I had always assumed that, without the application of heating, indoor temperatures would follow the same profile expected outside; warmer at day and cooler at night. However according to my thermonitor gadget that isn’t the case. I’ve been putting it on test for a couple of days in its completed project box and the graph suggests that the room is coolest in the middle of the day, gradually warming up into the evening until beginning to drop off again around the middle of the night.
This is in a corner with no direct light in a room facing north east so the results might be different in an alternative location (perhaps I can extend one of my sensor leads to situate it in another room?) but it appears that the shelter of the house acts as a significant thermal brake. It is still a bit hot up here for my brewing (the particular prompt to my present curiousity) so I would also like to check the situation downstairs in our larder (no direct light and no external walls – I expect this will be cooler overall).