I second using cats, every year when I close up the popup for winter, while winterizing I open every cabinet, drawer, etc and let my cat in to just wander around, rub up against stuff etc. then during the winter when there is snow, and the cat can't get out (we trained her to go outside to go do her business) we put a pee pad in front of the sliding door the cat uses, and I put the used pads under the popup (maybe 2 for the entire winter) and in 7 years not once have I had any mice issues. I know they are around because the cat will kill them and put them in front of the door as "presents" for us.. Lol