I live in Zone 6 Minnesota and need to upgrade the attic insulation (lumpy old fiberglass R19 batts) on my 105 year old home. Here's the deal: I'm planning to go with what seems a good choice of spraying a "lid" of 2 inch closed cell foam across attic floor (paying special attention to soffit/wall perimeter area) then cover with blown in cellulose to an R50. BUT my attic has a tough old pine floor covering most joists, wondering if I can spray a foam "lid" right over top the floor and then add cellulose??? I'd love to avoid tearing up 1200 square feet of wood to insulate between joists. The current cavity between ceiling and bottomside of attic floor is mostly empty. I'm also upgrading some old knob/tube electrical beforehand but leaving the subfloor seems a bit of insurance against any unseen exposed knob/tube in between joists. Is that empty gap (2x6 joist space) between room ceiling and bottom of attic floor a no-no? Won't a well sealed attic perform the same regardless of whether it's insulated between joists, or on top?