Ontario Design Temperature Lookup (SB-1)
Every heat loss calculation in Ontario starts with one number the province sets, not the designer. Type your municipality to see the January 2.5% design temperature from SB-1 Table 2 — or to learn that your municipality is not listed, which matters just as much.
Values are the January 2.5% design temperature from Ontario Building Code Supplementary Standard SB-1 (2024), Table 2. A municipality not in that table has no number to look up, and this tool will tell you so rather than borrow a neighbour’s. SB-1 on ontario.ca.
Why this tool says “not listed” instead of guessing
Supplementary Standard SB-1 lists a few hundred Ontario locations, not every municipality. For the rest it directs designers to Environment and Climate Change Canada and warns that interpolating between listed locations may not be valid because of local effects. A calculator that prints a neighbour’s number for an unlisted town is printing a guess with a decimal point on it. We would rather tell you the truth and then find the right value with your building department — which is what we do on every job.