How to Make Your Own Basement Ventilation System

Measure the width of your basement windows. Open them as widely as you can, then measure the height of the opening.

Purchase two fans sized to fit your basement windows if you are not planning on using the basement as living space. If you are planning on using the space as a living area, purchase one fan sized for a basement window and one for a window upstairs.

Place the fan in the basement window so that it will blow outward when it's turned on. This will exhaust the air from the basement to the outside. Screw the frame of the fan to the window frame so it stays securely in place and does not present a security risk.

Place the other fan in a window on the opposite side of the basement if you don't intend to use the basement as a living space. Orient this fan so that it will blow inward. Screw the frame of the fan to the window frame. This fan will draw fresh air from the outside.

If you intend to use the basement for living space, place this fan in an upstairs window. Placing the intake fan upstairs prevents negative pressure from occurring in the basement, which could cause gases to be sucked out of the ground and into the basement air.

Hook both fans up to automatic timers, following the manufacturer’s instructions. Set the times of day that you wish ventilation to occur. Make sure that both fans are set to turn on and off at the same times, and make sure ventilation is set to occur for at least eight hours of every day.