Attic roof fans, also known as gable-end roof fans or whole-house fans, are ventilation systems installed in a home’s attic with the purpose of removing hot air from the attic space and exhausting it outdoors. This in turn helps lower indoor temperatures during hot weather. But are attic fans really effective at cooling a home and worth the cost and effort of installing one? There are several factors to consider when determining if an attic fan is right for your home.
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How do attic fans work?
Attic fans are designed to remove hot air that builds up in your attic and replace it with cooler outdoor air. They are usually installed in the gable end or slope of the roof and contain a large fan that pulls hot attic air out through vents and pushes it to the exterior of the home.
This creates negative air pressure in the attic, causing cooler air from the house below to be drawn up into the attic through any gaps, vents or openings. The continual influx of cooler air from inside the home helps lower the temperature in the attic. And since hot air rises, reducing attic temperature also helps remove some of the heat in the upper levels of the home.
Benefits of attic fans
There are several potential benefits to having an attic fan installed in your home:
- Lower energy bills – By removing heat from your attic and home, attic fans can reduce the need for air conditioning on hot days. This can lead to lower electricity bills during cooling months.
- Whole-house ventilation – Attic fans provide ventilation that circulates air throughout the entire home, not just a single room like a window AC unit.
- Prolongs roof life – Excess heat shortens the lifespan of roof materials. Venting heat from the attic can help extend the life of your roof.
- Prevents ice dams – By reducing attic temperature and moisture buildup over the winter, attic fans help prevent ice dams and icicle formation.
- Removes musty odors – Stale, hot air can lead to musky smells in a home. Fans refresh attic air and filter out odors.
- Environmentally friendly – Using an attic fan to naturally cool your home cuts down on energy consumption from air conditioning.
Types of attic fans
If you decide an attic fan is right for your home, there are three main types to consider:
Gable-mounted fans
Gable-mounted fans are installed in the gable end or triangle section of the attic. They are a common type of powered attic ventilator. Gable fans have the benefit of being easier to install since they don’t require cutting into the roof deck itself. They simply mount into the gable vent area. Gable fans also maximize airflow from the attic since hot air naturally rises to the top. But they may provide less whole-house airflow than other fan options.
Roof-mounted fans
As their name implies, roof-mounted attic fans are installed into the slope of the roof. This positions the fan to blow hot air vertically out of the attic. Roof-mount fans often use a duct or cover to protect the fan housing from weather. While roof-mount fans provide effective attic venting, installation is more complex than a gable fan since it requires cutting into the roof.
Whole-house fans
Whole-house fans are a type of large attic exhaust fan. They have a diameter of at least 30 inches or more and are mounted in the lower part of the roof slope. This allows them to pull air in through open windows and exhaust it out through the attic and roof. Whole-house fans move a high volume of air and create a strong suction effect for maximum home cooling. But they also require more roof modification to install.
Key factors when deciding about an attic fan
Here are some important considerations when determining if an attic fan is a good choice for your home:
Your climate
Attic fans are most effective for homes in hot, humid climates where excessive attic heat buildup is an issue. Homes in milder climates may not benefit as much. Cool, low humidity areas don’t struggle as much with attic moisture and high temperatures.
Attic size and layout
The size and design of your attic impacts airflow. Fans will be more effective in attics with ample space for air circulation. Low pitched roofs or many partitions can restrict air movement. Inadequate attic ventilation will limit fan performance.
House layout
Ranch-style homes with open floor plans will maximize the impact of attic fan ventilation. Homes with many divided, closed off rooms restrict airflow from a fan throughout the house.
Insulation
Your attic’s insulation also influences attic fan effectiveness. Heavy insulation reduces airflow between attic and living spaces. Make sure insulation allows for proper ventilation.
Existing ventilation
Attic fans work best in combination with other passive roof and soffit vents. If your attic lacks sufficient ventilation openings, a fan won’t function optimally. Any attic fan installation should be paired with proper intake ventilation.
House air tightness
The less air leakage in your home from gaps and cracks, the less impact an attic fan will have. Newer, tightly sealed homes won’t draw as much cool air up from inside the home into the attic.
Time of use
Fans are only effective when in use. To lower household temperature, the fan needs to run long enough to exchange air throughout the home. Homes left vacant during the day won’t benefit as much.
Fan power and size
Larger, more powerful fans move more air and provide greater cooling capabilities. But more powerful fans can also be louder. Select a fan size and power level suited to your attic size.
Thermostat control
For convenience, attic fans should be connected to a thermostat that automatically turns the fan on and off at set temperatures. Fans controlled by a thermostat maximize effectiveness while minimizing energy use.
Potential downsides of attic fans
While attic fans provide many benefits, there are also some potential drawbacks to consider:
- Higher energy bills – Attic fans themselves consume electricity. Running a fan constantly can increase energy costs, offsetting efficiency savings.
- Noise – Attic fans can create disruptive noise in the home that makes them hard to run at night.
- Leakage – Gable and roof fans can create openings for water or pests if not properly weatherproofed.
- Drafts – Fans can potentially draw humid outdoor air into the attic, creating a draft through the home.
- Imbalanced pressure – Improper use can lead to negative pressure that pulls dirty air from garages or other structures into the home.
Installation and operation costs
Installing and running an attic fan represents a significant investment. Here are typical costs to keep in mind:
Purchase costs
Attic fans themselves range widely in price from about $100 to over $1000 depending on the power, size and features. Whole house fans are the most expensive option. You also may need to purchase additional equipment like thermostats, capacitors, shutters or ducting.
Installation costs
Hiring an electrician and roofer to install a new attic fan costs around $400-$800 in labor. Complex roof-mount fan installations can run even higher. Any roof patching, framing or ducting will also add to costs.
Operational costs
Larger attic fans can consume 600 watts of electricity or more when running. Operating costs depend on your electricity rate and fan usage, but may range from $5 – $15 per month. Controlling fans with a thermostat helps minimize costs.
| Attic Fan Type | Average Purchase Cost | Average Installation Cost |
|---|---|---|
| Gable fan | $100 – $300 | $400 – $600 |
| Roof-mount fan | $300 – $600 | $600 – $800 |
| Whole-house fan | $500 – $1000+ | $800+ |
Alternatives to attic fans
Instead of installing an attic fan, other options for removing heat from your attic include:
- Natural ventilation – Adding more passive vents, gable vents and ridge vents encourages airflow passively.
- Radiant barriers – Radiant barriers block radiant heat absorption in the attic.
- Additional insulation – Improving attic insulation keeps more heat out of the attic.
- Powered gable vents – Solar or electric powered vents provide ventilation without the larger fan.
- Reflective roof coating – Special coatings reflect sunlight instead of absorbing heat into the attic.
Conclusion
Ultimately, attic fans can be an effective way to remove heat from your attic and lower indoor temperatures during hot weather. But they work best for certain home configurations and climates. And installation, operation and maintenance represent an added cost. Carefully consider your specific needs and home setup to decide if an attic fan is a good investment for your home cooling and ventilation.