How to Finish a Basement Bathroom: Install and wire the combination exhaust fan & light, wall switches and vent duct.
This project is continued from How to Finish a Basement Bathroom – Part 16.
Basement Bathroom Exhaust Fan
The basement bathroom is connected to the central central air conditioning and heating system by a ceiling vent installed by the builder, however the basement bathroom did not have a ventilation fan. There was on a very basic light socket and wall switch:
I replaced the ugly ceiling light with a Broan Elite model QTR100L (the newer model is the QTR110L) combination ventilation fan that has 100 watt primary light and 4 watt night light. The night light is convenient when night trips to the bathroom and you don’t want to be blinded. I chose this model for the high air flow, reasonably quiet operation and lighting options.
Another view of the Broan bath fan/light combination and the HVAC vent:
How to Install a Bathroom Ventilation Fan
The steps to install the bathroom exhaust fan are:
- Install plywood decking in the basement bathroom ceiling crawlspace.
This was a huge convenience as it made working much nicer compare walking on the ceiling joists.
- Cut a hole in the exterior house wall for the exhaust vent.
- Install a bird-proof vent cover on the outside wall.
- Cut a hole in the drywall ceiling for the Broan QTR100L bath fan.
Note: The QTR100L (100 CFM) has been replaced by the newer QTR110L (110 CFM), otherwise the units are identical in function and wiring.
- Mount the bath fan to the ceiling joist.
- Install a metal junction box for the bathroom fan power and light switch wiring.
- Wire the bath ventilation fan and wall switches.
- Connect the flexible vent duct to the fan and outdoor exhaust vent.
This is the bath fan installation in the ceiling crawlspace:
I used uninsulated flexible vent duct because the duct is run in the heated crawlspace between the basement and main floor (i.e. inside the home “thermal envelope”) so condensation inside the duct should be minimal. If the duct were run in unheated attic then insulated vent duct should be used.
Closeup of the bathroom ventilation fan wiring. The junction box, flexible metal wire conduit and vent duct must be purchased separately. To minimize vibrations, I caulked the seam between the fan housing and ceiling drywall.
Bathroom Ventilation Fan Wiring
The ceiling junction box wiring is a bit “busy” for the Broan QTR100L ventilation fan due to the wiring connections for the fan motor, primary light and night light. See the Broan QTR110L installation guide for details (the newer QTR110L model wiring is identical to the now discontinued QTR100L).
NM-B 14/3 cable is required for the two light switch connections because it has two “hot” conductors (black and red wires). A separate NM-B 14/2 cable is used for the fan motor circuit and wall switch. The yellow NM-B 12/2 (12 gauge wire conductors) can be seen entering the armored flex conduit to the fan unit; I used heavier gauge NM-B 12/2 because I ran out of 14/2 cable, otherwise 14/2 would be fine.
Notice the #10 green ground screw and ground wire connection in the center of the junction box in the above photo. Metal junction boxes must be grounded per the National Electrical Code (NEC).
The nutted wires are folded into the junction box before attaching the metal box cover:
The bathroom fan, 100 watt light and 4-watt night light are controlled by 3-function switch to fit in one electrical wall box. The bathroom fan is on a separate branch circuit from the main electrical panel and isolated from the GFCI outlet and vanity light:
I’m very pleased with the Broan QTR100L bathroom fan/light combo unit. The Broan bath fan is attractive and reasonably quiet for the volume of air it moves out of the bathroom.
Related Project: Bathroom Exhaust Fan Replacement
More recently, I replaced an old and undersized exhaust fan in the master bath with a Panasonic WhisperCeiling™ super quiet unit.
Finishing a Basement Bathroom
The sewage basin closure and plumbing connections are described in How to Finish a Basement Bathroom – Part 18.
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