Considering an attic fan to cool your attic?
Have you ever been in your attic in the middle of the summer? It’s HOT! Attic ventilators were engineered and installed in some homes to assist in cooling the attic and lowering the utility bills. An attic ventilator exhausts the hot air from your attic and brings in cooler air from the outside. This circulation of air reduces the heat in your attic in more ways than one. Recent research has proven the attic fan also pulls air from within your home through penetrations in the attic floor. This air removed from within your home has been cooled with your air conditioner which is part of the monthly cost to run your air conditioner and at the same time your utility costs are increased with the energy it takes to run the attic ventilator. To make matters worse the air removed from within your home with the attic ventilator is replaced by warm air from out doors which now has to be cooled adding more dollars to your energy costs. Keep in mind that the original ventilation of your attic was designed for passive ventilation not powered ventilation. If you insist on installing an attic ventilator you must add enough additional openings in the roof, or a gable end, or other areas where air may enter your attic to allow the ventilator to pull air through the attic without causing the attic pressure to become negative relative to your home.
A simple and safe method to see if your attic ventilator is pulling air from within your home. with the ventilator operating (try mid or late afternoon on a hot day) using artificial smoke, blow the smoke towards a light switch on any wall and you will see the smoke drawn into the switch plate. The ventilator is typically set to start running when your attic reaches 95 degrees which will normally be when the outdoor ambient reaches about 80 degrees. For every hour the ventilator is running which can be as long as 16 to 18 hours on the hottest days you have not only the phenomenon described above but that ventilator motor is using as much energy as 500 watts hourly!
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