Get Started Cutting Your Cooling Costs Now: Whole House or Gable Attic Fans

Right now with these cooler autmn temperatures is the time to go an work in your attic adding insulation before winter's cold.

But you can also do some planning for the summer heat.

Air conditioning might be an effective way to cool your home but there are other active systems that can cool that cost less: the whole-house fan and the gable attic fan.

A whole house fan is mounted in the ceiling of an upper story area — typically a centrally located hallway. By opening windows, cooler outside air is pulled into the living space and hot, humid air gets sucked out from the home's thermal envelope and blown it into the attic space.  It is inturn vented through the attic vents. The US DOE has a handy publication online  which states a whole house fan can save $250 per cooling season (based on 8.5 cents/kWh).  Air conditioning might cost roughly 20 cents/hour run time while a whole house fan cost 1 cent per hour run time.

The trick to making a whole house fan save oney is know when to run it.  The best time is when temperatures are cooler outside than inside your home.  This is usually true in the early morning hours and particularly evening hours (when your home radiates heat it absorbed during the day).  Running it in the middle of the day would just suck in heat and humidty from the outside.

There are two potential drawbacks to whole house fans.  One is that traditionally whole house fans tended to be noisy and the vibration carries through out the house.    Newer models are better constructed so that both motor noise and vibration are dampened.  The other problem is that whole house fans need to covered up and sealed properly in the winter to prevent mold, mildew, ice dams, and heat being vented from the living space.  This happens because a whole house fan is a big hole in your ceiling; heat and water vapor can escape into the attic area unles that hole can be covered during the heating months.  Newer whole house fan installation kits include fan covers or mounting fasteners for fan covers.

Gable Attic fans are fan units that install onto one of the gable vents in your attic.  They blow cool outside air into your attic while hot air exhausts out the far end (or through other venting ducts in the roof).   This works because during the summer, temperatures in an attic can climb to 150 degrees fahrenheit.  Your upstairs rooms become hot and this adds to your air conditioner's cooling load.  Keeping your attic cooler means its easier for the air conditioner to maintain the desired temperature in your living space as well as help reduce humidity.  Your AC until will run less.  Also, by cooling the attic, it will help preserve your roof and make it last longer.  Gable fans can be controlled with a thermostat to switch on at a preset temperature.

Which one is best?  That depends on the climate where you live, the type of house you own, how big it is, how well your attic is ventilated, and how you prefer your home's temperature.  The best thing to do is collect your information and do some research and then decide.  You may decide that both might do the job: the house fan for those times it's not too hot to run the AC and the gable fan to assist the AC on those scorching days.