I am building a Lean-To office studio which is 8' x 14'. It is being built on a deck which is cantilevered off of a slope. I want to insulate the shed and the floor\deck cells as it will be fully finished inside with A\C. The deck is constructed of 4x6 rim joists and 2x6's joists.
My problem is that part of the deck sits very close to the ground. I plan of digging that away so I have a clearance of about 18" from the bottom of the 2x6 joists and the open earth - as per the code reqs. If I fill the open bays in the deck with batt insulation I am worried that it will get wet, critters will move in or something else perhaps.
I found this online and was thinking of implementing the approach but wanted a second opinion.
Apply 1x2 strips to each side of your floor joists. The bottom edge of the 1x2 will be even with the bottom of the floor joist. Then you'll need to drop in some 1/2" plywood, ripped 14 3/8" wide so as to fit between the floor joists. If you prefer, you can caulk the edges of the plywood so as to ensure you keep bugs and air out. Once you tack the plywood down, you'll be ready to lay your insulation in place. The only problem with this is that the plywood will be exposed to the soil under your shed, which isn't good. You could use an exterior grade marine plywood... or you could paint the plywood prior to installation... and it would probably be a real good idea to lay down a piece of heavy plastic so as to cover the ground and act as a sort of vapor barrier. It'll keep weeds down too.
I hope someone with experience insulating outdoor stand-alone structures can help me out.
Pics? Batt insulation is, IMO, a poor choice when exposed to air. Option 1. You may be a candidate for spraying closed cell foam on the underside. If you do, make sure the outer edges of the floor joists are covered, too. If not, they may well get cool, condense, and rot. Another option is to install rigid foam in between the joists, however much you want to, seal the gaps w/ Great Stuff, and then add a layer of rigid foam on the underside of the joists, taping the edges. Option 3: fill the joists w/ batt insulation, then air seal with rigid foam as in option 2.