Wanted to update the post with a pic and update that the fiberglass batts are unfaced.


Colbyt,
In both summer and winter the house should be dryer than the crawlspace, assuming air conditioning in summer. That means the moisture in the crawlspace will want to move up to that floor above. Placing the foil facing the CS will prevent it from reaching the subfloor which may be cooler with the ac running.
In winter and in winter, if the foil were up next to the subfloor then the floor joists and related framing would rise to the moisture level of the crawlspace.
I agree what you stated is the standard advice, but does the above explanation make sense?
@nemo , the only foil faced rigid insulation that is rated to be installed without an additional thermal barrier is Dow Thermax. Finding it is difficult in my area and the price a bit high, especially with the minimum order requirements I have. Orange box was where I could order it.
But, if you have sealed the floor and sealed the walls, there should be little need for floor insulation, rigid or batts. With adequate insulation it becomes very inexpensive to heat that space and essentially heat the floor above.
Bud
You can leave the batts and if you can find and go with the Thermax you can install it right over the 1/2" already there. Air seal and detail insulation in the rim joist above the foundation.
Once you insulate that space and seal it off from the outside, you can open it up as much as reasonably possible to the living space. Providing a small opening in a duct only connects that space to the conditioned space when the fan is running. An open doorway would be an example of combining the space with the inside. Remember, it needs to be part of the conditioned space 12 months of the year.
Bud
Hey Bud, what do u mean for now? When would this change? Thanks!1. Insulate the rim joists with Roxul or foam board(unfaced or foil faced?). Either
6. No holes needed in the ducts. For now
Bud