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The Stack Effect: What It Is and How It Impacts Your Home

stack effect

Building science experts say that 50% of the air you breathe in your home comes from your crawl space.

Anything that is affecting the environment of your crawl space, be it mold, humidity, or waste from pests, is going to be carried into your home as the air moves through your home by the “stack effect.”

How Does the Stack Effect Work? 

As mentioned before, hot air rises. This is the main driving force behind the stack effect, and it can cause tons of problems for your home ranging from unhealthy air to mold growth, to high electric bills. 

  • Air Enters the Crawl Space 

The stack effect begins when air enters your crawl space from the outside. There are several methods by which air enters the crawl space, the most typical way being via open vents. However, air may also enter through crawl space foundation walls if they have never been adequately waterproofed with a vapor barrier. No matter how the air gets in, the essential thing to remember is that it is coming from the outside. Whatever the conditions are outside, those same conditions will be entering your crawl space and may cause other issues on top of the stack effect.  

  • Air Warms Up and Rises 

Next, the air will eventually follow the rules of thermodynamics, which state that warm air always rises. This process can occur in one of two ways. The first scenario is that the outside air will already be warmer than the crawl space when it enters, causing the warmer air to rise right away. The second scenario is that the air from outside will be colder than the air within your crawl space; if this is the case, the air will warm up more the longer it remains under your home until it eventually becomes warm enough to rise into the lower levels of your house. 

  • Air Exits Through the Roof 

The stack effect concludes with hot air exiting the home from the top, generally through the attic. Not only can this cause major problems to the structural integrity of your home, but it can also transport mold spores and other contaminants into the top floors of your house. Not to mention, this process will continue indefinitely. The stack effect isn’t something that occurs just once. It is a revolving door process that repeats as long as there is a way for outside air to enter your crawl space. 

The Risks of The Stack Effect 

Unfortunately, the stack effect doesn’t just move outdoor air into your home. This process can also transport mold, humidity, and unpleasant odors throughout your living space – each bringing its own set of issues that you’ll have to contend with. 

mold in crawl space

1. Mold Growth

Mold spores are tiny and lightweight, and they can be carried long distances as air travels up from your crawl space. When the mold spores settle on a suitable surface, they will begin to grow and reproduce. The ideal conditions for mold growth are in areas with warm temperatures, high humidity, and poor ventilation. In your home, the stack effect airflow can create these conditions for mold to thrive. As a result, mold might begin growing in closets or under sinks as warm air continues to travel throughout your home. You and your family are likely to breathe in these mold spores as well, which could lead to health problems. 

2. Rising Energy Bills

You might be surprised to learn that high energy bills are often caused by the stack effect. See, the stack effect can cause the temperature in a room to fluctuate, which can make it difficult on your HVAC system to keep the room at a consistent temperature. As the warm air rises, it might also bring humidity with it which only pushes your air conditioning to work even harder. Plus, the humidity could cause wooden structures in your home to warp, such as floorboards or wall studs. If left unchecked, the stack effect will cause your energy bills to continuously rise. 

nasty, smelly crawl space

3. Musty Odors

Unpleasant smells can also spread throughout your home as a result of the stack effect. When warm air rises, particles from pollutants such as animal feces, decaying matter, and mold are drawn up along with it. These pollutants then spread throughout your house and emit their unpleasant odors. Even worse, your nose might become accustomed to the smell over time and not even realize it’s still there. When guests come to visit your home, they’ll be hit by a wave of unpleasant odors. 

Stack Effect FAQs

No, the stack effect simply happens in all buildings. However, you can prevent the negative effects that come with it by installing crawl space waterproofing solutions. These include crawl space vent covers, vapor barriers, and dehumidifiers. With these tools, you can feel confident that any air rising in your home is at least temperature-controlled and healthy to breathe.  

Mold is a fungus that may cause allergies, disease, and, in the worst-case scenario, dangerous respiratory issues. Since some mold can damage your respiratory system over time, a moldy crawl space is always a health risk. Due to the stack effect, mold can create health concerns or you and your family even if you don’t spend much time in your home’s crawl space. 

The crawl space is essential for one simple reason: it houses many of your home’s most vital structures and systems. This includes your HVAC system, electrical wiring, plumbing, insulation, support beams for your floor, and your foundation. All of these can be put at risk due to the negative consequences of the stack effect when the process is left unchecked.  

Mount Valley Foundation Services Can Help With Your Crawl Space Issues! 

Have you noticed musty odors in your home but can’t pinpoint where they are coming from? Do your floors feel like they are sagging, bouncy, or uneven? Are your energy bills rising out of nowhere? These issues indicate the presence of crawl space problems. At Mount Valley Foundation Services, our team of foundation experts can evaluate your crawl space and recommend the best course of action to keep your home protected. 

Now that you understand the reasons these issues arise, contact us today so we can help protect your Charleston, Columbia, Greenville, or Savannah home. You don’t have to let crawl space problems creep up on you, stay prepared with our many crawl space solutions. 

Let our Crawl Space Experts help you

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Michael Wilcher

Michael Wilcher

Michael Wilcher is the Content Lead at Groundworks, helping us to answer all of our customers biggest questions about foundation repair, basement waterproofing, crawl space encapsulation, and concrete lifting. In his free time, Michael enjoys collecting vinyl records, watching Formula 1 Racing, and reading philosophy. He holds an MPhil from the University of Cambridge.

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