What are the Alberta Building Code requirements for fireplace vent termination height above a roofline?

In Alberta, gas fireplace vent termination heights are governed by the Alberta Building Code (ABC) and the CSA B149.1 Natural Gas and Propane Installation Code, which is adopted by reference — the specific requirement depends on your fireplace type, roof pitch, and the proximity of the termination to windows, doors, and other openings.

Direct-Vent Gas Fireplaces (Horizontal Wall Termination)

Most Calgary homes use horizontal direct-vent terminations through an exterior wall rather than through the roof, so roof height rules don't apply in those cases. But when a direct-vent gas fireplace does terminate vertically through the roof, the vent cap must be:

• At least 300 mm (12 inches) above the roof surface at the point of penetration
• At least 600 mm (24 inches) horizontally from any vertical wall or parapet that could cause wind turbulence and downdrafting

For horizontal terminations through walls — the most common setup in Calgary — the termination must be at least 300 mm (12 inches) above grade, at least 300 mm from any inside corner, and at least 1,000 mm (approximately 39 inches) below and 300 mm horizontally from any window, door, or gravity air inlet that could allow combustion gases to re-enter the building.

Wood-Burning Fireplaces and Class A Chimney Systems

This is where roof height rules become more specific and more critical. Under the ABC and NFPA 211 (referenced for solid-fuel appliances), a wood-burning chimney must:

• Extend at least 600 mm (24 inches) above the highest point where it passes through the roof
• Be at least 600 mm higher than any portion of the roof within a 3-metre (10-foot) horizontal radius

This "2-foot/10-foot rule" (or its metric equivalent) is the standard most Calgary installers and WETT-certified technicians work from. It ensures the chimney clears the turbulent air zone created by wind flowing over the roofline — critical in Calgary, where chinook winds create significant pressure differentials that can reverse chimney draft if the termination sits in a low-pressure zone behind a roof ridge.

Why Calgary's Chinooks Make Termination Height Even More Important

The code minimums are a floor, not a target. Calgary's chinook events create rapid barometric pressure changes and strong directional winds that can overwhelm a chimney that barely meets minimum height. A chimney terminating just at the code minimum on the leeward side of a steep roof pitch may backdraft during a chinook event, pushing smoke or combustion gases back into the home. Many experienced Calgary installers recommend extending chimneys 300-600 mm beyond the code minimum on homes with complex rooflines or known chinook exposure, and installing a wind-directional chimney cap to further reduce backdraft risk.

Clearances from Windows and Mechanical Openings

Regardless of fireplace type, the termination must maintain clearances from any opening that could allow exhaust gases into the living space. For gas appliances under CSA B149.1, the general rule is 1,000 mm below and 300 mm horizontally from operable windows, doors, and mechanical air intakes. Violations of these clearances are among the most common deficiencies found during Safety Codes Officer inspections in Calgary.

Practical Tips

A licensed gas fitter pulling the required gas permit from the City of Calgary (or your municipality) will be responsible for ensuring the termination meets code — this is confirmed during the Safety Codes Officer inspection before the unit is commissioned. For wood-burning installations, your WETT-certified installer documents compliance with chimney height requirements as part of the WETT inspection report, which your insurance company will likely require.

If you have an existing chimney and are unsure whether it meets current termination requirements — particularly after settling, chimney repair, or a roofing project that changed the roof profile — a WETT inspection ($250-$400 in Calgary) will give you a definitive answer.

Need help finding a qualified fireplace installer or WETT-certified inspector in Calgary? Calgary Fireplaces can match you with local professionals for free through the Calgary Construction Network.