If you mapped our Guelph service calls on a calendar, you would see the same shape every year: the problems are created in February and paid for in November.
Many Guelph properties were re-roofed at least once without the flashing being re-detailed, leaving a cosmetic seal doing structural work.
Air-sealing and window upgrades have made Guelph homes far tighter than they were designed to be, and a tight house starves a natural-draft appliance of the make-up air it needs.
Across Clairfields, Pineridge, Westminster Woods, St. George's and The Ward, the housing stock changes street by street, and the correct method changes with it. A century home with a soft-brick stack does not get the same treatment as a 2010 build with a factory-built vent — using one method on both is how systems get damaged.
If you live anywhere near the University of Guelph, the practical takeaway is that a winter roof prep visit should start with an assessment, not a tool. Any crew that begins work before telling you what they found is guessing on your behalf.