I am new to the site and I am in the planning stages to fabricate my first oven. In looking for a local source for Mineral Wool Insulation, I stumbled across IDI. I contacted them with what I wanted and was happily surprised they had exactly what I needed. I asked for 3.5"x16" Mineral Wool that is designed for metal studs. Normal insulation bats are only 14.5" wide, while steel studs require a full 16". I am sure most of you already knew that, but like I said, I am new here. They sell it in bundles of 128 square feet, which just happens to be exactly what I need for my 3x4x6 oven! He said they stock it and it is $60 for the bundle. It is made by Thermafiber and is rated to 2000*F. I think this will work nicely for my oven build. IDI appears to have locations in several states. Hopefully this is new/helpful information...if not, feel free to ignore it

IDI Distributors Inc., Insulation Products and Accessories, Fireplaces, Shelving, Foam Insulation