I did a bit more to insulate over the weekend. I now have 2 full layers of greenhouse film separated by 4". One is stapled to outside of 2x4 frame and the other layer stapled to the inside. All seams are fully taped on the outside, but I have yet to tape the seams on the inside layer.
I also finished the Reflectix bubble layer on the north side. There are still some odds and ends to fix for air-tighness: the door does not seal well as I need to plane down one side, the greenhouse fan needs to come out and that area needs glazing, and the bottom of the base wall will be sealed with the addition of flower beds.
Today was one of those days without a cloud in the sky. The temperature never got above freezing, but at 1:30, after 5 hours of full sun, the greenhouse is 80 degrees. I am quite pleased.
In order to provide better data on the temps, I will need some better equipment that I can make graphs from. I would also like to start measuring the pond temperature to see how it fluctuates during the day.