I live in Manitoba and have the same issue. When I asked the technician about the exhaust and intake pipes (by the way, mine are not separate outside but are joined together just before exiting the foundation - should I be concerned about that?) and the slope of them, he brushed it off. After he left, second time, I went outside and I could actually look down into the pipe and see water droplets. I pushed the outside vent back on as it was barely attached and the furnace cut in and has been running fine since then. The guy never went outside to have a look. Just spent 2 hours running checks and looking for code issues and kept telling me the furnace was working even though the temp in the house was 17 and the thermostat was set at 21. I suspect I need to attach that exterior vent better but should I also replace it with 2 separate vents?