http://www.ltb.gov.on.ca/en/Key_Information/STEL02_111464.html
If a landlord provides heat, the Act requires the landlord to keep the heat to at least 20 degrees Celsius from September 1 to June 15. In addition, many municipalities have their own property standards or bylaws about heat. You should contact you local municipal government to find out if your community has a bylaw that sets minimum standards for heat.