ESP-r Glossary of Terms
Please note that there is also a
General Glossary of Terms related to
modelling and simulation for environmental engineering
- Air balance refers to the energy balance on an air node. The only method
of heat transfer to an air node is via convection (e.g. from surfaces,
ventilation casual gains or from heating).
- Air flow is the movement of air within or between zones and can be
- ACH (air changes per hour) with respect to the volume of a zone;
- A mass flow network entailing a more detailed analysis with defined
components of flow rate and direction within and between zones; and
- A CFD (computational fluid dynamics) network of even higher resolution
within zones where they are split into many nodes, pressures and momentums.
- Air Changes per Hour - unit used for quantifying default
infiltration and ventilation rates, as well as
a reporting unit of the mass flow analysis.
- boundary condition
- These are the temperature, flux and other environmental
conditions that pertain on either side
of a surface. According to the particular surface,
they may be obtained from the climate data file,
from the calculated values in an adjacent zone,
or from user-specified values.
- composite construction
- This refers to a type of database and its contents which
are made of one or more layers of primitive materials. A
composite construction may be opaque or transparent. In
the latter case additional information on its optical
properties is incorporated. Sample composite databases are
supplied in /usr/esru/esp-r/databases which the user
may wish to copy and extend. Depending on the type of
simulations carried out the user may wish to build a
different composite database for each project or develop
one which contains a variety of constructions and is
useful for a range of simulations.
- The topology of a problem is defined via the boundary
conditions defined for each surface. These may be
defined via two mechanisms: firstly, as a surface
attribute (which can be imported into the overall problem
description) or secondly, as a connection (located in the problem
description file, which may then the exported as a surface
attribute). The networks which define plant and mass flow
networks also contain connection lists.
- control law
- A number of items which are subject to control (depending
on time, temperature, radiation etc)
can exhibit specific characteristics via the use of
control laws. For example lighting casual gains may be
switched ON/OFF, step, proportional and proportional with
constant ballast loads.
- Controller type
In ESP-r, the controller type controls the
actuated property sensed by the sensor and actuated by the
- control function
- Generally, this term is used for the
operations carried out by an automatic control system.
However, in ESP-r, the BUILDING control strategy is comprised
of one or more control functions. They are then associated
with the building zones to define the time-dependent control
objectives. A PLANT system, on the other hand, is governed
by one or more control loops. In essence, control functions
and and control loops are the same, differing only in the
types of control laws used to link the sensorand actuator.
- control law
- In ESP-r, this defines a control algorithm
which represents the logic or "control action" of a
controller. For example, the control law implemented may be
- control loop
- Generally, this term means any control network
consisting of the control elements required for automatic
control. However, in ESP-r, this term is reserved
for those control loops which govern the PLANT network
control system - the BUILDING control strategy comprising of
one or more control functions. The control loop comprises
of three control elements:- a sensor, a controller, and an
actuator. For example, a plant network may consist of an
air-handling unit supplying hot air to one zone, and cold
air to a second zone. An ESP-r control loop for this system
could be:- a SENSOR located i n the centre of the zone to
measure the air temperature; a CONTROLLER (with PID control
action) to determine a correction signal such as to reduce
the magnitude of the error signal (measured value - desired
value); and an ACTUATOR to receive this signal, and operate
the final control element (in this case, a throttling valve
in the heating/cooling coil's hot/cold water supply line).
Thus, if the measured zone temperature is not equal to the
desired value, the air supplied to the zone will receive an
increase in energy from the coil in accordance with the PID
- default insolation
- User supplied static insolation distribution (as
opposed to dynamic shading and insolation patterns
found via the shading and insolation program).
- default window
- A default window is a simplified treatment of glazing
which is retained as a pragmatic expedient.
- diffusion resistance factor (DRF)
- Within the ESP-r materials database, the "diffusion res."
is the diffusion resistance factor (DRF), a dimensionless
Materials which have a very low or zero permeability (e.g. glass,
metal, etc.) are represented in the database with the value 19.
- DRF = permeability of air / permeability of material.
Permeability is also referred to as "vapour diffusivity".
The DRF values are converted internally into vapour resistances by:
- vapour resistance = (DFR * thickness)/19.2e-11
where air permeability is 19.2e-11.
- Infiltration is the movement of air from the outside.
- leakage distribution
- Term used in the past for network description
of mass flows.
- mass flow component
- Mass flow resistance (duct, opening, valve)
or inducer (fan, pump, constant volume)
defined and used within a mass flow network.
- mass flow connection
- Topology of the network in the form of:
- mass flow node
- A point within a mass flow network,
normally associated with a thermal zone or a
- mean radiant temperature
- Sensors may be set to MRT which is equivalent to the
reading from a black body globe thermometer.
- Obstruction introduces time-varying shading
and insolation which must be taken
into consideration when calculating the building thermal and lighting
performance. In shading calculations the effects of fins, trees,
other buildings and walls are approximated by one or
more obstruction blocks. There are several rules for
the composition and placement of obstruction blocks:
- a) they should not be in the same plane as the surface being
obstructed (a few mm of clearance is required)
- b) it is best not to cross the plane of a surface which
might be shaded; use 2 blocks in such cases.
- c) the blocks should be named so that they can be tracked more easily.
- Casual gains, ventilation and infiltration patterns
for a thermal zone are held in a zone operation file
in the form of diary entries with an associated control
syntax. A mass flow simulation will take precedence
over the infiltration and ventilation specifications. A
timestep casual gain file will take precedence over the
- plant component
- Device within a plant network such as a
boiler or pump.
- plant connection
- Topology of plant network.
- plant containment
- Boundary conditions of a plant component
which may or may not interact with a
- preconditioning period
- One or more days of simulation before the requested simulation
period. These are required to remove any effects that
may result from the assumed initial conditions of the simulation.
Calculated values during the preconditioning period (or start-up
period) are not saved.
- predicted percentage dissatisfied (PPD)
- Comfort rating derived from the work of Fanger.
- predicted mean vote (PMV)
- Comfort rating derived from the work of Fanger.
- primitive materials
- This is a type of database which holds the thermophysical
properties of basic materials such as aluminium, limestone,
and concrete which can be combined to form composite
One database (/usr/esru/esp-r/databases/constr.db1) is supplied
with the system, but the user may wish to copy this to
form custom versions.
- problem configuration
- This is the core description of a problem which contains
references to the various geometry, scheduling, mass flow
network, plant and thermophysical property files which constitute
the description of a problem. It is often referred to
as the system configuration file in the ESP-r user manual.
- This includes the latitude, longitude, average ground
reflectance as well as an index to the exposure of
a specific location. Site information resides in
the problem configuration file. Climatic patterns are taken from
one or several climate databases which are representative of
- A surface is a polygon with associated attributes such
as emissivity, area, orientation and a specific composite
construction. Surfaces have two sides, one facing the
zone (inside) and the other connected to a boundary
condition (another zone, ground, outside). It interacts both radiantly
and convectively with its environment. A surface may
be opaque or transparent. It may also
include "default" windows, which are simplified treatments
of glazing but which a user may find convenient to use.
The description of the layers of the composite construction
associated with a surface is from the outside to the inside.
If the surface is a partition composed of a
non-symmetrical composite construction, the user will need to
define two composites, with one defined in reverse order to the other.
- system control
- This file contains the definition of the controls which
act on the building and the plant.
- thermal zone
- This is a volume of air which is assumed to be well
mixed and bounded by closed polygons. This is the
primary reporting and descriptive unit of ESP-r and
may be used to represent a range of spaces which are
a direct mapping from reality, e.g. a room, a portion of a room or
a concatenation of several rooms. This concept is often
confusing to novice users, however, because the user defines
what a zone is. The part of a building (or other space) represented by
a zone may vary according to the aims of the particular
simulation study, and it requires experience to
determine how a particular problem might best be abstracted.
- TMC / transparent composite
- Glazing may be described as a composite construction with
full accounting of radiant exchange, thermal storage
and the like. Each composite construction which is
tagged as being transparent will have an associated
set of optical properties. It is possible to change
optical properties as a function of time and radiation
level. The ability to alter thermophysical properties
will be available in the near future.
- Ventilation refers to air movement between zones.