Ventilation--remove "mushroom" vent/fan? and zinc

I am in the process of getting estimates to rip off and replace my roof in Connecticut. I have two questions:

  1. I currently have an electric “mushroom” vent on the roof that is thermostatically regulated. It works fine. My new roofing project will include installing a ridge vent as well as soffit vents since I currently only have gable venting.

One roofer suggested removing the fan, deeming it unnecessary with the new ridge and soffit vents. He also suggested the gable vents be covered over with heavy plastic or plywood.

Another roofer said the more ventilation the better and to leave the functioning fan as well as the gable vents.


  1. I have a HUGE problem with lichen and moss. I will definitely get the algae resistant shingles but am considering zinc strips as well. None of the roofers seem to really believe in the zinc strips but are willing to install them. Online info says they work for about 20 feet below the strip. One roofer said that they need to be much closer (about every 5 feet) to have any effect.

Again, opinions?


Re ventilation, this info may help you decide. I would leave the fan installed and the gables open. … -Fans.html

The zinc/copper strips work, but relative to how much surface area is exposed.

I will say, just in plain english. Putting a power vent on a roof with ridgevent is well ventilating only the section between the ridge and the power vent. The idea from air vent to close off the gables are to produce the maximum airflow ratio of 18.5 iches of ventilation per foot. When the gables are open you will float depending on how many soffits and how long the ridge is around 14 at best so the manufacturers warranty could be comprimised. Since i became injured i have done hours of reaserch on this subject. Goto it will explain ventilation from a billion dollar level. Zinc strips never used them always used alge resistant shingles. Now Dennis is a great roofer and on this subject we will never agree. Like everyone we have our own opnions. I feel since i went thru the training and have used it in the world getting the roof past the certainteed rep if a failure had happened i was correct in my ventilation install. Airvent was sold 2 years ago by certainteed. And its theroy and proof still lives as of today. Like i said Dennis is very good at what he does but i just dont agree with his idea.

Anyone care to break the tie? I know how important it is to get this done correctly so I would love to hear other expert opinions.

“I would leave the fan installed and the gables open.”

I believe the vents will short circuit. Air will draw from the path of least resistance. With multiple types of exhaust there is a chance of some becoming intake and not circulating through your whole attic. I compared it to a straw with a whole in it. The exhaust (top) will draw air in through the hole and reduce the amount from the bottom (intake). I fought with Dennis about this when I first joined the forum. Actually I fought and he responded calmly. Now that I’ve seen his work and heard his input on other subjects I respect him and his work, just not his ventilation theory.

If your going with ridgevent and soffits remove power and gable vents,and make sure you got a clear path from soffit to ridge.