Heating ventilation and air conditioning HVAC
'HVAC' refers to Heating Ventilation and Air Conditioning, which can be used in buildings to:
- Maintain internal air quality.
- Regulate internal temperatures.
- Regulate internal humidity.
It is sometimes extended to include other services, such as refrigeration (HVACR). For more information see: HVACR.
Internal air quality can be maintained by a combination of introducing 'fresh' air into the building, extracting 'stale air' and by filtration. Ventilation may be natural, mechanical, or mixed mode (a hybrid system). See Ventilation for more information.
Internal temperatures can be regulated by heating and cooling. Typically, this is achieved by heated water (or sometimes steam) and chilled water that is generated by boilers and chillers and then used in heating coils and cooling coils as part of the ventilation system. Alternatively, hot water may be used to supply systems such as radiators, underfloor heating and so on.
Humidity can be regulated by ventilation, dehumidification and humidification. Dehumidification is often provided alongside cooling as cooling air reduces the amount of moisture air is able to 'hold', resulting in condensation. 'Close' humidity control (to within 10%) can involve cooling and dehumidification, then re-heating and re-humidification.
Very broadly, HVAC systems can be centralised in a building, or local to the space they are serving, or a combination of both (for example, local air handling units supplied by centrally-generated cooling). They may also be connected to a wider district heating or cooling network.
They may be integrated, with heating, ventilation and air conditioning provided by a single system, for example, air handling units connected to ductwork, or they may be a combination of separate systems, for example mechanical ventilation with radiators for heating and local comfort cooling units.
They may also include passive (or 'natural') systems such as natural ventilation.
In mechanically ventilated commercial developments, HVAC is often provided by air handling units (AHU) connected to ductwork that supplies air to and extracts air from internal spaces. Air handling units typically comprise an insulated box that might include some, or all of the following components; filter racks or chambers, a fan (or blower), heating elements, cooling elements, dehumidification, sound attenuators and dampers. Air handling units that consist of only a fan and a heating or cooling element, located within the space they are serving, may be referred to as fan coil units (FCU). See Air handling units for more information.
HVAC can consume large amounts of energy, and where possible, demand should be reduced and passive systems adopted.
Extracting internal air and replacing it with outside air can increase the need for heating and cooling. This can be reduced by re-circulating a proportion of internal air, or by heat recovery ventilation (HRV) that recovers heat from extract air and uses it to pre-heat incoming fresh air.
It is important that all aspects of HVAC systems are considered together during the design process, even where involve independent systems. This is because of the interaction between heating, cooling, humidity control and ventilation. This is particularly complicated when other elements of environmental behaviour are considered such as solar gain, natural ventilation, thermal mass, and so on.
The design of HVAC systems is generally a specialist task, undertaken by a building services engineer, and because of its interaction with other elements of the building it is important that it is considered from the outset, as a fundamental part of the design process, and not an 'add on' at the end.
HVAC may be controlled by a building management system to maximise occupant comfort and minimise energy consumption.
Regular inspection and maintenance is necessary to ensure that systems are operating optimally.
[edit] Related articles on Designing Buildings
- Air conditioning.
- Air handling unit.
- Building management systems.
- Building services
- Building services engineer.
- CFD.
- Dehumidification.
- Displacement ventilation.
- Drivers of change in global heating markets.
- Ductwork.
- Fan coil unit.
- Heating.
- Humidification.
- HVACR.
- Mechanical, electrical and plumbing MEP.
- Mechanical ventilation.
- Natural ventilation.
- Plant room.
- Refrigeration.
- Thermal comfort.
- Ventilation.
[edit] External references
Featured articles and news
Shading for housing, a design guide
A look back at embedding a new culture of shading.
The Architectural Technology Awards
The AT Awards 2025 are open for entries!
ECA Blueprint for Electrification
The 'mosaic of interconnected challenges' and how to deliver the UK’s Transition to Clean Power.
Grenfell Tower Principal Contractor Award notice
Tower repair and maintenance contractor announced as demolition contractor.
Passivhaus social homes benefit from heat pump service
Sixteen new homes designed and built to achieve Passivhaus constructed in Dumfries & Galloway.
CABE Publishes Results of 2025 Building Control Survey
Concern over lack of understanding of how roles have changed since the introduction of the BSA 2022.
British Architectural Sculpture 1851-1951
A rich heritage of decorative and figurative sculpture. Book review.
A programme to tackle the lack of diversity.
Independent Building Control review panel
Five members of the newly established, Grenfell Tower Inquiry recommended, panel appointed.
Welsh Recharging Electrical Skills Charter progresses
ECA progressing on the ‘asks’ of the Recharging Electrical Skills Charter at the Senedd in Wales.
A brief history from 1890s to 2020s.
CIOB and CORBON combine forces
To elevate professional standards in Nigeria’s construction industry.
Amendment to the GB Energy Bill welcomed by ECA
Move prevents nationally-owned energy company from investing in solar panels produced by modern slavery.
Gregor Harvie argues that AI is state-sanctioned theft of IP.
Experimental AI housing target help for councils
Experimental AI could help councils meet housing targets by digitising records.
BSRIA Occupant Wellbeing survey BOW
Occupant satisfaction and wellbeing tool inc. physical environment, indoor facilities, functionality and accessibility.
Comments
[edit] To make a comment about this article, or to suggest changes, click 'Add a comment' above. Separate your comments from any existing comments by inserting a horizontal line.
Ventilation systems help maintain a healthy environment by regulating moisture and humidity, controlling temperatures, removing contaminated or stale air, ridding the air of dust or allergens, providing the proper exchange of oxygen and carbon dioxide levels and exchanging fresh air throughout a confined space or spaces. Ventilation systems are used in various settings including homes and workplaces.