Question about an always interesting topic. ATTIC VENTILATION.

Some background and specs.

1980's Cape up in New England. It's single dormer. Front side pitch is 12 with an unconditioned kneewall (insulation bats in floor and against kneewall.) I believe it's sealed off from the upper attic above it.

Rear upper roof pitch is 4. Two stories up.

There are two large gable vents on each side of the attic, and a ridge vent running the length of the top. The upper attic area is roughly 800 sq ft. It's tough to work in. Everyone so far has had to commando crawl on their bellies or backs to work up there.

Moved in this past winter. Areas of R0 insulation on attic floor for the upper area. This combined with the low pitch caused terrible ice dams in the back.

A combination of DIY work and professional energy audit ended up seeing the air leaks in the attic and basement all sealed, along with the upper room ceilings (as much as possible) and then we had cellulose blown into the attic floor up to R49.

The ice dams seemed to subside for the second half of the brutal winter.

OK, now it's spring. Getting quotes to repair the shingles and some sheathing that were damaged by the ice dams and their subsequent removal.

Getting MANY conflicting opinions on whether I need to get soffit vents installed on the underside. I know there was cellulose blown into the soffit cavities, so it would require either scooping it all back and putting in baffles, or attacking the project from the top while the sheathing is removed.

Anyone have experience with retrofitting soffit vents into an older roof/attic? The kneewall side already stays cold in winter. In fact, I insulated the doors to the living space because they were cool and drafty during the winter time. However, I am getting conflicting quotes. Some say "you don't need soffits when you have the gables and ridge". Others are telling me "You need soffits to not void the shingle warranty, and you're gonna get attic 'hot spots' without them."

My head is spinning from the number of articles I'm reading about insulating, ventilating and the like.

Any experiences/opinions from similar situations, or what a soffit vent retrofit should generally cost would be greatly appreciated.