2.2d Solar Attic Fans

Feature	Many manufacturers now offer solar powered attic fans to ventilate attics and help keep attics cooler. Solar powered fans rely on a small (typically 10- or 20-watt) solar panel to power a DC motor when the sun is shining. The fans, which exhaust air at a rate of 800 to 1,200 cfm, (cubic feet per minute) are installed with intake vents (such as soffit and gable vents) to provide high-capacity powered ventilation without electric operating costs. Most vents are mounted high on the roof, near the ridge, and combined with soffit or gable vents for balanced intake and exhaust air streams. Solar powered gable ventilators are also available. (Source: NAHB Research Center) (Photo: SunRise Solar Inc.)
Cost Range	Retail prices range from about $350 to $600 depending on ventilation capacity, manufacturer, and optional features of the unit, such as a thermostat. Because these fans are powered by the sun, there is no cost of operation. Source: NAHB Research Center)
Installation	In new construction applications, roofers will usually install powered ventilating units. The solar units eliminate the need for an electrician to rough and finish wire the units. For retrofit projects, a roofer or do-it-yourselfer can install a solar-powered attic fan using conventional materials, tools, and techniques. Source: NAHB Research Center)
Challenges	If there is inadequate attic intake air and poor sealing between the conditioned space of the home and the attic, powered attic fans can potentially draw air from the house into the attic. Not only can this compromise energy efficiency, it can increase the risk of attic moisture problems as well as increase the risk of drawing the byproducts of combustion into the house (a process called backdrafting). Source: NAHB Research Center)
More	See more on attic ventilation from Energy Star Read more about green air conditioning