I went to look at a home that has a crawl space. There is sand and gravel under the house, a little musty smell, lots of spiders. The home also has windows with loovers that do not close under the home, I assume to ventilate the crawl space. The homeowner states that the floors are very cold in the winter. Also the hot water heater seemed to be turned very high so I asked about that. I was told that if it is not turned up in the winter especially, you won't get even warm water. The bathroom is on the opposite side of the house as the HWH. The plan is to insulate the complete attic to save on heat bills. Also replace the exterior doors.
Now my question - Any suggestions on insulating the crawl space? Vapor barrier needed? How about water pipes? Can the loovered windows be closed off?
The home is in Michigan.

You can, and should, insulate the floor above the crawl space, with as much insulation as you can fit, remebering that in a floor, in your climate, the vapor retarder goes UP against the subfloor!

Having done that, the next step would be to insulate the water pipes. You can buy a snap-on foam insulation which is a cinch to install. One trade name for the insulation is "Armaflex". It is manufactured for each specific pipe diameter.

Third, you MUST investigate to see what, if anything, is under the sand and gravel. There should be a vapor retarder, such as 6-mil polyethylene film, with all joints taped, and taped to all walls and other penetrations. If it isn't there, install one.

Fourth, you will read every kind of answer about closing the vents in winter, but it SHOULD NOT be done, and I'll tell you why. Moisture will get into the insulation (that is normal) and it must have a way to migrate out again. Otherwise it accumulates, and then you have the possibility of mold problems, or worse, structural damage.

Have you ever picked up a hot skillet with a wet pot-holder? If you have, you know that it's INSTANT burn! Why the difference between a wet potholder and a dry one? The MOISTURE conducts heat rapidly.

In your floor, you do not want moisture to conduct your expensive heat into the crawl space. It is normal that moisture will be occasionally present in the insulation, from activities in the home, or simply from humid weather. Therefore you must make certain that any such moisture has a way to escape, and the way to do this is to have open functioning vents in the crawl space, summer AND WINTER, ESPCIALLY WINTER!