Our family room is the only room above a crawlspace (rest of house is above heated basement) and the floor is cold, making the entire room cold. Five feet off the floor the room is about 2 degrees colder than the rest of the house, and the floor is 3-5 degrees colder. Floors in the rest of the house are same temp as 5 feet off the floor. Floor is on 2x6 joists and already has R-19 between the joists. I'm thinking about adding a couple inches of foam board or one of the radiant barrier reflective products to the bottom of the joists. I understand the RB products need an air space so I'd have to add wood strips to the bottom of the joists so the RB isn't against the existing fiberglass. Crawlspace already has foam board on walls of crawlspace and plastic on the dirt. As I type, the family room floor is 64, the crawlspace is 57, the heated basement is 65, and it's 27 outside, in Southeast Michigan. Any suggestions as to which would be more effective, foam board or radiant barrier?