Crawl space advice
Cover the FLOOR of the crawlspace w/6 mil plastic. Don't go stapling it to the bottom of the joists (where moisture would get trapped.) The Vapor Barrier, (as the plastic is referred to), should be NEAREST to the heated space (i.e., just under the sub-floor.) If the insulation is matted or bad, it should be replaced with Kraft-sided Insulation (which is installed with the Kraft side up against the heated floor.) DON'T go compressing the insulation in between the joists! It looses its R-value if you do so. Once it's loosely installed, then you can hang chicken wire under the joists (using staples), or criss-cross some NYLON string (not cotton string because it will rot) from joist to joist. It, too, can be stapled in place.
If you have vents under there, make sure they're not closed off. Make sure the plastic is 'held down' by something like pea gravel or pressure-treated lumber all around the edges. And lastly, insulate your pipes with the Pipe Insulation that's sold in the Home Centers. Make sure the 'seam' is facing DOWN (in case any condensation on the pipes needs to 'drip out'.) Do this first BEFORE you do the R-30 insulation installation. Remember, if the pipes are kind of in the way of the main insulation install, 'cut out' or 'slit' the necessary part of the main insulation to 'accommodate' the pipe. Then, if necessary, 'fill' the cavity with insulation. Batt Insulation needs to be 'loose' in order for it to work.
My best to ya and hope this helps.
Jay J -Moderator