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Louvers Blades, sometimes adjustable, placed in ducts or duct entries to control the volume of air flow. The term may also refer to blades in a rectangular frame placed in doors or walls to permit the movement of air. Makeup air unit (MAU) An air handler that conditions 100% outside air. MAUs are typically used in industrial or commercial settings, or in "once-through" (blower sections that only blow air one-way into the building), "low flow" (air handling systems that blow air at a low

Damper A plate or gate placed in a duct to control air flow by introducing a constriction in the duct. Deep lake water cooling The heat is rejected to deep lake regions to cool homes and offices, reducing the energy costs. ΔT ΔT (delta T) is a reference to a temperature difference. It is used to describe the difference in temperature of a heating or cooling fluid as it enters and as it leaves a heat transfer device. This term is used in the calculation of coil efficiency. Evaporator

Air changes per hour (ACH) The number of times per hour that the volume of a specific room or building is supplied or removed from that space by mechanical and natural ventilation. Air handler, or air handling unit (AHU) Central unit consisting of a blower, heating and cooling elements, filter racks or chamber, dampers, humidifier, and other central equipment in direct contact with the airflow. This does not include the ductwork through the building. British thermal unit (BTU) Any of

For the last 20–30 years, manufacturers of HVAC equipment have been making an effort to make the systems they manufacture more efficient. This was originally driven by rising energy costs, and has more recently been driven by increased awareness of environmental issues. In the USA, the EPA (Environmental Protection Agency) has also imposed tighter restrictions. There are several methods for making HVAC systems more efficient. Heating energy Water heating is more efficient for heating buildings

Air conditioning and refrigeration are provided through the removal of heat. The definition of cold is the absence of heat and all air conditioning systems work on this basic principle. Heat can be removed through the process of radiation, convection, and conduction using mediums such as water, air, ice, and chemicals referred to as refrigerants. In order to remove heat from something, you simply need to provide a medium that is colder—this is how all air conditioning and refrigeration systems w

There are different types of standard heating systems. Central heating is often used in cold climates to heat private houses and public buildings.

The HVAC industry is a worldwide enterprise, with career opportunities including operation and maintenance, system design and construction, equipment manufacturing and sales, and in education and research. The HVAC industry had been

Air conditioning engineers broadly divide air conditioning applications into comfort and process. Comfort applications aim to provide a building indoor environment that remains relatively constant in a range preferred by humans despite changes in external weather conditions or in internal heat loads. Air conditioning makes deep plan buildings feasible, for otherwise they'd have to be built narrower or with light wells so that inner spaces receive sufficient outdoor air via natural ventilation.

Early commercial applications of air conditioning were manufactured to cool air for industrial processing rather than personal comfort. In 1902 the first modern electrical air conditioning was invented by Willis Haviland Carrier in Syracuse, NY. Designed to improve manufacturing process control in a printing plant, his invention controlled not only temperature but also humidity. The low heat and humidity were to help maintain consistent paper dimensions and ink alignment. Later Carrier's technol

While moving heat via machinery to provide air conditioning is a relatively modern invention, the cooling of buildings is not. Wealthy ancient Romans circulated aqueduct water through walls to cool their luxurious houses.[citation needed] The 2nd century Chinese inventor Ding Huan (fl. 180) of the Han Dynasty invented a rotary fan for air conditioning, with seven wheels 3 m (10 ft) in diameter and manually powered.[2] In 747, Emperor Xuanzong (r. 712–762) of the Tang Dynasty (618–907) had the C