How To Effectively Use an Attic Fan? Can You Run It with Windows Closed?

An attic fan can be a useful asset in your home and help you get rid of excess heat, provide ventilation and significantly reduce humidity. But there’s no way you can get the best results from an attic fan if you do not use it the right way.

Perhaps, you’ve had a unit for a few weeks now but it just doesn’t seem to be giving you the result you want. If you’re sure the unit is a top-quality product, you may want to try out a few things before you start considering returning it. Maybe the problem isn’t the unit, but how you’re using it.

So, what is the best way to use an attic fan? There are so many factors to consider when you use an attic fan and we’ll run you through a number of them.

This includes whether windows have to be open or closed and if you can use the unit with a whole house fan or not. As a bonus, we recommend you use your attic fan at night when the outdoor air is cooler to allow the air in and hot air and humidity out.

Can You Run an Attic Fan with Windows Closed?

No, it is better to run the attic fan with the windows open. This will allow outdoor air into the house as the attic fan pulls hot air out.

But then you may ask, how do you run your air conditioner with windows open?

This is one of the reasons it may be difficult to run your AC and attic fan simultaneously. However, it is possible to run your air conditioner and the attic but leave only an opening in the attic for air to come in and escape.

Then you can turn off the air conditioner for a few hours and leave the windows open within that time.

For things to be easier, you can take turns between your air conditioner and attic fan and manipulate your windows accordingly.

Truth is, ventilation is necessary when you run your attic fan, but not really advisable if you’re also running an air conditioner. You need to find a balance to enjoy the best value that your attic fan offers.

How Many Windows to Open for Attic Fan?

For best results, you should open two or more windows. This also largely depends on the structure of your house and the number of windows available.

It is also important to open the windows halfway for air control. Furthermore, you need to know what windows in what parts of the house you should open.

An attic fan is installed in the attic, usually on the wall or roof to draw in cooler air from intake vents and push out hot air through the exhaust vent. It is advised to open windows in the attic if any, and in upstairs bedrooms.

It won’t be necessary to open all the windows in your home as this may amount to counterproductive results. Between two and five windows on opposite walls on different sides of the house should be opened to allow for cross ventilation.

Some people also install attic fans on the floor of the attic, usually above large living space or hallway. This would mean there’s a need to open the windows in the rooms directly under the attic so that the fan can pull in the air coming from outside.

What Is the Best Way to Use an Attic Fan?

Following some practical tips will help you make the most of your attic fan. We have put together these steps to help you use your attic fan the right way.

1. Use the right size attic fan

There’s no way to negotiate the sizing of your attic fan. It’s either you get it or you don’t.

Having the right size unit can be the major determinant for effective cooling of your attic.

This is measured in Cubic Feet per Minute (CFM), measuring the amount of air the unit is able to remove per minute.

2. Run the attic fan when the day is hottest

The higher the temperature, the higher the difference between the outdoor and indoor temperatures. In fact, during the hottest summer days, this difference can climb as high as 50 degrees.

By implication, an attic fan will help to keep the indoor temperature within a 10-degree range.

For instance, if the outdoor temperature is 85 degrees, the indoor temperature could climb to about 130 degrees.

Using an attic fan to replace indoor air with outdoor air can bring that down to around 95° to 100°.

3. Ensure the attic has sufficient venting area

Make sure your attic has enough ventilation. This is very important and a great way to use your attic fan.

The rule of thumb is to have exhaust ventilation of 1 sq foot per every 300 sq feet. You should also have the same value for intake vents.

Without proper ventilation for removing hot air and bringing in cool air, pressure can build up in your attic and this can be negative.

4. Use only recommended thermostat settings

The recommended thermostat setting for attic fans is 90 to 100 degrees Fahrenheit.

With the right setting, the attic fan will turn on automatically once the temperature begins to rise above the setting.

5. Run the fan in winter too

Just as it is important to run your attic in the summer, you should also run it in the winter.

This is to ensure the temperature in your attic also drops in relation to the outdoor temperature. Again, this is necessary to ensure ice build-up is prevented.

6. Set humidistat at 50% to effectively remove moisture

Some attic fans actually have a humidistat attached to them. Where it is absent, you can get a standalone humidistat.

This is one effective way to reduce humidity by triggering the fan to come on when humidity is detected to have risen to undesirable levels.

For an attic fan, it is advisable to set the humidistat at 50% to ensure the humidity in the attic doesn’t go beyond 50% at any point in time.

7. Service once or twice every year

Finally, the lifespan and effectiveness of your attic fan depend on the quality of maintenance you accord the unit.

Ensure you do this once or twice yearly, including oiling the parts, checking the alignment and balance of fan blades, and generally servicing the unit.

Can You Have an Attic Fan and A Whole House Fan?

Yes, you can have an attic fan and a whole house fan. An attic fan is not a substitute for a whole house fan, and neither is a whole house fan a replacement for an attic fan.

Although their functions are similar, their application is different. You can pull air up the house using the whole house fan and send it out of the house through the attic using the attic fan.

A whole house fan, like the Air King Window Fan, works to provide needed ventilation in the entire house, and this may not do so well in your attic. On the other hand, an attic fan focuses on the attic alone.

However, if you need to choose between a whole house fan and an attic fan, it is best to go with the whole house fan because it is meant to serve the entire house.

This will also serve the attic if it is connected to the ductwork. For emphasis, we need to state once more that it is totally okay to have a whole house fan and an attic fan for better results.

Final Words:

The best way to use an attic fan is to use it in a way that gives you the best results. This includes opening the windows the right way, setting the thermostat correctly, using it when the weather is hottest, using the right size in the right attic, and ensuring the attic has enough ventilation.

Maintenance is also important to keep the attic fan working the best way. Whatever the case, make sure you’re getting the right amount of air intake and exhaust to keep your attic fresher, cooler and with just the right amount of moisture.