Sunrooms

Isolated gain is the other type of passive solar heat. A solarium or sunroom has a glass wall designed to trap the sun's heat and warm a specific space that is somewhat removed from the main house space. The room will draw in plenty of winter warmth, but is harder to regulate than more traditional windows. They may not be ideal in some hot climates because they get too hot in the summer, and don't offer much of an advantage in the winter.

Passive solar energy can be used without solar panels or other devices. It simply maximizes the sun's winter heat gain and minimizes summer heat loss with windows, walls and floors.

Source: http://www.networx.com/article/harnessing-passive-solar