So it seems to be pretty consistent that if it’s 35-40 outside and sunny, it will get up to about 70 in the sunroom. We can open the doors to the living room and the temps will be about equal. Before we insulated, the temperatures upstairs lagged behind, a lot, but now the upstairs is generally warmer than downstairs. I still want better control of the vents from the sunroom to the upstairs – something that can be sealed shut and weatherstripped, but easy to open on both ends when we want the warm air to come through.
The thermal mass holds for about a day of no sun. For example, Tuesday was sunny, and everything got warm. Wednesday was cloudy, and the temperature was borderline; we could maybe have gone without any extra heating, but decided to light a slow fire. That never got super-hot, and the living room didn’t get above 68. Upstairs was about 63 this morning. Now (at noon), downstairs is 68 and up is still 63. Experience suggests the sunroom will stay warm until 7 or 8pm; then it’ll start being cooler than the living room. I’m guessing that will change as the season progresses. Though nights have been at or below 30 the last week or so, daytime highs are still around 40. I bet once winter really sets in, we’ll lose most of the remaining heat in the rock pile, and one day of sun won’t be enough to offset all the cold in the thermal mass.
Still, it’s December 5th, and we haven’t turned the furnace on at all this year. We’ve probably burned 1/2 face cord of wood so far, and I don’t feel cold all the time like I did in the last house.
The plants in the sunroom are barely growing, but we can harvest some kale and even the occasional cherry tomato still.