I live in Michigan (cold). I inspected a handy person renovated house today and a new water heater has been installed. The vent goes through the foundation wall and then rises two stories on the outside of the house above the roof line to vent. I know that you cannot vent a water heater as this one has been vented using single wall vent, but can one use B-vent to vent a water heater where the entire vertical length is outside in the cold? Also, if anyone knows a code reference it would be appreciated.