When building your subfloor you should not rely on the plate insulation or wood to wood to prevent air infiltration from happening. Rim joists and plates are a big source of air infiltration of homes. There are many different ways to seal these areas, including caulking, rubber gaskets, foam seals, closed cell spray insulation, house wrap, and maybe more that I didn't mention. As of other posts, I post this so you can know of it and do further research if desired. Also follow local building codes. It was not often done because of the extra time involved, it was thought that it wasn't needed and also adverse weather such as rain would prevent caulking or adhesive seals to stick to the wood or cement foundation delaying construction. You should run a continual bead of caulk between the plate and the basement walls or foundation close to the outside. The rim joists should also be caulked on the bottom between it and the plate. Between the top side of the rim joist and subfloor you can use a continual bead of adhesive used on the joists to prevent squeaks on the subfloor. Also caulk where rim joists butt together. The space between the joists on the rim joist should be insulated. If your subfloor or home is already built, spraying closed cell foam will seal and insulate the spaces between the joists on the rim joists. This space also can be susseptible to mold because of temperature change and higher humidity in basements. Making your home tight from air infiltration will require an air exchange system to bring in fresh air and expel inside air. I hope this will help so people can save on heating and cooling their homes making the planet a little greener.