Why Attic Fans and Ridge Vents Don’t Work Together

Double Ventilation
Erik Mattsson from Mattsson Roofing discusses a common roofing issue found on roofs in Bergen County, NJ. He explains the problem of having both a roof-mounted attic fan and a ridge vent on the same roof, which leads to inefficient ventilation.
Key points:
1. Roof-mounted attic fan:
Controlled by a thermostat (and sometimes a humidistat)
Forcibly exhausts hot air from the attic when temperature reaches a set point
2. Ridge vent:
A 3-inch opening at the roof's peak
Provides natural air ventilation
3. The problem:
When both systems are present, the attic fan pulls air from the ridge vent instead of the entire attic
This limits ventilation to a small area around the fan and ridge vent
4. Proper ventilation:
Choose only one exhaust mechanism: either a ridge vent or a power vent (attic fan)
Match the chosen exhaust with proper intake vents (e.g., at the soffits)
5. Solution for this house:
Installing new roof-mounted attic fans
Closing up the ridge vents to ensure proper whole-attic ventilation
The main takeaway is that using both ridge vents and attic fans together reduces ventilation efficiency, contrary to what homeowners might expect.
#mattssonroofing #roofmaintenance #homerepair #ventilation

[@AceDolo]

This is oddly exactly how to think about fans in your computer.