Extra living space in the attic is a plus to any household. However, the challenge is getting adequate attic ventilation from heat build-up at the top of the house.
Studies show that attic heat can rise more than 150˚F, and increase your energy costs by as much as 20%.
While you may opt for extra vents to improve ventilation, it’s worth it to consider installing an attic fan or solar fan. They are reasonable and easy to set up.
Most attic fans operate by a thermostat that will switch on and off when necessary.
Things to consider before choosing a fan
Some models also have devices that monitor humidity and adjust ventilation in the months when the climate is cooler.
For solar fans, you have to look at how much direct sunlight your roof gets during the day.
When choosing an attic fan, the right size is important for adequate ventilation. A good gauge is to allow for at least 1 square foot of venting for every 300 square feet of attic space.
If you have a high roof, you need to match each vent on the higher roof with the vents on the roof at the lower level.
The lower vents normally rest beneath the eaves in the soffit. Soffit vents help balance cool air going into the attic.
When hot air rises, it goes into the higher vents, while the lower vents draw in the cool air from the soffit vents.
Clean the vents
Blocked up vents will reduce free air flow into the attic and slow down the fan.
To ensure your attic fan will work well, check the soffit vents for the build-up of debris. Along with cool air, soffit vents can pull in leaves, seeds, and other particles onto the screen.
Check your roofing material for wear and tear, and repair if necessary. In the summer, rising heat can create moisture and warp roofing material like asphalt.
In winter, moisture build-up results in frost build-up on the roof. Unchecked frost can weaken the wood in the attic.
Types of Attic Fan
There are two types of attic fans:
Roof-mounted attic fans
- Need a vent hole close to the top of the roof.
- The fan sits on a metal or plastic base over the vent hole.
- After you mount the fan, place some sheets of shingle over and around the base flashing.
- Do not need a hole cut in the roof to set up. If you have an existing gable vent, the fan can sit in its place.
- You may need to make the opening slightly bigger depending on the size of the fan you choose.
- If your fan is big enough for space, you already have, position the fan right behind it.
How to Install an Attic Fan
- Hammer or nail gun
- Electric cable
- 5/8 inch bit
- ½ inch plywood sheets
- 1 ½ inch roof nails
- Roofing cement
How to Install the Vent Shutters
For Gable Vents
- If your fan width is wider than your gable vent, take out the vent and place it on an automatic shutter or a larger vent.
- Take out the screws or nails, and remove the vent from the space.
- Line up the shutter directly over the center of the vent opening.
- Make some markings around the vent frame with a pencil. The pencil markings will guide you in placing the flange correctly in position.
- Allow at least5/8 inches of edging on all sides around the opening.
Mounting the vents
- On a flat surface, use 1/3 or ¼ plywood strips to help mount the vents. The plywood will keep the vent flange in place.
- Cut out the siding along the outer edge of the vent opening if you have lap siding on your wall.
- If there’s a 2×4 blocking frame on the existing vent, cut through the nails with a saw to dislodge it. Set it aside.
- Next, use a saw and cut out the new vent opening.
- Use your pencil markings to guide you as you cut within the 5/8 inch edges along the shutter flange.
- Position the shutter into place and check that it is level. Use some 1-inch wood screws to secure it in place. Seal all outer edges with acrylic caulking.
- Next, re-install the old 2×4 blocking frame slightly beneath the base of the shutter.
The blocking provides extra support for the mounting panel of the fan.
How to mount the fan
I recommend you install a mounting base to project the attic fan off the wall. It will ensure the blades don’t but the wall as they spin.
The frame will also help keep the fixture in place more securely.
- Cut the plywood
- Use a sheet of cardboard and make a circle the size of the fan frame for the vent hole.
- Mark the shape of the fan opening with a pencil. Cut the card all around to the correct shape.
- Place the cardboard shape on the plywood sheet. Cut the circle to fit over the vent opening with a saw.
- Position the bracket that mounts the fan, and place it on the plywood circle.
- Put the fan in the middle of the opening and attach the bracket to the plywood with screws.
- Cover the screw with some washers to prevent the screw heads from jutting out.
- Align the fan assembly on the support side. Make a mark at the top of the panel that mounts the plywood.
- Next, take the fan assembly panel. Place it at the back of the shutter and nail it onto the gable frame.
You are now ready to wire the fan.
How to Wire the fan
The first rule:
turn off all power before attempting any wiring.
- Check your local building codes to determine how much load your circuit can hold. You’ll need enough power to drive the 3.2-amp fan motor.
- It there’s not enough reserve load in your circuit, make room for an additional 15-amp circuit in the service
- First, check the extra capacity in your circuit breaker.
- Turn off the breaker switch. Check the amount of light and boxes in the circuit.
- Allow at least 1.5 amps for each box and make a note of the totals.
- For example, ten boxes can operate with a 15-mp circuit, and 13 boxes will need a 20-amp circuit.
- Reserve capacity of 4 or 5 amps is ideal. If your circuit is short, take 14-2 w/g cable from the service panel into the attic.
- Mount the thermostat through a conduit on the fan box.
- Attach the box to the plywood with screws. Make sure it lines up directly within the path of the air flow.
How to wire the fan
- Locate the circuit box closest to the attic.
- Detach the fixture and lay it down.
- Make a few holes in the rafters in the spaces between the open fixture box and the gable wall.
- Drill the middle of the board with a 5/8 inch drill bit.
- Pull through a 14-2 w/g cable into the holes between the boxes.
- Attach the cable to the rafters. Leave atleast8 inches within the fixture box in the ceiling.
- Repeat the same steps for the cable closest to the thermostat box.
- Pull the wiring through the holes in the wood and connect them.
- Leave at least 8 inches of space between the thermostat box and the ceiling box.
- Next, allow at least 8 inches of insulation space insulation space and pull the cable through one of the fan’s support studs.
- Fasten a box connector to the cable.
- Push the wire inside the thermostat.
- Tighten the connector box with a screw. Attach the ground wire to the boxes’ green terminal.
- Attach the white circuit wire to the white circuit lead. Then connect the black wire to the black fixture lead.
- Turn the connectors to secure them in place.
- Put the cover box back in place.
- Turn on the thermostat to get the fan up to at least 105˚F.
See also: The Right Way to Insulate an Attic Fan
Complete the wiring
- Go back to the open fixture box.
- Join the two 8 inch lead wire to the pull chain fixture.
- Attach a black lead to the brass terminal screw.
- Join the white wire to the silver terminal.
- Connect all the same-colored wire in the twist connectors.
- Mount the fixtures on the box.
How to Install a Solar Attic Fan
- Mark the space between both rafters for the solar-powered vent.
- Put a nail in the middle of the vent position.
- Attach the roof brackets and fall arrest system to the roof.
- Use a dowel compass and trace the outline of the vent’s roof flashing.
- Use a utility knife and cut along the outline on the shingles.
- Remove the nails and loosen the shingles from the circle.
- Mark the whole area onto the roof sheathing for the vent.
- Use a saw and cut out the hole in the roof.
- Take out the shingles from the opening of the vent.
- Line all around the area of the hole with roofing cement.
- Position the vent over the hole.
- Screw the flashing onto the roof.
- Seal the flashing all around with caulking.
- Put the shingles back into position around the vent fan.
- Use 1 ½ inches of roofing nails to hold them in place.
Related article: Learn How to Replace an Attic Fan
Your attic fan works hard to keep your attic space cool and bearable. As heat rises periodically, your attic fan may often shift heat through the vents into other rooms in the home.
Extra heat filtering into the home will require added power from your attic fan to expel the hot air.
Although your attic fan can last up to 10 years, persistent heat building up in the motor can cause it to make strange noises, slow down, or stop running altogether.
A well-maintained attic fan will help save time and energy costs in the home. Replacing the fan will depend on the type of fan you have. Gable or roof-mounted fans may vary, but the necessary steps are just about the same.
Be sure to observe all safety rules and replacement guidelines to keep the process as seamless and hassle-free as possible.