When you are planning a residential project in Ontario, navigating the Ontario Building Code (OBC) can feel like decoded hieroglyphics. One of the most critical stages of securing your building permit is completing your energy efficiency evaluation—governed by Supplementary Standard SB-12.
For most straightforward projects, the Prescriptive Path is the fastest route. Instead of hiring an engineer for costly energy modeling, you simply choose a pre-approved compliance package from the OBC tables. If you match every building element (insulation, windows, and mechanics) to that package, you comply.
However, picking the wrong table or package can stall your permit or force expensive, last-minute design changes. Here is exactly how to choose the right SB-12 package for your project.
Step 1: Identify Your Build Type (New vs. Addition)
The very first filter you must apply is whether you are building completely from scratch or expanding an existing structure.
1. New Construction (Houses and Garden Suites)
If you are breaking ground on a brand-new project, you will use the primary compliance tables. This applies to all new construction, including standalone single-family homes and new detached accessory dwelling units like Garden Suites. Your table is determined strictly by your geographic location:
Climate Zone 1: Use Table 3.1.1.2. (For areas with fewer than 5,000 heating degree-days, which covers most of Southern Ontario).
Climate Zone 2: Use Table 3.1.1.3. (For areas with 5,000 or more heating degree-days, covering Northern Ontario).
2. Additions to Existing Buildings
If you are building an addition onto an existing home, the code cuts you some slack—provided the building has existed for more than 5 years.
For these established properties, skip the new construction tables and use Table 3.1.1.11. to find your prescriptive package.
Step 2: The HVAC Trap – Watch Out for "Electric Space Heating"
Once you know your table, you have to choose a specific lettered package (e.g., Package A, Package B, Package C). Your choice is heavily constrained by your heating, ventilation, and air conditioning (HVAC) system.
The absolute most important rule to keep in mind is the Electric Space Heating restriction:
⚠️ The Golden Rule: Whenever your primary HVAC system utilizes Electric Space Heating, you must use Package C (often designated as Package Cs).
If you design a house using traditional electric baseboard heaters, your insulation and window specifications must step up to meet the stringent requirements of the Package C tier to offset the energy footprint of electric resistance heat.
The Heat Pump Exception: Clarifying Garden Suite HVACs
With the massive surge in Air Source Heat Pump (ASHP) installations—especially in backyard Garden Suites—there is a lot of confusion regarding what counts as "Electric Space Heating."
Per the Ontario Building Code, an ASHP system is only classified as electric space heating if it features an electric backup heating source, such as an auxiliary electric duct heater installed directly at the central air handler.
To clarify: If you build a sleek new Garden Suite and heat/cool it purely with a standalone ductless mini-split system, it does not count as electric space heating. You are free to select any available compliance package that makes sense for your budget and wall assemblies.
However, the moment you supplement that mini-split with baseboard heaters in the bedrooms or electric duct heaters as a backup safety net for cold winter nights, the code automatically bumps you into the Electric Space Heating category. Your project is immediately locked into Package C.
Summary Checklist for Your Building Permit
Before submitting your Energy Efficiency Design Summary (EEDS) form to the municipality, double-check your roadmap:
New Home / Garden Suite in Southern ON? —>Table 3.1.1.2.
New Home / Garden Suite in Northern ON? —> Table 3.1.1.3.
Addition to a 5+ year old house? —> Table 3.1.1.11.
Using baseboards or electric duct heaters? —> Lock into Package C.
By choosing your table accurately and alignment-checking your mechanical systems early, you will cruise through municipal plan review and build a home that is fully compliant and optimized for Ontario's winters.
