What is a whole house fan

• Posted on October 30, 2018
• by mikew
• in Fix It & Use It
• No Comments.

There are two types I’ve come across…

On hot summer nights my good friends have an interesting solution to cooling their house. Windows are kept open but their secret weapon is engaged when they flip a switch near their bed. A large fan turns on, metal louvers installed in their hallway ceiling open, and air begins to move. Hot air is pulled into the attic and cool air from the open windows flows through their house. Cool air on demand. Occasionally I come across this cool air solution which people call “whole house fans.”

Most references to “whole house fans” relate to construction since the 1990s. The purpose of these fans is to ensure proper air exchange. We have wrapped houses so tight with new energy codes (aka Saran-wrapping our houses) that it is difficult to replace household air with fresh outdoor air. Imagine constantly breathing in a paper bag! Stale air is what we breath if we do not ensure a regular, full house air exchange. These little fan timers should operate 2-4 hours a day.

Two problems to mention.

First, in the Northwest winter months our windows are shut tight and front doors rarely opened. While older homes have drafts and gaps to naturally permit fresh air (and heat loss), newer homes need venting options. Many windows are installed with little vent slots. Ensure these are open. In some situations wall vents are installed with a pull cord to open the cover. It may seem counter-intuitive to keep vents open in the winter. Open them. It makes for proper air flow, healthier living environment and will reduce moisture trapped in the house.

Second, these fans are often installed in laundry rooms and other spaces where doors are shut. Sometimes the fans are installed on the main level rather than upper levels. Laundry room doors and closets should be left ajar as much as possible. Vents can be installed in these doors or walls to help with air flow. Keep vent screens vacuumed and clear of dust buildup. If you have a poorly designed whole house fan system or no system at all, take advantage of nicer days, open your windows and air things out regularly!