Guys, I have a build question. For a medium (MES40 or slightly larger) sized electric home brew build, where the unit will be lined inside with aluminum or stainless and the temp will never exceed 250*, do you have to use super high temp mineral wool insulation or can unfaced fiberglass or some other less expensive and locally obtainable insulation suffice? I'm thinking of using 1/4" Hardiboard cement board which is faced with metal to make clean up manageable. The hardi-board is 90% cement, with the remainder being sand and a slight binder content and is approved for a 1 hour fire rated wall. Should be enough mass to act like a heat sink to moderate temp swings, but no so much it will take forever to heat up. Weight of the board is 1.9 pounds per sq foot so it should help keep weight down too. I also like the idea of added fire resistance if we have a unplanned flambe. I would love to make a super smoke house cabinet, but as I'm not yet into sausage making and still on a budget (kids in college), scaling down to MES40 size is more real world right now. Of course the question of "why not just buy a MES" will come up. I have most of the parts needed and just seemed like it might be an interesting project.