What is the Stack Effect or Chimney Effect?

Most of us learned in kindergarten that hot air rises and that cool air sinks. This basic law of thermodynamics, convection, governs many of the processes we see happening every day, from the rising of a hot air balloon to the way heat passes between the burner and the pot on your stove.

Convection also occurs in your home. And it's not something you should be excited about.

In cool winter months, indoor air that has been warmed by your heating system rises via convection to the upper areas of your house. Unfortunately, if your attic has not been insulated, this warm air doesn't stop moving. Rather, it escapes out the gaps and cracks in your attic roof, never to be seen again.

Stack/Chimney effect illustration for winter and summer

The reverse happens in summer. In warmer months, hot air outside an air-conditioned house can actually push cooler indoor air down from the sealing and out cracks in your basement. Throw in increased humidity and you have a recipe for water damage.

If it's all going to escape anyways, why, then, are you paying for heating and cooling?

Losing the air you've paid to warm is bad enough, but this isn't where the problem ends. Escaping air creates negative pressure inside your house - a vacuum that creates open space for cold outside air to swoop in and infiltrate your living space. Without attic insulation, there's no recovering!

Insulation experts call this the "stack effect." Symptoms of the stack effect include:

Feeling cold drafts near exterior walls, especially around windows and outlets
Super cold flooring, especially if directly above a basement or crawl space
Skyrocketing electric bills, particularly during winter months

Sound familiar? According to Department of Energy research (and our own personal experience working with this issue every day), the best thing you can do to keep your house comfortable (and your utility bills from drowning you) is to invest in attic air sealing and attic insulation. In fact, making an upgrade like this can cut your heating and cooling costs nearly in half!