Whole House Fan FAQ
What is the difference between whole house cooling and air conditioning?
Whole house fan cooling draws hot trapped air out of the home while bringing fresh cooler air inside. Air conditioning uses a compressor to remove humidity and chill air.–A much more energy intensive process. Many folks find that extending the hours of natural cooling and limiting the hours the air conditioner is run, not only saves energy, but also increases the comfort of the home.
Can I use both an air conditioner and a whole house fan?
YES, definitely, but not at the same time. In Hawaii, the whole house fan is most often used when the outside air temperature is 86 degrees or below. The air conditioner can then be saved for when temperatures are above 86 degrees or on days of high humidity. In homes without A/C, or where natural air is preferred, the whole house fans can provide year round cooling, but are less effective in temperatures over 86 degrees, or on days with high humidity.
How can a Whole House Fan cool your house when the temp outside is 84?
With a whole house fan properly sized for your home, it will be able to exchange the air volume of your home every 3-10 minutes. This rate of air movement gives you a cooling effect of 4-6 degrees, so your home can feel as if it is 78-80 degrees.
How do you calculate the ideal rate of exchange in CFM?
The square area of your home in feet is multiplied by the height of your ceiling for the volume of the home in cubic feet. The CFM output of the fans are listed on the Products page. Divide the volume in cubic feet by the industry air exchange standard of 3 and you will get the targeted CFM. For example, a 1,200 square foot home with 8 foot ceilings will have a volume of 9,600 cubic feet. Divide 9,600 by 3 minute target air exchange and you have an ideal air exchange rate of 3,200 CFM.
Does a Whole House Fan have to be centered in your home to work effectively?
No, but it does matter where your open windows are located. Air, like water, flows in the path of least resistance. The bigger the window and the closer to the fan, the less resistance that location provides. This can mean opening windows strategically to channel air to specific areas of the home that you want to cool. Please note that jalousie windows cannot usually be sealed completely and even when closed may affect the path your air takes to the fan.
In zones where there is no circulation, additional fans can be used to target those specific areas.
How do I get the Breeze Effect from my Fan?
A Whole House Fan is very effective in moving a large quantity of air. The QC4500, for example moves 4500 CFM. If 4,500 cubic feet of air per minute is moved through only one window you will feel a very consistent breeze. To decrease the strength of the breeze simply open another window. Now the 4,500 CFM is divided between two windows at 2,250 CFM per window, 4 windows would change the air flow per window to 1,100 CFM. (A room fan moves about 1,400 CFM) Opening more windows doesn’t decrease the overall airflow, but decreases the airflow per opening for less breeze per window. To increase the Breeze Effect, target the area of the house by closing some windows.
Please note that jalousie windows cannot usually be sealed completely and even when closed may affect the path your air takes to the fan.
Can I put a Whole House Fan anywhere I want?
The placement of the whole house fan depends on how your house is built. Traditional belt-driven fans usually required 5 feet of attic clearance, while ducted QuietCool fans can be installed in as little as 24 inches of clearance. An inspection is helpful to determine where it should be placed.
What about ventilation?
A whole house fan can only pull in as much air as it can push out of your attic. The 2009 IECC (Hawaii Energy Code), the FHA and many roofing companies recommend 1 foot of attic ventilation for every 300 square feet of attic space. This means that a 1200 square foot single-story home should have four feet of attic ventilation. As part of the inspection process, we will check to make sure that you have adequate ventilation and make recommendation for correction if venting is insufficient.
Are they noisy?
Past fans had a reputation for being noisy. Using insulated ducts, and optimized motors, QuietCool whole house fans are the quietest systems available with sound levels that vary from 43dB (decibels) to 57dB depending on the size of the system. For comparison, this is similar to a normal oscillating fan on low or high.
While these sound levels are considered very quiet, not all systems are appropriate for installation in all areas. (You wouldn’t want to put a larger unit in a bedroom). Also, since many Hawaii homes lack insulation, it’s important to talk with a consultant who can help you to determine the correct system and location for your home.