Acceptance criterion
A result, tolerance or observable condition declared before a test and used to decide whether a requirement was met.
Shared technical language
Say exactly what the measurement means.
These definitions support the ICY science library and field record. They are explanatory, not substitutes for adopted definitions in a code, standard, contract or manufacturer document.
Accuracy
Closeness of agreement between a measured value and the value of the quantity being measured; it is not a synonym for resolution.
Airflow
Movement rate of air through a defined area or path, reported in a suitable volume or mass flow unit such as L/s or kg/s.
Baseline
The documented pre-change condition used for comparison, including relevant weather, occupancy, schedule and operating assumptions.
Calibration
An operation that establishes the relationship between an instrument's indication and reference quantity values under stated conditions.
Coefficient of performance
A dimensionless ratio of useful heating or cooling effect to required energy input for stated conditions.
Commissioning
A quality-assurance process used to verify that building systems are installed and operate according to defined project or owner requirements.
Condensate
Liquid formed when water vapor condenses; in cooling systems it commonly forms on a coil operating below the entering air's dew point.
Condensation
Phase change from vapor to liquid, possible when moisture-bearing air reaches a surface at or below the relevant dew-point temperature.
Condenser
The heat exchanger at which refrigerant rejects heat to an external sink and condenses during a conventional cooling cycle.
Cooling boundary
The explicitly defined space or system boundary across which heat transfer is being evaluated.
Cooling capacity
Rate at which a system removes heat under stated conditions, normally expressed in W or kW; Btu/h may appear on U.S. equipment.
Cooling load
Rate of heat removal needed to maintain a defined indoor condition under stated weather, occupancy and use.
Dew point
Temperature at which the existing water-vapor content would reach saturation during cooling at approximately constant pressure.
Dry-bulb temperature
Ordinary air temperature measured by a sensor shielded from moisture and inappropriate radiant influence.
Emissivity
A surface property describing thermal-radiation emission relative to an ideal blackbody; it materially affects infrared temperature measurement.
Energy efficiency ratio
A cooling-output-to-electric-input rating for defined test conditions, commonly expressed in Btu/(W·h) in U.S. equipment literature.
Enthalpy
A thermodynamic property useful for representing the sensible and latent energy of moist air relative to a defined reference.
Evaporator
The heat exchanger at which refrigerant absorbs heat and evaporates during a conventional cooling cycle.
Exfiltration
Uncontrolled outward air movement through openings or leakage paths in a building enclosure.
Exhaust air
Air intentionally removed from a building or zone and discharged outside the defined boundary.
Functional performance test
A planned test that observes whether a system produces the required physical response across defined operating modes.
Heat balance
Accounting of heat-transfer rates entering, leaving and accumulating within a defined boundary.
Heat gain
Heat-transfer rate added to a building or zone through envelope, solar, outdoor-air or internal sources.
Heat rejection
Transfer of absorbed heat, plus relevant equipment input, from a cooling system to an external sink.
Humidity ratio
Mass of water vapor associated with a unit mass of dry air, commonly expressed as kg/kg of dry air.
Infiltration
Uncontrolled inward air movement through openings or leakage paths in a building enclosure.
Installed performance
Operation of equipment as part of the actual building, including distribution, controls, loads and boundary conditions.
Integrated energy efficiency ratio
A commercial cooling-efficiency metric combining performance at specified load points using defined weighting.
Issue log
A controlled record of a deficiency, its evidence, responsible party, disposition, retest and final status.
Latent heat
Energy associated with a phase change; in air-conditioning work it commonly refers to moisture removal or addition rather than dry-bulb change alone.
Measurand
The quantity intended to be measured, defined with the conditions needed to make the result unambiguous.
Measurement and verification
A planned process for determining and documenting performance or savings using a stated baseline, boundary and method.
Measurement uncertainty
A parameter describing the dispersion of quantity values that could reasonably be attributed to a measurand.
Operational verification
Confirmation through observation and measurement that installed equipment is present, commissioned and capable of intended operation.
Outdoor air
Air intentionally brought from outdoors into a building or system, distinct from uncontrolled infiltration.
Part-load performance
Capacity and efficiency behavior when equipment operates below full rated load or in cycling or staged modes.
Pressure difference
Pressure at one point relative to a defined reference, commonly reported in pascals for building diagnostics.
Rated condition
The prescribed input and operating conditions under which a published equipment rating was determined.
Relative humidity
A measure of water-vapor content relative to saturation at the same temperature and pressure, expressed as a percentage.
Repeatability
Closeness of agreement among results obtained under the same specified measurement conditions over a short interval.
Replacement air
Air entering a zone or building to replace air that has been exhausted or otherwise removed.
Reproducibility
Closeness of agreement among results obtained under changed conditions such as operator, instrument or location.
Resolution
Smallest change in a quantity that produces a perceptible change in an instrument indication.
Return air
Air removed from a conditioned space and conveyed back toward air-handling equipment.
Return path
The intended and unintended route by which air leaves a supplied zone and returns to the air-handling system or another reference space.
Sensible heat
Energy transfer associated with dry-bulb temperature change without accounting for phase-change energy.
Sensible heat ratio
Ratio of sensible cooling to total cooling for a stated air-conditioning process and condition.
Sequence of operation
Documented logic defining how controls and equipment respond to conditions, schedules, commands, limits and alarms.
Single-duct portable air conditioner
A portable unit that rejects condenser air through one duct and commonly draws that air from the conditioned space, creating a replacement-air requirement.
Supply air
Air delivered by a mechanical system to a building zone.
Systematic effect
A repeatable influence that can shift measurement results in a consistent direction and may not be revealed by repetition alone.
Thermal storage
Energy accumulated in or released from building air, contents or assemblies as their temperatures change.
Total cooling
Combined sensible and latent heat-removal rate for a stated air process and operating condition.
Vapor pressure
Partial pressure exerted by water vapor within a gas mixture.
Ventilation
Intentional supply or removal of air to or from a space for indoor-environmental or process purposes.