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Do Attic Fans Save Electricity?

My second home is Phoenix has 3 attic fans, one on each end and one in the center of the attic. Some websites say that attic fans will save you electricity running your A/C. Other websites say the opposite that attic fans do not save on electricity. Are attic fans a good idea to save electricity or do they consume more electricity than they save? All the energy saving articles I have read avoids this issue.

- Bryan G. Prescott, Arizona

We have answers from two of our members with different thoughts concerning this question.

Going with the new solar powered attic fans would certainly put this question to rest and makes for a very short answer.An attic fan circulates air from outside of the home through the attic and is suppose to reduce the temperature in the attic.In the interest of the question, a normal attic fan pulls less than three amps which are about the equivalant of five lighted 60 watt light bulbs.Usually an attic fan runs around 12-14 hours per day coming on by about 10:00 am (at the high heat of the day when attic temperature is at about 100 degrees; and cycling off at night when the temperature reaches 60 degrees.Of course, the fan will run, depending upon the attic fan settings, types of insulation and amount of insulation installed in the attic.For an example, let’s say that the fan operates 14 hours a day, and in those 14 hours a day, properly sized and installed 4 ton a/c system would cycle 28 times.Your a/c system will pull 50 amps on start and then go back to 24 amps each cycle during normal running time.By running and operating an attic fan to remove heat from your attic you are clearly saving approximately two plus cycles on the a/c system.The savings on the a/c cycles will pay for the operation of the attic fan.That said, removing latent heat from your attic will always save energy plus maintenance costs on your a/c system.Attic fans require only a small fraction of energy to run, pulling much less power than an a/c system.

(Answer Mike Moyer, Owner, Moyers Heating & Cooling, Prescott Valley)

I have found that it is not a smart idea to run an attic fan in most homes.A better value would be to make sure the “envelope” of the home is tightly sealed and the ducting has no leaks.Most homes have numerous small holes in the “envelope” allowing it to “breathe”, which causes energy loss.These small holes come from such items as recessed can lighting, unsealed wire penetrations and dropped ceilings.Installing an attic fan increases the air changes within the occupied area of the home through the numerous holes in the “envelope” and this can drag in unfiltered, dirty, hot air into the home. This uses more energy and will make your a/c work harder and increase your electricity bill.If the ceiling is tight and insulated properly, new studies have indicated that homes are more efficient with no attic air movement.Many newer homes are moving the insulation to the roof line in lieu of the ceiling, to stop this air exchange to the attic.A qualified BPI Certified Building Analyst can perform testing on your home to see where your leaks are occurring and make recommendations for repairs.APS has several rebate programs to help with the cost of having this work done.Here are some webs sites that have interesting information in regards to exhaust fans.

(Answer Troy Koski, Owner, TDK Comfort Systems, Chino Valley, Arizona)

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