Sealing and Insulating a Stone Foundation Wall with Spray Foam

Dec 10, 2020

The typical basement is fairly easy to heat during the winter. A large portion of it is buried in the ground, and the ground temperature is quite constant year-round.
Why then are most basements so cold and uncomfortable during the winter time? Why are they such a huge source of energy loss?

There are three major reasons. The first is the humidity. Ground moisture seeps through the walls and evaporates into the basement, increasing the relative humidity levels. Moist air is very hard to cool and heat.

The other two major sources of heat loss can be found in the portion of the basement that protrudes from the ground. This area includes the exposed basement walls and the rim joists and when under-insulated and improperly air sealed, the space loses heat due to air leakage and conductive heat transfer.

The air inside a house has a tendency to travel upward and can leak of the home through the roof and upper levels of the building. This air movement generates negative pressure on the lower levels of the building, causing a lot of outside air to be sucked in through any holes and gaps in the rim joist and the exposed portion of the basement wall.

That exposed part of the basement wall is also made out of very conductive material, and without a layer of insulation, heat is constantly being transferred and lost to the outside.
Due to the moisture present in the basement walls, the best insulation materials are those that are both inorganic and impervious to water. Although fiberglass is often used for this application, this doesn’t mean it’s the best choice. For block and poured concrete walls, rigid foam board is usually the recommended material, because the walls are regular enough to have boards attached to them.

With stone walls, however, things are much different. In this episode of “On The Job,” Larry Janesky, owner and founder of Dr. Energy Saver, shows us the process of insulating stone wall basements using two-part polyurethane spray foam.

Closed-cell spray foam is an excellent choice for this type of application because of its high insulation R-value (R-7 per inch!), as well as its ability to expand to fill every gap and cavity in the basement wall, air sealing in one step. Closed-cell spray foam also acts as a vapor barrier, keeping ground moisture from evaporating into the basement.

Two-part spray foam application in such a large project requires massive power, and heavy equipment, tons of material, and experienced technicians in full protective gear. Home occupants and their pets need to leave the premises for a few hours, due to the fumes produced during the application.

When spray foam in used to insulate basement walls, it also needs to receive a special coating that acts as a thermal barrier. With only a couple of inches of two-part polyurethane spray foam, these basement walls have now an R-14 insulation value and the homeowner can enjoy added comfort and energy savings.

If you are paying too much for your heating and cooling bills, or have rooms in your house that are too cold or too hot, Dr. Energy Saver can help. Contact us to schedule an estimate with a dealer in your area.

For more videos and tips to save money and energy at home, watch our “On The Job” video series and subscribe to our YouTube channel for the latest updates.

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