Cockroaches are tropical insects that evolved over millions of years. They are not like most insects you have seen before and are closer to an arachnid in their structure. They do not have a liquid centre with free-floating organelles like flies and ants they have actuarial organs and a digestive tract as well as blood. Their blood is very much like the blood of reptiles which means they are cold-blooded.
What is Cold Blooded
This allows the cockroach to survive without food or water for weeks but also makes it impossible for them to survive or breed in cold temperatures. At temperatures below four degrees celsius, the cockroach ceases to be able to mate. At temperatures below ten degrees Celsius, they start to die. Anything below that and they are icicles.
Cold Blood in Cold Climate
This is why, if they want to live in the north where there is a winter then they need to find a warm place to live in the winter. This means finding human homes and businesses where they can gain access to food and water and enjoy the residual heat of the kitchen and bathroom.
Killing cockroaches with cold
Aside from picking them up and throwing them into the freezer which may not even work as the freezer is only about zero degrees and cockroaches don’t die at that temperature, trying to kill cockroaches with cold will not work. Turning the heating off, and leaving the door and windows open will not cause the house to get cold enough as most buildings and houses built after the 1700s are structurally made to retain heat even if door and windows are left open. One of the reasons a lot of people like to keep the window cracked even in the dead of winter. This will not kill the cockroaches and they will still be able to survive in wall cavities and other areas that retain heat better.
Cockroaches can be killed with poison bait, insecticide dust and pesticides, however. While some of these things are dangerous to humans they are a requirement when getting rid of cockroaches which are a serious threat to human health. Much more so than domestic pesticide sprays. Permethrin which is derived naturally from the chrysanthemum flower is only dangerous if you inhale it directly. Holding the can a foot away from you and spraying the wall with it will not put you in danger. Insecticide dust is silica dioxide and is safe for humans to eat. If you want a safe treatment you can use that but it is rarely enough to kill off an infestation.
The best method is to call a professional licensed pest control technician and have them do a commercial-grade treatment that will treat the infestation quickly. It is effective and guaranteed often coming with a warranty of multiple months to ensure the infestation is gone and has a very high success rate. Getting professional treatment in Ontario is also very safe as all the pesticides used are monitored and controlled by the ministry of the environment of Ontario. They are designed to be safe after a very short vacancy.