Stack Effect

The "Stack Effect" is a term that refers to the way that air moves throughout a home.

As the air in a home warms, it naturally begins to rise upwards, passing upwards from the lower levels.  Eventually, as this air is heated, it passes to the attic or top of the upper levels, exiting the home through the top of the house.  As this happens, it creates a vacuum in the lower levels of the home- one that is filled with new air from the basement, crawl space, and the air outside.

In a healthy home, a little air circulation is a good thing, as it keeps new air moving in at a reasonable rate.  However, if the basement or crawl space is infested with mold, mildew, dust mites, odors, or other unpleasant airborne pollutants and allergens, all of those things are pulled upwards into the home along with the air.  This can lead to many unpleasant health problems, as homeowners spend a great deal of time in their house every day.

In addition to causing health effects, the stack effect also means that any humidity in the lower levels, as would be common in a damp basement or vented dirt crawl space, will also be drawn upwards into the home.  This humidity can collect in the insulation on the crawl space ceiling, and it enters the home, it will raise utility bills by making the air more difficult to heat and cool.

Any basement wateproofing or crawl space encapsulation project you take on should keep this in mind.  Seal off crawl space vents, encapsulate the crawl space with a durable vapor barrier, and be sure to dehumidify your basement or crawl space to keep the moisture out of the home and to help prevent the growth of mold, mildew, and dust mites.