BCAB #1901

January 19, 2023               

Re: Vertical HVAC Shaft

Project Description

The subject building is eleven storeys in building height, with the upper 9 storeys being Group C major occupancy, and the lower 2 storeys a combination of Group A and Group C major occupancies. The building falls within the scope of Subsection 3.2.6. Additional Requirements for High Buildings.

The building’s HVAC system supply and return air ducts are located in shafts, approximately 1.5 meters by 3.0 meters that extend from the third floor through to the floor of the uppermost eleventh storey. The shafts are separated from these floors by a fire separation with a 2 hour fire resistance rating, equal to that of the required fire resistance rating for the floor assemblies, except for the uppermost eleventh floor. The design considers the shafts to be interconnected with and an extension of the of the uppermost eleventh storey floor area. The shafts facilitate the building’s HVAC ducts and flow controllers.

Applicable Code requirements: (BCBC 2018)

1.4.1.2. Defined Terms (Division A)

1) The words and terms in italics in this Code shall have the following meanings:
Vertical service space means a shaft oriented essentially vertically that is provided in a building to facilitate the installation of building services including mechanical, electrical and plumbing installations and facilities such as elevators, refuse chutes and linen chutes.

3.2.8. Mezzanines and Openings through Floor Assemblies
3.2.8.1. Application

1) Except as permitted by Article 3.2.8.2. and Sentence 3.3.4.2.(3), the portions of a floor area or a mezzanine that do not terminate at an exterior wall, a firewall or a vertical shaft shall
a) terminate at a vertical fire separation having a fire-resistance rating not less than that required for the floor assembly and extending from the floor assembly to the underside of the floor or roof assembly above, or
b) be protected in conformance with the requirements of Articles 3.2.8.3. to 3.2.8.8.
2) The penetration of a floor assembly by an exit or a vertical service space shall conform to the requirements of Sections 3.4., 3.5. and 3.6.

Decision being appealed (local authority’s position)

The local authority has determined the subject shafts shall be considered to be vertical service spaces, as they meet the criteria of the defined term vertical service space in Sentence 1.4.1.2.(1) (Division A). (i.e., they are vertically oriented and contain building services). The local authority considers the applicable Code requirement to be Sentence 3.2.8.1.(2) related to a vertical service space.

Appellant's position

The appellant considers the subject shafts to be an extension of the uppermost storey floor area, and the fire separation with a 2 hour fire resistance rating separating the shaft from the storeys below complies with the requirements of Sentence 3.2.8.1.(1).

The appellant states this is supported by the decision of BCAB # 1654.

Appeal Board decision #1901
It is the determination of the Board that the subject shafts are vertical service spaces and the requirements of Sentence 3.2.8.1.(2) (referencing Section 3.6.) are applicable.  

Reason for decision

The Board considers the subject shafts have been constructed exclusively for the installation of the HVAC services and not for uses usually considered as part of a floor area. The Code specifically identifies a vertical service space and the construction requirements that would be applicable.

Lyle Kuhnert
Chair, Building Code Appeal Board