Your attic requires natural ventilation, and a solar attic fan will help nature get the job done. On a summer day here in the San Joaquin Valley, attic temperatures can approach 150 degrees. That accumulated heat conducts through the ceiling into living spaces. It also saps coolness from air conditioning ducts routed through the attic. In winter, unventilated attics may accumulate water vapor rising from the living spaces below and provide a moist environment for mold and mildew. These unwanted particulates may later infiltrate your home, not to mention rotting the wood structure and degrading electrical wiring. Most existing home construction incorporates lower attic vent openings at the soffits — located under the eaves of the roof — and upper vents at the gables on either end of the roof. Natural ventilation depends upon the chimney effect of warm air rising out of the gable vents, pulling fresh air into the soffits.
Natural is not always enough, however. If your soffit vents are undersized, they may provide insufficient air flow for proper ventilation. In very hot or humid climates, it may be impossible to sufficiently expand soffit venting without making aesthetically undesirable retrofits to the exterior of the house.
Installation of a solar attic fan on a south-facing portion of the roof can boost natural ventilation of attics, without putting a hit on your electricity budget. Attic fans increase airflow through the soffits and improve circulation through the entire attic space.
A solar attic fan is generally available in 10-watt or 20-watt output. A fan rated at 10 watts provides sufficient ventilation for attics up to 1,200 square feet. 20-watt models vent up to 1,600 square feet. Because most residential attics are larger than 1,200 square feet, either multiple 10-watt fans or a single 20-watt may be required. Soffit intake ventilation is also a limiting factor. Exhausting attic air in excess of the volume the soffits can intake may result in drawing conditioned air out of the living spaces.
Donald P. Dick Air Conditioning has led the way in energy-efficient cooling in the Fresno area for almost 40 years. Contact us for even more effective uses of technology to enhance interior comfort.
Our goal is to help educate our customers about energy and home comfort issues (specific to HVAC systems). For more information about solar attic fans and other HVAC topics, download our free Home Comfort Resource guide.