Rigid Foam Boards for Crawl Space Ceiling Isulation?

The floor in my house is supported by 4x8 beams on piers. The beams are about 4 ft apart. I'm trying to decide what to use for insulation. The narrow depth of the beams (8 inches) along with the 4ft distance between them seems to not lend itself well to regular fiberglass insulation. Additionally, the vents and access hatch would be blocked by it. Spray foam might work, but the price is out of my budget. I'm considering applying 2 inch foam boards directly to the ceiling with glue (and some sort of fastener if needed) and filling any cracks or gaps with spay foam. Does anyone see any problems with this or have any better ideas? The main drawback I can see is the low r value (about 13), but i figure it is better than not doing it at all.

The beams are 8 inches tall and about 4ft apart.

The top of the vents are about 2 inches below the bottom of the ceiling.

The top of the access hatch is about 2 inches below the bottom of the ceiling.

The beams rest on the foundation wall inside of a plastic insert.

 

Where are you located? Two inch foam board (R13) will be more than enough to insulate the floor above. However if you really want to offset the feeling of a cold floor you should consider underfloor radiant heating before installing the insulation. Your situation appears to be ideal for that, especially if you already have a hot water source for heating.

 

2john02458, thanks for your reply. I'm in Salem, OR. I hadn't considered installing radiant heat in the floor. I'll give that some thought.

 

This appears to be a vented crawlspace. If so, your plan would be fine.

 

Thanks stickshift. Yes, it is vented.