The Stack Effect occurs when warm air rises out through air leaks in a home's upper floor and attic and at the same time draws outside air into the home through leaks in the lower floor and crawlspace or basement. The diagram at the top of the page does a good job of illustrating many common places air leaks occur.

One of the most cost effective things you can do to make your home more energy efficient is to create an air barrier by air sealing. An air barrier holds conditioned air in and unconditioned air out.  Every home has hidden air leaks that are robbing you of heating and cooling dollars. An air leak in a home occurs when air unintentionally leaks in and out of the living spaces (depending on weather conditions) through cracks and holes in walls, foundation, attics, the basement or crawlspace. For example, common places for air leaks to occur include anywhere there are electrical and plumbing penetrations in the walls, floors, and ceiling.

We always recommend air sealing and insulating the whole house at the same time because insulation is not an air barrier, it's a thermal barrier.  Insulation is very good at keeping cool or warm air in the home depending on the season, yet air can still pass through and around the insulation into the living spaces of your home. To learn more about insulation and air barriers, visit our insulation page.

It's important to align the thermal and air barrier in a home for optimal energy efficiency and comfort. When these weather barriers are not aligned, cold air leaks into conditioned spaces causing cool drafts in the winter, and high energy bills. A common example of this type of problem is an old enclosed porch that is insulated but doesn't have an air barrier. In this scenario, cold air leaks around and through the insulation into enclosed porch and into the home.

 

In this situation, our Building Analyst will work with the home owner to decide if it's better to "push" the old enclosed porch outside of the thermal/air barrier, or bring it inside the thermal/air barrier. Pushing the enclosed porch out of the thermal/air barrier means to create an air and thermal barrier on the wall bordering the house. To bring the old enclosed porch into the thermal/air barrier means creating a thermal/air barrier on the walls of the porch. These type of decisions are made on a case by case basis to accomplish the goals of the home owner.

To learn more about getting your home air sealed, visit the Getting Started page.