I discovered a ton of freezing cold air coming from the top of the hood recently. I took a ladder, and it looked like this:
Cold air just pours through the opening.
Any suggestions for how to seal up the holes in the wall? Keep in mind this is not visible unless you are on a ladder, so something that is quicker/easier will win over something that looks pretty. Also, I'm not interested in pulling out the piping to wrap something around it, if at all possible, as that dramatically increases the level of complexity for me.
Additionally, is there any risk to sealing up the top of the range hood, or does it need to be left opened?