How To Install a Solar Attic Fan

A solar attic fan is an innovative solution for keeping your attic cool and reducing energy costs. By harnessing the sun’s power, these fans can effectively ventilate your attic space without relying on your home’s electrical system. This Old House general contractor Tom Silva explains the installation process and the steps required to mount this energy-efficient device on your roof.

How Solar Attic Fans Work

Solar attic fans are roof-mounted ventilation systems that use solar energy to power a fan that expels hot air from your attic. These fans offer several benefits, including improved energy efficiency, reduced cooling costs, and extended roof life by preventing moisture buildup. They are an eco-friendly solution that can add value to a home by enhancing comfort and reducing the stress on HVAC systems.

Solar attic fans have a fan unit, a solar panel, and a mounting system. The solar panel converts sunlight into electricity, which powers the fan motor. The fan draws hot air from the attic, creating negative pressure that pulls cooler air through existing vents. This continuous airflow helps maintain a balanced attic temperature, protecting roofing materials from excessive heat during the summer months.

Benefits of Solar Attic Fans

Installing a solar attic fan can provide various advantages for your home, including:

• Reduced energy costs
• Improved attic ventilation
• Extended roof life
• Decreased indoor temperature
• No impact on your electricity bill
• Environmentally friendly operation

Choosing the Right Solar Attic Fan

Selecting the right solar attic fan for your home is important for optimizing performance. Consider these factors when making your choice:

Fan Size and Capacity

The size and capacity of your solar attic fan should align with the square footage of your attic. Manufacturers often provide guidelines on the appropriate size based on attic dimensions. For larger attics, you may need multiple fans to get optimal ventilation.

Solar Panel Efficiency

Higher-efficiency solar panels produce more power and enhance the fan’s performance, especially on partly cloudy days. Look for panels with high energy conversion rates and durable construction to withstand various weather conditions.

Material and Build Quality

Choosing a fan constructed with rot- and mildew-resistant materials increases longevity and reliability. Quality materials prevent corrosion and withstand extreme temperatures, further extending the life of your solar attic fan.

Preparing for Solar Attic Fan Installation

Before beginning the installation process, gather some necessary tools and materials and take the proper safety precautions. 

Tools and Materials Needed

To install a solar attic fan, you’ll need the following tools and materials:

• Hammer
• Flat pry bar
• Utility knife
• Reciprocating saw
• Drill/driver
• Caulk gun
• Solar attic fan kit
• Tri-polymer roofing cement
• 1 1/2-inch roofing nails
• Safety harness and fall-arrest system

Safety Precautions

Working on a roof can be dangerous, so prioritize safety. Silva emphasizes the importance of using proper safety equipment in the video. Here are some key safety measures to follow:

• Install roof brackets and a fall-arrest system
• Use a safety harness attached to a secure anchor point
• Wear non-slip shoes and work gloves
• Avoid working on wet or icy roofs
• Check weather conditions before starting the project
• Keep tools and materials organized to prevent accidents

Step-by-Step Solar Attic Fan Installation Process

Follow Silva’s steps for a successful installation:

1. Locate the Installation Site

Choose a location between two roof rafters and close to the ridge. Measure down 20 inches from the ridge and mark the center point. Then, make sure the fan is centered in the rafter bay to avoid cutting structural elements.

2. Mark and Cut the Opening

Drive a nail through the roof at the center point, then create a compass using a dowel with a 9-inch radius. Scribe a circle on the roof shingles using the compass. Cut along the circular outline with a utility knife and remove shingles and nails within the marked area.

3. Cut the Roof Sheathing

Use a compass to mark a 14-inch diameter circle on the roof sheathing. Cut the hole in the roof sheathing using a reciprocating saw. Be careful not to cut into any rafters or electrical wires.

4. Prepare the Flashing

Remove additional shingles around the opening to accommodate the fan’s flashing. Apply a continuous bead of tri-polymer roofing cement around the hole.

5. Install the Fan

Place the solar attic fan’s flashing over the hole, taking care to align it properly. Secure the flashing to the roof sheathing using screws. Then, apply additional roofing cement around the edges of the flashing.

6. Replace Shingles

Now you can reinstall the shingles around the fan, trimming them as necessary to fit. Secure the shingles with 1 1/2-inch roofing nails. You want to make sure there’s a watertight seal around the entire installation.

Optimizing Performance of Your Solar Attic Fan

To get the most out of your solar attic fan, consider these tips for optimal performance:

Proper Sizing and Placement

Calculate the attic’s square footage to determine the appropriate fan size for your attic. For larger attics, consider installing multiple fans as recommended by the manufacturer. Place the fans near the roof ridge for optimal airflow and performance. Also, position the solar panel to receive maximum sunlight exposure throughout the day for the best performance.

Maintaining Your Solar Attic Fan

Periodically clean the solar panel to support optimal power generation, and inspect the fan and surrounding area annually for any signs of damage or wear. On sunny days, check that the fan is functioning correctly and make sure no obstructions are blocking the airflow.

Common Solar Attic Fan Installation Mistakes To Avoid

When installing a solar attic fan, be aware of these potential pitfalls:

• Improper sizing: Choosing a fan that’s too small or too large for your attic space.
• Inadequate sealing: Failing to properly seal around the flashing, leading to leaks.
• Incorrect placement: Installing the fan too low on the roof or in a shaded area.
• Neglecting existing ventilation: Blocking or removing existing vents that are still necessary for proper airflow.
• Overlooking safety measures: Not using a safety harness or ignoring weather conditions can result in accidents.

Additional Considerations for Solar Attic Fans

For the long-term success of your solar attic fan, consider these additional factors:

Local Building Codes

Always check your local building codes before installing a solar attic fan. Regulations may vary, and compliance is necessary to avoid fines or required modifications. Consulting with a building inspector can clarify any specific requirements in your area.

Professional Installation

While installing a solar attic fan can be a do-it-yourself project, some homeowners prefer to hire a professional. Professionals have the experience and tools to complete the job safely, quickly, correctly, and efficiently. 

Warranty and Support

Select a solar attic fan that comes with a warranty and customer support. This provides peace of mind and assistance if any issues arise. Warranties typically cover defects in materials and workmanship.