I am seeking a technique of venting a flat roof (1/4″ in 12″). I have argued with the building inspector that this should be a sealed system but the code requirement for ventilation is clear. This particular roof abuts a 2nd floor wall and will be used as a roof deck. Unfortunately I have searched manufacturer’s literaature( mod. bit, epdm, liquid roofing, etc.) for years and have found no recomendations on venting. Mostly the details are related to commercial installations. I need a practical solution that will meet the code requirements for exhausting the air.
Thanks in advance.
M
Replies
I once did something similar, EPDM, but no roof deck. IIRC, we called it a sun room. Only solution we came up with was to omit insulation in the ceiling. Uninsulated didn't require ventilation. Looked pretty ugly, but the inspector had nothing to complain about.
Once the inspections were over, we sealed the insulation into the ceiling. No ventilation. So far so good.
PAHS Designer/Builder- Bury it!
What direction are the joists running? Is there a parapet that you could install vents in?
I have used 2" louver pop-in vents installed through the rim joist. I have also installed venting underneath a small overhang or on the inside of a parapet wall. These vents were all installed in the siding as opposed to the roofing. To create continuos venting at the second floor side I have used a cora vent product such as http://www.cor-a-vent.com/sidingventsv3.htm. I have installed this behind the roof membrane creating a path to flat roof vent space. Then countered with a extended z flashing.
Make sure to use baffles to keep the insulation from closing the vent space.
A little creative thinking and some similar products and I bet you will find a solution.
Wood is Good
Adam Greisz
My house has 3 flat roofs: a garage and dining room both having 3 exterior walls that have continuous soffit vents and baffles (2x10 joists on 16" centers). Holes were drilled in the joists and pop up vents (the roofer refers to them as 'witch hats') were installed (3 per roof). An entry hall that is 6'x 24' has 2x8 joists running in the 6' direction and tapered 2x6's running from the high point to the soffits (12') in the perpendicular direction - thus allowing for airflow to a couple of witch hats at the high point.
You can insulate above the roof deck with a product called ACFoam panels. You will get close to R-30 with no thermal bridging and no requirement for ventilation. It will require a new facsia detail and a bit more budget. It is a great way to go. The inspector will look for the exceptions that are used for these systems on countless commercial buildings. I'm sorry but I can'tquote chapter and verse on that.