Heating, ventilation, and air conditioning (HVAC) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer. "Refrigeration" is sometimes added to the field's abbreviation as HVAC&R or HVACR, or "ventilation" is dropped, as in HACR.
A furnace, referred to as a heater or boiler in British English, is an appliance used to generate heat for all or part of a building. Furnaces are mostly used as a major component of a central heating system. Furnaces are permanently installed to provide heat to an interior space through intermediary fluid movement, which may be air, steam, or hot water. Heating appliances that use steam or hot water as the fluid are normally referred to as a residential steam boilers or residential hot water boilers. The most common fuel source for modern furnaces in North America and much of Europe is natural gas; other common fuel sources include LPG, fuel oil, wood and in rare cases coal. In some areas electrical resistance heating is used, especially where the cost of electricity is low or the primary purpose is for air conditioning. Modern high-efficiency furnaces can be up to 98% efficient and operate without a chimney, with a typical gas furnace being about 80% efficient. Waste gas and heat are mechanically ventilated through either metal flue pipes or polyvinyl chloride (PVC) pipes that can be vented through the side or roof of the structure. Fuel efficiency in a gas furnace is measured in AFUE.
A central heating system provides warmth to a number of spaces within a building from one main source of heat. It is a component of heating, ventilation, and air conditioning systems, which can both cool and warm interior spaces.
Hydronics is the use of liquid water or gaseous water (steam) or a water solution as a heat-transfer medium in heating and cooling systems. The name differentiates such systems from oil and refrigerant systems.
Cross-linked polyethylene, commonly abbreviated PEX, XPE or XLPE, is a form of polyethylene with cross-links. It is used predominantly in building services pipework systems, hydronic radiant heating and cooling systems, domestic water piping, insulation for high tension electrical cables, and baby play mats. It is also used for natural gas and offshore oil applications, chemical transportation, and transportation of sewage and slurries. PEX is an alternative to polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC) or copper tubing for use as residential water pipes.
Designated as an American National Standard, the Uniform Plumbing Code (UPC) is a model code developed by the International Association of Plumbing and Mechanical Officials (IAPMO) to govern the installation and inspection of plumbing systems as a means of promoting the public's health, safety and welfare.
A forced-air central heating system is one which uses air as its heat transfer medium. These systems rely on ductwork, vents, and plenums as means of air distribution, separate from the actual heating and air conditioning systems. The return plenum carries the air from several large return grills (vents) to a central air handler for re-heating. The supply plenum directs air from the central unit to the rooms which the system is designed to heat. Regardless of type, all air handlers consist of an air filter, blower, heat exchanger/element/coil, and various controls. Like any other kind of central heating system, thermostats are used to control forced air heating systems.
Variable air volume (VAV) is a type of heating, ventilating, and/or air-conditioning (HVAC) system. Unlike constant air volume (CAV) systems, which supply a constant airflow at a variable temperature, VAV systems vary the airflow at a constant or varying temperature. The advantages of VAV systems over constant-volume systems include more precise temperature control, reduced compressor wear, lower energy consumption by system fans, less fan noise, and additional passive dehumidification.
Underfloor heating and cooling is a form of central heating and cooling that achieves indoor climate control for thermal comfort using hydronic or electrical heating elements embedded in a floor. Heating is achieved by conduction, radiation and convection. Use of underfloor heating dates back to the Neoglacial and Neolithic periods.
Building officials of developed countries are generally the jurisdictional administrator of building and construction codes, engineering calculation supervision, permits, facilities management, and accepted construction procedures.
Designated as an American National Standard, the Uniform Swimming Pool, Spa and Hot Tub Code (USPSHTC) is a model code developed by the International Association of Plumbing and Mechanical Officials (IAPMO) to govern the installation and inspection of plumbing systems associated with swimming pools, spas and hot tubs as a means of promoting the public's health, safety and welfare.
Uniform Codes are codes of practice developed and maintained by the International Association of Plumbing and Mechanical Officials (IAPMO) using the American National Standards Institute's (ANSI) accredited consensus development process working on a three-year cycle. This process brings together volunteers representing a variety of viewpoints and interests to achieve consensus.
IAPMO Standards are the plumbing and mechanical standards of the International Association of Plumbing and Mechanical Officials (IAPMO). For more than thirty years, IAPMO’s standards-developing efforts have primarily focused on plumbing product standards. This concentration was primarily due to IAPMO members’ expertise from more than 50 years of writing and updating the Uniform Plumbing Code (UPC). IAPMO is an American National Standards Institute (ANSI)-recognized Standards Development Organization (SDO).
HVAC is a major sub discipline of mechanical engineering. The goal of HVAC design is to balance indoor environmental comfort with other factors such as installation cost, ease of maintenance, and energy efficiency. The discipline of HVAC includes a large number of specialized terms and acronyms, many of which are summarized in this glossary.
IAPMO R&T was started in 1936 as a third-party listing agency specializing in plumbing and mechanical products. IAPMO R&T is accredited to certify products that meet the criteria of the Uniform Plumbing Code, Uniform Mechanical Code, Uniform Solar Energy Code, Uniform Swimming Pool, Spa and Hot Tub Code and other nationally recognized codes and standards in North America.
The International Mechanical Code (IMC) is a convention concentrating on the safety of heating, ventilation, and air conditioning systems. It is published by the International Code Council (ICC) through the governmental consensus process and is updated on a three-year cycle to include the latest advances in technology and safest mechanical practices. The current version of this code is the 2021 edition. The IMC protects public health and safety for all building heating, cooling and ventilation related design, installation and inspection by providing minimum safeguards for people at homes, schools and workplace. Fuel burning appliances, cooling systems, heating systems appliance venting, location and protection of appliances and many other such issues are addressed in the IMC.
Copper tubing is available in two basic types of tube—plumbing tube and air conditioning/refrigeration (ACR) tube, and in both drawn (hard) and annealed (soft) tempers. Because of its high level of corrosion resistance, it is used for water distribution systems, oil fuel transfer lines, non-flammable medical-gas systems, and as a refrigerant line in HVAC systems. Copper tubing is joined using flare connection, compression connection, pressed connection, or solder.
The International Association of Plumbing and Mechanical Officials (IAPMO) coordinates the development and adaptation of plumbing, mechanical, swimming pool and solar energy codes to meet the specific needs of individual jurisdictions both in the United States and abroad.
Mechanical, electrical and plumbing (MEP) refers to the installation of services which provide a functional and comfortable space for the building occupants. In residential and commercial buildings, these elements are often designed by specialized MEP engineers. MEP's design is important for planning, decision-making, accurate documentation, performance- and cost-estimation, construction, and operating/maintaining the resulting facilities.
Designated as an American National Standard, the Uniform Solar, Hydronics and Geothermal Code (USHGC) is a model code developed by the International Association of Plumbing and Mechanical Officials (IAPMO) to govern the installation and inspection of solar energy, hydronic heating/cooling systems, and geothermal energy systems as a means of promoting the public's health, safety and welfare.
