After making the changes discussed earlier and monitoring the values and the graphs of those values, I can draw some conclusions about the interior conditions at the cabin.
First, conditions downstairs are more stable than the upstairs, both temperature and humidity do not fluctuate nearly as much as they do upstairs. Makes sense as there are only two small windows downstairs, while the upstairs has five windows.
Second, it is cooler upstairs than downstairs – but a larger difference than I would have expected. It is 4-5 degrees cooler upstairs, and more humid by 4-5 percent. Some of the humidity difference is attributable to the temperature difference, but not all of it. Solar heating during the day does warm the upstairs more than the downstairs – presuming that the sun can supply the solar energy. On cloudy days, you’re on your own.
But my main interest was to see how close to freezing it gets inside, with no heat source to maintain a set temperature. I can’t risk frozen pipes, so I drain the water system and put RV antifreeze in the traps and the toilets. Maybe I’ve been wasting time and RV antifreeze when it isn’t really needed, but now I have a reasonably reliable way to monitor the situation.