I have a cape with a shed dormar on the back. The pitch of the dormar is about 3/12. The front is about a 5/12. Is it going to be a problem putting on a ridge vent with the dormar being a low pitch as far as leakage? I live in northeast with snow that sits on the roof.
I do it all the time under the same weather conditions, but in the Chicago Area.
I would Only use the Shingle Vent II or Cobra Snow Country Ridge Vent Products and I also install a J-Channel in the center of the vent over the decking on the low slope 3/12 roof, without cutting out the wood on that side of the roof peak and cut an extra 1/2" to 1" on the 12/12 side, for that area only. The rest of the 12/12 equal on both opposing sides get done the normal way.
The longer leg of the J-Channel gets installed so that the top course of shingles, which get cut horizontally, slides Under the top course shingle edge. I also make sure that there is a heavy bead of Geocel or NP-1 sealant under the External Baffle portion of the plastic ridge vent product on that side, especially when being installed over an architectural shingle which has a few up and down tab configurations.