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Question DetailsAsked on 10/28/2015

Should the 750 vents be kept or eliminated when a ridge vent is added?

We're replacing our roof. One estimator told us his company would remove the 750 vents, because that would work better. Another company told us they would leave the 750 vents, because that would work better. Which is better?

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First and foremost, is there is no 100% correct answer that will apply to all homes since all homes have different roofing designs.


But, with that being said, most of the time if your home was a standard ranch home and you were installing ridge vent, this would eliminate the need for mushrooms. You do not want the "750" mushroom vents still on the home and active. The standard plan for ventillation is; homes should have equal amounts of intake as out put. The intake should come from as far down the roof as possible, normally near your eaves. Then the air should be expelled as close to the peak of your roof as possible. The process is called "convection" and it works off of the premise of heat rising. If you do not remove the mushrooms and those mushrooms are currently near the upper portion of the roof, your ventilation is being short curcuited and only the upper portion of the roof is being vented and the lower portion will heat up. If a home has mushrooms and ridge near the upper portion of the roof the intake will end up being the mushrooms and then the exit will be the ridge. This is a horrible situation.


Now, occasionally there are roofs that will have both, this occurs when the roof has many facets or there is not enough ridge linear footage to properly vent the home. If this is the case, then the mushrooms should only be present in areas where there is not ridge to compete with. Remember we want the air to come in the eaves or bottom of roof and we want it expelled out the top. Please use this as your overall plan then make adjustments for your home design.


BTW, if the roofer who suggested you do both, was going to have the mushrooms right next to your ridge and ultimately "competing with your ridge", DO NOT, I REPEAT DO NOT ALLOW HIM TO WORK ON YOUR HOME. He or she does not understand ventilation.


I hope this explanation helps you and others with the same question.


Exterior Upgrader is owner of

Euro-Tech, Inc.

Servicing much of Illinois and Wisconsin


800-215-8712

Answered 4 years ago by ExteriorUpgrader




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