An air conditioner can make a home much more comfortable in the summer months, but it can also send your electricity bill skyrocketing. Plus, central AC systems are often very expensive to install. A whole house fan offers a more energy-efficient and affordable way to cool your home.
In the video above, This Old House expert Tom Silva installs a whole house fan, highlighting his key steps and considerations. This guide will walk you through what a whole house fan is, how it works, and how to tackle the installation.
What Is a Whole House Fan?
A whole house fan is a large, powerful fan typically installed in the ceiling of a home’s top floor. It works by pulling hot air from inside the house and expelling it into the attic space, where it’s vented outside through existing vents. This creates negative pressure inside the home, drawing in cooler outside air through open windows and doors.
Installing a whole house fan can offer several advantages for homeowners:
- Energy efficiency: Whole house fans use significantly less energy than air conditioning systems, potentially lowering your cooling costs.
- Improved air quality: By constantly circulating fresh air, these fans can help remove indoor pollutants and odors.
- Quick cooling: Whole house fans can cool a home much faster than traditional air conditioning systems.
- Extended HVAC lifespan: Using a whole house fan can reduce the workload on your air conditioning system, reducing wear and tear and potentially extending its lifespan.
Whole house fans aren’t right for every home, and they aren’t equally effective in every climate. You may need to increase your attic ventilation or have dedicated circuit wiring installed first. Later, we’ll cover some safety considerations to take into account when deciding whether this appliance is the right choice for you.
Choosing the Right Whole House Fan
To get the best performance from your whole house fan, you need to choose the right size and model for your home.
Fan Size and Capacity
The size and capacity of the fan should be based on your home’s square footage and the volume of air it needs to move. While specifications will differ by climate and floor plan, the U.S. Department of Energy recommends choosing a fan that can change the air 15–23 times per hour. You can speak to an HVAC professional or use an online calculator to determine the right cubic feet per minute (CFM) rating for your home.
Noise Level
Noise can be a concern with whole house fans. Look for models that offer quieter operation, such as those with belt-driven motors or multi-speed options that allow for lower, quieter settings. You can also mitigate noise by placing the fan in a less central location or adding soundproofing materials around it to help quiet things down.
Energy Efficiency
Look for fans with energy-efficient motors and insulated dampers to minimize heat loss when the fan is not in use. Some models, like the Tamarack fan Silva installs in the video, come with insulated doors that open only when the fan is operating. Opting for energy-efficient models can offer significant savings over time.
Whole House Fan Installation Process
Installing a whole house fan requires careful planning and execution. While the process shown in the video provides a good overview, we recommend professional installation because of the complexity of the task and potential safety concerns. A licensed HVAC professional will also be able to tell you whether you need upgraded attic ventilation or electrical circuits.
Here’s an overview of the installation process.
Preparation
First, decide where to install the fan. It’s usually placed in the ceiling of a hallway on the top floor, but use these steps to help pick:
- Pick a central location where the fan can pull air from multiple rooms.
- Make sure your attic has enough vents to let out the hot air.
- Check for any wiring, pipes, or ducts that might be in the way.
Creating the Opening
You’ll need to create openings in the attic floor and the ceiling below it to install the fan:
- Remove any attic floor plywood and insulation in the chosen location.
- Build a frame, or chute, in the joist bay by inserting 2-by-10s between the joists.
- Replace the plywood, measure, and cut an opening for the fan.
- Cut another opening in the ceiling below, being careful of any existing wiring.
- Carefully staple any wires out of the way.
Fan Installation
You need to install and seal the fan carefully to prevent air leaks:
- Seal any gaps between the ceiling and joists with spray foam insulation.
- Place the fan unit in the prepared opening.
- Secure the fan to the framing using appropriate fasteners.
- Install weatherstripping to create a seal and reduce vibration.
- Have a licensed electrician connect the fan to a power source.
Finishing Touches
To complete the installation, a few final steps are necessary:
- Attach the ceiling grille in the room below.
- Install any controls.
- Test the fan for proper operation and airflow.
Whole House Fan Safety Considerations
While whole house fans offer many benefits, there are important safety considerations to keep in mind.
Combustion Appliance Safety
If your home has gas- or oil-fired appliances, such as a furnace or water heater, there’s a risk that a powerful whole house fan could pull flue gasses back into the house. This is especially dangerous in well-sealed, energy-efficient homes. Consult with an HVAC professional to assess this risk and implement necessary safeguards.
Indoor Air Quality
Whole house fans can potentially draw in air from undesirable sources, such as moldy basements or garages with toxic fumes. To avoid this risk:
- Install proper weatherstripping on basement and garage doors.
- Use threshold sweeps to create better seals.
- Open enough windows when operating the fan to draw air from desired locations.
Proper Ventilation
For a whole house fan to function effectively and safely, your home needs adequate attic ventilation to release the hot air. This may mean adding soffit vents, ridge vents, or gable vents if your current setup is lacking. Poor ventilation can lead to moisture buildup or reduced fan efficiency.
Operating Your Whole House Fan
To get the most out of your whole house fan, use it strategically:
- Use the fan in the evening or early morning when outdoor temperatures are cooler than indoor temperatures.
- Open windows in rooms you want to cool and aim for even airflow throughout the house.
- Close your windows and turn off the fan during the hottest parts of the day to keep hot air out.
- Remember to close windows and doors if you’re using air conditioning after running the fan.
