Airflow Networks Definitions

Term	Definition	Units
Airflow Network Model	A simulation method in EnergyPlus that calculates the airflow through building components and zones based on pressure differences.	-
Node	A point in the airflow network where air properties like temperature, pressure, and humidity are defined.	-
Linkage	A connection between two nodes that represents a pathway for airflow, such as through a door, window, or duct.	-
Zone	A space or collection of spaces within a building with uniform air properties used in airflow calculations.	-
Surface	The physical boundary in a building, such as walls, floors, ceilings, and roofs, that interact with airflow.	-
Pressure Coefficient (Cp)	A dimensionless number that characterizes the effect of wind pressure on building surfaces.	-
Crack	A small opening in the building envelope that allows uncontrolled air leakage, typically due to construction imperfections.	-
Opening	A controllable opening like windows, vents, or doors that can be adjusted to regulate airflow.	-
Infiltration	Uncontrolled air leakage into a building through cracks, gaps, or openings in the building envelope.	m³/s
Ventilation	Controlled air exchange between the building and the external environment, which can be natural or mechanical.	m³/s
Exfiltration	Uncontrolled air leakage out of a building through cracks, gaps, or openings in the building envelope.	m³/s
Mechanical Ventilation	The use of mechanical systems, such as fans and ducts, to supply, distribute, and exhaust air within a building.	m³/s
Natural Ventilation	The process of supplying and removing air through natural forces like wind pressure and thermal buoyancy, without mechanical assistance.	m³/s
Airflow Path	The route taken by air as it moves through the airflow network, including through openings, ducts, and around obstacles.	-
Local Wind Pressure	The wind pressure exerted on specific building surfaces, which varies with wind speed, direction, and building geometry.	Pa (Pascals)
Air Distribution System	The network of ducts, vents, and registers that distributes conditioned air (heated, cooled, or ventilated) throughout the building.	-
Stack Effect	The movement of air into and out of buildings due to temperature differences between the indoor and outdoor environment, creating pressure differences.	Pa (Pascals)
Wind-Driven Ventilation	Natural ventilation driven by wind forces, where the wind creates pressure differences across the building envelope, promoting airflow.	m³/s
Buoyancy-Driven Ventilation	Natural ventilation driven by buoyancy forces, where warmer air rises and cooler air enters the building to replace it, creating airflow.	m³/s
Duct Leakage	Air leakage from ducts in the air distribution system, which can lead to energy losses and reduced system efficiency.	m³/s
Effective Leakage Area (ELA)	A measure of the total area of all leaks in a building envelope, standardized to a reference pressure difference, indicating the tightness of the building.