How Do Whole House Fans Work? The Pros and Cons

Whole house fans are still commonly found at our home inspections they come in a few different varieties. While most of them are very old units, many of them are still in working condition. There are also newer versions which we see on occasion as Colorado has a decent climate for a whole house fan system.

This type of powered cooling system became popular in the 1950s. It was a cheaper alternative to an air conditioning unit, had lower maintenance than an evaporative cooler, and worked fairly well in specific parts of the country.

However, the units had their shortcomings as well and fell out of popularity over the years as building science evolved.

In this article, we will quickly cover what a whole house fan is, the positives and negatives of having one, and the ideal scenarios for having one installed today.

What is a Whole House Fan?

A whole house fan is a large fan with a very high CFM (Cubic feet per minute) rating that is typically installed at the top floor of a home in the ceiling. This large fan is used as a type of exhaust fan to move hot air from your home to the exterior.

As heat in your home rises in the warmer months, it tends to build up near the highest floor ceiling as the attic insulation will keep the heat from transferring through to the attic.

When a whole house fan is operated, it would blow the heat build-up in this area into the attic space which is typically vented, and the air would be pushed out.

This would create a negative pressure within the house itself, and pull cooler air from the lower areas of the home.

A common technique used while running a whole house fan is cracking or opening windows on a lower level of the home to pull cooler air upwards.

This is a nice way to cheaply cool a home when the temperatures outside are not too extreme. This is particularly effective in the evenings and mornings.

Pros and Cons Of A Whole House Fan

The main benefits of a whole house fan system are the cost, ease of installation, and maintenance. The cost to install a system is far lower than a traditional central air system. All that is required is the fan assembly itself, and a place to vent it.

A traditional AC system requires a very expensive compressor unit, coolant lines that run through your home, and a duct and blower system. While many homes already have a furnace with ducts, some do not which makes installing a traditional air conditioning system very difficult and expensive. A whole house fan can be a great option in this scenario.

Whole house fans also offer the benefit of basically zero maintenance.  The fan is always ready to go and newer units require no winterization.

So for a relatively low cost, you can add a simple cooling system to your house. But what are the drawbacks?

Let’s start with the standard unit you see installed in most homes today.

For starters, the fan is usually very large as it needs to be able to turn over the volume of air in your home in a reasonable amount of time. Because of this, the fans are usually loud. Older fans can be VERY loud. This can be bothersome for some people. We see these older fans very often during our inspections around Denver.

Next, their cooling capacity is limited. Using the natural cooling methods mentioned above can only go so far. Once the ambient air temperature of the exterior air gets above a certain degree, cooling performance drops off significantly. This can go further in homes with basements but in general, whole house fans are really only useful in some climates.

Finally, they can cause a substantial amount of air leakage in the winter months. It’s nice to have a cooling system when it is hot, but how about when it is cold? Having a large hole in your ceiling during the winter months can lead to unwanted air leaks no matter how well you try to seal it.

While this seems like a large list of negatives, there are newer models of whole house fans that try to mitigate the noise and winter problems.

Newer versions of whole house fans move the fan further into the attic and have a flexible duct that runs to a vent in the ceiling. This significantly reduces the noise.

The vent piece that connects to your ceiling also has a motorized insulated damper that will close when the fan is not in use. This reduces the heat transfer in the winter. Although these systems are still not perfect, it is a great improvement from the legacy models.

When Is Installing A Whole House Fan A Good Idea?

So how do you know if a whole house fan is right for you? The ideal climate to maximize your whole house fan usage is typically areas with all four seasons and somewhat mild summers, or coastal areas where the summer heat does not reach the 90s often.

The United States is split up into climate zones by the International Energy Conservation Code. Using this code, we can determine which areas of the United States can benefit from a whole house fan.

We would suggest that a whole house fan be used in climate zones 5-7 with some exceptions. Climate zone 4 can be acceptable if you live in a more humid area or coastal area where the temperature extremes are more regulated. A whole house fan will work well in climate zone 7, but if the winters are very cold a whole house fan may do more harm than good.

Of course, this is not an exact science. If you are in doubt, asking a local professional is always recommended.

Hopefully, this article gives you a solid understanding of whole house fans and aids you in your purchasing decision. During our home inspections, we always test and inspect a whole house fan from the interior and the attic to ensure they are in proper working order.

If you are interested in a home inspection in the Colorado Front Range area, learn more here.