The important concept for energy efficiency in buildings is the building envelope, which is everything that separates the interior of the building from the outdoor environment: the doors, windows, walls, foundation, roof, and insulation. Various approaches could be done to improve the building envelope. For instance, windows with special glazing can let in daylight without heat gain and storm windows and doors can reduce heat loss when temperatures drop. These techniques can significantly improve a building's energy efficiency.
Cooling and lighting systems typically use the most energy in a building in our country. The addition of efficient controls, like a programmable thermostat, can significantly reduce the energy use of this system. For commercial buildings, maximizing the use of Building Energy Management System (BEMS) can provide the best approach to energy-efficient cooling. The energy used to heat water can be reduced by both heating water more efficiently and by reducing hot water use especially in hotel and hospital application. A wide variety of fixtures, such as low-flow showerheads and faucet aerators, can reduce hot water use. In a home, the older water heater can be replaced with a newer, more energy-efficient one, and the water heater and hot water pipes can be insulated to minimize heat loss.
Today, most common appliances and electronic devices are available in energy-efficient models—air conditioner, washing machines, fans, refrigerators, copiers and computers. Several energy-efficient lighting options, such as compact fluorescent light bulbs, are also available. There are many ways to determine energy efficient in building, measures and improvements can be made. Owners can conduct energy audits on their premises or have professional audits done.During the commissioning of new commercial buildings, a number of tests and adjustments can be performed to ensure that the heating, cooling, lighting, ventilation, and other mechanical systems work together effectively and efficiently. Once the systems are commissioned, their proper operation and maintenance is critical to efficient energy use.