Broan Model QTRE100S Ultra Silent Humidity Sensing Bath Fan. 100 CFM, 1.5 Sones, 4" ducting.

Sensaire® technology detects rapid increases in moisture levels at the ceiling, where steam and humidity naturally rise. Regular humidistats located on the wall simply detect absolute humidity levels and are prone to false triggers, or not operating when they should.
An automated solution to fight excess humidity and mold.Our humidity sensing fans turn on and off automatically to help prevent cosmetic and structural problems associated with excess moisture.
Hands-free operation.Since you never have to worry about turning the fan on, Broan Ultra SilentT is ideal for problem areas in residential, institutional and light-commercial applications. Our exclusive Sensaire® technology is a perfect solution for high-traffic bathrooms, or a kid's bathroom.

It turns off automatically, and that saves money.Humidity sensing fans are ideal for anyone who leaves the house before humidity is properly vented. With a fan this quiet, you can't forget to turn it off when the job is done. That saves energy and money.

NOTE: There are 2 different wiring options for this fan - see wiring guide.   Use 2-function switch model 68W for option # 2.

FEATURES: 

.  Nearly silent operation 1.5 Sones
.  100 CFM
.  Sensaire® technology detects the rapid rise in humidity over time
.  Integrated 20 minute auto shut-off timer
.  Energy Star qualified
.  Hanger bars for Easy, Fast and Universal installation in all types of construction
.  UL Listed for use over bathtubs and showers when connected to a GFCI protected branch circuit.
.  Housing Dimension: 10-1/2" x 11-3/8" x 7-5/8"- Fits 2" x 8" construction
.  Grille Dimension: 13" x 13-3/4"
.  ENERGY STAR® qualified

ADDITIONAL INFO:
BLOWER:
. Plug-in, permanently lubricated motor - engineered for continuous operation
. Dynamically balanced centrifugal blower wheel for quiet, efficient performance
. Maintains a high percentage of rated CFM in less than ideal installations
. Low RPM for quiet operation
. Resilient anti-vibration motor mounts
HOUSING:
. Rugged, 26 gauge, galvanized steel construction
. 4" round ducting for superior performance
. Polymeric duct connector with tapered sleeve and no metallic clatter
. 7-5/8" height allows for 2" x 8" (nominal) joist installations
. Sturdy, easy, four-point mounting directly to joist
. Includes unique spacer (patent pending) for mounting to engineered "I" joists
. Includes hanger bars to position housing anywhere between 16" to 24"-on-center joists
. Two sets of mounting holes for hanger bars allow flush installation with bottom or top of drywall
GRILLE:
. Polymeric construction
. Innovative design - the result of extensive research with designers and consumers
AUTOMATIC CONTROL:
. Humidity control automatically turns fan ON when either of these conditions is detected:
- a rapid to moderate increase of humidity
- humidity above factory set-point
. Two wire manual operation for odor control - Turns fan ON when power line through wall switch is cycled ON, OFF and back ON
. Remains ON for 20 minutes after humidity has stabilized and is below factory set-point or after manually initiated through power line cycling
. Saves energy because unit runs only for the time required. A unit controlled with a wall timer may keep fan ON longer than required or turn it OFF before room is sufficiently ventilated