I recently encapsulated my crawlspace (in central Maryland). Now it’s time to insulate. We want to incorporate rigid mineral wool- Roxul’s RockBoard 60, to be specific. The heavy vapor barrier, a DrySpace product, goes all the way up the interior foundation walls and stops just a few inches shy of the sill for future termite inspections. If I want to insulate these interior walls with RockBoard, what is the best approach? I ask because it seems few builders have much experience with this material..particularly in this application. I was thinking of anchoring the material directly to the walls with hardware penetrating through the vapor barrier into the cinder block walls. I read something that suggests I should leave an air gap via furring strips and anchor to those, but that doesn’t seem to make much sense to me. Alternatively, I could insulate the joist bays if I thought it would be at an advantage.

Have any among you done this sort of thing? What do you suggest as a “best” approach?

FWIW, The heat source is hydronic with perimeter baseboard (using a Polaris unit) with future plans of going full radiant in-floor. We do not have central air conditioning. We have no duct work of any kind in the crawlspace- just water lines. Moisture is a problem in the summer, but I now have a dehumidifier up and running.

Thanks in advance,
Mike.