How to Install a Bathroom Vent Fan

Bathroom moisture is relentless. Every hot shower pumps humidity into the air, and if it has nowhere to go, mold blooms on walls, paint peels, and the smell lingers. A vent fan solves this completely—it captures moisture at the source and sends it outside before it can settle into your walls. The difference between a bathroom that stays fresh and one that deteriorates is often just one fan. Installing one yourself means you own the process: you know the ductwork is clean, the venting is correct, and the fan fits your space exactly. This is not complicated work, but precision matters. A fan installed halfway will collect dust in the attic, reduce efficiency, or worse, exhaust humid air into your ceiling cavity instead of outside. Do it right the first time.

Map your straightest path out. Locate the bathroom ceiling position that's closest to an exterior wall or roof exit, ideally within 10 feet. Mark the spot on the ceiling from below, then go into the attic to confirm there are no obstructions—pipes, electrical, framing—and that a clear path to outside exists. Measure the distance to your intended vent termination point (wall or roof). Sketch the path: straight runs are best; if you must turn the ductwork, use smooth 45-degree bends, never hard 90s.
Cut the hole cleanly. Shut off power to that ceiling area at the breaker. Use a drywall saw or jigsaw to cut the hole marked on the ceiling. The opening size depends on your fan housing—most are 14 inches by 24 inches or circular at 8 inches; check your fan manual. Cut carefully and straight. Sweep drywall dust from the attic and the room below.
Route the ductwork outside. Slide the rigid or flexible ductwork from the attic down through the ceiling opening into the fan housing. If using flexible duct, avoid kinks—run it in a gentle curve. Secure the duct to the fan outlet with a hose clamp or duct tape, then run the other end to your exterior termination point (wall vent or roof cap). Use duct hangers or straps every 3 feet to support the weight and prevent sagging. Seal any joints with mastic or foil tape; never use standard duct tape, which deteriorates.
Lock the housing tight. Set the fan housing into the ceiling opening from below. Most units have flanges that rest on top of the drywall. Screw or nail the flanges to the ceiling joists or blocking—use at least four fasteners. Make sure the housing is level and sits flush. If the joists are not aligned with the opening, install blocking (2x4 or 2x6 between joists) and fasten to that.
Run power safely. Run Romex cable (12/2 for most fans) from the nearest existing circuit or from a new circuit breaker—most fans draw 0.5 to 1.0 amps, so you have flexibility. Run the cable through the attic or wall cavity to the fan housing, then down to the switch location. Use staples to secure the cable every 16 inches. Do not leave live wire exposed in the attic. If you're uncomfortable doing this, hire a licensed electrician.
Verify the fan spins. Inside the fan housing, connect the incoming hot wire (black) to the fan's hot wire, the neutral (white) to the neutral, and the ground (bare copper or green) to the green ground screw. Use wire nuts and wrap with electrical tape. Connect the switch wiring in the wall box. Screw a blank cover plate to the switch box for now, leaving the switch disconnected. Turn the breaker on and test the fan at the housing directly by touching the hot and neutral wires together briefly—the fan should spin. Disconnect and finish switch installation after drywall repair.
Trim and seal it all. Cut drywall patches to fit around the flanges, tape the seams, and mud as you would any ceiling patch. Once dry, paint to match. Install the fan grille and damper into the housing opening from below—it should click or screw in place. Install the switch cover plate. Final step: from the attic, verify the damper moves freely and the exterior vent cap opens and closes with the fan. Clean any ductwork debris before closing the attic.