This is the hottest part of the year, and my underground bunker is keeping it’s cool:

The ragged sort of sine wave line was the outdoor temperature over the last 24 hours. The other lines are the temperatures of the rooms with thermostats in them. There has not been any artificial heat in weeks and never any cooling. The bedroom is a little warmer that Barb likes for sleeping but I think if we opened two windows at night and put fans in the windows, we could cool the bedroom down to her ideal of 66 F.

The humidity varies from 45.2% to 53.3% That’s near ideal.