In the winter I noticed that my garage (and the den next to it) get really cold by the morning. As in very close to the outside temp cold. I didn't know where to borrow tools to detect where the leak was so I did a couple of basic inexpensive things like insulated the garage door, foam sprayed the gaps in the garage everywhere I found them, insulated the interior door to the garage etc. It helped, but not that much.
The other day while cleaning I discovered that the gas water heater vent terminates on the side wall and there's almost an 1'' gap around it going directly outside without any insulation. I understand it's probably a legitimate part of the design as the pipe might get hot and needs some clearance. But at the same time, does it mean that there's nothing I can do to reduce leaking and not have to heat the space the entire winter?
Does anyone know of any solutions to that?
This is in the PNW, US.