Do you want to know the difference between whole house fans and attic fans?
Both provide good home ventilation, but for entirely different purposes.
In this guide, you will learn…
- How whole house fans can cool down your home
- Why attic fans protect your attic (and roof)
- The primary differences between whole house fans and attic fans
- The possible safety risks of attic exhaust fans and whole house fans
Let’s get started with this guide!
What Is A Whole House Fan?
Whole house fans are powered fans that will ventilate an entire house (including the attic). Whole house fans are used to cool entire homes so owners don’t have to use the HVAC. It can be up to 80% cheaper to cool a home with a whole house fan rather than a standard air conditioner.
Many users also enjoy the breeze effect that a whole house fan can provide, it gives a nice outdoorsy feeling to the homes interior.
Even though a whole house fan is primarily used to cool down your entire home (without the A/C), at the same time it will also ventilate and cool your attic. Of course, a whole house fan would not be used during cold weather, when an attic fan may still be used to prevent ice damming and mold growth.
There also may be a time conflict between when the attic needs ventilation and the whole house needs cooling. Again, that's why attic fans and whole house fans have different purposes.
For certain climates, a whole house fan can eliminate the need for traditional air conditioning altogether.
A whole house fan is installed on the ceiling of the top level of the home. When operating a whole house fan, opening a few windows or doors (on the bottom level) is required. Fresh and cooler outdoor air is pulled through the open windows, and is eventually expelled out of the attic --- an entire air cycle.
Read Also: How Do Whole House Fans Really Work?
What Is An Attic Fan?
Attic fans are either installed on the roof or gable wall and are used to ventilate only the attic. These specialized fans have thermostats so when the attic’s temperature reaches around 95 degrees, it will automatically turn on.
Attic fans are used to expel hot air during the warm season, but it is also valuable during the cold season to prevent ice damming, condensation, and mold growth.
In the past decade, solar powered attic fans have become popular as well. These attic fans have an attached solar panel so the fan turns on automatically when the sun is out.
There are also turbine attic fans. These fans have a wind turbine which turns when there is enough wind. The turbine attic fan uses no electrical energy at all.
To summarize, attic fans are used to ventilate only the attic and not the whole house. Even though having attic fans may help cool a house by reducing heat radiating from a very hot attic --- it would be a very poor substitute for a whole house fan or HVAC system.
Read Also: The Best Solar Attic Fans (Review)
Whole House Fan Benefits
The main difference between whole house fans and attic fans is that whole house fans cool down your whole home. An attic fan primarily cools down just the attic.
Whole House Fans For Home Cooling
Whole house fans are only used during during warm weather when the home’s interior is hotter than the outdoor air. This is especially true when the sun goes down, and the outdoor temperature drops, but the home’s interior is still very warm.
Many people love whole house fans because when the sun goes down, they only have to run the whole house fan for 15-30 minutes and the home will be cool for the rest of the night. Whole house fans work best in drier climates and when there are large dayto night temperature differences as reported by Kansas State University.
Attic fans are also heavily used during warm weather, but they should also be used year round to ventilate the attic. During the cold season, an attic fan’s main benefit is to remove moisture from the attic and to prevent ice damming.
Whole House Fans For Breeze Effect
Some homeowners absolutely love the breeze effect. This is when the whole house fan is used more for the breezy feeling of a well ventilated home rather than for the cooling.
It feels almost like having a regular desk fan on your skin, but it happens everywhere in the home. I guess its a nice substitute from having a house on the beach?
Read Also: What Is An Attic Fan?
Attic Fan Benefits
Attic Fans Help Standard Air Conditioner
Attic fans can help a regular air conditioner in cooling down the home. During warm weather, if the attic gets hot, then heat will radiate from the attic and into the home (especially the top level).
This just makes it that much harder for your air conditioner to cool down your home. The A/C will use more energy, will turn on more frequent, and it will make your home less comfortable.
In my experience as a home inspector, the most uncomfortable homes, those with large temperature differences, such as a hot upper level --- always comes back to a poorly ventilated attic.
Attic Fans Prevent Ice Damming
During the cold season, if warm air enters your attic from the homes interior, excessive heat can lead to a phenomenon known as ice damming that can cause severe damage to a home. Basically, your attic gets too hot when its cold outside, and it melts snow on the roof.
When this melted snow gets close to the roofs edge, it refreezes, and creates a quasi ice dam. This ice dam holds back more water, and can lead to water infiltration and roof damage.
Attic Fans Prevent Mold Growth
Too much attic moisture can also lead to hazardous and costly mold growth. Moisture primarily occurs when two air masses meet with different temperatures. For example, if the attic is cold, but the homes interior is hot --- or when the attic is hot but the home is cold.
When these two air temperatures meet in the attic, it can cause moisture to form on the roof sheathing, framing, and paper-faced insulation.
And mold only needs three things to grow; a food source, moisture, and darkness. If excess moisture is formed in the attic, then mold has everything it needs to take root.
Attic Fans May Protect Asphalt Roofing
A commonly overlooked benefit of attic fans is that they can help protect and prolong asphalt roof shingles. Asphalt shingles will prematurely age if they get excessively hot.
When the attic becomes an inferno during peak hot weather, the suns rays quickly heat up the shingles, and this heat transfers to the roof sheathing and wood rafters. This heat transfers to the attic air and becomes a type of heat trap just like how your car heats up with the windows rolled up when parked.
Read Also: The Best Whole House Fans (Review)
Which Ventilation Fan Should I Choose?
If you want an air conditioning substitute during warm weather, then a whole house fan is the product for you. However, if you want to protect your roof, prevent attic moisture buildup, or help your standard air conditioner --- then an attic fan is the right choice.
Many people don't know that a whole house fan actually uses the oldest and natural A/C known to mankind. It uses something known as the stack effect which is when hot air rises, just like hot gases going up a chimney stack.
When a whole house fan is installed at the highest point of the home, it takes advantage that all of the hot air is already rising up through the home.
Even Thomas Jefferson’s home at Monticello was designed to use this stack effect by installing a central cupola that exhausted out the hot air. Thomas Jefferson specifically designed Monticello with a large central hall so the home would naturally draw all of the hot air through the central cupola. Jefferson researched ancient air conditioning methods of the Romans as well as Renaissance manuscripts.
Read Also: Steam Vs Evaporative Whole House Humidifier