I'm new to this woodstove and bought this house in June. It's a Pacific Energy D Series insert stove installed in the late '90s. We had an energy assessment done on our home, which included a blower door test that said the silver rectangular vent (?) on the chimney is a major source of air leakage. Is this a vent? If not, what is it and what purpose does it serve? And yes, this stove should have a blower. It's on order but in the meantime we're getting by with a fan.