November 2012: Whole-House Fans
Guy’s Corner: Whole House Fans
Whole-house fans, when properly installed, operated and utilized, during the most beneficial part of the day, can substantially reduce the cooling load and provide almost immediate comfort. But let’s breakdown what properly installed means. Most of existing units we see out there today are loud, vibrating monstrosities which try to employ a louvered grate positioned on the surface of a centrally located ceiling. Seldom do we see an effective air tight box that encases the fan in the attic—one which the homeowner can easily access/remove/reinstall when necessary. When not in use, many whole-house fans are basically nothing more than a nine feet square opening into a vented attic, which may or may not have enough intake/exhaust capability.
In terms of operation, they can be used during nights when the outdoor temperature falls and cool air can be drawn into the house during after the sun goes down. Obviously, one of the biggest concerns is having enough windows open, so that when the fan is turned on, it does not draw combustion gases into the living spaces. Another concern is that whole-house fans are not well suited to very humid climates because they bring in moisture with the air, and it is up to the homeowner to judge outdoor humidity.
The best use of whole-house fans is really then driven by climate and locale. In the northeast, there are considerably more evenings when a whole house fan can be employed. In western states, were the climate is dry, there are also many nights when employing a house fan makes sense rather than running an AC unit. But in a mixed humid climate or predominantly a humid climate like ours, their hours of effective operation fall off dramatically.
Tamarack Technologies has been making quiet, efficient, maintenance-free fans for more than a decade that can service homes from 1,000 to 3,000 square feet. They have air tight, gasketed, well-insulated, motorized doors (R-22-R-38) that when closed remotely provide almost no exchange between spaces. Some findings have calculated that they could be one tenth or a one hundredth of the cost of running a window or central AC unit respectively. Making a sealed, insulated panel for the face of them can be done, but the cost and appearance must be weighed against removal or replacement.