I'm glad you are getting suggestions from people in your general area. They should have more credibility than someone that lives where I do for you. The reason you see so many different opinions is that so many different things work. Many people do things for ther chickens thinking they need them but they really don't.
I don't know how warm you get in the summer. I'd think the nights are pretty pleasant compared to some of us and nights are when the chickens are on the roosts. But daytime heat can be a risk too, especially in the coop when they are laying. Chickens can handle cold much better than heat.
What I suggest you consider is to leave the top of some or all walls open for about 4" to 6" and cover that with hardware cloth to keep predators out. The areas between the rafters are usually under the overhang and are hard to fit the siding in anyway. Covering those openings with hardware cloth is a great way to provide ventilation. Leave that area open year round and put your roosts low enough so the chickens are not sleeping in the cross-draft. That should be all the winter ventilation you need.
During the summer, a direct draft hitting them when they roost is not a problem at all. It can even be pleasant for them. So consider a window or some type of opening at or below roost level that is predator protected but can stay open all the time in the warmer months but you can close off in the winter.
Duckinnut makes some good points about why you might want to insulate, but keeping them warm is not one of them in your area.
I'll give links to some articles that might be a real help to someone building a coop and run. The lady that wrote these lived in Ontario so she should have some credibility to you.
Pat’s Big Ol' Ventilation Page
Pat’s Cold Coop (winter design) page:
Pat’s Big Ol' Mud Page (fixing muddy runs):