What is the best way to seal the gap between the wall and the vent?
The first thing that comes to mind is Styrofoam. But then the pipes are stuck forever. Are there special solutions for this? Expandable tape that you squeeze into the gap, or can you tape the gap shut? Can you tape it over the pipe and wall?
The back of the hole goes out into our garage. That's where I put acrylic on everything and painted it.