Sunny & warm in winter/
Shady & cool in summer
Passive solar houses are designed to flow with the seasons. Anyone who has ever lived in a house that had its seasons backwards can surely appreciate a house that gets its seasons right. Our design imperatives were born in backwards houses: houses that were cold and dark in winter (and expensive to heat), and hot and sunny (and expensive to cool) in summer.
Once you have ever lived in a house that is sunny and warm in winter and shady and cool in summer – there's no going back.
Although it was lost for perhaps 1500 years, passive solar orientation was understood by the ancients. This includes even our ancestors who lived in caves - most of which faced south in the northern hemisphere. The Greeks built their earliest houses to take advantage of the sun: the houses had a high thermal mass, were open-air and faced south. The Romans built similar houses, and when sheet glass was invented about the time of Christ, they used that glass to trap winter sunlight in their homes.
How could we have lost such basic technology? We marvel at this, and the fact that the recipe for cement was also lost with the collapse of the Roman Empire; portland cement was not reinvented until 1824.
Thank goodness we live in a time when much ancient knowledge has been recovered for us to employ and add to if we only will!