Learn About the Stack effect

Why the stack effect is a cause for concern

Doc Crawlspace LLC makes every attempt to protect your home from HVAC issues and save you money. We'd like you to know about the stack effect so you can be ready to handle it if you notice your utility bills being higher than usual.

The stack effect is the movement of air as it circulates in and out of your home due to temperature differences between the indoor and outdoor environments, largely controlled by HVAC systems.

In cold winter weather, we aim to keep our homes warm by using fireplaces and heating our HVAC systems. Conversely, during the summer, we strive to keep our homes cool and comfortable. These temperature differentials cause the stack effect, driving air through the attic and crawlspace repeatedly.

To put it simply, hot air rises and cold air settles. During the heating season when we are running our furnaces, heaters, or burning wood, we are producing heat. Hot air rises. As that hot air is rising it is pulling cool air upwards. If you have a crawlspace that air that is being pulled up is coming right from the crawlspace. It is the same thing with a basement.

During the cooling season, the cold air settles. As that cold air is settling it is pulling warm air down from the attic.

What Happens During Winters?

During the Michigan winter months, the arrival of harsh and cold weather prompts homeowners to use heaters or switch their HVAC units to the heating mode to maintain a cozy temperature indoors. As the dense cold air outside causes warmer air inside to rise towards the upper levels of the home, a pulling effect is created in the lower areas such as the basement and crawl space, allowing cold air to move upwards. This movement of cold air displaces the warm air, which then escapes through uninsulated areas like attics and exits outside.

What Happens During Summers?

Something similar happens in summer but in reverse. By turning on air conditioning units to circulate cool air throughout the home, the intense heat outside becomes more tolerable. The cycle of the stack effect resumes as cool, dense air is drawn downwards into the lower areas of the house and exits through the non-air-sealed basement. Consequently, hot air from outside is drawn inside through an uninsulated attic, thus reversing the stack effect.

Is the Stack Effect Bad for Your Home?

It certainly is! The stack effect, with its ongoing cycle of hot and cold air exchange, places added strain on your HVAC system as it struggles to regulate the desired temperature, leading to increased energy consumption. The lack of proper insulation in the crawl space and attic further exacerbates this issue, driving up energy costs and necessitating more frequent maintenance and repairs.

Can I do anything to combat it?

Stack effect is also known as the chimney effect. It is the movement of air into and out of buildings through unsealed openings, chimneys, ventilation flue stacks and crawl spaces. This results from temperature and moisture in air from air buoyancy differences with indoor to outdoor air densities. These differences result in either a positive or negative buoyancy force. The greater the thermal difference and the overall height of the structure the greater the force that creates stack effect.

The stack effect plays a significant role in home heating mainly in colder climates. Warm air is lighter and rises and escapes through any openings or gaps in the roof. This is a major contributor to loss of heat making your home less comfortable and causing more energy usage to maintain the desired temperatures. With the ever-increasing cost of natural gas, we should be doing everything we can to conserve our energy.

How does stack effect impact indoor air quality? Ever since forced air was brought into our homes, we have been facing indoor air quality issues. Our HVAC system is a circulatory system. As the system is blowing air into the different areas of our home, another function of the system is pulling air into the system. This causes air to be pushed and pulled which in return pulls microscopic particles from every part of our living space and delivers it throughout our home. As the hot air rises it pulls things from the crawlspace into the home. Earthy smells come from the crawlspace. These are soil gases. When Radon is present in the crawlspace stack effect can pull these gases into the home. Mold spores are also lighter than air and tend to get pulled into the home as well.

Most homes that have duct work in their crawl spaces have vents directly blowing in their crawl space. This contributes to the bad air coming into our homes. Properly sealing your crawl space and insulating your attic will help to reduce the overall impact stack effect is having on our home, health and wallet. Give us a call today for a free consultation.