We started building the solar tank yesterday. My in laws are here for the weekend and we're getting a lot done on
the office and the solar system.
I ended up just going with 3/4" plywood because that is what they had and I really don't want this thing failing over time. I don't know how much wood weakens over 20-30 years but I want it to last that long.
The base plywood piece is 4'x6' with a 2x4 frame glued and screwed from the plywood side. The tank is a full 4' tall. We precut all the pieces before taking it into the basement to make assembly easier once we were down there.
This is the insulation that is going under the tank. I miscalculated / overbought insulation for it. Oh well, it is now insulated to R57 on the bottom instead of R45. I have 8 inches of polyiso and one inch of polystyrene on the bottom to block any moisture.