Many attics have insulation blocking the required ventilation source from your soffits. The Ontario building code requires that you have 25% of your required ventilation come from your attic, 25% from the top of your roof and the remaining 50% can be from anywhere.  1 square foot of ventilation is required for every 300 square feet of attic space.

This picture shows what soffit baffles do and how they should be installed.

Many older homes have had insulation stuffed into space between rafters or trusses on the assumption that blocking the cold air which was entering the home was a good thing to do.  This concept actually hurt your sheathing and roofing materials by allowing heat and moisture to be trapped in your attic.

Regards

Roger Frost

Napoleon Home Inspections

http://www.napoleon.cc

Cell 705-795-8255