I have had cold air coming in from where the vent for my Jenn-Air grill goes through the wall. I was planning on ripping it out, and redoing it, but haven’t wanted to do it in the freezing weather. But yesterday the temperture outside was over 40 degrees. Woohoo! A heat wave! Well, at least not freezing. I pulled the vent off, cauked around the trim, and rescrewed it into place. I was looking at how to better seal the part that connects to it, when I decided to go to Home Depot to get some mastic (I read about mastic in a book). At Home Depot I found a brand new vent piece that would replace the one I had. The old vent had gotten stuck open a few times. I also decided to replace the piece that connects to it as well. I asked the guy about sealing and he recommended silicone caulk. I asked about mastic, and he said that silicone caulk would work as well or better than the mastic. And I already had silicone caulk. So I went home, and pulled the old vent off (the caulk hadn’t fully solidified yet), and installed the new one with some fresh caulk. I also used some new screws as the old ones were a little rusty. I used some screws that were meant for exterior use. So now that the vent was in place, I looked at connecting the next piece. There was a space in the drywall around the venting, but I cut a little more out in one spot. I fit the new piece on, and caulked heavily around where they connected together to seal the gaps. I then used some Great Stuff exanding foam (kind for doors and windows) around the vent to fill out the gap between the vent and the drywall. Now I attempted to hook up the remaining parts (a couple 0-90 degree 5 inch swivel type duct pieces). I couldn’t get them to fit right. They wouldn’t swivel easily or at all on some joints. So I headed back to Home Depot, and bought some new ones. With a bit of playing, I got them hooked up. I sealed the remaining seams with duct tape. I will probably still rap the duct with some insulation, but I don’t notice a signifcant draft coming from the cabinet now.