After a brief search, I couldn't find anything that exactly matches our scenario, so here it goes:
We own a 1920 farmhouse in southern New Hampshire with a fieldstone foundation under the original part of the house. The joists of our living room floor are a mere few inches off of dirt, supported by horizontal timbers with stones underneath of them. (Can you picture it?) This "crawlspace" is normally inaccessible by humans, but you can peer into it from an adjacent basement. We recently had a pipe burst in the living room and the floor has to be replaced, so we'll briefly have rare access to the foundation. I'd like to ask about two areas of concern: radon and insulation.
For radon, I understand that I can put down a thick, 20 mil vapor barrier. I've found and can purchase a suitable material, but I'm wondering how to attach it to the 6 inches of fieldstone. Some sources recommend parging with some kind of mortar/filler product and then attaching "strapping" (wood strips) to the parged surface using some kind of adhesive. Then the barrier is stapled to the "strapping". I'm imagining that I'd have to additionally caulk between the barrier and the foundation to get a nice seal. To make matters worse, how do I work around the stones supporting the timbers? I have a bad feeling about this. Sadly, I don't have the means right now to hire a professional, though insurance is covering the floor. I know that a professional would be best. What's the best way to handle this situation?
For insulation, I've heard conflicting opinions. The word is that fiberglass in the joists is inexpensive and cost effective. However, while it's not outright "wet" down there, it does get moist in the summer and I've read that fiberglass breeds mold under such conditions. What about foaming the exposed foundation? (after parging and vapor barrier installation?) I've also found professional grade foam available for purchase. Would radiant barrier on the bottom of the joists be worth my while in the absence of batts down there? I've read that it only works well when there's an air gap between the barrier and the floor.
Again, you have no idea how much I'd love to hire the pros, but it's just not happening right now. Thanks in advance for helping to ease the stress.