A roof fan can lower your cooling bills dramatically, especially if your current attic venting is poor. Newer homes are built with more vents than older homes, but often they're just grate vents that don't do a good job of ventilating an attic. New homes should have at least one soffit vent in addition to other kinds of venting. But even with several vents, the addition of a roof vent fan can make a noticeable difference in both the attic temperature and the size of your energy bills.
How Roof Fans Work
It is not unusual for summertime temperatures in an attic to reach 160 degrees. Many people use attics for storage and may not realize how hot the air can get in those spaces. The high temperature may damage some stored items while creating a safety hazard to anyone who enters the attic when the temperature is extreme.
Attics that are properly ventilated with some kind of vents or roof exhaust fans will never approach dangerous temperatures. The fan pulls the hot air out, preventing it from heating the rest of your home and forcing your air conditioner to work harder to cool the house. A well-ventilated attic should stay close in temperature to the outdoor air, not rising more than 5 or 10 degrees above it.
Exhaust roof fans and proper ventilation not only cut your energy costs in the summer, they can extend the life of your roof by removing humidity in the winter. Heat that gets trapped in the attic in the winter can melt snow on your roof, creating ice dams in the eaves, which can damage them. Humidity trapped in a poorly ventilated attic can form frost and condensation, which can rot the wood in the attic and leach through and damage your roofing. Roof fans keep the air circulating to prevent moisture build-up in the first place.
Powered Roof Fans
Roof fans that run on electricity are common. Though commonly installed by a professional, you can install this fan yourself if you are familiar and comfortable working with wiring. The electricity is typically run from an existing attic light fixture. Creating the hole for the fan and making sure that it doesn't leak, however, can be more difficult. Most fan manufacturers recommend that if you have any kind of roofing other than asphalt shingles, you should contact a professional. Even with asphalt shingles you may wish to hire the job out if you're not comfortable working with roofing.
Solar Roof Fans
A solar roof fan that draws its energy from the sun is an option for homeowners who want to go green while avoiding the need for electrical wiring. Both types of fans have thermostats that you set to a desired temperature, generally about 95 degrees. Once the air in the attic reaches that temperature, the roof fan turns on, removing heat and humidity and lowering your energy bills.