I have a home built in the 1950's, currently uninsulated in a vented crawlspace. I am thinking about adding in open-cell spray foam between the floor joists,however the hardwood flooring above does not have a subfloor. Instead, roofing felt was placed under the hardwood floor. This felt sits on top of the floor joist. It sags down a bit, maybe a half inch away from the flooring above it in some places. My question, if I spray foam (or insulate in any way), do I need to remove this roofing felt so the insulation can have direct contact with the flooring?
On the topic of open-cell...the humidity levels in my crawlspace are under control, which is why I consider it over closed-cell.