Last week, we examined how “stack effect” robs homes of their HVAC efficiency by funneling warm, treated air upward through multi-level homes and allowing it to escape through the attic. This week, we’ll take a look at “reverse stack effect”, which pushes cooled air out of a home through basement air leaks during the warmer seasons.

While the summertime reverse stack effect doesn’t have as large of a negative impact on climate control as the wintertime stack effect, it’s still an inefficiency worth investigating and correcting. And with warm weather on the way, now is a great time to prepare to address this issue.

The Flip Side

The principle that makes stack effect work is the exact opposite of reverse stack effect, and it’s based on the law that cold air is denser and heavier than warm air. During winter, cold air leaks into homes at ground level, pushing the lighter, heated air upwards. When this reaches the top level of the home, it can easily escape if the attic floor isn’t sufficiently insulated.

During summer, the pressure created by the hot outdoor air pushes air conditioned air lower. If there are cracks or air leaks in the basement, the air you paid to treat is forced out. Even small leaks, if numerous enough, can make a big difference in your summertime cooling bills.

Plug the Leaks

Whether you have a finished basement or an all-concrete space you use for storage, locating air leaks can be a challenge. They’re not always obvious or easy to access. If you really want to track them down, the best way is often to arrange an energy audit in which technicians use heat-detecting radar technology to see air actively leaking, even though it’s invisible to the naked eye.

Once you know where the leaks are, the next step is to seal them well. High-quality caulk is a good choice for fine cracks in concrete. Closed cell spray foam insulation is often the best choice for most basement applications because it’s easy to apply, it adheres well to a variety of surfaces and it creates an air and watertight barrier.

Traditional fiberglass insulation is an option for some basements, but not all of them, and the difference comes down to moisture. If your basement is often damp, installing fiberglass insulation can be a big mistake. The insulation can trap moisture and eventually develop mold, ruining the material and presenting a health hazard.

That’s the Spot

Placement of insulation is also a consideration. Some homeowners install insulation in their basement ceilings to create a barrier separating the first floor of their homes, but this is rarely an effective measure. All of the pipes, cables and other necessary household arteries that permeate this layer allow air to pass between the two floors, and that’s not to mention the basement door, which allows plenty of air movement.

The most critical parts of a basement to insulate are the sections of wall that sit above ground level. These are often pure concrete, which is a poor material for insulation, and the exposure to the outdoor air on the other side allows a fair amount of treated air to escape and outdoor air to seep in.

If you’re in need of an HVAC specialist who can assess your energy efficiency and find hidden air leaks, reach out to your local climate control experts for a no-obligation consultation.

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