Solar Attic Fans by primusboy


									Solar Attic Fans
Easily installed and free to operate, solar attic fans are a smart choice
for homeowners who want to save money cooling their homes in summer,
prevent ice dams in winter, and extend the lives of their roofs.
Operating Principle
A solar attic fan uses photovoltaic panels to convert sunlight into
electrical power. The electricity generated is used to turn a fan motor,
exhausting air from the attic of a home.
In summer, temperatures in an unventilated attic can exceed 160 degrees
F. A properly sized solar attic ventilation system will reduce attic
temperature to 5-10 degrees F above the outdoor temperature. Ventilating
the attic reduces the amount of heat transferred from the attic to the
home, decreases the load on the air conditioning system (reducing your
electric bill), and extends the life of the roof.
In winter, heat trapped in the attic may melt snow on the roof, which
trickles down and creates destructive ice dams in the colder eaves.
The attic becomes warmest when the sun is the strongest. A solar attic
fan runs the hardest when the sun is strongest.
Everyday home activities such as cooking and showering create moisture
which collects in the attic and promotes mold and mildew growth, reduces
the effectiveness of insulation, and attacks the wooden attic structure.
Year round fresh air circulation from a solar attic fan removes this
moisture and prevents moisture related problems.
Zero operating cost.
Installation can be done by a handy homeowner. No electrician is
Quiet operation.
Things to Consider
· The cost savings due to reduced air conditioner load depends on the
price of electricity in your area, the amount of attic space in your
home, the efficiency of your attic insulation, and the amount of
ventilation your solar attic vent is able to provide. A typical
installation will usually pay for itself in savings within 1-2 summers of
· A solar attic fan should not be used when air from the living areas of
the home can freely enter the attic. This would result in conditioned air
being removed from the home. Any openings between the attic and the home
should be sealed before a solar attic fan is installed.
· Properly sized attic vents are required to allow fresh air to enter the
attic and replace the hot air removed by the solar attic fan.
· Solar attic fans should be mounted away from ridge vents and gable
Solar attic fans are available three configurations:
1. Self flashing roof solar attic fan: The fan base is flat and designed
to slide under shingles and attach directly to the roof.
2. Curb mounted solar attic fan: The fan base is a cap designed to fit
over a curb which is attached to the roof.
3. Gable fan: The fan exhausts horizontally through the gable end of the
In addition, solar attic fans are available with fan mounted or remote
solar panels.
Installation Overview
1) Cut hole in roof (South side is recommended), taking care not to cut
through any roof framing members.
2) Slide unit under shingles
3) Reshingle around fan as necessary.
Commonly Asked Questions
1) What size fan do I need?
ANSWER: A solar attic fan should be sized to provide 10 attic air volume
changes per hour.
To figure out what flow rate this works out to, figure out the volume of
your attic in cubic feet. Multiply your attic volume x 10 air changes per
hour to get the total flow required per hour.
Since fans are sized in terms of their cfm (cubic feet/minute) output,
divide your total flow per hour by 60 to get cubic feet per minute.
Required flow rate in cfm = (attic volume x 10) / 60
Now check the fan specifications to find the fan or combination of fans
required to meet your ventilation needs.
It is also very important to make sure there is enough air inlet area in
your attic to allow fresh air to enter and replace the hot air being
exhausted. A minimum of 1 square foot for every 360 cfm of exhaust is
required. Typically soffit vents are used as inlets.
2) How long will a solar attic fan last?
ANSWER: Solar attic fans are designed to provide many years of trouble
free operation. The length of manufacturers' warranties are a good
indicator of the high standards these fans were designed to:
Attic Breeze Fans - Lifetime parts warranty
Solar Star Fans - 5 Year parts on solar panel and motor, 10 years on all
other parts.
Natural Light Fans - 25 Year parts warranty
SunRise Solar Fans - 5 year parts warranty on motor, 10 years on all
3) How is a solar attic fan controlled?
ANSWER: A thermal switch is often used to control a solar attic fan. This
switch only allows the fan to run when the attic is warmer than 80-90
degrees F. Running the fan only when the attic is hot extends the life of
the fan motor and results in less heat loss to the attic in winter, but
does not allow the fan to reduce moisture build-up in the attic at all
times and does not allow the fan to prevent ice dams during the winter.
Where can I find more information and pricing on solar attic fans?
ANSWER: Follow this link: Solar Attic Fan
Kevin McErlean
Product Specialist
H-Mac Systems, Inc.

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