We live in an area of deep snow and crazy winter temperature fluctuations (northern BC, Canada). We've owned this house for two years and have made significant improvements to sealing the attic/ceiling and improving ventilation. Last year we replaced the roof but I am still seeing some problems that I'd like to fix. I insulated the 2 skylight tunnels to R30, and installed continuous ridge vent, and while we still get ice dams, they are significantly smaller than they were last year. I have included a drawing of the roof design, and showed the four areas where we are still experiencing ice damming.
In areas where there is continuous cold air wash from the soffits to the ridge vent, there is very little ice build up. On the other hand, at the left side of the drawing between the dashed lines, there is no soffit ventilation, and I believe the heat build up and poor circulation in this area is resulting in warmer temperatures. I have two ideas on how this might be solved:
1) install soffit vents from the eaves at the left of the photo up under the dutch gable. This would allow cold air to come up through the soffits and into the attic in an area that is too warm. I am guessing that a baffle of at least 6' would be needed to span the distance from the outside wall to the underside of the dutch gable wall. Are there any reasons I shouldn't do this?
2) remove excess roof sheathing in the attic to improve air circulation between well-vented areas and poorly vented areas. For example, the dashed lines show where the roof sheathing is present in the attic. Openings large enough to walk through were cut in the sheathing in these spots, but there is very little air circulation between the main part of attic and the top and bottom bits at left of the drawing. Is there any harm in cutting away some of this sheathing?
Lastly, there are 4 gable vents left in place at each gable. I've read many discussions on here about whether to leave them or remove them. What do you think?
I appreciate your input, as I've had a difficult time getting a straight answer from those I've talk to where I live.