Solar Heat Gain

I am planning a move (hopeful my last) to retire, I think I'll be ok financially if I do as much of home improvements as possible myself, which after 30 years in front a computer, I'm looking forward to.
Over the past year I've created a bunch of small single-purpose spread-sheets to study different aspects home energy needs and now I'm combining them all into one spread-sheet to study their inter relations.
I have a sheet that to calculate R-Values for envelope design elements which are then combined for top, bottom, right, left, front, and back for 1° Heat-Loss Per-Day for each of the six envelope sides using the basic formula:
Heat Loss Rate = Area x (Temp inside - Temp outside) / Thermal Resistance of structure
Based on calculations from here:
They build on this general formula to calculate 1° Heat-Loss Per-Day, and from there incorporate heating and cooling Degree Days for total heat-loss for whatever time period. I down-loaded Typical Meteorological Year (TMY) data for all 239 reporting stations to calculate Tin, Tout, HDD, & CDD for all locations (I'm, still not certain on the best location to move to).
I think I'm ok up to here, but now I'm looking to modify the general formula to include solar heat-gain, and my envelope design sheet already includes general compass direction, I image that TMY has whatever data is needed, just looking for help in modifying the general formula.
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