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ATTIC POWERED VENTILATION
DH100W Humidistat
• Sold separately for use
with all Broan powered
attic ventilators. Humidistats
automatically turn on the
fan when moisture in the
attic is detected
Model 73
• High Temperature
Cut-off sold
separately for use
with all Broan
powered attic
ventilators. High temperature
controls automatically turn off
the ventilator at 204°F
• For additional switches see page 52–53
433 Automatic Shutter for
Gable Mount Attic Ventilators
• Feature counter-balanced aluminum
vanes that automatically open and close
when the ventilator turns on and off
• Better air flow than stationary attic louvers
• Extruded aluminum frame fits flush with
outside wall
• Weather-tight
closure
• Easy to install
For use with Broan Models 353,
35316, 345GOBK or 345GOWW.
19"
19"
16
1
⁄4"
1
1
⁄2"
1. Calculate the volume of your attic, in cubic
feet, depending on the style of your home’s
roof.
Attic Volume for Gable Roof:
Volume = Length x Width x
Height x
1
⁄2
Attic Volume for Hip Roof:
Volume = Length x Width x
Height x
1
⁄3
2. Attic Volume x 10 Air Changes per Hour
= Total Cubic Feet per Hour of ventilation
recommended.3. Total Cubic Feet per Hour
60 Minutes/Hour = Cubic Feet Per Minute
(CFM) of Ventilation Recommended.
Example: Average Gable Attic Volume =
58
3
⁄4' x 29' x 7
1
⁄4' x ½ = 6,176 Cubic Feet
6,176 Cubic Feet x 10 Air Changes/Hour =
61,760 Cubic Feet/Hour ÷ 60 Min./Hour =
1,029 CFM
3. Replacement air is drawn through vents
in your soffit. To determine the minimum
soffit vent area required (in square inches)
multiply the total CFM of your powered
ventilator(s) by 0.48. This number is the total
square inches of soffit venting required by
your powered ventilator(s).
Example: 1,029 CFM x 0.48 = 494 Square
Inches of soffit vent area recommended
DETERMINE YOUR VENTILATION NEEDS
PUT MONEY BACK
IN YOUR WALLET.
433
ACCESSORIES
Prevent heat and moisture build-up. In summer, attics
can reach 150°F or more, warming your living area,
increasing the air-conditioning load, and adding to your
energy bill. In winter, ice dams can result, and moist air
can condense causing mildew, rotting wood and wet
insulation. Year-round attic ventilation ensures a cooler,
drier attic that can extend roof life by preventing rot,
premature aging and shingle distortion. A cooler attic
extends the life of your air conditioner and lowers air
conditioning expense.
How Much Ventilation Do You Need? Effective ventilation
requires air to exit at or near the peak of the roof
with replacement air drawn through soffit venting
and louvers. The Home Ventilating Institute (HVI)
recommends at least 10 air changes hourly to equalize
temperature. Determine your attic ventilation needs
below, or try the Attic Ventilation Calculator at broan.com.
PULL THE HEAT OUT OF YOUR ATTIC.
46