Solar Attic Fan Info Center: Solar Attic Fan Frequently Asked Questions
Check out Solar Attic Fan Faq's Section for common questions and answers about solar attic fans:
Commonly Asked Questions:
1) Does a solar attic fan qualify for a federal tax credit?
ANSWER: YES! Both the Purchase Price AND Installation Cost of a solar attic fan qualify for a 30% federal tax credit. The credit applies to equipment placed in service between January 1, 2009 and December 31, 2016. IRS Form # 5695 (Download pdf here) is needed to apply for this credit. Enter the installed cost on line 1 of the form.
2) Does a solar attic fan qualify for a state tax credit?
ANSWER: State tax incentives vary from state to state. Please check http://www.dsireusa.org/ to see if your state offers an incentive.
3) 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.
4) 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 other
5) 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.
6) Where can I find more information and pricing on solar attic fans?
ANSWER: Follow this link: Solar Attic Fan
7) Can my attic have too much Ventilation?
ANSWER: The amount of ventilation an attic needs is determined by many factors, but in general the more the ventilation your attic has, the better off you will be. As attic air turnover is increased and fresh make-up air is brought into the attic, the attic temperature will begin to approach that of the ambient outside air temperature, which in turn minimizes heat transfer into your home. As long as your attic has plenty of fresh air make-up ventilation, more airflow through the attic will only increase the cooling performance of your solar attic fan.
8) What is a solar powered attic vent and what does it do?
ANSWER: A solar powered attic vent is an attic ventilation fan which runs solely off solar power. These ventilators fall into the category of active (powered) attic ventilation, where outside air is forced through the attic and out the vent to effectively cool the attic space. This method of attic ventilation is many times more effective than passive (natural) ventilation since the air inside the attic is exchanged more times per an hour with a powered vent than with a passive vent.
9) Why would I want to cool off my attic?
ANSWER: During the summer, as the sun radiates heat onto your roof, your roof's shingles or tile becomes very hot. This heat is transferred through the roof and in turn heats up the air inside your attic. If the hot air stays inside your attic, the heat from this air will eventually enter your home.
While attic insulation slows this process, it does not eliminate the heat transfer process entirely. If your attic is not very well insulated, it will do very little to stop the heat from getting through. Additionally, a hot attic stays hot long after the sun goes down, so the process of heat transfer into your home never really ends.
By removing the hot air from your attic, the process of heat transfer into your home is minimized. The less attic heat that is transfer into your home, the less your air conditioner will need to work. If your air conditioner unit doesn't need to run as much to keep your home cool, you save energy and money.
10) What are the cost benefits of installing a solar attic fan?
ANSWER: How much money you will save is greatly dependent 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. In our experience, a typical installation will usually pay for itself in savings within 1-2 summers of use.
11) How are ridge vents, turbine vents, or gable vents different from a solar attic vent?
ANSWER: Ridge vents, gables vents, and dormer vents work by passive (natural) draft air convection. This means that as hot air rises in your attic, it should flow out from these vents creating a natural draft through the attic. However, as you have probably noticed if you currently have any of these vents installed on your home, they are not very effective at reducing the temperature of your attic.
Turbine vents are designed to pull hot air out of your attic when the wind blows. These vents are equally ineffective at removing attic heat due to frequent mechanical problems, low air moving capability, and a dependence on the wind to supply the power needed to induce a draft through the attic.
Solar attic vents operate on the principle of active (forced) draft air convection. Our vents create an air draft through your attic many times more powerful than that of natural draft air convection techniques. By inducing a greater air daft through the attic. these solar attic vents can effectively cool your entire attic and keep it cool throughout the day.
12) Are these solar attic fans very loud when operating?
ANSWER: No, not at all. You can barely hear them running when you're standing right next to one. The fan blades used in our solar attic vents are specially designed for whisper quiet operation.
13) Is any wiring required to install your solar attic vents?
ANSWER: No, our solar attic vents ship completely assembled and ready for use. All you need to do is install the unit.
14) Should I order a thermal switch or not?
ANSWER: That depends on where you live and what you need the fan to do. If you live in an area with cold winters (Michigan, Massachusetts), a thermal switch is recommended to prevent the fan from operating when the attic is below 80-90 degrees F. Running the fan only when the attic is hot in a cold climate results in less heat loss to the attic in winter. If you live in an area with warmer winter weather (Florida, Texas), heat loss to the attic in winter is less of a concern and a thermal switch is not recommended. 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.
15) Do solar attic fans prevent ice damming?
ANSWER: Solar attic fans may be helpful in reducing attic temperatures so snow on the roof does not melt and then re-freeze in the colder eaves to create ice dams. We do not recommend using solar attic fans to prevent ice dams because bringing cool air into the attic allows more heat loss from the home to the attic, and solar attic fans only run during the day doing nothing to prevent ice damming at night.
16) If I have ridge vents and gable vents, where should I locate my fan? If I have ridge vents and soffit vets, where should I locate my fan?
ANSWER: The fan should be located in a central location relative to intake vents and near the peak of the roof where the warmest air is.
17) I live in Illinois and am looking for better ventilation in my attic. It has a ridge vent and soffit vents all around. I was in the attic this winter and it was very humid. Is it possible and/or wise to have a vent with a humidistat and thermostat? I've seen that option on electric powered vents but not solar powered. Please help me choose the correct solution.
Mechanically ventilating an attic during the cold winter months would reduce attic humidity, but it would also bring cold air closer to the heated living spaces in your home and increase your heating costs. Please keep that trade-off in mind when considering wintertime mechanical attic ventilation.
You may want to find other ways to reduce winter attic humidity levels - if bath exhaust fans vent into the attic duct them outdoors, check your passive ventilation system (ridge and soffit vents) for obstructions, etc.
For cold climates like yours, we recommend solar attic fans with thermal switches that only allow them to operate when attic temperatures reach 80 degrees F. The extra heating cost caused by running the fan in winter offsets the reduced humidity and reduced risk of ice damming benefits. Plus, solar attic fans only run during the day and would do nothing to help humidity and the risk of ice damming at night.
There are many brands and models of solar attic fans out there. Try using our solar attic fan sizer at http://www.solar-attic-fan-info.com/solar-attic-fan-sizer.php to choose the right fan for your attic.