Helpful or Harmful?

Solar attic fans are touted as the solution to heat and moisture build up in your home’s attic. Manufacturers claim their fans help to lower your energy costs by cooling your attic and preventing heat transfer between your attic and your home. But do they really work? Or are they costing you more money? And could they potentially be dangerous?

It is true that heat and moisture accumulating in your attic can cause serious problems. If an attic is not properly insulated, you can lose a great deal of your valuable conditioned air to your attic, but even properly insulated attics act as large pockets of hot air sitting directly on your ceiling, causing your air conditioner to work harder to cool your home, which is more expensive for homeowners trying to escape the Florida heat. A hot attic can also affect your roof by damaging your shingles or other roofing materials, and the build up of condensation due to humidity in your attic can lead to mildew and mold which can also harm your roof.

In northern states where the climate is milder, homeowners opt for a different kind of attic ventilation system called a whole-house fan. It is a cheaper alternative to using an air conditioner because it draws cooler air through your windows at night, expelling the warmer air through your ceiling and eventually your attic vents. Unfortunately, it is not a practical choice in Florida’s warmer climate. So powered attic ventilators, of which solar attic fans are one, were created to cool your attic by drawing in air from your attic vents and expelling it through your roof. In principal, the attic is cooled entirely through outside air coming in through your soffit and gable attic vents, but unfortunately, it has been shown that when solar attic fans depressurize your attic even the most well insulated attics will draw air in from your house. So you could pay a premium for a solar attic fan just to see your energy bills go up as you pull your conditioned air through your attic at a greater rate and cost. Several complaints with the Better Business Bureau attest to the issues with solar attic fans causing rising electricity costs.

There is also the threat of back drafting in homes using gas powered appliances and hot water heaters. The threat was documented by researchers in Florida and North Carolina who have seen solar attic fans depressurize a house to such a degree that carbon monoxide from combustible gas appliances and water heaters begin to collect in the house instead of escaping through flue vents.

While a hot and humid attic can cause issues with your roof and your energy costs, solar attic fans do not seem to be the answer. Instead, making sure your attic has proper ventilation through soffit and gable vents and sufficient insulation and sealant between your attic and ceiling, will be your greatest guarantee against a hot and humid attic and higher energy costs.