No permit for a furnace swap, but one for a new fuel or a woodstove
With a furnace replacement, added air conditioning or heat pump, and a gas fireplace all exempt from a building permit, the permit question for a Fergus job turns on what else changes. Fireplace plans are one trigger: converting an existing fireplace from gas to wood or another solid fuel needs a permit, as does installing any wood-burning appliance. Related work is another trigger: the Township's list also requires a permit to re-insulate walls, ceilings or floors or to finish a basement, so mention either if it is planned alongside the HVAC job. Ductwork is not named on the list, and the list does not say whether a heat pump replacing a gas furnace as the main heat source counts as a new fuel source, so ask the Building Division before work starts.