Ok, I've been reading through the threads, but I don't see something yet like my roof issue. I live in NH, and I do have ice damming issues, and I know it's from the roof ventilation. I'm not much of a carpenter though, so I'm trying to figure out what needs to be done, then determine if it's something I can do myself or if I need a contractor.
My house was initially built as a two story, 18' x 18'. No attic, upper story is a bedroom, roof looks like a 45 degree pitch to me. Bedroom is regular height, btw. Ridge vent is around 10-12' long, in the center (the very ends of the roof drop down, not sure why).
This roof seems to be ok, doesn't dam unless if I turn on the heat tape which is over the eaves. It does not have enough vents in the soffit: I think there is 10 or 20 of those little 2" diam vents. I'm tempted to put more in, though. I can get into a crawlspace and see that the pink foam vent thing was put inbetween the boards that hold up the roofing sheathing is there, so this roof is sorta ok.
The problem is the addition. It's a 12' x 18' on the other side of the house, 1 story, much more shallow roof, say 30 degree. The crawl space above this room is maybe 3' tall, and the rooms have a sloping section that is 5' or so long. Problem is, that sloping section is stuffed with insulation, no pink tray between it and the roof, and no soffit vents. The ventilation for this roof is a single 4" x 6" vent on the side (gable vent?). It's the center of this roof that leaks.
I can get into the crawlspace, and it looks like the old soffits (blocking?) just was never drilled out to allow airflow to go from this crawlspace into the other roofs ventilation system. This crawlsppace is basically sealed from the rest of the house. I'm thinking, I should drill some 2 or 3" diameter holes in all those pieces, so at least air can go up. Problem is, where do I get air into this space?
I think, if I'm understanding the math, that I need at least 1 square foot of ventilation per side (probably more like 2 or more even on this side), but since I can't get air from the soffits w/o ripping out ceilings, what can I do?
Back of house, faces east:
Side of house, with leak, faces south:
Front of house, faces west:
Last side of house (side with soffit vents):
Those skylights are the biggest heat wasters in the upstairs bedroom, but that's a different issue... I think I have some photos of the shingles, they all seem to lie flat after all the ice damming, but I did chip a couple corners when I chipped away the ice (temper got the better of me).