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Last edited 30 Sep 2020
Cooling systems for buildings
It can be necessary to provide cooling to buildings during warm weather, or where there are significant thermal gains (such as solar gain, people and equipment). This cooling is sometimes referred to as comfort cooling. Cooling may also be necessary for refrigeration or for some industrial processes.
Passive or 'natural' cooling can be provided by:
Active cooling can be provided by:
 Earth-to-air heat exchanger (ground coupling)
This draws ventilation supply air through buried ducts or tubes (sometimes referred to as earth tubes). As the temperature of the ground below 3 m is practically constant, it can be use to substantially reduce ambient air temperature fluctuations, with the incoming air being heated in the winter and cooled in the summer.
 Open or closed loop water-to-air heat exchanger
 Mechanical, or forced ventilation, driven by fans
Chilled water is typically provided by chiller units using absorption refrigeration or compression refrigeration. It can then be used to provide cool air, in air handling units (to be ducted around the building), chilled beams, chilled ceilings, and so on. Chiller units use a refrigerant that boils at a low temperature and pressure, removing heat from the chilled water, and then condenses to release that heat, which is rejected to the outside (or recovered).
Refrigerants can be used to provide cooling directly to spaces in variable refrigerant flow (VRF) systems. This is based on the flow of refrigerant between an external condensing unit and multiple internal evaporators (typically fan coil units).
This can be provided by simple systems, such as misting fans and by spraying water over the roof of a building, or by more complex packaged units that draw hot, dry air through a continually dampened pad and supply cool, humid air to the building.
Indirect evaporative cooling can be provided by the incorporation of heat exchangers, by the use of cooling towers, or by spraying water over the cooling coils of conventional chiller units. Typically, evaporative cooling is best suited to hot, dry climates.
Active cooling might be provided as part of a heating, ventilation and air conditioning system (HVAC) which may also include air filtration and humidity control. The cooling process itself can result in dehumidification, as cool air is less able to ‘hold’ moisture than warm air. The term air conditioning is sometimes taken to mean control over air temperature and humidity, rather than just temperature control in the case of comfort cooling.
NB: Direct evaporative cooling results in humidification of air.
'Cooling plant means that part of a cooling system that produces the supply of cooling
medium. It does not include means of distributing the cooling medium or the delivery of the cooling into the relevant zone. It may consist, for example, of a single chiller or a series of chillers.'
'Cooling system means the complete system that is installed to provide the comfort cooling to the space. It includes the cooling plant and the system by which the cooling medium effects cooling in the relevant zone and the associated controls. This will in some cases be a complete packaged air conditioner.'
Ref Non-domestic Building Services Compliance Guide For Scotland, 2015 Edition v1.1, published by the Scottish Government, Building Standards Division in April 2018.
 Related articles on Designing Buildings Wiki
- Absorption refrigeration.
- Air conditioning.
- Air handling unit.
- BREEAM Impact of refrigerants.
- Chiller unit.
- Chilled water.
- Complex system.
- Cooling degree days.
- Cooling tower.
- Cooling tower design and construction.
- Corrosion in heating and cooling systems.
- COVID-19 and the US HVAC sector.
- Data centre cooling.
- Evaporative cooling.
- Heat load
- Night-time purging.
- Passive building design.
- Passive ventilation.
- Thermal labyrinth.
- Thermal storage for cooling.
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