First, I'm glad I could start such a lively debate and I truly appreciate everyone's time and opinions.
Yes, I have what I believe are clear glass dual pane windows, circa 1991.
The rear of the house faces south (slightly south-west actually).
I have a two story with a walkout basement. Two DH windows are in the basement; they're both 42"x55". One of the two basement windows is under the deck and is shaded most of the day. The other is in full sun till late afternoon.
The first story is the problem. No shade EVER; bakes in the sun all day. It's has two DH 38"x54", two casements 24"x61", one picture 48"x61", one DH 37"x38", one DH 33"x38". There's also a 5' patio door that I'll replace someday, but I has internal blinds we keep closed most of the time. The first floor is where we spend the most time and where most TV viewing occurs. Unfortunately the TV faces the windows. We have wooden blinds, but keeping them closed is the problem. We have a nice view out the back and my wife likes to enjoy it.
The second floor only has has three windows: two DH 37" x 54", one 33"x38". They receive a little shade from the overhang. They all have blinds that are kept closed most of the time.
This afternoon is a bright sunny day, but it's only about 70 degrees. AC is on. At 5:30 pm the two basement windows were mostly shaded, the 1st floor was in full sun, and the 2nd floor windows were about 35% shaded. It's about 69 degrees in the basement, about 74 on the first floor. It's probably 5 degrees warmer on the second floor.
My infrared thermometer shows a temp of over 90 degrees on the basement sash rails near the glass. I got 108 degrees on the 2nd floor casement and picture windows on the edge of the sash!
The info at
http://www.efficientwindows.org/city_all.cfm?id=30 reinforces what you guys have said about wanting a higher SHGC. Looking at the variance in total costs, though, I'm not sure that the added winter heat gain with a medium solar-gain window is worth keeping the blinds closed in the summer and making the wife unhappy. The again, I suspect anything I choose will be a HUGE improvement over what I have now!
Thanks,
Randy
800-399-4623