A friend of mine is remodeling his 1980s house and was asking advice about keeping it cooler in the summer. The house currently has the original double pane windows, many of which have "popped" and are clouded. The house is east facing and gets tons of morning and early afternoon sun. It gets really hot during the day in the summer. It doesn't currently have any A/C. It's heating system is a wood stove and old fashioned baseboard heat. He's thinking about a mini-split system for heating and cooling, but I'm worried that it will be expensive to run the A/C unless he deals with the solar radiation heating the house.
One thing I suggested was to close off some of the upper windows in the prow, insulate and drywall over the openings. That would change the look, but might help control the solar radiation.
Another consideration is how much additional insulation could be expected with replacing the windows? How much difference could that make? Again, they are double pane, but now about 35 years old.