The document discusses passive solar building design. It begins by noting that population growth and urbanization have increased energy consumption. About 35-40% of energy is used by buildings, mostly for heating. The rest of the document discusses various passive solar design elements that can be used to collect, store, and distribute solar energy for heating buildings in winter and cooling in summer. These include south-facing windows, thermal mass materials, shading devices, and thermal storage walls like Trombe walls. The benefits of passive solar design are reducing energy consumption and heating/cooling costs.