In buildings, energy efficiency means using less energy for heating, cooling, and lighting. It also means buying energy-saving appliances and equipment for use in a building. All the components of the building envelope need to work together to keep a building warm in the winter and cool in the summer. Your home's insulation, for instance, will be less effective if the roof, walls, and ceiling allow air to leak in or allow moisture to collect in the insulation.
Various approaches can help improve the building envelope.
Storm windows and doors can reduce heat loss when temperatures drop. In warm regions, windows with special glazing can let in daylight without heat gain. Even some simple weatherization techniques, such as weatherstripping doors and windows, can significantly improve a building's energy efficiency. Heating and cooling systems typically use the most energy in a building. In homes, the addition of efficient controls, like a programmable thermostat, can significantly reduce the energy use of these systems.