Installing a bathroom vent

MATERIALS: Bathroom vent fan, ducts, end cap or roof cap, straps and screws, roofing cement, shingles, roofing nails, caulk, wire nuts, cable with clamps, duct tape, electrician’s tape

TOOLS: Drill, fish tape, keyhole saw or reciprocating saw, hammer, combination stripper, lineman’s pliers, screwdriver

DUCT THROUGH THE ROOF. You may have no choice but to run ductwork through an attic and out the roof. Choose a short, straight path and cut the roof and shingles correctly to avoid leaks. Moist air inside can condense on the ducts and drip onto insulation; you may want to wrap the duct with pipe insulation.

A vent fan considerably improves the atmosphere in a bathroom by pulling out moisture, odors, and heat. Codes require bathrooms to have vent fans if there is no natural ventilation, such as a window. When choosing a fan, use these guidelines:

• Make sure the fan will move the air. Unfortunately, many bathroom fans do little more than make noise. This happens when either the fan is not strong enough or the path through the ductwork is not free and clear. Measure your room and determine how far the ductwork has to travel. Then ask a home center salesperson to help you choose a fan and the ductwork to do the job. Keep in mind that air travels more freely through solid ducts than through flexible hoses.

• Consider a fan equipped with a light. Some units have a fan only, while others include one or more added features: a ceiling light, a low-wattage night-light, or a forced-air heating unit.

• Consider the wiring options. In some locations, local codes require that the fan activates whenever the overhead light is turned on. Given the choice, some people prefer separate switches for the fan and light.

• Check local practices. In hot, sunny climates, venting through the roof may be asking for leaks. If so, vent through the wall, as shown in installing a range hood.

Ductwork And Vent Fan Installation

RUNNING DUCT THROUGH A WALL. Choose the shortest and straightest route. A wall vent is the easiest to install because no roofing is involved. However, it may be difficult to run ductwork between joists.

1 CUT THE HOLE. From the attic, hold the fan against a joist and mark its outline with a pencil. Cut out the opening. If there is no attic, from the bathroom use a stud sensor to locate a joist and cut the opening from below. Shut off power to the circuit and provide power if none is present.

2 ATTACH THE FAN AND DAM OFF INSULATION. Attach the fan to the joist with screws. Some models require a 6-inch gap between the unit and insulation. Cut or push back the insulation, then cut pieces of 2x4 lumber to fit between the joists, and attach the lumber with screws or nails.

3 CUT A HOLE IN THE ROOF. On the underside of the roof, trace a circle just large enough for the roof cap tailpiece. Drill a hole large enough for the saw blade, then cut with a reciprocating saw, saber saw, or keyhole saw.

NOISE CONTROL - A label on the fan packaging will indicate how many square feet of bathroom space the fan can successfully clear. If there's any doubt, or if your ductwork will be more than 5 feet long, get a slightly more powerful fan than you need. (However, don't overdo it. Keep the power of the fan appropriate to the size of the room.) Fans are rated by sones. The higher the sone rating, the noisier the fan will be; the lower the sone rating, the quieter it will be.

4 CUT AWAY SHINGLES. Remove shingles from around the cutout without damaging the underlying roofing paper. The lower part of the roof cap flange will rest on top of the shingles, and the top part will slip under the shingles.

5 INSTALL THE ROOF CAP. Smear roofing cement on the underside of the cap flange. Slip the upper flange under the shingles as you insert the cap into the hole. Install the shingles on the side, smearing the undersides with roofing cement. Attach the flange with roofing nails; cover the nail heads with roofing cement.

6 CONNECT THE DUCTWORK. At both the roof cap and the fan, slide a clamp over the flexible duct and slip the duct over the tailpiece. Slide the clamp back over the tailpiece and tighten the clamp. Wrap the joint with duct tape.

7 WIRE THE FAN. If wiring does not exist, run cable to the fan and to a switch. If you are installing a fan/light, run three-wire cable from the switch to the fan. Connect the wiring according to the manufacturer's directions. Plug the motor into the built-in receptacle.

8 WIRE THE SWITCH. For a fan/light switch that has power entering the switch box, splice the white wires and connect the grounds. Connect power to both switches through two pigtails spliced to the feed wire. Connect the red wire to one switch terminal and the black wire to the other terminal.

INSTALLING A WALL VENT - If a bathroom is not located directly beneath an attic, you must vent air out through a wall. Even if there is an attic above, it may be easier to run the vent out through a gable wall rather than through the roof. When running ductwork through a ceiling cavity, it is sometimes easier to shove a piece of solid ductwork through rather than snaking flexible ducting. From inside the attic, drill a locator hole through to the outside, then cut out the siding with a reciprocating saw, saber saw, or keyhole saw.

1 MAKE A TAILPIECE. Press the duct pipe into the cap. Use sheet metal screws to attach a piece of solid duct to the cap, then caulk the joint or wrap it with duct tape. Apply a bead of caulk to the back of the flange so that it will seal against the siding.

2 ATTACH THE VENT. Caulk around the hole and push in the tailpiece. Secure it with four screws. Caulk around the edge of the vent. Complete the connection to the fan indoors using solid or flexible ductwork.

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