What are the energy efficiency requirements for new additions under Ontario Building Code?

When you build an addition in Ontario, the Building Code's energy efficiency requirements (Supplementary Standard SB-12) apply to the new construction. Knowing the basics helps you budget accurately and avoid surprises at inspection.

For additions, SB-12 offers two routes. The addition can meet one of the prescriptive compliance packages, or it can meet the values in the addition table. In Ottawa's climate zone, the addition table calls for a ceiling with attic space of R-60 and above-grade walls of R-19 plus R-5 continuous insulation. Other parts of the assembly, such as foundation walls, floors over unheated space, cathedral ceilings, windows and doors, have their own requirements, and your designer will confirm them for your project.

The "continuous insulation" part matters. Studs interrupt cavity insulation and conduct heat, which is called thermal bridging. A continuous layer of rigid or semi-rigid insulation over the sheathing reduces that loss. A common way to build the wall is 2x6 framing with cavity insulation plus a layer of exterior insulation. Ask your designer what product and thickness the drawings call for, and how windows and cladding will be detailed around it.

The existing house is treated differently. Renovations and alterations to an existing building fall under Part 11 of the Building Code, which in general requires that performance after the alteration be at least equal to what it was before. In practice, that means work on the existing house where it connects to the addition shouldn't make things worse.

Going beyond the minimum is worth pricing. Better windows, tighter air sealing and extra insulation make the addition more comfortable and reduce the heat it needs, which can affect whether your existing heating can serve it. Ask your designer what an upgrade would cost on your drawings.

Air sealing and ventilation deserve attention whatever the route. A continuous air barrier, sealed at every penetration and at the junction with the existing house, prevents drafts and moisture problems. A tight addition also needs mechanical ventilation, and the designer will confirm what the Code requires for your house and whether the existing system can serve the addition.

Your permit drawings need to show how the addition meets the energy requirements, and inspectors check insulation and air sealing during construction. The City's Building Code Services can tell you what your submission needs. When you collect quotes, ask each contractor to list the insulation, air barrier and window specifications they've priced so you are comparing the same assembly.

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Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:

• Homeupgraders
• RenoMotion Inc.
• Somar Contracting Inc.
• JMY Renovations
• ALTIOR CONSTRUCTION