The wood was supposed to be oak vainer plywood, but we figured it was just 3/4 plywood. The edging around the door is hickory (box and door) with an oak panel for the door. The wood for the shelving ended up being stock 2x6 pine I think, stripped up.
Used interlocking joints, wood glue and nails. Stained the outside and added semi-transparent gloss finish. Used water-heater bubble insulation on the inside.
I have more pictures on the album. A 200Watt ceramic simple on/off heater will bring the entire box up to 122-125F easily. Added 2 fans to force hot air down from the top and draw pooling air from the bottom.
When under a humidity load, the door being thinner will condense a lot more. Walls have some condensation, even though the air is maintained inside the box at temperature. Around 85% humidity, the slightest temp difference makes for water to form.
A fancy heater that would pull air from the middle and shoot the hot air up along the walls would help, or use of a few ceramic infrared bulbs shining on the walls would help as well I think.
The door should be just a thick as the box.
Box works quite well. Making it smaller would be good too, as I have enough capacity to make 4-6x koji at one sitting that I need to.
Some other plans is to add the ability to cool the box down as well.
Makes great tempeh as well.