I'm installing a 45k BTU gas heater in my garage. It will be a vertical vent installation with 3" b vent pipe and I'm going to insulation the attic with about 18" of cellulose insulation.
No one in town has an attic insulation shield in stock so I was thinking of building one. Either Plywood that would be about 6x6" or 7x7" and go from the firewall support to the roof or getting a 6" piece of pipe and put a storm collar on the top. Depending on the final heater placement the distance from the ceiling to roof could be less than 18". Suggestions?