1. Since cold air is more dense warm air, it will always sink while warm air rises.

2. The stack effect occurs when there is a difference in both temperature and pressure between the indoor and outdoor environments. This differential creates a vacuum that draws in the cooler outside air through gaps in the bottom of the home.

3. As the cooler air enters the base of the home, the warmer, less dense air inside has nowhere to go but up.

4. Eventually, the less dense air is forced out through the top of the home, via cracks or holes in the roof.

5. As the warm air leaves, it creates space for more cold air to enter, and thus, a cycle is created.