There are lots of older homes in Ottawa Ontario that does not have significant ventilated soffit installed to increase the fresh air flow into the attic. Majority of the older homes did not come with that feature and those homeowners replace the roof way more often than they should.
Roof vents are designed to help all the fumes, hot air from your attic to escape so that the temperature of your attic is same or similar to outside. In order for the roof vents to work properly it requires fresh air to enter from the soffit. When there is no intake/fresh air entering the attic ventilation process is very slow maybe even non. You can install as many vents as you like but it requires fresh air to create a force to complete a cycle.
During winter months it is very easy to point out which house does not have proper air circulation just by looking at the ice dams. When the snow covers the vents on your roof it suffocates your attic and that causes condensation, forces the hot air to exit from the soffit instead of the roof vent itself. Hot fumes exiting from the soffit creates a thaw action daytime and allows it to freeze overnight. After few weeks of that will give you a massive ice dam that will form along the eavestrough and it will work its way along the metal valley. It can get messy once this ice starts to melt and cause major water damage to the houses.
It is not a very big job to do but there are only certain roofing companies who will be able address that issue. Many roofing companies would want to get paid for removing ice dams instead of fixing the lack of air balance. We offer residential and commercial soffit and fascia sales, installations, repairs and services in greater Ottawa region. We also do offer free quotes and estimates to potential customers who is experiencing that types of problems.