I'm located in a hot Southern climate. We're technically north of Atlanta in latitude, but much flatter in altitude which can make a big difference. Someone south of Atlanta is likely to experience similar weather. I have friends in Warner Robbins, and our summer weather is usually within a few degrees of each other. Delta heat and humidity is brutal. We get MUCH hotter and humid springs and falls than most realize. And "humidity season" is about 10 months long. The Gulf is always swirling up massive amounts of moisture into the region. It's basically summer from April til October. Heating season is only 3-4 months long here while cooling season can run 8-10 months. There are months that overlap. Hot in the day and cool at night. It's not so much the temperature in those overlap months as it is the humidity. 81 degrees and 95% humidity is pretty darn clammy and miserable and so needs the AC to dehumidify the air. Same with 55 degrees and 90% humidity. It feels colder than it actually is because of the humidity and putting on a sweater only helps marginally. Gotta run the heat a bit to make the temp more comfortable. There are about three weeks in fall and three weeks in spring when you can actually open the windows and not suffer due to letting the humidity into the house. Planning for solar heat gain in the winter is practically ludicrous with those conditions. It's not that darn cold to begin with! Add in a bit of low sun solar gain to your average 40-50 degree winter high temperature and the house will get to 80 in no time. My neighbor's attached Southern facing un-HVAC'd sunroom regularly gets to 95 degrees on a sunny December day. In summer, even with decent overhangs, it's 130 in there by noon. Try to work with that for your home's cooling load! This is why I stated that solar planning for the South is more about minimizing the solar gain rather than trying to harness it for the brief heating period that happens. Your major energy dollars spent here are in cooling. Minimizing loads to the cooling system with the home's design is what pays off here---IF, as David says, the homeowner has the luxury of enough room to accomplish that. 95% of those building will do so on lots too small to do much more than trying to get the right windows for those Southern facing heat gainers.

Thanks to all-- no one I could find makes and sells cellular blinds (at least in this country) over 144 inches long. Our carpenter suggested putting a 2+ inch piece of cedar across the top of each window and then installing 144 inch shades. Today, as we sit around the table discussing Thanksgiving timing, my dad suggested, instead, a white piece at each window top which, when the shaded were installed, would become part of the stack. I think it's a better solution, although I don't love a 4 inch stack.

If you are only talking about daytime privacy then solar shades will work for you. You will be able to look out during the day and no one can look in. However, at night it is the opposite. You can’t look out but anyone outside can look in. That’s the only product I know of that will allow you to look out during the day and keep your privacy without raising a shade or tilting a blind.

Carol - Energy star makes some generalizations and some mistakes. Particularly when it comes to passive solar and window orientation. Don't feel you have to be ES certified unless you need to be for a rebate or house certification. There are 2 numbers to care about SHGC - which is the amount of heat gained through the window. A low number means good for reducing a/c. Means very little on a North facing window or appropriately shaded South window. U. factor. This is probably what you care about in Mass. This is the resistance to ambient heat flow. It is how cold the window would feel in the winter. It is minor in the summer. Yes Anderson charges a lot for their low u window. Do you have an energy rater to decide if it makes financial sense? $5000 extra on windows that should last 30+ years isn't a huge deal. Note that low u windows will make the temps in your house more stable in the winter since windows won't be robbing the heat. So it isn't just energy savings but comfort also. What I know about Mass. is energy costs are high and it gets cold. I hear shocking numbers on what people pay for heat. Down here in NC, different story and I couldn't come close to justifying low u windows. Not with heat pumps using $.10c a kwh electricity. Solar panels pay off decades faster.