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The Stack Effect: Everything You Need to Know

If heat is escaping from your home despite a functional heating system and adequate insulation, the problem could be the stack effect.

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The stack effect is a phenomenon that causes warm air to rise from the lowest to the highest point of a building due to variances in temperature and moisture levels. As the warm air rises, it creates a negative pressure at the building’s base, pulling in cold air to fill the void. This phenomenon is relatively common in homes with a basement or crawl space and can affect air quality and utility costs in a household. 

Home contractors and designers are generally aware of it, but most homeowners have no idea what it is. Let’s explore what the stack effect is, how it affects your home, and how to mitigate the issues associated with it. 

Understanding the Stack Effect 

Generally, the nature of heat and airflow is a confusing topic for most homeowners. Those in the home improvement sector believe that warm air rises, but heat does not. So, how can warm air rise and leave the heat behind?  

Warm air is typically lighter than cool air. When the air in your home warms up, it rises to the building’s upper levels. This reduces the pressure in the lower areas, allowing cold air to get in through windows, doors, and other openings.  

The stack effect is common during winter when the air outside your home is colder than your indoor air. During this period, the stack effect causes warmer air and your conditioned indoor air to rise. Cold air from outside seeps into your home’s lower areas to fill up the void left by the warm air.  

For every cubic foot of warm air that leaks out, another cubic foot of cold air leaks in to replace it. The greater the leaks within your house the higher the temperature fluctuations. 

Factors That Contribute to the Stack Effect 

Some of the conditions and factors that give rise to the stack effect include: 

Ventilation and cracks or gaps in the building: Cracks and gaps provide an entrance for outdoor air and an exit for conditioned indoor air. If these openings exist in your home, you are going to experience the stack effect. To prevent this scenario, seal these exit and entry points.  

Rising air:  When warm indoor air rises, it creates space for cooler outdoor air to replace it. Both types of air have different densities and will automatically arrange themselves regardless of the temperature. The warm air rises to the top and the cool air settles at the bottom.  

Airborne particles: Studies show that about 50% of the air in your basement or crawl space ends up in your living areas, thanks to the stack effect. This air not only brings with it moisture from the basement or crawl space, but also tiny airborne particles like dust mites, spores, allergens, and a host of other harmful microorganisms. These microbes can affect your health. 

Problems Caused by the Stack Effect 

Apart from contaminating the quality of air in your home, the stack effect can also instigate several other issues such as: 

Health issues: Air circulation is vital as it ensures a fresh supply of air. However, this can be a problem if your basement or crawl space is infested with mold, dust mites, odors, and other allergens. All these can rise into your home and trigger respiratory health issues, especially if you spend a great deal of time indoors.   

Mold and mildew: As outside air moves up your home, it can bring mold spores and water vapor into your living space too. Runny nose, allergic reactions, watery eyes, and persistent headaches that disappear when you go outside are indications that mold is present in your home.  

High energy costs: Energy goes to waste whenever conditioned air escapes your living space. In its place, cold outdoor air enters your home, forcing you to run your heating system. Ultimately, this results in higher energy costs. 

Moisture damage: Moisture rides on air currents. As moisture accumulates in your basement or crawl space, it causes staining, spalling, and efflorescence from the freeze-thaw cycles. You may start seeing its effects on brick.  

If your home is being impacted by the stack effect and excess moisture, contact a Foundation Recovery Systems professional for a free inspection and repair quote today.

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