Date of Publication: June 11, 2026 [2023.28.V-02.C]
Subject: Energy Efficiency for Drive-Through Car Washes 2024 OBC UPDATE
2024 Ontario Building Code [O.Reg 163/24 Amended to 5/25] References:
Sentence 1.3.3.1.(2) of Div. A
Clause 12.2.1.2.(2)(b) of Div. B
Article 9.25.1.1 of Div B
Article 9.25.2.1 of Div. B
Supplementary Bulletin SB-10
Incoming Request:
An automated car wash building has been proposed, with a drive-through car wash bay and an overhead rolling door separating the wash bay from the exterior. The building will also have a mechanical room which will house piping and pumps for the car wash system and a second electrical room.
How should the energy efficiency requirements of Part 12 be applied to this building, and in particular, what level of insulation is required in the building envelope?
Executive Summary:
Buildings that have large openings to the exterior or are used for occupancies where the interior temperature is governed by the processes contained in the building, may be exempt from complying with SB-10.
Other buildings which have very low space conditioning requirements or are unheated may be exempt from the building envelope requirements of SB-10. If a designer is proposing an exemption, they must provide documentation and ensure the architectural, electrical and HVAC plans all support the exemption.
Discussion & Considerations:
In this example the proposed building is classified as having an F3 Occupancy, similar to a storage garage (see OBC Table 11.2.1.1.N.). The building is single storey, free-standing and has a building area of less than 600 m2, so it will fall under Part 9.
The typical code path that takes one to SB-10 is as follows: Sentence 1.3.3.1.(2) of Div A. àPart 12 àClause 12.2.1.2.(2)(b) states that the building must comply with SB-10 Division 1(General) and either Division 3 (compliance via referenced energy efficiency standards) or Division 5 (simplified requirements).
Note that SB-10, Article 1.2.1.1 of Chapter 1 of Division 3 describes buildings, parts of buildings, processes and occupancies that are exempt from complying with SB-10. Specifically, Sentence 1.2.1.1.(1) exempts certain occupancies from compliance with all aspects of Div 3 and 5, Sentence (2) exempts certain occupancies from the building envelope requirements only, and
Sentence (3) references exemptions contained in the referenced standards. These exemptions are also applicable when using Division 5 for compliance, via Sentence 1.1.1.1.(5).
OBC Article 9.25.1.1. of Div.B. also requires walls that separate conditioned space from unconditioned space to be provided with thermal insulation, a vapour barrier, and an air barrier system. To determine thermal insulation requirements, Article 9.25.2.1.refers the user to Section 12.2., then to SB-10, where the exemption found in SB-10 Article 1.1.2.1. of Chapter 1 of Div. 3 may apply. Note that conditioned space is a defined term:
Conditioned space means space within a building in which the temperature is controlled to limit variation in response to the exterior ambient temperature or interior differential temperatures by the provision, either directly or indirectly, of heating or cooling over substantial portions of the year.
Exterior building envelope is an undefined term used in SB-10. For a building that contains both conditioned and unconditioned spaces, one might consider an interior wall separating these spaces to be treated as an extension of the exterior building envelope.
If the building is not subject to the above-mentioned exemptions, and compliance is being achieved through SB-10 Div.3, (referenced standards) Chapter 2, ANSI/ASHRAE/IES 90.1 contains detailed definitions of conditioned space, semi-heated space and unconditioned space, and makes allowances for semi-heated spaces. The standard also defines exterior and semi-exterior building envelope. See Sentence 1.1.1.4.(2) of Div. 3, Chapter 2 of SB-10 and the ASHRAE standard for details.
One further consideration is related to the mechanical systems, specifically the plumbing. Although there will likely be some plumbing in the building, any piping, pumps, valves, etc. (drainage or supply) that solely function within the car washing system would be considered process piping and therefore would not be subject to any OBC requirements for protection from freezing, approved fittings, materials, etc. The mechanical designer must clarify exactly where the process piping begins and the OBC-regulated plumbing system ends. Backflow prevention and possibly a sand/oil or grit interceptor may be required, depending on type of equipment and local sewer use and backflow prevention by-laws.
Risk/Benefit Analysis:
A poorly designed building envelope may contribute to shortened service life of the building or an unhealthy environment for the occupants, both of which represent a risk to the municipality. Where a building design is atypical and includes large exterior openings or unconditioned spaces, extra attention must be paid to identifying and documenting conditioned vs semi-heated vs unconditioned spaces, and what assemblies (interior or exterior) are used to separate them from one another. If necessary, the designer may need to add notes to further clarify.
Final Recommendation:
Where a proposed building contains large openings to the exterior or otherwise appears to contain spaces that may be unconditioned, the designer must clearly indicate this on the plans and provide building envelope sections and details indicating conditioned vs unconditioned spaces and typical walls. This information should be confirmed by the HVAC and electrical drawings. If a designer proposes that the building or parts of it are exempt from complying with SB-10, or portions of it, this must also be clearly spelled out and noted on the plans so inspection staff are aware of it.
Recommendation to Ministry of Municipal Affairs and Housing:
None at this time.
Referenced Documents:
- 2024 Ontario Building Code O.Reg 163/24 Amended to 5/25
- ANSI/ASHRAE/IES 90.1 Energy Standard for Buildings Except Low-Rise Residential Buildings
- City of Guelph: Buildings exempt from compliance with Supplementary Standard SB-10 available at https://guelph.ca/wp-content/uploads/BuildingsExemptfromSB-10Compliance.pdf
Disclaimer:
This guidance document is intended to assist building officials by gathering relevant information to interpret the OBC Act and the prescriptive requirements of the Ontario Building Code, and is intended to be a best practice aid for building officials.
The views expressed within this guidance document should not be considered as the official interpretation of legislated requirements based on the Ontario Building Code, as the final responsibility for interpretation rests with the local Authority Having Jurisdiction.
The views of this advisory committee should not be construed as legal advice.