When buying a whole house fan, there are a number of issues to consider beyond how much air it moves, how it installs, and how much power it consumes. 

By design a whole house fan is mounted between the house and the attic.  When the fan is not running, the hole that the air moves through must be positively closed, or the air will continue to move from the house to the attic!  It is like leaving a window open.  In a cold climate warm, humid air from the house will flow into the attic.  The moisture in the air will condense on the cold surfaces (just as it does on cold window surfaces), and water will drip on the insulation and mold will grow.  Closure systems that do not seal positively will not only lose conditioned air but can cause serious damage to the house.

Flow through a fan changes as obstacles are put in the path.  Grilles, ducts, and gravity dependent backdraft dampers will all reduce the amount of air a fan is able to move.  In some products, such obstacles can reduce the installed air flow by 40% or 50%!  Independent laboratories (such as HVI) can rate the air flow of the product as a system.  For example,  a fan rated at 1500 cfm that uses a grille, ducting, and gravity damper will have a true flow rating of 750 cfm or less! 

Air blown into the attic must be allowed to escape from the attic to the outside otherwise the air will seek other outlets like flowing back down the walls of the house and in through outlets and light fixtures. If you do not have the required net free area, you will not only be pumping heat back into your home but the dusty, smelly attic air as well. Divide the fan’s flow by 750 to determine the necessary, clear opening to the outside.  (Insect screens are particularly restrictive to air flow.)  For example, a 3000 cfm fan would require an open hole of 4 square feet to the outside.  If the hole is covered by an insect screen, the hole would need to be twice that size.

Any sound rating of a fan in “sones” must be performed in a certified laboratory.  At this time, there is no laboratory or standardized test for sound level of whole house fans.  Any sound rating in “sones” in the specifications of a whole house fan is only a manufacturer’s guess.


REWCI.COM is proud to feature fans manufactured by Tamarack Technologies Inc.  We firmly believe that the Tamarack fans are top of the line in their class.  Over the past several year, a "copy-cat" prototype of the Tamarack HV series fan has appeared from another manufacturer.  Caveat Emptor - Although the products may look similar, they are not.  We are dedicated to educating and informing consumers regarding the use of whole house fans.  We stand behind every claim we make which we know is the truth.     
 

Tamarack Technologies Inc. has been making its Whole House Fans since 1994.  They have been installed in thousands of homes in all climates.  They have been independently tested at the HVI laboratories at Texas A & M University for air flow and seal.  Air flow rates are accurate and true.  They have been tested in numerous houses that have been “blower door” tested and have been found to have virtually no leakage.  Test results are available upon request.