Do attic fans lower the cost of cooling your home?
Are solar attic fans worth installing? Common sense suggests they would be but are powered attic fans really a good idea for energy efficiency based on research and science? I have a master’s of science degree and my initial belief was it made sense. It just seems logical that a cooler attic would lower the cost of cooling the house in summer. While researching radiant barriers for the attic and reflective paint (Kool Seal Premium White) for our metal roof, I came across a few articles strongly suggesting powered attic fans were a dumb, and possibly dangerous, idea based on science. Here’s what I found so far and why I removed my attic fan:
- The Scientific Spin on PAVs (powered attic ventilators – fans): Cooling off hot attics with powered attic ventilators (PAVs) seems like a good idea. After all, doesn’t cooler attic air mean less work for the HVAC system, longer shingle life, and reduced energy costs? Unfortunately that’s more myth than fact.
- Drawbacks Of Powered Attic Ventilators:Powered attic ventilators, already suspected of using more energy than they save, can also create excess moisture, structural problems, discomfort, and combustion safety problems for home occupants, according to a recent study. John Tooley of Natural Florida Retrofit, and Bruce Davis of Alternative Energy Corporation’s Applied Building Science Center in North Carolina, presented “The Unplanned Impacts on Houses by Powered Attic Ventilators” at the 1995 meeting of the Energy Efficient Building Association.The paper describes research conducted on eight homes over a period of three months. As a result of this research, Davis said that he wouldn’t recommend the use of powered attic ventilators. He emphasized, “If someone chooses to use a powered attic ventilation strategy, they need to do additional performance tests and take responsibility to be sure that it won’t cause other problems.” The potential for hazardous conditions is particularly high in homes with combustion gas appliances, because the ventilators can create negative pressures that cause backdrafting.
- Energy Star: Attic Fan Ventilation – Attic fans are intended to cool hot attics by drawing in cooler outside air from attic vents (soffit and gable) and pushing hot air to the outside. However, if your attic has blocked soffit vents and is not well-sealed from the rest of the house, attic fans will suck cool conditioned air up out of the house and into the attic. This will use more energy and make your air conditioner work harder, which will increase your summer utility bill.
- Ask the Builder: Powered Attic Fans – Attic Insulation Facts: “I used to recommend PAVs [powered attic ventilators – fans] for houses, but I don’t anymore.”
- Building Science, Unvented Roof Summary Article
The best solution appears to be making sure your attic is well insulated and well-ventilated using passive vents and natural air flow. Inspect your attic insulation and ventilation, or have a contractor do so for you. Just add more insulation or natural (passive) ventilation, if needed. Both measures will reduce the cost of cooling and heating your home; no electricity required and they are perfectly quiet.
ADDITIONAL ENERGY EFFICIENCY RESOURCES
- Contact the local power company website and local energy associations for more information on constructing an energy efficient home in your area.
- Building Science Corporation, Unvented Roof Summary Article: Excellent resource with in-depth research and hard-core science. Building Science is dedicated to teaching and providing factual information concerning building science and energy efficiency. This resource is used extensively by builders “in the know” when it comes to energy efficiency.
- Building Science Guides and Manuals: Good place to start if you want reference documents for some of the most important building science topics.
- Building Science Information Sheets: Fact sheets and overviews; another great place to start for those relatively new to the field.
- Energy Star : The Energy Star website has extensive information on energy efficiency.
- Geothermal Heat Pump Consortium: Geothermal is the most energy efficient method known today for heating and cooling. However, you will benefit by first making sure your home or building is insulated properly and as air tight as possible (within the limits of the appropriate building codes and safety concerns) before considering an expensive geothermal system.
ENERGY EFFICIENCY PRODUCTS
Whether or not you are using an attic fan and you own a fireplace, a great product to consider is a fireplace plug. Battic Door sells several energy conservation products including a simple fireplace plug; stops drafts and saves energy by sealing the chimney when not in use:
The Fireplace Draft Stopper is an inflatable urethane chimney plug balloon pillow measuring 38″ x 16″. A round Fireplace Plug is also available. It is quickly and easily installed in the fireplace just below the damper level. The Fireplace Plug can be adapted to work in almost all fireplaces. Even if you have an unusual construction, the Fireplace Plug can be successfully installed in less than 2 minutes.
The Fireplace Plug is provided with 5 “slittable” areas that can be cut to provide an opening for a damper handle. As the Draftstopper is inflated it seals around the damper handle sealing the opening (helps reduce energy costs). Easy, quick and clean installation.