Canvas does breath a bit, but if you have the windows and doors closed up, it can get pretty warm during the summer months. If heat is a problem, you can either open up both windows on the front and back of the tent to get some cross-ventilation; or, you can look at getting the 6010 Kodiak tent, which has 2 additional windows for more ventilation. This tent is not designed to have a heater in it as canvas is flammable and there is not a place in the tent design to let off the exhaust from your heating source.