Living in Ontario and especially our service areas of Orillia, Barrie, Midland, Gravenhurst, Bracebridge, Muskoka, Simcoe and Georgian Bay we experience some pretty extreme weather conditions and your protection from the elements has a lot to do with insulation. You want your attic space ideally to be the same temperature as outside to minimize shingle damage. So it should be freezing cold in the winter and not cooking hot in the summer. Ventilation and insulation play a key role in achieving this.
It is important to make sure you have adequate and sufficient insulation not only for the energy performance of your home but also for the life span of your roof. And your insulation should be checked every 3-4 years as it can compress or shift in the attic. If insulation compresses it may lose its R value or insulation properties and if it shifts it can cover over areas such as baffles which in turn affect amount of ventilation. Blown in insulation should be 8-12 inches deep as a general rule. Depending on type of insulation (blown in, bat or foam) the required levels vary so it is good to know what your own requirements should be. The blown insulation is what we most commonly see and sits on and in between your roof joists just above the ceiling portion in your home in the open attic space. Some people think the insulation goes right under the plywood on your roof. This would only be the case if you have a cathedral ceiling and even then there's still an open cavity requiring ventilation.
Is it possible to have too much insulation? Yes it is! Too much insulation can create a greenhouse effect within your attic space causing condensation and sweating and what appears to be a rook leak as water drips through and into the house. This can be resolved by either removing some of the insulation or adding more ventilation. Gable vents if possible are a good choice in this scenario.
What are baffles? Baffles are the vents that come up from the side of the roof line where your over hang starts and meets the soffit area. They are meant to help with circulation of air and ventilation of the attic space. Sometimes insulation can shift and cover over these areas making them ineffective.
So before addressing your ventilation concerns and making sure your roof is properly ventilated it is of equal importance to check your insulation.