The passive solar element has also had a workout. With a cold snap with clear skies, I've had the house heat up from 62 F to 68 F with out any heat input other than the sun.
The roof angle is 30 deg., the winter solstice sun angle. Shown here the noon sun from
the four upper windows casts light on the concrete panels. Heating them so they can
radiate heat later.
The house is also nice because the heat is uniform, no blowing vents, and there are no drafts.