What is HVAC?
Heating, ventilation and air conditioning: the systems that keep people comfortable, buildings healthy and equipment cool.
Controlling temperature, air and humidity.
HVAC stands for heating, ventilation and air conditioning. It is the set of systems that heat and cool buildings, bring in fresh air, remove stale air and control humidity. In offices and homes it keeps people comfortable. In hospitals, laboratories, factories and data centres it protects health, products and equipment.
HVAC is easy to overlook until it fails. In hot climates such as the Gulf, or in a data centre full of heat-producing equipment, losing cooling can stop operations within minutes.
What is in an HVAC system.
Chillers
Cool water that is piped through the building or data hall to remove heat. Often the largest cooling plant.
Cooling towers and condensers
Reject heat to the outside air, sometimes using water that evaporates.
Air handling units (AHU)
Move, filter, heat or cool and humidify or dehumidify air before supplying it to rooms.
CRAC and CRAH units
Computer room air conditioners and air handlers used in data halls to supply cold air to equipment racks.
Pumps, pipework and valves
Circulate chilled and condenser water. Failures here can disable a whole cooling loop.
Ductwork, fans and dampers
Distribute air and control flow. Fire and smoke dampers also help limit fire spread.
Controls and building management system (BMS)
Sensors and software that monitor temperatures, pressures and alarms, and adjust the plant.
Power supply to HVAC
Cooling needs electricity, often large amounts. Backup power must be sized to run HVAC as well as IT.
When heating or cooling fails.
Data centres and server rooms
Equipment gives off heat and can shut down or be damaged if rooms get too hot. Guidance such as the ASHRAE thermal guidelines sets recommended temperature and humidity ranges for IT equipment.
Hospitals and laboratories
Controlled air flow, pressure and temperature protect patients, samples and medicines. A failure may stop procedures or spoil stock.
Hot climates
In the Gulf, summer temperatures make cooling a life safety and operational need for buildings, vehicles and outdoor work. See also Emergency Planning.
Health and air quality
Ventilation helps control infection risk, odours and pollutants, and poorly maintained water systems can create risks such as Legionella.
Fire and smoke
Ventilation and dampers must work with fire alarms and smoke control, and HVAC may need to shut down or switch mode in a fire.
Product and process quality
Manufacturing, food storage, pharmaceuticals and cold chains rely on stable temperature and humidity.
How to make HVAC more resilient.
Redundancy
Extra chillers, pumps and units (N+1 or 2N), and separate cooling loops, so one failure does not stop cooling. See What is Redundancy?.
Backup power
Generators and UPS sized for cooling as well as IT, and fuel and refuelling plans.
Maintenance
Planned servicing, filter and water treatment, and spare parts for critical items.
Monitoring and alarms
Temperature, humidity, leak and equipment alarms with clear escalation, including out of hours.
Plan for failure
Agree what to shut down first, how to bring in portable cooling and who decides.
Test
Test failover between units and run through loss-of-cooling scenarios.
Design for the extremes
Size plant for hotter summers and peak load, and protect it from flooding and dust.
Single points of failure
Check shared pipes, controls and power feeds. See What is a Single Point of Failure?.
When cooling fails.
July 2022, London heatwave
Record temperatures were reported to have overwhelmed cooling at some data centres, causing outages for some cloud services.
October 2023, Singapore
A cooling problem at a data centre was reported to have disrupted services at two large banks.
April 2023, Paris
A water leak and fire in a data centre building was reported to have affected a cloud region for some customers.
Gulf summers
High temperatures stress cooling plant, increase power demand and make cooling failures in offices, schools and warehouses more serious.
Examples are drawn from public reports and are simplified. Check the original reports for details.
HVAC questions.
Is HVAC part of business continuity?
How hot can a server room get?
What should we do if cooling fails?
Talk to ADVOX about infrastructure resilience.
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Related reading: What is Redundancy? | What is a Single Point of Failure? | What is Concentration Risk? | What are Data Centres? | What is HVAC?