My house is in an area which often gets -30c winter days and 30c summer days.
It's shaped like this (note that ventilation holes are also the same on the other side of the house):
Note that the roof is totally straight, not curved. On the 2nd floor which is shaped like an A, in winter the house easily gets cold and in summer, it easily gets hot which, IMO, probably signifies a lack of insulation or some kind of ventilation problem maybe.
The main issue is that almost every winter, water is leaking from the roof, especially in the beginning of the spring, where an ice dam is already formed at the end of the roof, near the gutters.
(Always refer to above picture for colored items mentioned below)
In March, I went in the soffit area (the last 3 feet below green line, sorry, there's probably a term for this area) and the water leaking is indeed aligned with the ice dam, which is in center of the roof. Many 2x6 rafters were soaking wet, actually DRIPPING water. Most of this is going inside my house through the plywood and sheet rock :(
There is insulation wool everywhere between the 2x6 rafters from the green line to what seems all the way to the attic and this is all across the entire roof. I've been told by somebody recently that this should not have been built like this as it prevents hot air from escaping through the roof ventilators as the air can never leave below the green line, causing ice dams in the winter and when spring comes, it's hot enough to quickly melt and drip inside of the house. NEED EXPERTISE ON THIS PLEASE.
All the vents on both sides of the house are OPEN and wind is going through, I've verified this by entering the last 3 feet, which is outside of the house. I have access to both the front and back soffit areas. I've been told that when roof ventilators are installed, all the side vents of the house should be shut/closed to prevent disrupting the normal ventilation process of hot air going up and escaping through the roof ventilators. NEED EXPERTISE ON THIS PLEASE.