HVAC Technology and Energy Solutions Glossary

Browse this glossary of energy services, smart building technology, and HVAC terms to learn the definitions, phrases, and acronyms you need to know to make informed decisions for your building's infrastructure.

    AI Cooling System

    An AI cooling system refers to the tools, techniques, and processes used to cool high-density servers. The system’s top priority is maintaining server (chip) temperatures.

    Air Conditioner

    An air conditioner is a mechanical system that removes heat and humidity from an indoor space by transferring that heat to another place (typically outdoors) using the refrigeration cycle.

    Air-Cooled Chiller

    An air-cooled chiller is a refrigeration system that provides cooling for commercial and industrial applications.

    Air Handler

    An air handler, also known as an air handling unit (AHU), is a large metal box that contains the necessary components to move and condition air within an HVAC system.

    ASHRAE

    ASHRAE (pronounced "ASH-ray") is an acronym for the American Society of Heating, Refrigerating and Air-Conditioning Engineers. It is a global professional organization.

    Asset Management Software

    Asset management software is a centralized digital platform designed to track, monitor, and optimize the lifecycle of a building’s physical equipment and infrastructure.

    Boiler

    A commercial boiler is a heating appliance that uses a combustion fuel or electricity to heat water and is typically part of a hydronic heating system.

    Btu

    Btu stands for British thermal unit, a standard unit of measurement for energy. It represents the amount of heat required to change the temperature of one pound of water by one degree Fahrenheit.

    Btu/hr

    Btu/hr means British thermal units per hour. This metric is commonly presented as BTUH, Btuh, or Btu/hr. It is a measurement that quantifies the rate of energy transfer.

    Building Analytics

    Building analytics refers to the continuous process of collecting, aggregating, and analyzing data generated by a building’s operational systems to produce actionable insights.

    Building Automation

    Building automation is the use of integrated controls, sensors, software, and communications to automatically monitor, control, and optimize building systems.

    Building Automation System

    A building automation system is an integrated system that monitors, controls, and automates a variety of building equipment and functions to improve operation, comfort and efficiency.

    Building Automation Systems Integration

    Building Automation System (BAS) integration is the process of connecting multiple-vendor products from one or more building subsystems into a single, unified network.

    Building Management System

    A building management system (BMS) is a tool to help monitor, control, and analyze various components of a building.

    Carbon Footprint

    A carbon footprint is defined as the total amount of greenhouse gases an organization, product, building, or activity emits over a defined boundary and time period.

    Chiller

    In HVAC, a chiller is a critical component of commercial systems designed to cool large buildings by lowering the temperature of a liquid, typically water.

    Chiller-Heater

    A chiller-heater, more commonly known as a heat pump chiller, is a hydronic heat pump that can either heat or cool a hydronic fluid using the refrigeration cycle.

    Chiller Plant

    A chiller plant is a centralized cooling system that provides chilled water for air conditioning and/or process cooling in large commercial and industrial buildings.

    Commercial HVAC

    Commercial HVAC (Heating, Ventilation, and Air Conditioning) refers to the systems and technologies used to control the temperature, humidity, and air quality in commercial buildings.

    Compressor

    The purpose of the compressor in a refrigeration system is to raise the pressure of the refrigerant vapor from evaporator pressure to condensing pressure.

    Computerized Maintenance Management System

    Computerized maintenance management system (CMMS) software is a digital platform designed specifically to centralize, schedule, and track all maintenance activities within a facility.

  • Computer Room Air Handler (CRAH)

    A Computer Room Air Handler (CRAH) is a cooling unit used to regulate the temperature and ensure optimal operating conditions for IT equipment.

    Connected Building

    A connected building is a commercial or residential structure that uses internet-connected devices, sensors, and software to link, monitor, and manage its core operational systems.

  • Coolant Distribution Unit (CDU)

    A coolant distribution unit (CDU) is a key component in data center liquid cooling systems, responsible for managing and circulating the coolant to maintain optimal server temperatures.

    Cooling Capacity

    Cooling capacity is the measure of how much heat an HVAC system can remove from an indoor space over a given period, typically expressed in kW, BTU per hour (BTU/h), or tons of refrigeration.

    Cybersecurity

    Cybersecurity is the practice of protecting digital systems, networks, devices, and data from unauthorized access, disruption, damage, or theft.

  • Data Center Infrastructure Efficiency

    Data Center Infrastructure Efficiency (DCiE) is a metric that measures the energy efficiency of a data center by looking at the ratio of the IT equipment's power to the total facility power.

    Decarbonization

    Decarbonization is the process of significantly reducing or eliminating carbon dioxide (CO2) and other greenhouse gas (GHG) emissions from the atmosphere.

    Dedicated Outdoor Air System (DOAS)

    A dedicated outdoor air system is an HVAC system that processes 100% of the outdoor air brought into a building for ventilation separately from the building's primary heating and cooling system.

    Dehumidifier

    A dehumidifier is a device that removes moisture (water vapor) from air to control indoor humidity.

  • Direct-to-Chip Cooling

    Direct-to-chip (D2C) cooling is an advanced thermal management technology that cools microprocessors by running liquid coolant directly on the surface of the chip.

    Dual-Fuel Heat Pump

    A dual-fuel heat pump is a packaged rooftop HVAC unit that combines an electric heat pump with a secondary fossil-fuel heating source and automatic controls that switch between the two heat sources.

    Ductwork

    Ductwork is the system that distributes heated, cooled, and ventilated air from a commercial HVAC system throughout a building.

    Electric Heat Pump

    An electric heat pump is an HVAC solution that provides both heating and cooling using electricity.

    Electrification​

    In the HVAC industry, electrification refers to the transition from fossil fuel-based heating systems to all-electric solutions, most commonly, electric heat pumps.

    Energy Storage

    Energy storage is defined as the process of capturing energy produced at one time for later use. It's commonly used with batteries of all sizes, but there are other kinds of energy storage.

    Facilities Management Software

    Facilities management software (FMS) is a category of digital tools designed to help facility managers oversee the day-to-day operations of commercial buildings.

  • Fan Coil Wall

    A fan coil wall is a cooling solution that utilizes a fan array to pull in warm air and push it through a cooling coil.

  • Free Cooling

    Free Cooling (also known as economizing) is an energy-efficient HVAC method that uses naturally cool outdoor air instead of mechanical refrigeration to provide cooling for a building or process.

    Furnace

    A furnace is one possible component of an HVAC system that adds heated air to ductwork to the space being heated.

    Geothermal

    The term geothermal means "of or relating to the internal heat of the earth." Geothermal energy is a renewable and sustainable source of thermal energy that originates from the Earth's core.

    Global Warming Potential (GWP)

    Global Warming Potential (GWP) is a metric used to quantify how much heat a greenhouse gas (GHG) traps in the atmosphere over a set period, which depends on the type of gas.

    Green Energy

    Green energy is energy derived from natural resources that replenish themselves over a short period and do not harm the environment.

    Greenhouse Gas (GHG)

    Greenhouse gases (GHGs) are gases that trap heat in the Earth’s atmosphere — a process known as the greenhouse effect.

    Heat Pump

    A commercial heat pump is a mechanical system that transfers heat from one place to another using a refrigeration cycle.

    Heat Pump Chiller​

    A heat pump chiller is a specialized HVAC system that provides heating and cooling by sourcing heat from water, air, or other fluids and transferring it to a fluid.

    HVAC

    HVAC stands for Heating, Ventilation, and Air Conditioning. It includes essential systems that regulate temperature, humidity, and indoor air quality (IAQ) across commercial and industrial spaces.

    HVAC Controls

    HVAC controls are the hardware and software systems that monitor, regulate, and automate HVAC equipment to maintain occupant comfort, air quality and energy efficiency.

    Immersion Cooling

    Immersion cooling is an advanced liquid cooling technique used in data centers. It involves submerging IT hardware directly into a thermally conductive, electrically non-conductive liquid.

    Indoor Air Quality

    Indoor air quality (IAQ) refers to the condition of the air inside your facility and the presence of pollutants, particulates, and irritants that affect building occupants.

    Indoor Environmental Quality

    Indoor Environmental Quality (IEQ) refers to the conditions inside a building that significantly impact an occupant's experience of that space, including air quality, temperature, acoustics, and lighting.

    Infrastructure Resilience

    Infrastructure resilience refers to the ability of essential systems to withstand, adapt to, and recover from disruptions while continuing to provide critical services.

    In-Row Cooling

    In-row cooling is a precision thermal management architecture used in data centers where the cooling equipment is installed directly within or alongside the rows of server racks.

    Integrated Workplace Management System (IWMS)

    An IWMS is a unified software platform that streamlines and centralizes all aspects of facilities management, consolidating data from various business and building systems into a single interface.

  • Liquid Cooling

    Liquid cooling is a method of heat removal that involves the circulation of a liquid, typically a 25% propylene glycol mixture, to transfer heat away from graphics processing units (GPUs).

    Mini-Split HVAC

    A mini-split HVAC system is a versatile heating and cooling solution ideal for commercial and mixed-use facilities that require comfort without the limitations of traditional ductwork.

    Occupancy Sensor

    Discover what occupancy sensors are and how integrating them into your facility's systems can benefit your business.

    Packaged Unit

    A packaged unit is an all-in-one heating and cooling solution where all the primary system components are housed within a single, weather-resistant outdoor cabinet.

  • Power Usage Effectiveness

    PUE is defined as a metric that measures a data center's energy efficiency. It is a ratio of the total energy used by the facility to the energy used by the IT (information technology) equipment.

    Process Chiller

    A process chiller, also known as an industrial process chiller, is a cooling system that removes heat from a manufacturing process or a piece of equipment.

    Process Cooling

    Process cooling is the removal of heat from industrial processes to ensure operational safety, equipment efficiency, and product quality.

    Programmable Thermostat

    A programmable thermostat is a temperature-control device that allows users to pre-set specific heating and cooling schedules based on the time of day and day of the week.

    Refrigerant

    Refrigerant is a chemical compound used in commercial HVAC systems to facilitate the transfer of heat, enabling efficient cooling and heating processes.

    Refrigeration Cycle

    The refrigeration vapor compression cycle is the path that refrigerant takes through your commercial HVAC system’s components to facilitate heat transfer and cooling.

    Rooftop Heat Pump

    A rooftop heat pump is a packaged rooftop unit that provides heating and cooling for commercial buildings in a weather-resistant cabinet installed on the building’s roof.

    Rooftop Unit

    A rooftop unit (RTU) is a self-contained heating, ventilation, and air conditioning (HVAC) system that’s typically installed on the roof of a building but can also be installed on the ground.

    Smart Building

    A smart building, also called an intelligent building, leverages building automation for energy efficiency, comfort, and resilience, using data and automation to improve occupant comfort and energy usage.

    Smart Thermostat

    A smart thermostat is an internet-connected device that allows you to control your HVAC system remotely via an app on a smartphone, tablet or computer.

    SOC 2

    SOC 2 (System and Organization Controls 2) is a compliance standard that specifies how organizations should manage customer data and related systems.

    Split System

    A split system is an HVAC system that separates its primary components into an indoor unit (an air handler, furnace or indoor coil) and an outdoor unit (a heat pump or air-cooled condensing unit).

    Sustainable Building

    A sustainable building is a structure designed and constructed to minimize its negative environmental impact, conserve resources, and promote the health and well-being of its occupants.

    Thermal Energy

    Thermal energy is the total energy a system contains, as measured by its temperature: kinetic energy (motion) and potential energy (position) of the atoms and molecules (particles) in random motion.

    Thermal Management

    Thermal management is the strategies and technologies used to control temperature and heat flow within a system or space. In HVAC, this involves using cooling and heating systems to provide warmth.

    Variable Air Volume

    Variable air volume (VAV) is a type of heating, ventilating, and/or air-conditioning (HVAC) system that regulates airflow to different zones in a building to meet specific heating or cooling demands.

    Variable Frequency Drive​

    A variable frequency drive (VFD) is an electronic device used to control the speed of electric motors by adjusting the frequency and voltage supplied to them.

    Variable Refrigerant Flow

    VRF is an HVAC technology that uses refrigerant as the primary cooling and heating medium, allowing a single outdoor compressor to serve multiple indoor units with individualized temperature control.

    Water-Source Heat Pump

    A water-source heat pump (WSHP) in HVAC uses the same technology as water-to-water heat pumps, but is smaller and meant for distributed systems.

    Water-to-Water Heat Pump

    A water-to-water heat pump, also known as a heat recovery unit, is a commercial HVAC unit that transfers heat between two fluid sources (commonly water) and may include a reversing valve.

  • WUE (Water Usage Effectiveness)

    Water Usage Effectiveness (WUE) is a data‑center metric developed by the Green Grid that quantifies how much water a facility consumes to support IT operations.