Thanks guys! It is coming together just in the nick of time. Since the last update I finished the platform on the compost bin, added a relatively well sealed door hatch and plumbed in the fan to aerate it. The pile started cooking two days ago and steam (or possibly more accurately water vapor) was rising off the pile. Yay!! Now that it's capped I can run the fan. It blows air from the fan, through the South planting bed and exhausts into the room robustly. The intake under the pile is drawing air but not nearly as much as the fan is pushing. So I'm sure there are lots of leaks but at least some air is moving though the pile.
Now I just need to figure out how long to run the fan each day/week to keep the pile active. Along with that I think a huge thing is that the hot/steamy compost air is cooling down in that planting bed and condensing a fair amount of water out. I believe that counts as a phase change so the energy transfer to that soil is much greater than just the temperature of the air. That's great but it does mean I'll have to add water to the pile to make up for it. How much, I have no idea...
Yesterday I got to experience the temperatures and what I will have to play with. I got out there after a cold night and worked inside the greenhouse from 7:30-8:30. It was 28F inside
I headed into the house for breakfast and found that the outside temp was a balmy 13F. So overnight it held the temp 15 degrees above the outside. That's with the E/W walls insulated but not vapor barriered AND 2" gaps between the 6 vent doors along the south wall.
I headed back out at 9 and was working above the compost bin finishing some insulation around the moveable insulation drive mechanism. The sun had come out about at 9 and by 11 it was really hot in there. I checked them temp and it was 100F (near the peak). Nothing like going from frozen fingers to working topless in three hours... It was in the 70s at ground level. Once the sun went behind some clouds at 3:30 it started cooling off. By 4:30 it was down to 45 at ground level. After an 8 degree night last night, it was 22 this morning inside.
I also measured the temp of the air leaving the aeration exhaust pipe after the fan was running for an hour. It was around 55F. So the hot air from the compost is transferring some heat to the bed and still comes out with some warmth for the room.
Construction wise, I got visqueen up on the West wall yesterday. Still need to do the East wall. I also talked to an electrical engineer buddy about operating the moveable insulation with a garage door opener and he said it would be perfect. All I need is an older opener with a worm gear limit switch set up and some kind of timer to trigger it at dawn and dusk. He'll help me figure it out so that's wonderful.
Tomorrow is supposed to be a near tropical 36 for the high so I'm going to close the gaps in the South vents and do some other exterior work while I can. The missus sewed up some felt weights for the moveable insulation so I can get moving on that part of the project soon.
Thanks for the support and envy!