Adding a secondary suite to my 1960s split-level in Parkland - do I need a separate furnace, or can I zone the existing one?

You can typically zone your existing furnace for a secondary suite in a 1960s split-level, but you'll need to upgrade your system to handle the additional load and meet Alberta Building Code requirements for separate temperature control.

Most 1960s split-levels in Parkland have adequate furnace capacity to handle a secondary suite addition, especially since these homes often have oversized heating systems by today's standards. However, your existing ductwork will need significant modifications to properly serve both units. The Alberta Building Code requires secondary suites to have independent temperature control, which means installing a zoned system with separate thermostats for each unit.

A zoned system uses motorized dampers in the ductwork controlled by separate thermostats for each zone (your main house and the suite). When one thermostat calls for heat, only that zone's dampers open. This approach is typically more cost-effective than installing a completely separate furnace system, with zoning upgrades running $3,000-$8,000 compared to $8,000-$15,000 for a second furnace system.

Calgary's climate considerations make proper heating design critical. Your HVAC contractor will need to perform a Manual J heat load calculation to ensure your existing furnace can handle the additional square footage. Most 1960s furnaces in Calgary are 80,000-120,000 BTU units, and a typical secondary suite adds 15,000-25,000 BTU of heating load. If your existing furnace is undersized, you may need to upgrade to a larger unit anyway.

Code requirements under the Alberta Building Code include fire separation between units (typically achieved with drywall to the underside of the subfloor above), which can complicate ductwork routing. Your HVAC contractor must maintain proper fire ratings where ducts penetrate the fire separation. All work requires an HVAC permit through the Safety Codes Council of Alberta system and inspections by accredited Safety Codes Officers.

Professional guidance is essential here. An experienced HVAC contractor will assess your existing system capacity, ductwork layout, and electrical supply (many 1960s homes need electrical panel upgrades from 100A to 200A service). Don't attempt this as a DIY project - improper zoning can cause pressure imbalances, comfort issues, and equipment damage.

Next steps: Get quotes from licensed HVAC contractors who specialize in secondary suite conversions. They'll perform the heat load calculation, design the zoning system, and handle all permits and inspections. Also remember you'll need a development permit from the City of Calgary for the secondary suite itself - apply through calgaryplanningpermit.ca before starting any work.