In other words, your basement or crawl space works like a vacuum and pulls cold, outside air inwards. This result is cold floors, drafty rooms, and high heating costs.

It is common to cut into the rim joist, making way for pipes, gas lines, and wiring, further contributing to air leakage.  A cold rim joist means that not only is cold air moving in, but it causes warm air to want to leave through the rim joist through what is called conductive heat loss.

How will DBS fix it right?

Our Dr. Energy Saver services offer a couple of solutions for insulating your rim joists:

Spray Foam and Foam Board Insulation

The all-star of rim joist insulation is closed-cell spray foam. This polyurethane insulation is a two-part system that once combined with the right pressure and temperature, expands to evenly coat the entire rim joist. It is able to navigate around ducts and wire, with an R-value of 11 per square inch.

Rigid foam insulation is another solution. We use a polystyrene expanded foam board that is cut to fit snugly against the rim joist. It is then sealed with expanding foam around the edges. DBS uses SilverGlo™, a graphite-infused foam board with an R-11 value.

DBS offers these insulation solutions for crawl spaces, basements, and attics in both homes and cabins throughout our service area of Minnesota and Wisconsin. Once this work is done, you won’t have to do it again, and the return on investment for lowering your fuel and electric bills is unmatched. 

Call us today at 1-855-259-9625 for a free, no-obligation estimate with one of our energy-saving experts. 

our service area

We serve the following areas

  • Brownsville
  • Caledonia
  • Canton
  • Dakota
  • Eitzen
  • Hokah
  • Houston
  • La Crescent
  • Mabel
  • Rushford
  • Spring Grove
  • Winona
Our Locations:

DBS Residential Solutions, Inc.
5116 Jean Duluth Road Suite 300
Duluth, MN 55803

DBS Residential Solutions, Inc.
6900 Shady Oak Rd Suite #120
Eden Prairie, MN 55344
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