Part 6 Requirements Applicable to Houses
Part 6 of the OBC is the general technical part for heating, ventilating, and air-conditioning systems. It addresses design, installation, operation, duct systems, ventilation, exhaust, combustion air, clearances, controls, and fire protection interfaces. For a house, Part 9 contains the primary simplified rules-especially Section 9.32 for ventilation and Section 9.33 for heating and air-conditioning-so do not apply Part 6 in isolation. The practical approach is: use Part 9 where it specifically governs the house; use Part 6 and its referenced standards for matters Part 9 does not fully cover; and always apply the manufacturer's certified installation instructions.
Concepts to know include 'HVAC system,' 'air duct,' 'plenum,' 'outside air,' 'exhaust air,' 'make-up air,' 'design temperature,' and 'clearance.' Part 6 is concerned with performance and safety, not just equipment efficiency: a furnace can be efficient but still fail because the duct system, venting, or combustion air is wrong. Part 6 also interacts with fire separations and with energy requirements, so an HVAC change can trigger envelope, fire, and electrical coordination.
A common question trap is to present a house and ask which part controls. The answer is usually Part 9 for the specific residential requirement, with Part 6 filling gaps. Another trap is to treat ventilation as the same as infiltration; Code ventilation requires a designed outdoor-air supply and local exhaust, not accidental leakage.
Worked example: a house has a forced-air furnace, a bathroom exhaust fan, and an HRV. Part 9 governs the residential ventilation and heating provisions; Part 6 principles still require the system to be designed, installed, and controlled so it performs safely. Check the HRV balanced airflow and the duct design, not just the furnace nameplate.