The Ultimate 2020 Guide On Attic Fans

Do you want to learn about attic fans?

Attic fans can be an effective way to keep your attic cool and dry. 

As a home inspector, I have inspected many hot and humid attics and sometimes passive venting just don’t properly ventilate. I have been in attics where without attic fans it felt like I was in the Sahara desert.

Attic fans turn on and off automatically because they are wired to their own thermostat. In addition, some attic fans also have humidistats so you can control at what humidity it will turn on (working together with the thermostat).

The biggest reasons to make sure you have a properly ventilated attic includes home temperature comfort, HVAC efficiency, mold prevention, stopping wood rot, as well as preventing ice dams on the roof.

In this guide, I will go over…

  • My #1 top pick for the best gable attic fans
  • The pros and cons of attic ventilation fans
  • The best rated roof mounted attic fans
  • Why attic fans can help protect asphalt roofing
  • Using attic fans to vent an attic if there are no soffits
  • How exactly attic fans work
  • My list of top rated Natural Light attic fans
  • How to install attic fans

What's In This Guide?

Gable attic fans are one of the most popular types of attic fans on the market.

Gable fans are installed vertically behind the gable vent on the ends of a home.

One of the biggest advantages of gable attic fans is that you don’t have to cut a hole in the roof which creates a potential leaking risk. 

Also, it’s just easier to install a gable fan because their is less work involved (and usually easier access).


My overall top pick for the best rated gable attic fan goes to a fan made by QuietCool. This gable attic fan has a 10-speed variable motor so the fan speed adjusts based on the temperature of the attic. 

The low speed is around 1000-cfm and the higher speed is 3000-cfm. Also, this gable fan comes with a thermostat and a humidistat. 

So the attic fan will turn on automatically when it reaches a particular temperature such as 95-degrees — but it will also turn on if the humidity rises on its own. And you don’t even have to hardwire this gable fan — you can just plug it into a regular 120-volt outlet.

If you would like to read my detailed review on the best gable attic fans, check out my full article.

Even though attic fans can be amazingly effective at ventilating attics — it isn’t all rosy.

There are some potential downsides to installing attic fans. One of these cons is known as backdrafting.

If you have gas-burning appliances, then there is a possibility that an attic fan could create a negative air pressure in your home, causing a gas appliance to send exhaust gases into the home (rather than to the outside).

In addition to the cons, there are some advantages to attic fans that many people don’t think about.

One of these little-known pros is that increasing your attic ventilation can protect and prolong your asphalt roof because a hot attic can act like a heat trap.  Asphalt shingles is a oil-derived product, and excess heat can prematurely crack and age asphalt shingles.

Installing one or two attic fans can significantly lower your attic temperature and thereby protect one of your largest home investments — the roof.

Another major benefit of attic fans is that they can prevent mold problems. Mold growth in a dark and humid attic can become a costly problem.

If you would like to hear more about my seven pros and cons for attic fans, you can read my full guide here.

Roof mounted attic fans are installed directly on the roof and exhaust hot and humid air to the outside.

These fans work similar to gable fans in that they turn on and off automatically by using an adjustable thermostat.

Roof mount attic fans can be hardwired directly into the homes electrical system or they can be plugged into a standard 120-volt outlet.

Roof attic fans can also have humidistats so that the fan will turn on when their is excess moisture in the attic.

In general, these ventilation fans come in the 500-cfm to 2000-cfm range which stands for cubic feet per minute of exhaust capacity.

One nice thing about roof mounted fans is that you can install as many as you need or want. With gable attic fans, you are limited to at most two — one on each gable vent. In addition, hot air rises so roof mounted fans towards the top of the attic may work better than gable fans.

And if you want solar capacity, there are roof mounted fans with solar panels built into the fan unlike gable fans.

My detailed review on the best roof mounted attic fans can be read here.

attic fans

As a home inspector, I noticed a pattern of extremely hot attics and prematurely aged roofing shingles.

Asphalt shingles are derived from crude oil, and when they get extremely hot — the heat stress actually accelerates the aging process.

Many people don’t realize that your attic ventilation doesn’t just impact your HVAC system and home comfort, but it can make a major impact on one of your largest investments — the roof.

You can increase attic ventilation by installing more passive venting such as soffit venting, ridge vent, turtle vents, or even wind turbines.

Unfortunately, sometimes passive venting just doesn’t work for whatever reason. Perhaps it is an old home with a weird attic layout. Or maybe your soffit venting is covered by insulation and the homeowner doesn’t realize it.

Sometimes it is just difficult to know why passive vents don’t work. This is when installing an attic fan or two is the easiest solution.

Check out my full article on how attic fans can help protect your roof.

attic fans

Installing a roof mounted attic fan is a relatively simple process if you have the right tools. It’s important to also be safe with eye protection during the cutting process.

The first step is choosing the best location to install the fan.

You want to install the attic fan as close to the ridge as possible because hot air rises. However, you want to keep it at least 24-inches away from the ridge so it doesn’t interfere with the ridge vent.

The main part of the installation is when you cut a hole in the roof.

Before you cut, you want to pencil an outline on the roofing shingles with a cardboard template of the attic fan — you don’t want to mess this part up.

Also, when you are close to finishing the cut, you want to make sure you don’t let the cut roof sheathing fall back into the attic. It can damage the drywall ceiling and really spoil your day.

The most important finishing work is likely to be the flashing and caulking. Since attic fans are roof penetrations, they are liable for leaks. Always make sure to caulk over any nail heads and make sure the flashing is tight and sealed.

Here is my detailed guide on how to install attic fans in a roof.

Natural Light Energy Systems is one of the leading manufacturers of solar attic fans in the USA.

The company was formed in 1999, and Natural Light makes, stores, and sells solar attic fans from their main facility in Phoenix, Arizona.

Natural Light makes solar attic fans for residential and commercial properties as well as a unique tubular skylight.

There are a variety of solar attic fans made by Natural Light. They make solar gable fans where the solar panel is installed remotely in any desired location.

Natural Light also makes roof mounted solar fans where the solar panel can be tilted towards the sun.

There are also low profile solar attic fans where the solar panel is a built-in part of the fan — giving it a sleek and small profile. The solar panel wattage of these attic fans made by Natural Light is in the 10-watt to 40-watt range.

If you would like to read my full article on the best Natural Light solar attic fans, check it out here.

attic fan temperature setting

Attic fans work by exhausting hot and humid air from the attic to the outside.

And at the same time, it pulls in fresh exterior air into the attic.

Attic fans pull in fresh air from the passive vents such as the ridge vent, gable vents, continuous soffit venting or turtle vents. It’s important to make sure that you have enough passive venting in your attic otherwise the attic fan won’t work properly.


Most attic fans turn on and off automatically by using a thermostat. This is usually a small metal box that is mounted to a rafter right next to the fan inside the attic. There is a small knob on this box that allows you to change the temperature for when the attic fan turns on.

In addition to the thermostat, some fans have humidistats so that it will also turn on if the moisture in the attic reaches a certain level — a nice feature to help prevent mold growth.

Besides the thermostat and humidstat, you can also operate an attic fan by connecting it to a simple wall switch. You connect it to a wall switch at your upper level hallway. 

Just make sure to place some tape on the switch if you want the attic fan to remain on so someone doesn’t accidentally turn it off.

And here is my guide on exactly how attic fans work.

What's The Bottom Line On Attic Fans?

Attic fans can be very helpful tools to help keep your attic cool and dry.

Most people just think about helping their HVAC and keeping their home comfortable — but attic fans have many other hidden benefits.

The main benefits of increasing attic ventilation include…

  • Prevention of mold growth
  • Prolong asphalt roofing shingles
  • Prevent wood rot & structural damage
  • Repel insects & pests attracted to moisture
  • Stop hazardous ice damming on the roof
I hope you enjoyed my guide on attic fans.