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.

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2 Answers 2


The pipe looks newer if it is double wall it could be sealed using fiberglass insulation with the foil on the outside (paper) not touching the pipe. If it is single wall rock wool would be the product I would use. Wrap insulation around pipe and slide to the opening.


You need a vent firestop that can help provide a seal against air leaks. You should not insulate inside the firestop but you can run insulation around the firestop. Look for the manufacturer of your vent pipe and see what they offer in terms of firestops.

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