My 1969 rambler has 3x10s 4' on center with 2x6 car deck t&g subfloor. I had R-30 unfaced fiberglass batts in between held by twine strung across and stapled. Rats had got up on the insulation and made condos and a social club till I bade them farewell. Now I have these expansive joists and nothing solid to span the 45-1/2" tween the joists. Is spray foam the only choice? There is about 24"-30" from ground to joist and no center beam in 24' of joist span. I live near Seattle so we get a fair amount of ground moisture, too. What's the best route?