We are turning an old grainery into a small economy apartment for my retired parents to stay in when they come to visit during the summers. Need help figureing out how to keep the mice out, and insulate the floor. The grainery sits on a cement foundation with 6x6's running the length and then 2, 2x6's nailed together on top of them running the width, there is a 2' crawl space under the floor with a dirt floor. The grainery is 28x20. Also wondering the best way to keep the vault ceiling, but it is only 2x4 construction and it needs to be insulated, would sistering on 2x8's alow enought room to get insulation in there? oh yeh we are in southwest minnesota, although this will only be used during the summers!