And still useful. I use it to control a water pump to push water to sprinklers on my roof for the hot Atlanta summer months. 1 Gal of water evap from the roof is ~8000BTU's (I'm told - someone correct me if that's wrong).
re: "doing any good", yes, that's hard to say. The ROI may not be for years, if ever. It was as much a "I have an idea,let's see it through" project as a real money saver.
The attic is insulated, and with a radiant barrier, to boot.
But if you were going for cooling, you wouldn't go for a dark asphalt roof.
The controller app is a bash shell script. :-)