GDE -
as you aaid, it's all about compromise. What I'm starting to wonder is when we're going to see someone install a minisplit - not the back, but mounted on the roof with two zones. that will be a game changer - because of the efficiency of the Minisplits - and dual zones - plus the quiet. Of course, most are designed for 220 for dual zones - but it'll happen eventually.
I think your insulation has made 105 degree weather on a 20 amp circuit feasible. With an R3, there's almost no way to keep the heat out and the move the remaining heat outside. I ran into that a few years ago up in the Gold Country in central CA. it was 105 and no matter how early I ran the AC, it just couldn't move the BTU's outside the 5er as quickly as it gained it through the roof (and windows). upgrading that insulation will make all the difference.
And letting the relatives pay for the Electrical circuit... genius! :)
Josh
