No trouble. I was just done with making a big pot of chili (sorry Rewahoo, I put two kinds of beans AND lentils in it. My bad. We live in California and a guy comes to certify that our chili contains a minimum amount of beanlike material and we suffer enormous fines for not complying) and thought I'd check in.
Building envelope and insulation are pretty important, but sort of boring. But like the pro's always tell me, you only have to pay for insulation once and then it pays off for 30-40 years. You can get little foam 'plates' that go behind your outlet covers and close off the gaps and good thick glass dual pane windows can really knock a lot off your heating and cooling expenses, along with cutting noise substantially. You can do a lot of good stuff in an afternoon with a stack of those foam outlet plates and a tube of caulking.
A reasonably well insulated home at 2100 square feet should be reasonably well serviced by a single heating and air conditioning unit. Does one look like an add-on? Dual systems can allow you to set one area at one temp and the other at something different. I had that in my old mcmansion and it was nice to have the upstairs/bedroom unit flip off during the day and go to a high heat/cool level at night, while the downstairs unit did the opposite.
Trouble is, you have two units to maintain and replace.
Attic fans are okay if you keep an eye on your bills and they're doing right by you. I had a powered attic fan in my old mcmansion and a two panel solar one in the last smaller house I had. They both delayed the onset of full bore air conditioning by an hour or so in the mornings. In my mcmansion, the electric bill didnt go down at all, so it was a wash powering the attic fan vs the air conditioner. In my last house, the electric bill didnt change much either and the $300 I spent on the solar powered attic fan (self installed) didnt taste that good either.
