Yes. Heritage permits are routinely granted for installation of more energy efficient doors and windows as long as replacements are in keeping with the original character of the house and the existing doors and windows can not be repaired to make them more energy efficient. The replacements must be painted wood, which is the original material used in all Cabbagetown heritage homes.
Finding replacement windows and doors that are in character has become much easier as upgrading for energy savings has become common. Several suppliers now have lines of energy-efficient replacements that match the window and door styles of period homes.
It should be noted that in some cases, such as with stained glass transom windows, the original frames should not be replaced unless absolutely necessary. They can be repaired or upgraded in ways that that make them more energy efficient.
Window and slate repair and restoration are often candidates for the City’s Heritage Grant Program.