I am installing a Zero clearance direct vent Kozy Heat gas fireplace in my existing cement fireplace. The Kozy Heat came with a vertical heat shield to be used with venting vertically. The space in the existing firebox isn't tall enough for it though, i am using 2 90's to jog the pipe back 12 or so inches to get it up the flue. Can i cut the heat shield down to fit the space? The top of the existing firebox is all non-combustible. Thanks!!
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