What is the Stack Effect and How Does It Impact Homes?

Think of your house like a chimney – air enters at the bottom, rises through the structure, and is expelled at the top. Air pressure also is a factor. Air flows from areas of high pressure to areas of low pressure. When there is a greater difference between indoor and outdoor temperatures, the more significant this airflow becomes. (Source: Fine Homebuilding) 

While you can’t see airflow, it might help to see this in action to get a better understanding of the stack effect. The Cold Climate Housing Research Center has several YouTube videos, including ”Your Nothern Home: Stack Effect” that illustrates the stack effect. 

Here are some other problems that result from open crawl space vents and the stack effect: 

• Water intrusion
  Any kind of water in your crawl space – whether it comes from the ground, through walls, through vents, or from plumbing leaks – is a problem. Standing, leaking water invites pests and promotes mold growth, and it can weaken wood and corrode metal support systems.
   
• High Humidity
  Along with leaking water, humidity is a major issue affecting homes. Humidity above 50% contributes to mold, unpleasant odors, failing support systems and more.
  
  High relative humidity and moisture is common in crawl spaces. These conditions promote mold growth, especially on organic materials like wood and insulation. Any crawl space moisture also can enter other areas of the home through wall, ceiling and floor cracks, and contribute to mold growth there. (Source: EPA)

• Wood Rot and Sagging Floors
  You’re probably well aware of how oppressive the North Carolina humidity can be. Your home is no stranger to its effects, either. When water, moisture, and humidity are present in the crawl space, this is a recipe for structural issues. As wooden beams and other supports are exposed to water and humidity, they can easily rot and begin to sag. These systems will no longer be able to support the above floor, and the floor will develop soft, bouncy spots and begin to sag.
   
• Energy Loss
  Open crawl space vents allow hot air to enter during the summer, causing your air conditioner to work overtime to cool the rest of the house. And the same happens with cooler wintertime air that makes your furnace struggle to keep up in maintaining a comfortably warm living environment. Floors often may feel cold because of the cooler air from the crawl space underneath. Rather than wasting money on high energy bills, close the crawl space vents for better energy efficiency!