Wider scope than most
Section 4.13: "Every building, except for an industrial occupancy, shall be provided with heating facilities capable of maintaining an indoor ambient temperature of 21 degrees Celsius (70 degrees F.) in all occupied areas."
Note what is missing: any limitation to rented or leased accommodation. Most municipal heat provisions apply to a landlord and tenant relationship. Guelph's attaches to the building.
"Indoor ambient" and "all occupied areas" are also broader than the habitable-rooms formulations used elsewhere, and unlike Barrie, Oakville or Richmond Hill the section fixes no measuring height, so there is no equivalent of the 1.2-metre or 1.5-metre test.
Capability plus upkeep
Section 4.14 pairs the capability requirement with a maintenance duty: every heating system, fuel burning appliance, chimney and other mechanical system "shall be operated and maintained in good working order and free from unsafe conditions".
Read together, those two sections are close to a working obligation without ever naming a date or an air temperature to be achieved on a given day. A system that cannot reach 21 degrees, or that is not in good working order, is a breach whatever the weather.
The document to work from is the 2024 office consolidation, which carries the amendment list on its first page. The original bylaw dates from 2000, so any unconsolidated copy is a quarter of a century out of date.
The provincial layer still applies
A capability standard with no season gives a Guelph tenant a weaker municipal hook than a Toronto or Oshawa tenant has, in the same way as Barrie, Pickering and Richmond Hill.
Section 20 of the Residential Tenancies Act still requires a good state of repair and fitness for habitation, and section 21 still treats heat as a vital service the landlord may not withhold or deliberately interfere with.
In practice that means the annual service record on the heating plant is the document that matters most here — it is the direct evidence that the facilities remain capable, which is precisely what section 4.13 asks.