I have a bad mosquito problem here in Ontario too. I was told to sweep all the hay, etc that was on the floor out of the coop. My coop gets flooded a bit when it rains and the hay would stay damp for days. I was also given a spray for spiders that I was told to spray on the walls, roosts, nesting boxes, etc. It is safe for the chickens. I have 2 guineas that eat a lot of the mosquitoes. A lite in the coop at night is supposed to let the birds see the bugs better. I was also told that ducks eat mosquitoes but mine are sleeping ont he pond and wont come into the coop at night. Another spray that is safe for chickens is listerine the mouthwash. Havent ried that one yet, but will soon!
I hope some of these suggestions work for you.