Want to know the best attic fan temperature setting?
The best attic fan setting should keep your attic within 10-15 degrees of the outdoor temperature on hot days.
In this guide, I will go over...
- The best attic fan temperature setting
- How to adjust the attic fan thermostat
- The ideal attic temperature
- Testing your attic fan
Let's get started with this guide!
What Is The Best Attic Fan Temperature Setting?
I have been into hundreds of hot attics, and sometimes I even get close to passing out because it's so hot. The correct attic fan temperature setting will help prevent the attic from getting desert levels of heat.
In general, most homeowners should set their attic fan temperature to in-between 90 and 110 degrees Fahrenheit. Unfortunately, it is impossible to state a single number as the correct temperature. A house in sweltering New Orleans should have a completely different temperature setting than a home in northern Seattle. If the thermostat setting is too high, then the attic fan won't turn on or it will turn on too briefly.
And if the temperature setting is too low (such as 90-degrees in Miami) then the attic fan will be running more often than it needs to, possibly running 24-hours — wasting energy. Ideally, you want your attic to be close in temperature to its outdoor surroundings.
In this article, I will go over the ideal attic temperature, how to adjust it, and why you should install an attic thermometer...
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What Is The Ideal Attic Temperature?
The ideal attic temperature will be about the same as the exterior.
This makes sense because the attic has numerous passive vents such as the ridge vent, soffit vent, gable vents, and turtle vents — constantly sucking in fresh exterior air.
When the attic starts to exceed by around 10-15 degrees above the exterior temperature, then you know you have a problem of excess heat.
How To Adjust The Thermostat?
Some attic fans have a WiFi connection, and you can adjust the thermostat through your phone — but most attic fans will have a small metal box mounted next to the attic fan.
On this small metal box, there is a little dial where you can adjust the temperature setting. All you have to do is take a flathead screwdriver and adjust the temperature dial to your target temperature.
Most attic fans have thermostat dials with a range of 60-degrees to around 120-degrees.
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How To Test An Attic Fan?
And if you aren't certain whether the attic fan is working, now is a good time to test it.
To test an attic fan, you just have to adjust the temperature dial to above the current attic temperature.
If the attic is around 90-degrees, then just as you hit 90-degrees, the attic fan should turn on. And then adjusting the dial to below 90-degrees, the attic fan should turn off.
Why Install An Attic Thermometer?
It's a good idea to install an attic thermometer so you can know the actual temperature of the attic.
Plus, attic fan thermostats aren't always accurate, so you really shouldn't 100% rely on it. Installing an attic thermometer will also allow you to quicky gauge the true temperature of the attic, and if your temperature setting is correct.
If your attic thermometer is 20-degrees higher than the exterior, and your attic fan still hasn't turned on — then you will have to adjust the attic fan thermostat lower.
I recommend installing an attic thermometer by fastening it to a rafter roughly in the middle of your attic to get an average temperature. I also recommend buying a digital thermometer that will record the highest temperature attained during the day.
Why Attic Fan Temperature Setting Is Important?
In my opinion as an inspector, the number one reason is home comfort. When you have a cooler attic, it just makes the whole house much more comfortable. The HVAC doesn't have to run as hard or long to reach its target temperature.
Houses with really hot attics almost never reach their target temperature, and the house is very uncomfortable — especially the second home level.
And the second reason is that it helps extend the life of your HVAC system. Since your HVAC isn't running as hard, it can be more efficient, and therefore it will last longer. When the A/C is constantly running, it can add serious wear to its components.
And the third reason is something that most people don't think about. Controlling your attic temperature can help extend the life of your asphalt roof.
Asphalt shingles is an oil-derived product, basically paper soaked in crude oil, and so these molecules lose their elasticity when heated up.
Well, attics can reach a temperature of 160-degrees on really hot days with poor ventilation. This will cook your shingles, making them brittle, and subject to cracking. It will also give your shingles a faded look, greatly reducing its life.
Lastly, the correct attic fan setting will help avoid moisture problems.
Attics and moisture simply don't mix. I have seen attics plagued by mold problems due to excessive moisture.
Mold simply needs three things to grow: moisture, food, and darkness. Well, your attic has all three.
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Final Thoughts: The Best Setting?
The ideal attic temperature setting is in the range of 90 to 110 degrees, but it really depends on where your house is located in the country, and on the season.
Ideally, you want to keep your attic temperature within around 10-degrees of the exterior air.
It's a good idea to install an attic thermometer so you can know the true temperature of your attic, and to give you an idea whether the attic fan thermostat is even accurate.
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