Two questions: Can anyone point me to blinds with side channels and sill seals? And what's your opinion of the solar fabrics that block uv but allow some light? And, no, windowquilt.com is great but not an answer for me. I had a hit and a miss with window coverings 12 years ago building a passive solar house in south central PA. I installed cellular shades for regular duty and patio rollups backed with bubble foil insulation to pull down over them on the relatively rare nights below 20 degrees. Trouble is neither seals, resulting in condensation and chilly air falling behind them. I prefer to keep the rollups and the flexibility of two window coverings. It's rather easy to seal the rollups with sheet-metal angles on the jambs and magnetic strips on the blinds. The unpleasant side effect is blackout in a coal mine. On most gray days, of which there are plenty, the cellular shades are sufficient. But there's condensation even at 32 degrees as the overnight low was today.

Windows are over rated.....just block them off...

For what you want I think I would do the old plastic shrink on stuff and regular cellular shades.

Ever thought if shutters would seal better?

The only way to effectively deal with window condensation is to understand the relationship between dew point temperature and relative humidity and design the house and windows for the local climate so it can't happen. Window condensation can't happen if the window surface temperature is warmer than the dew point temperature. The dew point temperature gets lower (i.e., gets condensation resistant) as the relative humidity gets lower.

https://www.borstengineeringconstruction.com/Psychrometrics_Calculator.html

You can use windows that provide enough R-value for the local climate to keep the interior window surface temperature above the dew point temperature. You can use ceiling fans in the vicinity of the windows to move warm air around them to keep their surface above the dew point temperature. You can use a HRV or dehumidifier to lower the relative humidity.

Passive solar design is an entirely different design subject. Lots of people claim they have passive solar, but few actually have a proper passive solar design. Ones needs to fully quantify every BTU entering and leaving the building every month of the year to accomplish a proper passive solar design. Lots of free information on our website about how to accomplish a proper passive solar design for those actually interested in doing so.