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Technical Papers

What Is The Stack Effect

Sunday, January 15th, 2023 by Aaron Stull

The "stack effect" is a phenomenon that occurs in buildings due to the difference in temperature and pressure between the inside and outside of the structure. This difference causes air to move in and out of the building through various openings, such as windows, doors, and vents. The stack effect is particularly relevant in tall buildings, but it can also occur in single-story homes.

 

What Is The Stack Effect - Image 1

 

The stack effect is created by the fact that warm air rises and cold air sinks. In a building, warm air inside the structure rises and escapes through openings at the top of the building, such as a skylight or attic vent. At the same time, cold air is drawn into the building through openings at the bottom, such as a crawlspace or basement. This creates a constant flow of air in and out of the building, which can have a significant impact on the home's energy efficiency and indoor air quality.

 

 

One of the biggest issues associated with the stack effect is the potential for moisture to be brought into the building through the crawlspace or basement. Moisture can cause a variety of problems, including mold, wood rot, and increased energy bills.

Mold is a common problem associated with moisture in buildings. When moisture is brought into a building through the stack effect, it can lead to the growth of mold on walls, floors, and ceilings. Mold can cause a variety of health problems, including allergies, asthma, and respiratory infections. It can also weaken the structural integrity of the building and cause damage to finishes and furnishings.

 

 

Wood rot is another problem that can occur when moisture is brought into a building through the stack effect. When wood becomes wet, it can begin to rot and weaken. This can lead to structural damage, including sagging floors and ceilings, and can also make the building more susceptible to pests.

 

 

Increased energy bills are another issue that can occur when the stack effect brings moist air into a building. When air is brought into a building through the crawlspace or basement, it is typically cooler and more humid than the air inside the building. This can cause the HVAC system to work harder to maintain a comfortable temperature and humidity level, leading to higher energy bills.

 

 

To combat the stack effect and the associated problems, there are several steps that homeowners can take. One of the most important is to ensure that the crawlspace or basement is sealed to prevent outside air from coming inside.  Additionally, the air in the lower levels of the home or building should be conditioned to have the appropriate amount of humidity. This can be accomplished by installing basement waterproofing and/or encapsulation practices as well as dehumidifiers.

 

 

Another important step is to seal any gaps or openings in the building that may be allowing air to move in and out. This can include sealing around windows, doors, and electrical outlets, as well as sealing gaps in the foundation and around pipes and ducts.

Homeowners should also be sure to monitor the humidity levels in the home. If the humidity level is too high, it can indicate that there is a problem with the stack effect, such as an insufficient amount of ventilation or too many gaps and openings in the building.

 

 

In addition, regular inspection of the basement and crawlspace for any signs of water damage or mold growth can prevent bigger issues down the road.

 

 

In conclusion, the stack effect is a phenomenon that occurs in buildings due to the difference in temperature and pressure between the inside and outside of the structure. This can cause air to move in and out of the building, bringing moisture with it and creating a number of problems such as mold, wood rot, increased energy bills and other damage to the home. To prevent these issues, it is important to ensure the crawlspace or basement is sealed and any gaps or openings in the building are fixed.  Additionally, monitor humidity levels, and regularly inspect the basement or crawlspace for any signs of moisture.

About the author
Aaron Stull is a second generation foundation repair specialist from the greater Pittsburgh, Pennsylvania area.

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