Today I did some plumbing for the solar loop. In the picture you can see the delta-T pump (at the top), the air separator, the expansion tank, the pressure relief valve, the fill and drain valves, a ball valve, one of two temperature gauges, and a bunch of fittings and pipe to connect everything. I feel good about everything except one solder joint... the connection to the air separator. My propane torch was a little too wimpy to heat up such a mass of metal so I'm not entirely sure I got a good connection.
I still am waiting for a 3-way valve, but that is the last thing before the solar will be fully plumbed. The 3-way valve is a safety measure: when the temperature of the tank exceeds a threshold, say 180F, the valve will open and send the hot water through an underground loop to dissipate excess heat.
Tomorrow my dad and I will fill up the attic with the 2nd layer of insulation. We've got the whole attic covered with R13, so tomorrow with the addition of R30 (perpendicular to the first layer) we'll be up to R43.