Skip to Main Content

A Complete Guide to Understanding The Stack Effect

stack effect rendering

Wondering why your upstairs is always so much hotter than downstairs? That’s because of the Stack Effect.

Does the Stack Effect cause other problems (like mold) in my home? Sadly, yes.

Is there anything you can do about it? Yes!

In this article, we answer all your questions about the Stack Effect and what you can do to reduce its impact on your home and health.

What Is The Stack Effect?

The Stack Effect happens when cold air rises through your home, increasing in density and temperature with each subsequent level, and creates a continuous cycle of airflow from bottom to top.

In your home, the Stack Effect works like this:

  • Warm air enters the crawl space below your home.
  • The air goes up through your floor, seeping through access hatches, duct chases holes around wires and pipes, and joints in floorboards.
  • The air rises to higher levels, increasing in temperature.
  • As it escapes out of the uppermost level of your home, it creates negative pressure at the base of your home, drawing more air into your crawl space.
  • Rinse. Repeat.

While you’ll definitely feel the heat in the upper levels of your house during the summer, the Stack Effect is actually the most active when the difference between the temperature inside your home is significantly warmer than it is outside (ie. in the winter months).

Why The Stack Effect Is a Problem

The Stack Effect highlights three basic issues with your home. Each of these issues has to do with your crawl space.

moisture meter in a crawl space

1. Relative Humidity Issues

Relative humidity is the amount of water vapor that the air can hold at a particular temperature. For example, 100% relative humidity means the air is saturated and cannot hold any more water. When the air in your home cools, the water vapor condenses into water droplets, making the walls and floor damp.   

The ideal relative humidity range is between 30 and 50%. Higher humidity levels make the indoors uncomfortable, lead to mold growth, and can worsen asthma or allergies. Lower levels resulting in dry air can cause wood shrinking and wall and ceiling gaps, and you may experience eye and throat irritation.  

crawl space mold

2. Mold and Bad Air Quality

Building scientists say that up to 50% of the air you breathe on the first floor comes from your crawl space. If there’s moisture and mold in your crawl space, you’re breathing it throughout your home.

If your crawl space is taking in moisture with the air, mold spores will come up into the upper levels of your home with it. This is usually how you get mold in your attic.

Money paid for higher energy bills representation

3. Higher Energy Bills

With air flowing up into your home from your crawl space, your HVAC system is overworking itself to keep the interior at a set temperature. This naturally means higher energy bills that can increase by up to 25%.

Air in your crawl space may be too cold, and your upper floors may be too warm. That’s a big job for one HVAC system, and it’s not always up to the task.

What to Do About It: Crawl Space Encapsulation

According to the EPA, “If mold is a problem in your home, you must clean up the mold and eliminate the sources of moisture. Molds have the potential to cause health problems. Molds produce allergens (substances that can cause allergic reactions) and irritants.” The best thing you can do to put a stop to the Stack Effect is to fully encapsulate your crawl space.

Encapsulation seals off your crawl space from outside air and moisture, putting a hard stop to mold growth and needlessly high energy bills. To learn more about it, check out our Crawl Space Encapsulation page.

Put a Stop to Stacking Bills, Heat, and Mold. Call Tar Heel Basement Systems Today!

Tar heel basement systems box truck

If you live in North Carolina, call Tar Heel Basement Systems today. We’re the leading crawl space repair experts near you with decades of experience fighting the root causes of the Stack Effect.

We’ll get you on your way to a smarter, healthier home with a free inspection and estimate. Reach out today to schedule yours!

Let our Crawl Space Experts help you

Schedule free inspection
Schedule free inspection
Production crew installing ventilation.
Holly Richards-Purpura

Holly Richards-Purpura

Content Writer

Holly is a Content Writer for Groundworks who has written and edited web content for the foundation services industry for almost 10 years. With a background in journalism, her passion for the written word runs deep. Holly lives in Columbus, OH, with her husband. Along with educating homeowners, she also has a big heart for the Big Apple.

Publish Date:

Last Modified Date:

TarHeel Basement Systems Service Map

Our Locations

Fayetteville Location

3400 Walsh Pky, Suite 220
Fayetteville, NC 28311

Greensboro Location

611 Summit Ave, Suite 5
Greensboro, NC 27405

North Raleigh

208 Millbrook Rd. Suite C
Raleigh, NC 27609

Raleigh / Durham / Chapel Hill Location

3333 Air Park Road
Fuquay-Varina, NC 27526

Wilmington Location

2155 Enterprise Dr. NE
Leland, NC 28451

Winston-salem / High Point Location

2910 Griffith Rd
Winston-Salem, NC 27103