I have just purchased a fifty year old house that needs insulation badly. My problem is there is " X " crossbracing between the floor joists. Using fiberglass batts would be best but difficult. What is best way (and most economical way ) to insulate this area?
Much of the recent research indicates you'll be much better by placing a minimum 6 mil vapor barrier on the floor of the crawlspace, then insulating the walls instead of the floor....depending on where you live. Where are you?
Was there a picture posted? It did not come through to me, if there was. Therefore I am not sure what the situation is, exactly. From the reply you got, I assume it is a crawl space, and, yes, put poly or Tu Tuff on the floor and glue it to the walls with something like Tremco Acoustical Sealer; black death. Make sure your "glue" is compatible w/ your choice of vapor barrier on the floor. Insulating may be OK (I did not yet read the article referred to above), and if you want to insulate then closed cell spray foam may be your best option. I would never in a million years install fiberglass in that situation (Note: I will never in a million years install FG again, but here it would be a poor choice). You asked for "best and most economical method", but those are usually, in my experience, incongruous requests.