Ridge Vent Hole & Membrane

Guest User
10/31/2017
I'm having a local company install metal roofing overtop our existing shingles. They've already cut open the hole for the ridge vent, laid down the moisture membrane overtop the entire roof and applied strapping. My concern is with the ridge venting. I have an older home with a low slope 3/12 roof. Ice damming occurs. I've already had insulation blown in and opened all my rafter vents. Its seems good to go. However my understanding with the ridge vent is the metal roof crew will be using their Utility Knife to cut a simple slice in the membrane but leave the entire fabric overtop the ridge hole. Wont this greatly impede the heat exhaust at the ridge? Shouldnt they cut away the entire membrane from the 3" wide ridge hole for the entire run to allow maximum exhaust? The installer said he advises against anything beyond the microscopic slit down the centre despite the fabric still blocking the hole bc IF water enters then it will land on the membrane and not enter the home. Is this a common problem at the ridge cap for all metal roofs? I would very much like for them to open the hole up in FULL. Is there any problem with doing such a thing on my 3/12 slope roof? Thanks!
Todd Miller
Classic Products, Inc.
11/1/2017
Generally speaking, yes, the underlayment is cut away. However, if the underlayment is slit in a way that allows it to "open up" when air is rising up out of the attic, it may be okay. A great deal depends upon your balance of intake and exhaust vents. I would suggest making sure that the ridge vent manufacturer is okay with the product being installed on a 3:12 pitch.

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