About two weeks ago I turned off the heat in my underground bunker in Idaho. I wanted to see what the baseline temperature would be. It varies by room. This is probably because of the computers I have in the office and proximity to other miscellaneous heat sources like the hot water heater and depth of the overhead earth for each of the rooms.

But what is most interesting to me is that the temperature is almost independent of the outside temperature:

With the exterior temperature removed from the graph you can see the coupling to the outside temperature is, at best, a very small fraction of the outside temperature and with a phase shift of about one day.

That means the heating system does not have to deal with the daily extremes. It only has to deal with the daily average. And I think this means that it will not need any cooling. I will know for certain in about six weeks when we will be through the hottest part of the year in my neighborhood.