insulating window shades in a passive solar house
We're building a passive solar house with 18- 7' high south facing windows. Energy-10 calculations suggest that leaving the windows uncovered at night has a big effect on heat loss.
We plan to use cellular shades to insulate all the windows, but have the dilemma of what to do when we are not home. The windows on the south side must be raised and lowered each day. We'd like to use motorized shades with a timer, but find they are very expensive (~$700/window + wiring and controls). Does anyone have any experience with these? Are there better solutions?