"The house is 1962 vintage 3 bedroom, 2700 sq. ft. cinderblock ranch, nothing fancy except the entire back of the house is made of glass, with louverd windows that leak, and all single pane, with 3 10 foot x 10 foot sliding doors to look at the lake. They do not retain either heat in the winter or cool air in the summer, so the A/C unit is running all the time, oh, and with 4 teenage kids (3 of them girls) the washer and dryer never stop either."

Replacement double pane windows w/uv covering would help a lot and you could probably recoop most of the cost in the electric savings. A porch/awning over that side of the house would probably help in the summer too.