Solar attic fans, an energy improvement with a quick payback
By Barbara Kessler
You want to improve the Casa energetically, but you are a bit scarce on the green.
Not enough green to green is a common problem these days. However, there are some changes that you can hardly afford not to make. One of these simple solutions is to fix the heat build-up in your attic this summer. If you live in a location south of Washington, Maine, and Michigan, you will experience a few days when the home is difficult to cool, and the typical attic adds to the problem by trapping heat over it. If your AC unit is installed up there, the situation is even worse. The extreme heat causes the air conditioner to work harder and run longer when it pushes cooled air through hot pipes.
A roof fan, especially one powered by solar energy, is one way to get around this problem.
This costs a few hundred dollars compared to the thousands you might spend on other energy bills like rooftop solar panels, new HVAC systems, or even a solar water heater.
And the effects can be great. By cooling the attic and thus the house, the electricity bill can be reduced throughout the season.
“From our point of view, this only pays off for a very short time,” says Geoff Foreman, CEO of US Sunlight Corp., which makes a 12-watt roof fan with a 38-volt motor.
That payback period – the point where the energy savings match the initial cost – will likely only be months and easily within a year, Foreman says.
Here’s why: The company’s solar-powered roof fan costs $ 399 (uninstalled; about $ 125 for professional install, according to Foreman). It qualifies for a federal energy efficiency tax credit of 30 percent of the cost, which brings the cost to about $ 280 (or about $ 400 if installed professionally).
If you live in California or any other state with state or local incentives, get even more back. In Burbank, California, the attic fan is eligible for an additional tax credit of $ 200. If you install the device yourself, the cost is less than $ 100 – little more than the price of a 12-pack of high quality CFLs.
That’s the efficiency of paperbacks.
US Sunlight isn’t the only company that makes solar roof fans. For the Californians, however, they are a local company based in Livermore in the Bay Area. Other companies include: SunRise Solar Inc., St. John, Indiana; Solatube, which makes the Solar Star Attic Fan and Phoenix natural light energy systems.
Foreman promises that US Sunlight offers one of the best warranties after the solar panel on the attic fan is guaranteed for 20 years. The device will ventilate about 1,250 square feet of loft space and provide about 10 air changes per hour for a typical ranch house of about 1,700 square feet, he says.
This amount of airflow is much better than that provided by more passive ventilation systems like roof ridge vents and the “vortex” turbines in many homes. These systems rely on the relatively weak movement of hot air out of the house. The solar-powered fan works like an electric fan and actively dissipates the hot air. In contrast to the electric roof fan, however, it runs on sunlight and does not add to the electricity bill.
The fan’s solar panel needs to face the south or west sun, although the panel can be placed remotely for best sunlight absorption. (As a side benefit, keeping the attic ventilated during the winter can help reduce moisture build-up, which can promote mold and mildew.)
According to Foreman, customers were “extremely satisfied” with the product and he is one of those customers.
“I have just rethought my house and put two of my units on my roof. I have one facing south in one part of the attic and one facing west but tilted and rotated to catch the southwest sunlight in another part of the attic. “The heat in the hottest part of the house has gone from being“ unbearable ”to being pleasant, he says.
Like many new energy entrepreneurs, Foreman prides itself on the fact that its operations are environmentally friendly.
“This is an inexpensive way (homeowners have) to do something useful,” he says, “not only for the comfort of their home but also for the environment.”
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