Perennial herbs that are not hardy in your region can be overwintered indoors, then brought back outdoors in the spring. For example, in USDA Zones 7 and colder, bring rosemary and lavender plants indoors in late fall. Maintain them in a cool, bright spot over the winter, and move them outdoors again in the spring. In USDA Zones 8 and warmer, rosemary and lavender can be left outdoors year-round.
To stop airflow between walls and floors, Install foam gaskets on all outlets and switches, and use child safety plugs backed with punch-outs to keep the cold air from coming through the sockets. Remember, be careful whenever working around electricity.