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Whole House Fan or Solar Attic Fan?
| Natural Light Solar Attic Fan |
Actually, your home could put them both to good use. Although a whole house fan
and a solar attic fan are designed to serve different needs, they work well together
to keep your home comfortable in hot weather.
During the day a solar attic fan will exhaust hot air from the attic. In the evening,
when cooler temperatures prevail, an electric powered whole house fan would draw
cooler outside air into the house and force hot, stagnant air outside through gable
or ridge vents in the roof.
The cost to run the solar attic fan is zero, and the cost to run a whole house fan
averages 7 cents an hour. Even though a whole house fan is capable of moving
vast quantities of air it uses 60 – 70% less power than a typical space heater.
and a solar attic fan are designed to serve different needs, they work well together
to keep your home comfortable in hot weather.
During the day a solar attic fan will exhaust hot air from the attic. In the evening,
when cooler temperatures prevail, an electric powered whole house fan would draw
cooler outside air into the house and force hot, stagnant air outside through gable
or ridge vents in the roof.
The cost to run the solar attic fan is zero, and the cost to run a whole house fan
averages 7 cents an hour. Even though a whole house fan is capable of moving
vast quantities of air it uses 60 – 70% less power than a typical space heater.
Solar attic fan
Daytime temperatures in an attic can reach as
high as 150 in hot weather. These extreme
temperatures not only impede the efforts of
your air conditioner, they hasten the
deterioration of roofing shingles and shorten
the life of the roof.
A solar attic fan will prevent the accumulation
of hot air and reduce the temperature of the
rooms below.
Daytime temperatures in an attic can reach as
high as 150 in hot weather. These extreme
temperatures not only impede the efforts of
your air conditioner, they hasten the
deterioration of roofing shingles and shorten
the life of the roof.
A solar attic fan will prevent the accumulation
of hot air and reduce the temperature of the
rooms below.
If you have central air installed, a 10 degree drop in room temperature equals a
30% reduction in work load. Any reduction at all to the work load of your A/C
system means a smaller electric bill at the end of the month.
If you live in areas where humidity is a problem, a solar fan will help reduce
moisture build up and impede the growth of mold and mildew.
Solar attic fan sizing
Solar attic fans are rated in cubic feet per minute (CFM). This number represents
the cubic feet of air moved per minute; the higher the CFM, the more powerful the
fan.
According to the Home Ventilating Institute, to determine the correct cubic foot per
minute (CFM) rating needed, multiply attic square footage by 0.7. For example, a
1500 square foot attic x 0.7 would require a fan with a minimum rating of 1050 CFM.
To achieve this amount of air flow you would need at least one, 20 watt solar fan
according to manufacturer specifications. The smaller 10 watt fans are rated at 850
CFM (1,200 sq ft) and more powerful 30 watt models are rated at 1,550 CFM (up to
2,500 sq ft).
Does the fan need a thermostat?
A thermostat or humidistat is standard on some fans and an option on others. In
general, if you live in a climate that is predominately hot and/or humid you wouldn’t
necessarily need a thermostat since you would want the fan to be operational the
majority of the time.
In cooler climates like the northeast where attics stay cool (cold) most of time, a
thermostat would prevent the attic fan from turning on during the heating season.
Solar attic fan installation
The most common installation is through the roof but solar powered gable fans are
also available. The installation is relatively simple if you can follow directions and
have the DIY skills of an experienced homeowner. If you’ve successfully installed a
solar tube skylight then installing an attic fan should be no problem.
What happens when the sun goes down?
Some models of solar fans can operate after sunset powered by either a small
amount of electricity (2 watts), or passively using the Venturi Effect. The Venturi
Effect occurs when wind passes through the louvers of the vent causing the air to
spin creating natural suction.
Cost
Solar attic fans aren't cheap. Prices range from $350 for the 10 watt model to $600
for the more powerful 30 watt units; thermostat is extra. Solar attic fans may be
eligible for a 30% Federal energy tax credit up to $500. Qualifying models are
issued a certificate of eligibility.
If you are unwilling or unprepared to pay a premium price for solar powered
ventilation, you might want to look into a conventionally powered gable attic fan for
around $60.
30% reduction in work load. Any reduction at all to the work load of your A/C
system means a smaller electric bill at the end of the month.
If you live in areas where humidity is a problem, a solar fan will help reduce
moisture build up and impede the growth of mold and mildew.
Solar attic fan sizing
Solar attic fans are rated in cubic feet per minute (CFM). This number represents
the cubic feet of air moved per minute; the higher the CFM, the more powerful the
fan.
According to the Home Ventilating Institute, to determine the correct cubic foot per
minute (CFM) rating needed, multiply attic square footage by 0.7. For example, a
1500 square foot attic x 0.7 would require a fan with a minimum rating of 1050 CFM.
To achieve this amount of air flow you would need at least one, 20 watt solar fan
according to manufacturer specifications. The smaller 10 watt fans are rated at 850
CFM (1,200 sq ft) and more powerful 30 watt models are rated at 1,550 CFM (up to
2,500 sq ft).
Does the fan need a thermostat?
A thermostat or humidistat is standard on some fans and an option on others. In
general, if you live in a climate that is predominately hot and/or humid you wouldn’t
necessarily need a thermostat since you would want the fan to be operational the
majority of the time.
In cooler climates like the northeast where attics stay cool (cold) most of time, a
thermostat would prevent the attic fan from turning on during the heating season.
Solar attic fan installation
The most common installation is through the roof but solar powered gable fans are
also available. The installation is relatively simple if you can follow directions and
have the DIY skills of an experienced homeowner. If you’ve successfully installed a
solar tube skylight then installing an attic fan should be no problem.
What happens when the sun goes down?
Some models of solar fans can operate after sunset powered by either a small
amount of electricity (2 watts), or passively using the Venturi Effect. The Venturi
Effect occurs when wind passes through the louvers of the vent causing the air to
spin creating natural suction.
Cost
Solar attic fans aren't cheap. Prices range from $350 for the 10 watt model to $600
for the more powerful 30 watt units; thermostat is extra. Solar attic fans may be
eligible for a 30% Federal energy tax credit up to $500. Qualifying models are
issued a certificate of eligibility.
If you are unwilling or unprepared to pay a premium price for solar powered
ventilation, you might want to look into a conventionally powered gable attic fan for
around $60.