Created this new thread for HVAC discussion. Will leave it here under solar.
Here again is a link to the Load Calculator I've been using:
I'm still tinkering with my numbers. Windows seem to be the biggest problem in my house. They were single pane but I've replaced two already with double and have two more on order.
The next biggest issue depends on heating or cooling season. For heating, my floors are the next biggest problem and I can't really do much. A slab is a slab. For Cooling season, the second biggest issue is either duct load or ceiling. I have to go up in my attic and decide what R value my ducts actually are. Currently I'm running with the setting at R-19 for attic, R-13 for walls and R-4 for ducts. These could all be wrong. Knowing your inputs are vital to get good numbers out of the calculator. I've measured everything else, windows, doors, etc. I've tried measuring the attic insulation but its a mix of blown and bat, and the blown in fiberglass is uneven. It is a late 80's house in the desert in CA so R-19, while it sounds low, might be correct.
For Design temp inputs for cooling I have put in indoor of 75f without Outdoor 110f, and for Heating outdoor 20f and indoor 68f.
Currently with these inputs I'm getting a Load of:
Total Btu's Cooling: 43347
Sensible Load: 42747
Latent Load: 600
Total Btu's Heating: 50479
More to come on my past usage for my NG furnace and systems I'm looking at, their design BTUs and DIY issues, and fitting it in with my Solar.