I have only installed turbine ventilators on a roof before the shingles. Maybe someone else has more experience with a retrofit situation.Thanks! I was looking at styles like these. Would they just replace the vent on the rear of my roof? Any harm in doing one of each over those vents?
This is what I have currently on the back of the roof (just a stock pic I found online).
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Just like my electric vent fan, I put hinged plywood covers to block the hole under them to hold the heat in during the winter.