I have an existing 8" roof opening which the previous 65% gas furnace and water heater was vented thru . The last owner abandoned both and went with electric furnace and electric water heater...and simply placed an 8" sheetmetal cap over the roof opening .
I want to install a 95% gas furnace requiring two 2" dia. PVC Pipes (intake and exhaust) and would like to utilize the present 8"roof opening . I could cut two seperate holes thru the existing cap , or, is it better to use one rubber roof jack for both pipes to go thru if such a thing is offered ? I want to have it sealed good against the elements.
Your help is appreciated.