Passive houses are an innovative new type of home design that is build save energy. This passive house, in the Washington, D.C., suburbs, is so well sealed and insulated that it requires no expensive heating or cooling equipment. It uses building techniques to keep the air inside comfortable year round. The energy costs are reduced by 90 percent by using triple glazed windows and rigid foam insulation, and making sure there are no leaks in window seams. The windows also are designed to make maximum use of sunlight and shade for heating and cooling.