Installing an attic fan can provide several benefits for your home, but there are also some potential downsides to consider. This comprehensive guide examines the pros and cons of attic fans to help you decide if adding one is right for your home.
What is an Attic Fan and How Does it Work?
An attic fan, also known as a whole house fan, is a ventilation system installed in the attic that pulls air in from open windows and pushes hot air out through attic vents. This creates a cooling airflow through the home without the need for air conditioning.
Attic fans are typically powered by electric motors and have large blades like a ceiling fan. They are mounted in the attic floor or gable end and connected to ductwork leading outside. The fan is operated using a switch, remote control, or thermostat.
When running, the attic fan draws cooler outdoor air in through opened windows and pushes hot interior air out through attic vents. This airflow removes heat and creates a wind chill effect that can make your home feel up to 10°F cooler.
Attic fans are best suited for homes in mild to temperate climates. They work most effectively at night when outdoor air is cooler.
Pros of Installing an Attic Fan
Installing an attic fan can provide the following benefits:
1. Cools Your Home Without AC
Attic fans can keep your home feeling cool and comfortable during spring and fall when temperatures are mild. By drawing in cool outdoor air and removing hot air, attic fans can reduce the need to run your air conditioner, saving energy and money.
Studies show attic fans can lower indoor temperatures by up to 10°F. This natural cooling effect lets you turn off the AC for longer periods or avoid running it altogether on cooler days and nights.
2. Reduces Humidity and Prevents Mold/Mildew
Attic fans remove both heat and humidity from your home. By expelling warm moist air, they help keep indoor humidity levels under 50% to control mold and mildew growth.
Lower humidity also eliminates that sticky feeling and creates a more comfortable environment. Attic fans complement other humidity control solutions like dehumidifiers and ventilation.
3. Improves Indoor Air Quality
Attic fans bring in fresh outdoor air and filter out dust and allergens. This air exchange improves indoor air quality and ventilation to create a healthier home.
Replacing stale indoor air with fresh air can also help reduce odors from pets, cooking, and more. Improved ventilation and air quality leads to better comfort and health.
4. Extends Roof Life by Venting Hot Attic Air
Venting hot air out of your attic space lowers temperatures in your attic by up to 30°F. This helps prevent premature deterioration and damage from extreme heat.
Lower attic temperatures extend the life of your roof shingles and framing. Ventilation can also prevent moisture issues like ice dams in cold climates.
5. Compliments Insulation for Energy Savings
Attic fans work with proper insulation to make your home more energy efficient. Using an attic fan allows you to balance fresh air intake and ventilation with insulation that seals conditioned air.
This one-two approach helps reduce electricity usage and cooling costs in summer. The ventilation improves insulation performance for greater savings.
6. Provides Whole House Ventilation
Unlike window fans, attic fans ventilate your entire home, not just one room. The all-encompassing airflow removes hot air from every bedroom, living area, and the attic space.
Whole house ventilation ensures comfortable temperatures throughout your home. And unlike window ACs, attic fans don’t leave certain rooms under-cooled.
7. Easy to Install DIY or Professionally
Adding an attic fan is a relatively straightforward DIY project if you have basic skills. Fans mount easily in the attic floor or gable-end wall. The most difficult part is running ductwork.
You can also hire an HVAC pro for installation. Costs vary but installing an attic fan runs $600 to $2,000 depending on the unit and labor. DIY installs cost much less.
8. Low Maintenance Required
Attic ventilation systems don’t require much regular maintenance. You’ll just need to clean dust/debris from the attic intake vents 1-2 times per year.
The fan motor is the only part that needs servicing. Have an HVAC pro lubricate and inspect the motor every 2-3 years to ensure long life.
9. Long Lifespan with Proper Sizing
When sized correctly for your home’s square footage, attic fans typically last 15-20 years or more. Large attic fans can even last up to 30 years.
Choosing an attic fan with enough CFM airflow for your space ensures the motor and parts aren’t overworked, extending the lifespan. Oversized units run easier and last longer.
10. Resale Value Addition
Adding an attic ventilation system increases your home’s value, especially in hot climates. Homebuyers look for energy-efficient features like attic fans.
Features that reduce energy costs are highly desirable. Recent studies show attic fans add 1.5% to a home’s value, translating to thousands in resale value.
Cons of Attic Fans to Consider
While attic fans have definite benefits, there are some potential drawbacks to weigh when deciding on installation:
1. Effectiveness Depends on Climate
Attic fans work best in temperate climates without extreme heat or humidity. In hot southern climates, attic fans often can’t keep pace with high temperatures.
And in very humid climates, attic fans are less effective at moisture removal since humid outdoor air is drawn in. Carefully consider your climate to determine if an attic fan can provide enough cooling and dehumidification.
2. Must Open Windows and Doors
For an attic fan to draw air through your home and ventilate properly, you need to open windows and interior doors. This allows the air to easily flow out but also leaves your home less secure.
Some people don’t like having open windows at night or remembering to close them in the morning. Smart controls that automatically open windows are an option, albeit an expensive one.
3. Can Cause Backdrafting of Appliances
Powerful attic fans can create negative pressure inside your home. This reverse airflow can cause backdrafting where exhaust gases spill back inside instead of venting outside.
Backdrafting can be a deficiency with gas furnaces, water heaters, wood stoves, and fireplaces. Having a HVAC pro assess your appliances for backdrafting risk is wise.
4. Adds Some HVAC System Complexity
Attic ventilation systems require ductwork running from the attic fan to the outside. This adds complexity to your HVAC system, along with another electrical connection.
More parts means more opportunities for problems. And if the attic ducting leaks, it compromises the system’s effectiveness. Proper installation is key.
5. Can Draw in Pollutants
Although attic fans ventilate a home with fresh outdoor air, they can also draw in pollen, car exhaust, and other outdoor pollutants through the open windows.
Allergies or asthma can be aggravated if you live near pollution sources. Use the fan during times when outdoor air pollution is lower to minimize effects.
6. Can Be Noisy
The large fan blades used in attic ventilation systems move a lot of air but also create noise in the process. This can make it difficult to sleep with the attic fan running high.
Selecting a quieter fan, insulating the attic floor, closing windows, and soundproofing attic vents will help reduce noise. But some fan noise is unavoidable.
7. Requires Insulation Improvements
For maximum effectiveness and energy efficiency, an attic fan needs proper attic insulation. Most homes could benefit from additional insulation when adding an attic fan.
Improving the attic insulation seals off conditioned, cooler air from hot attic air. This costs more upfront but pays off through enhanced performance.
8. Can Increase Dust and Allergens
Although attic fans bring in fresh outdoor air, the high velocity airflow can also draw in dust and allergens from outside.
Window screens help filter airborne particles to some extent. But attic fans moves air so quickly that dust still enters and can circulate through your home.
9. Won’t Work During Rain and Cold Weather
Attic fans are designed to be used with open windows and vents. This isn’t practical during rain, storms, or cold weather.
They also lose effectiveness when outdoor air is nearly as warm as or warmer than indoor air, providing little cooling benefit. Options like a thermostat can help maintain sensible operation.
10. May Not Lower Energy Bills as Much as Expected
Some homeowners expect substantial savings on summer energy bills by using their attic fan instead of AC. In reality, the cooling costs avoided often don’t offset the fan’s operating costs though.
Do some calculations using the attic fan power consumption and hours used to determine realistic energy and cost savings in your climate. Include the costs of any insulation improvements needed as well.
Key Considerations for Your Attic Fan Installation
Optimizing the performance and benefits of an attic ventilation system requires careful planning and proper installation:
- Climate – Consider your climate zone’s temperature and humidity levels to determine if an attic fan can provide adequate summer cooling and dehumidification. Compare the hours of comfortable conditions an attic fan can provide vs using your AC.
- Fan Size Calculation – Size the attic fan based on your home’s square footage using this formula: CFM = Square Feet x 0.2. For example, for a 2,000 square foot home you would need an attic fan with at least 400 CFM airflow capacity. Oversizing is better than undersizing.
- Fan Features – Look for features like thermostat controls, quiet operation, weather sealing, and automatic shutters to maximize performance and convenience. Smart technologies provide even more control options.
- Attic Ventilation Assessment – Ensure your attic has sufficient ventilation. Calculate the existing net free vent area to determine if additional vents need to be added when installing the new fan.
- Ductwork – Use the shortest, straightest duct path possible from the fan to the attic gable vent, with smooth curves and no kinks that restrict airflow. Insulate the ducts to prevent condensation.
- Wiring – Have an electrician install a dedicated circuit and switch to handle the amperage load of the attic fan motor. Place the switch near the attic entry for easy access.
- Insulation Improvements – Once the fan is installed, seal any attic air leaks and examine your insulation. Adding insulation improves the attic fan’s efficacy and reduces energy costs.
Proper installation combined with the right size fan and features for your climate will ensure you maximize the benefits of an attic ventilation system. Work with experienced HVAC pros to get your attic fan correctly spec’d and installed.
Common Questions About Attic Fans
Here are answers to some of the most frequently asked questions about attic fans:
How much does an attic fan cost?
Attic fan costs range from $600 to $2,000 installed depending on size, features, labor, any ductwork needed, and required wiring and insulation improvements. DIY installs cost much less, around $300 to $700 just for the fan unit.
Do attic fans really reduce air conditioning costs?
Attic fans can lower air conditioner usage in milder climates where temperatures aren’t too extreme. By ventilating at night when temps drop 15-20°F lower than the daytime highs, attic fans can reduce AC runtimes. Just don’t expect dramatic savings in hotter locations.
Where should an attic fan be located?
Attic fans work best installed in a gable end or sloped ceiling close to a vent. This provides the shortest, most direct path to ventilate hot air out of the attic. Position it far from attic stairs to minimize noise entering living spaces.
How long do attic fans last?
With proper sizing and maintenance, attic fans last 15-20 years on average. Large capacity fans that run easier because they aren’t maxed out can even last up to 30 years before the motor or bearings need replacing.
Should my attic fan run continuously?
Never run attic fans continuously. They are designed for intermittent operation to remove built-up heat and provide ventilation. Use a thermostat or automatic shutters to run the fan only as needed. Letting it run 24/7 can shorten motor life.
Do attic fans work with AC?
Attic fans and AC should not be used simultaneously. Doing so disrupts the airflow of both systems. Use attic fans at night to cool the home then shut them off when the AC is needed the next day. The exceptions are dual-motor combo units designed to run both simultaneously.
How do I maintain my attic fan?
Attic fans require minimal maintenance. Inspect and vacuum intake vents seasonally to remove dust buildup. Have the motor professionally serviced every 2-3 years to lubricate bearings and ensure it operates efficiently and safely.
Conclusion
Adding residential attic ventilation is an effective way to cool your home naturally and reduce air conditioning usage and humidity. When sized and installed properly for your climate, key benefits include lower energy bills, improved air quality, added comfort, and extended roof life.
Of course, attic fans also come with some downsides like noise potential, climate limitations, and the need for open windows. There are also important steps for ventilating attics properly and calculating the right fan capacity.
If you live in a location with mild to moderate summer temperatures and want to minimize A/C usage, attic ventilation can be a smart addition. Just be sure to realistically compare costs vs savings and weigh the benefits and drawbacks before deciding if installing an attic fan is right for your home.