tl Outside light is much stronger than what gets inside, so even if the plants are getting bone dry and going limp outside of that window, inside doesn't get same intensity - and the sun is much higher now so amount getting thru the window is less too. I have 2 large south windows and it is interesting to see how much less sun is getting in now comparing to just couple months ago.

Thank you all for your comments. I do have a "master" setting on the main duct leading from the furnace that has a summer and a winter setting - this makes some difference - and there is a return air vent upstairs as well as on the first floor. The energy audit representative discouraged me from completely closing some air vents (like on the first floor). He said the system was designed for air flow through all ducts. Two zones/separate a/c units would be optimal but not sure I want to put that kind of money into solving the problem. But the heat pumps in my development seems to starting to fail so, when mines goes and has to be replaced, I will investigate potential solutions with two zones. At this point, for the bedrooms, I'll go with good insulated drapes that I will keep closed in the summer. For the window above the door, I finally found someone knowledgeable about shades (at my local Lowe's), He showed me a double cellular shade that will be included in a 40% off sale in February. A motorized shade will be in the $250 range plus installation. I used Lowe's for all the windows in this house and my last one and been very satisfied. The only issue now is that the motorized mechanism has batteries housed in a unit in the shade header. This will be 16' above the floor, so replacing batteries is going to entail my handyman coming over (I'm 70 and don't do ladders!) with at least a 12' ladder when this is needed. Thanks again for all the good thoughts.

Where is the home located? If it is covered and will not be exposed to direct radiant energy from the sun, the necessity of something in the 3-coat Low-e range (i.e. Cardinal Low-e 366) goes away. You still do want a Low-e to assist with heat flow in either direction, i.e. saving energy in the winter as well, but you can certainly go with a Low-e 2 range or even higher VT rated coating. https://www.cardinalcorp.com/technology/reference/loe-performance-stats/

Thanks for your reply, that is interesting to learn. I located a tool where I can change the SHGC for my location and window type (among a few other variables) at Sustainable by Design. However, I have no idea how the values relate to real life room temperature and comfort. Comparing SHGC's of .20 and .49 I get the following outputs: .20 HighestWinterBtu/ft2: 780 @ noon, monthly 5,300 (Feb & March), but lowest monthly total is January (4,600). Highest Summer Btu/ft2: 450 @ noon, monthly 3,100 (both June). .49 Highest Winter Btu/ft2: 1900 @ noon, monthly 13,000 (Feb & Mar), but lowest monthly total is January (11,000). Highest Summer Btu/ft2: 1100 @ noon, monthly 7,500 (both June). That second set of values looks alarming compared to the first set, but I have no idea if that actually means the ~2100 ft3 room will become uncomfortable and I should change the window order to a SHGC of .20 like the east-facing window will be. I can open the double glass doors if that would make a significant difference (spouse's current COVID home-office). Further comments are greatly appreciated. Thanks!