What is the stack effect? Folks often feel like their home is drafty, but the science behind it is not often understood. We are here to break it down into five important facts about the stack effect, and how it relates to energy efficiency in a home.

1. The stack effect is one of three forces that move air through a house. The other two forces are HVAC equipment and wind. Though not as widely understood as HVAC equipment and wind, the stack effect is often the most powerful force moving air through a home.
2. Hot air rises because it is less dense than cool air. This creates pressure near the top of the house, when it is cold outside, and depressurizes the bottom of the house. Air escapes through cracks at the top of the house, as it moves from an area of high pressure to an area of low pressure, and cold air from outside finds its way into the bottom of the house, creating a flow of air inside the house.
3. During the heating season, the stack effect is strongest. When the outside air temperature is low, and the home is being heated, there is a greater difference between the outside air and the indoor air temperatures. This increases airflow, causing the stack effect to be greater.
4. In the summer, during the cooling season, the stack effect reverses. Because outdoor temperatures are higher than indoor air temperatures in the summer, there is a pressure difference between the air inside the top floor of the home, and the outside air. Air moves from an area of higher pressure (outside) to lower pressure (inside), which causes warm air from outside to move into the home through cracks and unsealed areas on the top level of the home. At the same time, cooler air contained in the bottom floor of the house is pushed out, creating a reversed flow of air. Warmer air enters the top of the home, and cooler air exits the bottom of the home.

• You can reduce airflow in your home from the stack effect! By identifying areas in your home where air is escaping or coming in, and sealing those areas, you can mitigate the stack effect and reduce air flow inside your home. This will help keep your home warm in the winter and cool in the summer. You may be thinking you need airflow in your home for indoor air quality; however, there are many ways to ensure ventilation for healthy air. 

What does this mean for energy efficiency in your home, and what are the first steps to address the stack effect? 

Enroll for an energy assessment from Energy Smart Colorado at Walking Mountains to identify the areas in your home that are leaky. After you know where to focus, there are a few different ways that you can air seal your home. Whether you decide to do-it-yourself, or hire a contractor, Walking Mountains is here to help you battle the stack effect to improve the energy efficiency of your house! When there is less air leakage, you won’t need to spend as much energy to heat or cool your home - a win for you and the planet!