Flat roof ventilation
Hello have a question about two way breather vents. I had a Roofer come and install a TPO roof and I want to be sure that the correct ventilation has been installed. It is a masonry residential construction (parapet wall wall around) with a flat roof on top using open webbed joists. Originally the home Had blow in fiberglass insulation in between these joists which created a problem with mold and moisture (previously the roof was had some types of vents where the roofer only cut into the rubber and not the roof deck) . All of the fiberglass insulation has been removed and I had 6 inches of iso poly boards installed on top of the roof deck. The project is approximately 10 squares with six two way breather vents installed. We are located in the Midwest and my concern is with the cold winters here will these breather vents bring in too much cold into the home possible causing condensation issues? Should they have installed one way vents?
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Do you have any photos and/or sketches of the vents and roof assembly? I'm having trouble imagining it.
There is a parapet wall all around
This article should cover everything you need to know: https://www.greenbuildingadvisor.com/article/insulating-low-slope-residential-roofs. With foam insulation above the roof deck, you should not have any venting at all; it will render the insulation useless. Unless there is something that isn't clear from your description.
My only issues is the space between the drywall and the roof deck is exposed to the masonry wall (I did install rock wool in between the trusses). the brick does get periodically sealed but I am certain that moisture still is coming through that wall and this is the reason why vents were installed. With this information, do you still think it’s better to get rid of the vents?
raskoosk657,
As Michael said: if you have vents there is no point having the roof top insulation. It's like getting your walls insulated and leaving the doors open. The masonry walls at the perimeter should also be insulated with either foam board or spray foam as they are both a thermal bypass, and a source of potential moisture in the roof cavity.
raskoosk657,
I think your original vents in the TPO roof were correctly installed. I have a PVC membrane roof and was offered similar vents for two areas that might suffer uplift from wind flow across the roof. I declined as they are quite tall and would have been right outside a window.
The purpose of the vents is to equalize pressure under the membrane to counter the uplift effect. Think of the valves as AAV for your roof membrane. Not sure why a two way valve would be needed. And yes I do partially regret not using the vent, ugly as it would have been. We gets winds up to 60mph that cause the two sections to lift up almost 8 inches.
Malcolm is right about negating the insulation layer. These vents should be corrected.