Minimal Crawlspace in 97 Year Old House

[Al2 House]

I recently purchased a 97 year old house built with very little crawlspace (only a couple of inches, in some places).
There is one vent on one side of the house which is just large enough to crawl into (if there were room), a couple of tiny vents on the opposite side, a full-length porch with no vents on the front, and a slab addition on the rear. The foundation is stone.
There's no vapor barrier, nor insulation (under the floor or on the foundation) whatsoever.
I currently have the floor removed in the bathroom (was original 1" thick planks + 1/2 plywood.

1. Should I attempt to put a vapor barrier on the ground in the bathroom or is it possible to put it between the joists and subfloor? :stupido2:

2. Aside from closing-off / insulating the vents, I'm at a loss as to what can be done for floor or foundation insulation...? :dontknow:

Any advice will be greatly appreciated!

[pushkins]

If it were me I'd add the vapor barrier in the area you have open at least, although vapor barriers need to cover the entire crawl space area to be truly effective. Yes add insulation to the bathroom's floor joists (R19 min.) while you have the floor pulled up and anywhere else you can get to at the same time.

[suemarkp]

Don't close off your vents. The specific handling of crawl space venting is location dependent (close some or all in summer or winter or never). If you close the vents off, you may have a lot of moisture build up in the crawl space (especially with no moisture barrier on the dirt).

A crawl space should be outside temperature, and you insulate between the joists to keep the house warm. Covering as much of the dirt as possible with visquene would be the first thing to try and do unless you live in a desert.

Some house designs keep the crawlspace warm (like a short basement). This requires insulation on your foundation (usually foam sheets are put on the outside after the foundation is poured). And you still put plastic under the floor. In this case, you don't need or want any venting.