A lot of people mistake whole house fans as attic fans. And that is justified because in some cases a whole house fan is actually an attic fan with some extension.
For example, check this QuietCool whole house fan;
It is basically an attic fan that has a louver extension!
But actually they have more differences than similarities. Here is a brief comparison;
Attic fan vs whole house fan – what are they for?
Attic fans are used to cool the attic. It draws the hot air from the attic and disperses it to the outside. This also creates a negative pressure in the attic which draws cooler air from the outside thereby reducing the attic temperature.
Whole house fans are used to cool the living areas in a house. It draws air from inside the house and releases it into the attic. This creates a negative pressure inside the house which draws cooler air from the outside thereby lowering the temperature in the living areas. The process also builds up higher pressure in the attic which is released through attic ventilation.
Location and installation
Attic fans are installed either in the gable or on the roof of the attic. They are much more easier to install and in most cases, you can do it yourself.
Whole house fans are installed on the ceiling between the living areas and the attic of a house. The installation often requires professional help since you have to make a hole in the ceiling and properly insulate it.
Attic fans are usually smaller in size and have a lower CFM rating. The power needed for an attic fan is approximately calculated as ‘Area in sq. ft x 0.7. For an attic with 1000 sq.ft area, the minimum CFM requirement for an attic fan is 700. If it is a dark roof or a particularly steep roof this value needs to be 15% more. So 1000 sq.ft steep attic will require a fan of 805 CFM.
If you like to know more here is a detailed post about calculating attic fan size.
Whole house fans are generally more powerful than an attic fan because they have to circulate air throughout the house. The minimum CFM required for a whole house fan is approximate ‘Sq.ft area of the house x 3’. That means for a house with area 1000 sq.ft the power of the whole house fan should be at least 3000 CFM.
All kinds of fans make noise.
Since an attic fan is located in the attic the noise levels are low inside the home. The latest models are much quieter so you won’t know they are running. Here is a list of the quiet attic fans for your reference.
Whole house fans, on the other hand, are installed on the ceiling of the living areas. Therefore the noise from them is easily heard in the house. There are of course quiet ones but still, no fans are truly silent.
Which is more effective – Attic or whole house fan?
Attic fans are not as energy efficient as whole house fans. They do lower the attic temperature by 10-20 degrees but according to experts, that is not enough to reduce a considerable load off the air conditioning system.
Whole house fans can be used as a temporary replacement for air conditioning. Running these fans lower the in house temperature and reduce much load on the air conditioning.
However, whole-house fans cannot be run along with the air conditioning unit as the conditioned air will be pumped into the attic. But attic fans can be operated any time since there is no direct connection between the living areas and the attic.
How much do they cost?
The cost of attic fans ranges from 80 USD to 400. If you hire a professional the installation may cost around $150 to $500 depending on location.
Whole house fans, on the other hand, cost more because they are usually bigger in size and so more powerful. They cost from 160 to 560 USD. It often requires professional installation which costs 200 to 1200 USD depending on your location.