When you simulate this model you get the following behavior:
Temperature follows a sawtooth pattern over the course of the day. The rate of cooling varies modestly around a value of 4 Degrees Farenheit/Hour. The furnace switches from on for a little less than an hour and off for a somewhat longer period of time.
If we do an experiment in which outside temperature is lowered to 10 degrees (from 35) we get the behavior:
Here the furnace is on much more, heating takes longer and cooling is more rapid.
