Two numbers and two clocks
Section 1.1 defines "adequate and suitable" in reference to vital services as sufficient to enable, among other things, "the heating of the unit on and between the 15th day of September of one year and the 15th day of June of the following year to a minimum temperature of 20 degrees Celsius (68 degrees Fahrenheit) between six o'clock in the morning and eleven o'clock in the evening of the same day, and to a minimum temperature of 18 degrees Celsius (65 degrees Fahrenheit) at all other times".
Ottawa also splits day from night, but runs at all times with no season. London does both at once, which makes it the most specific heat obligation in this set — a landlord has to get the temperature, the hours and the calendar right together.
The overnight figure of 18 is higher than Ottawa's 16.67, so London's setback is shallower. A building holding 20 around the clock satisfies both; a schedule tuned to Ottawa's floor would not satisfy London's.
Heat sits inside a wider definition
London's drafting folds heat into a list. The same definition requires the vital services to be sufficient to enable "the refrigerating, freezing, preparing and cooking of food for human consumption", "the washing of dishes and utensils used for food", "the operation of a toilet", and cleansing.
That framing matters when something other than the furnace fails. A unit at 21 degrees with no working toilet or no hot water for dishes is not delivering adequate and suitable vital services under this bylaw, even though the heat limb is satisfied.
The by-law also defines "Act" as the Residential Tenancies Act, 2006, and is drafted to sit alongside it rather than to replace it.
A note on the source
London publishes PH-6 as a web page rather than a PDF. The page is the office consolidation and carries the full operative text, and London's own disclaimer notes it is an unofficial electronic reproduction.
For operations that is the reference to use; for a hearing you would want the certified copy from the City Clerk.
Because the heat figures are inside a definition rather than in a numbered heat section, a search of the by-law for the word "heat" will not land on them directly. Read section 1.1 in full.