Help... cold outside air is drafting into my inner microwave and all around the outer cabinets. It is an Over the stove type.. an older whirlpool.. it appears to be vented up through the upper cabinet above it with a section of y-shaped galv. Duct that is taped with silver tape to a section of accordion type duck. It was ducked to the open floor area between my downstairs kitchen and floor above. I was told this was common since reaching the roof would be costly.
What confuses me is why does it back draft so much.. can I break the seal at the taped run of duct work and install some kind of inline damper... I don't think one exist or has stopped working. When it was installed I was told it would pull in the exhaust air, run it through carbon filter and circulate it back into the face of front and into room, but this is not the air that concerns me, it is a constant leak of cold draft that floods the inner microwave body as well as all around the outer cabinet and the cabinet above it. I have checked the duct run, it is secure and taped.. but a smoke gun shows a massive cold draft all around the whole thing, even inside the inner unit. What can I do, I'm a senior on SS and this draft keeps my kitchen so cold I avoid it. I need a fix that I can understand and do myself or guide my teenage grandson to help me do. I know I am losing $$ on utility bill due to this leak. Please help wiyh some ideas. Grandma K

Usually a draft flap is present, either at the hood outlet where the vent duct connects or at the exterior vent termination. If this problem is a new development, one or the other is stuck open.

Thanks KC, think this will call for a two person team & need to take her down and see where she vents to.. maybe it was never "set" to vent UP.. just found the carbon filter behind front grid.. no manual when I moved in, so never knew it even had one inside.. this forum is what owning a PC is all about when you are 60+ young.. thanks for help.. guess you need some sunshine up your way.. coldest winter my little rural TX town has ever recorded.. stay warm, grannyK