Similar to another user, we are looking to insulate our attic kneewalls. We have a 2 1/2 story double brick home; the pitched section of the attic is insulated with interior vapor barrier but the kneewall sections are uninsulated. We're looking to use blown cellulose to the floor area and then either fibreglass bats or polyurethane to the backs of the kneewalls. The insulation contractor we spoke to told us we need to make sure the cold attic spaces are properly ventilated. Between him and a roofing company I spoke to, I understand we should have soffit venting coupled with roof vents. We have a few roof vents and could install a few more. Any air from the kneewall spaces will have to pass through the fibreglass bats that currently insulate the pitched sections as we can't assume they left a decent gap on the cold side for air to pass through. The problem seems to be soffit venting. The house has gorgeous wood dentil detailing on both the soffit and fascia that would be destroyed by installing soffit venting. The detailing is absent along the back of the house, so we could do soffit venting there, but it runs the entire length of the front of the house, as does the front kneewall. What we'd like to understand is how crucial adding the soffit venting really is? Are we going to rot out our roof if we don't install the venting? How is this handled in other old homes? We're trying to do the best we can but also keep historical character, but we need some help here. We need to use that attic space and it is COLD in the winter and HOT in the summer (despite having AC up there), plus our winter heating bill is outrageous!
Thanks so much!