from Nancy in Wauwatosa, WI :
#208
Can you explain air flow in a house which has a basement, a first floor and a second floor? Is there such a thing as negative flow which causes cooler air to flow down basement stairs much like a cold air return? If the second floor is not used at all, should I close all the vents and the door to that level to save energy? What about an unused room on the main floor?
Typically, air flows out of the top of a home.
Typically, air flows out of the top of a home (called exfiltration) with most of the replacement air, (known as infiltration), coming into the home in the lower regions, especially through openings in and around the foundation walls. This is known as stack effect, causing negative air pressure in the basement which is why the basement and the first floor are cooler. Because cooler air is more dense, it is heavier, therefore, dropping or falling into the lower areas of the home. While some energy savings can be achieved by closing off unused rooms or areas, it is not recommend to close all vents completely because lower air temperatures causes the relative humidity (how moist the air is) of the air to become higher. This may lead to unwanted condensation forming on surfaces (exterior walls, windows, ceilings, etc.) that fall below the dew point temperature.
Published Tuesday, May 19, 2009