I've been doing a lot of research lately on whole house fans, and wanted to share some of my findings. All whole house fans do one thing - and that is to bring night time air through the house and out through the attic. This cools off the attic (that can get up to 190 in the summer) and the house as well. You close up the house in the morning to keep that night time air inside. Some things that make a whole house fan work better - multi-level homes instead of large one floor ranch houses, a tight home, willingness to open windows at night, close them during the day.
Energy wise, a whole house fan is definitely a better alternative to an air conditioner in climates where nights are cool and days are hot. As an example, a typical central air conditioner costs in the neighborhood of $3500.00. A low-energy insulated whole house fan costs in the neighborhood of $1000.00 The operating cost of a low energy fan is about .14/kWH in an area where the cost of a Kilowatt hour is .25 and a home is around 2000 sq. ft. In the same area, same house, the cost per kWH for running an energy star central air conditioning unit is about $1.52/hour. You save money, and help reduce strain on the environment.
There are several things that are important to look at when buying a whole house fan (or, in my case, deciding which are the best fans to put on a website like ours - www.positive-energy.com).
1. CFM rating (cubic feet per minute of air that the fan will move) A good rule of thumb is to purchase a fan with a CFM rating double the square footage of your home. Many folks buy oversized, over noisy fans which leads to too much energy consumption, and an uncomfortable living environment.
2. Does the fan meet our requirements that it be a low energy user, and that it has some form of insulation that closes with a tight seal when the fan is not in use. The fans that I've seen that meet this requirement are the Tamarack HV series, the Airscape, and the Quiet Cool fans, with the Tamarack providing the best insulation.
3. Is the fan quiet enough that it will actually be used, and still allow you to carry on a normal conversation in your home? All of the above do this to a less or greater extent - the quietest being the Quiet Cool Series.
Yes, an air conditioner will work better for day time use for those of us living in a hot climate, but here are two options: One, use a whole house fan until inside air gets too warm, and then turn on the AC (maybe just a bedroom window unit). Two, if you live in a dry hot climate, use an evaporative cooler during the day for much lower energy usage. Better yet, use a whole house fan with an Envirocool two part evaporative cooler. The wet media and pump part of this swamp cooler is mounted in an exterior wall. The second half of the swamp cooler, the unit pulling this cooled air through your home, is the attic mounted whole house fan. Your home is cooled day and night while energy usage is kept to a minimum!
See our website, www.positive-energy.com for further info on low energy whole house fans and the Envirocool.
By the way, in many states evaporative coolers, whole house fans, and many other energy efficient products are eligible for rebates and tax credits. Here's an excellent website that let's you look at what incentives are available in your state. http://www.dsireusa.org/searchby/searchstate.cfm
