Homeowner Romeo Carsello from New Jersey had these questions concerning gable end vents:
“I'm getting conflicting advice. Does having gable end vents (one of which has a gable end fan) work against soffit vents and a ridge vent. Should I power down the fan and block off the gable end vents? Roof is a typical A frame, ridge vent runs the entire length of the roof. I recently installed baffles, increased openings in all of the soffits for better air flow, and added a layer of R30 unfaced insulation throughout the attic.”
Our resident expert roofer, John Stout, with the help of Martin Stout, with Go Roof Tune Up™, had this to say in response:
Thank you for such an interesting question. The question is so interesting that I had to go to my “Big Guns” (my son Martin) to get the answer. Having conflicting advice is sometimes worse than having no advice at all. Martin’s answer is simple and to the point. I hope his answer helps.
The short answer is “it could.” It’s all in the details: How many square inches of soffit ventilation do you have? How many square inches of ridge vents do you have? How many square inches of gable vents do you have and how far are the gable vents from the ridge?
If the gable vents are very close to the top of the gable and you have close to 50% of your total ventilation in your soffits and you turn off your fan, your system will work just fine.
If the gable vents are down from the top of the gable a bit (three feet or more), then blocking them is a good idea.
Air flows just like water, to the line of least resistance. If hot air is exhausting out the ridge vent and air can be drawn from the gable vents, then the air below the gable vents will not move as you would like for it to.
Your goal should be to get as close to 50/50 high low ventilation as you can. For sure, turn off the fan.
I hope this information helps.
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