How to Install a Power Loft Vent

There are two types of power loft exhaust fans. One sits near the top of the roof, under a mushroom cap that is exposed to the elements. The fan motor is attached inside the cap, protected from the elements. The other type is a gable end fan, which is installed behind a louver opening in the gable end wall. Both types of power loft exhaust fans are controlled by an adjustable thermostat on the fan. loft temperature turns the fan on and off to exhaust hot air.

Things You’ll Need:

loft vent assembly
Measuring tape
Circuit breaker
Electrical wiring
Support clamps
Power saw
Reciprocating saw
Roofing nails
Roofing tar
Decorative louver vent

Step 1

Measure the loft in cubic feet. Select the exhaust fan recommended for efficient exhausting of hot air from the loft. An electrician or home loft building specialist can be of assistance; two or three fans may be required. It is preferable to have two fans working intermittently than one fan running constantly.

Step 2

Locate a spot on your roof where you want the roof-mounted power exhaust fan to be installed. The higher on the roof and closer to the ridge, the better. Hot air rises to the fan.

Step 3

Check the manufacturer’s specifications for the required size circuit breaker. In most cases, a 20 amp breaker and number 12 wire is recommended. Run a power feed from the service panel to the location where installing the power exhaust fan. A hot wire, ground wire, and neutral wire connected to both the service panel and circuit breaker and to the power exhaust fan are required.

Step 4

Following manufacturer’s specifications, cut a vent hole in the roof with a power saw or reciprocating saw. Twelve inches square is standard.

Step 5

Mount the mushroom cap, using roofing nails, by tucking it under the head shingles per the manufacturer’s flashing specifications. Seal the mushroom cap valance with roofing tar. Every mushroom cap is a bit different; follow the flashing detail exactly to avoid water leakage.

Step 6

From inside the loft, mount the fan and blade assembly with brackets and screws provided by the manufacturer.

Step 7

Turn off the circuit breaker. Wire the electric connections to the thermostat by connecting the neutral to neutral, hot to hot, and ground to ground wires. Support your electric feed line according to local code. Do not use an extension cord.

Gable End loft Vent

Step 1

Install a decorative louver vent on one vertical end of the loft, if one does not already exist.

Step 2

Mount the fan motor, blade, and thermostat control assembly inside the loft at the louver location, following manufacturer’s specifications. Use the brackets and screws provided with the assembly.

Step 3

Turn off the circuit breaker. Wire the electric connections to the thermostat by connecting the neutral to neutral, hot to hot, and ground to ground wires. Support the electric feed line following local building code; do not use an extension cord.