framed floor insulating

[billconner]

Suspended 12 x 16 room addition - kind of like a deck with ledger on house (superior wall) with two concrete piers supporting a beam, and 2x12 joists. Advanced tech or similar floor with carpet, 2x6 walls with R19, don't know roof. Basically a sleeping room.

How would you insulate floor? One suggestion was 2" XPS and battens (I suggested a robust sheathing under all for rodents, etc.). My plan was fiberglass (or rockwool or cellulose), house wrap, and a tightly sealed OSB bottom. Both would be ideal perhaps.

 

[Firebrick43]

Fill the joist with rockwool, place at least 1" Celotex with aluminum facing up continuous over the bottom of the joist, and then cover with tongue and groove ply or Advantech. Don't use standards osb it will have issues with moisture.

Foam Stops most of the thermal bridging and seals for wind. No need for house wrap.

 

[Zeke]

Or a lightweight metal?

 

[Kpaige]

I built this exact thing but I used floor trusses set them on the existing wall. When I built it I put batt insulation in with 1/4” plywood on the bottom but the room was always cold. I reworked it with a 1” space under the subfloor that joined into the existing house floor system then spray foamed it them plywood the air could then circulate under the floor and it was much better