Attic Ventilation FAQ

Answer

Use the calculator on the Broan.com website, or follow the example below:

1. Calculate the volume of your attic, in cubic feet, depending on the style of your home’s roof
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 of ventilation recommended. Many Attic Ventilator manufacturers provide ratings for their products’ Cubic Feet per Minute (CFM) 
   
   Example: Average Gable Attic Volume = 58.75’ x 29’ x 7.25’ 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

Answer

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.

Answer

If you have eve vents or gable vents multiply the length by width of each one. This will give you the square inches (if the opening is covered with screen divide by 2). The net free area may be stamped in the frame on the vent. Add up all the totals from all of the vents to get your total existing free air area.

Answer

We recommend adding additional free air area to insure that your Attic Ventilator works at optimal efficiency.

Answer

This varies depending on the climate of your home and the sun exposure of your roof. A starting point to determine an on/off temperature is to measure the summertime temperature of the attic in the evening, when there is no sun. Use this temperature as a baseline; when the temperature gets warmer, the ventilator should operate.

Answer

Yes. The dome may be painted using a normal water base exterior house paint.

Answer

No. Gable Ventilators are designed to be installed on vertical locations.

Answer

No, except for Gable Mount styles, Broan attic ventilators are to be installed on horizontal or sloped surfaces.

Answer

Yes. Note that a curb will need to be built so that the housing is higher and snow and water levels would not affect product performance.

Answer

Yes. Use model DH100W.

Answer

Yes, Model 72W or 72V variable speed controls may be used with the Models 350BK, 350BR, 353, 35316, 355BK, 355BR and 358. Do not use these controls with Models 356BK or 356BR.