ISO 16818:2008

INTERNATIONAL ISO
STANDARD 16818


First edition
2008-02-15
Building environment design — Energy
efficiency — Terminology
Conception de l'environnement des bâtiments — Rendement
d'énergie — Terminologie




Reference number
ISO 16818:2008(E)
©
 ISO 2008

---------------------- Page: 1 ----------------------
ISO 16818:2008(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.


©  ISO 2008
The reproduction of the terms and definitions contained in this International Standard is permitted in teaching manuals, instruction
booklets, technical publications and journals for strictly educational or implementation purposes. The conditions for such reproduction are:
that no modifications are made to the terms and definitions; that such reproduction is not permitted for dictionaries or similar publications
offered for sale; and that this International Standard is referenced as the source document.
With the sole exceptions noted above, no other part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland

ii © ISO 2008 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 16818:2008(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 1
3 Terms and definitions . 2
Bibliography . 32

© ISO 2008 – All rights reserved iii

---------------------- Page: 3 ----------------------
ISO 16818:2008(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 16818 was prepared by Technical Committee ISO/TC 205, Building environment design.

iv © ISO 2008 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 16818:2008(E)
Introduction
This International Standard is intended to provide general terms and definitions used in building environment
design. Other standards produced by ISO/TC 205 can contain additional definitions more specific to the needs
of the individual standard.

© ISO 2008 – All rights reserved v

---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 16818:2008(E)

Building environment design — Energy efficiency —
Terminology

1 Scope
This International Standard gives terms and definitions for use in the design of energy-efficient buildings. This
International Standard is applicable to new buildings and retrofitted existing buildings.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 6707-1, Building and civil engineering — Vocabulary — Part 1: General terms
ISO 7345, Thermal insulation — Physical quantities and definitions
ISO 7730, Ergonomics of the thermal environment — Analytical determination and interpretation of thermal
comfort using calculation of the PMV and PPD indices and local thermal comfort criteria
ISO 9229, Thermal insulation — Vocabulary
ISO 9251, Thermal insulation — Heat transfer conditions and properties of materials — Vocabulary
ISO 9288, Thermal insulation — Heat transfer by radiation — Physical quantities and definitions
ISO 9346, Hygrothermal performance of buildings and building materials — Physical quantities for mass
transfer — Vocabulary
ISO 13789, Thermal performance of buildings — Transmission and ventilation heat transfer coefficients —
Calculation method
1)
ISO 13790 , Energy performance of buildings — Calculation of energy use for space heating and cooling
ISO 15927-6, Hygrothermal performance of buildings — Calculation and presentation of climatic data —
Part 6: Accumulated temperature differences (degree-days)
ISO 16813, Building environment design — Indoor environment — General principles


1) To be published. (Revision of ISO 13790:2004.)
© ISO 2008 – All rights reserved 1

---------------------- Page: 6 ----------------------
ISO 16818:2008(E)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in the normative references and the
following apply.
3.1
access hatch
door
NOTE An access hatch is defined as a door, thereby allowing it to meet less stringent envelope requirements. If not
defined as a door, it is necessary that it be insulated as a roof or wall, depending on where it was located.
3.2
accessible
admitting close approach; not guarded by locked doors, elevations or other effective means
NOTE As applied to equipment; see also readily accessible (3.189).
3.3
adjusted lighting power
lighting power, ascribed to a luminaire(s) that has been reduced by deducting a lighting power control credit
based on use of an automatic control device(s)
3.4
adopting authority
agency or agent that adopts this International Standard
3.5
air-conditioned floor area
area equipped with air conditioning equipment measured at floor level from the interior surfaces of the walls
See gross conditioned floor area, (3.106).
3.6
air-conditioned space
space equipped with air conditioning equipment
See air-conditioned floor area (3.5).
3.7
air economizer
duct and damper arrangement and automatic control system that together allows a cooling system to supply
outside air to reduce or eliminate the need for mechanical cooling during mild or cold weather
3.8
air handling unit
encased assembly consisting of sections containing a fan or fans and other necessary equipment to perform
one or more of the following functions: circulating, filtration, heating, cooling, heat recovery, humidifying,
dehumidifying and mixing of air
3.9
alteration
rearrangement, replacement or addition to a building or its systems and equipment
NOTE Routine maintenance and service or a change in the building's category shall not constitute an alteration.
2 © ISO 2008 – All rights reserved

---------------------- Page: 7 ----------------------
ISO 16818:2008(E)
3.10
area factor
multiplying factor which adjusts the unit power density for spaces of various sizes to account for the impact of
room configuration on lighting power utilization
3.11
area of the space
A
horizontal lighted area of a given space measured from the inside of the perimeter walls or partitions, at the
height of the working surface
3.12
authority having jurisdiction
agency or agent responsible for enforcing this International Standard
3.13
automatic
self-acting, operating by its own mechanism when actuated by some impersonal intervention, such as a
change in current strength, pressure, temperature or mechanical configuration
3.14
automatic control devices
device capable of automatically turning loads off and on without manual intervention
3.15
average daily temperature
average of the temperatures readings over a 24 h period
3.16
ballast
device used in conjunction with an electric-discharge lamp to cause the lamp to start and operate under the
proper circuit conditions of voltage, current, wave form, electrode heat, etc.
3.16.1
ballast, electronic
ballast constructed using electronic circuitry
3.16.2
ballast, hybrid
ballast constructed using a combination of magnetic core, insulated wire winding and electronic circuitry
3.16.3
ballast, magnetic
ballast constructed with magnetic core and a winding of insulated wire
3.17
ballast efficacy factor
ratio of relative light output to the power input
3.18
ballast efficacy factor
〈fluorescent〉 ratio of the ballast factor expressed as a percent to the power input in watts, at specified test
conditions
3.19
ballast factor
BF
ratio of a commercial ballast lamp lumens to a reference ballast lamp lumens, used to correct the lamp lumen
output from rated to actual
© ISO 2008 – All rights reserved 3

---------------------- Page: 8 ----------------------
ISO 16818:2008(E)
3.19.1
ballast factor
ratio of the lumen output of a lamp/ballast combination to the lumen output of the same lamp in combination
with a piece of laboratory equipment called a reference reactor
NOTE Because a ballast may be designed to operate more than one lamp type, the same ballast model can have more
than one ballast factor value.
3.20
below-grade wall
see wall (3.244)
3.21
boiler
device to raise the temperature of a fluid or generate steam
3.22
boiler capacity
rated heat output of the boiler, at the design inlet and outlet conditions and rated fuel or energy input
3.23
budget building design
computer representation of a hypothetical design based on the actual proposed building design
NOTE This representation is used as the basis for calculating the energy cost budget.
3.24
building
construction as a whole, including its envelope and all technical building systems
3.25
building area
greatest horizontal area of a building above grade within the outside surface of exterior walls, or within the
outside surface of exterior wall and the centreline of fire walls
3.26
building entrance
any doorway set of doors, turnstiles or other form of portal that is ordinarily used to gain access to the building
by its users and occupants
3.27
building energy cost
computed annual energy cost of all purchased energy for the building
3.28
building envelope
elements of a building that enclose conditioned spaces through which thermal energy can be transferred to or
from the exterior, or to or from unconditioned spaces
3.28.1
building envelope, exterior sheltered
elements of a building that separate conditioned spaces from the exterior
3.28.2
building envelope, semi-exterior sheltered
elements of a building that separate conditioned space from unconditioned space (as far as it is not designed
for human occupancy) or that enclose semi-heated spaces through which thermal energy can be transferred
to or from the exterior, or to or from unconditioned spaces, or to or from conditioned spaces
4 © ISO 2008 – All rights reserved

---------------------- Page: 9 ----------------------
ISO 16818:2008(E)
NOTE 1 Building envelope defines the surfaces that require insulation or weather-stripping. The outer shell of the
building is not necessarily the same as the building envelope, particularly where the building contains semi-heated or
unconditioned spaces.
NOTE 2 In some cases, the designer can determine the location of the exterior building envelope by the location that
they place the insulation. For instance, it is not uncommon for a stairwell to be at the outside edge of the building. If that
stairwell does not have any heating or cooling supply, it can be insulated on the outside edge or the side adjacent to other
heated or cooled space. If insulated on the outside, the stairwell becomes indirectly conditioned and the outside wall is the
exterior building envelope. If insulated on the inside, the inside wall is likely to become the exterior building envelope
(unless the outside exposure is so small that it would still be indirectly conditioned space).
NOTE 3 Where a building with conditioned space also contains semi-heated spaces or unconditioned spaces, the
building envelope for the conditioned space is the roofs, walls, floors, doors, fenestration, etc. that separate the
conditioned space from the exterior. These elements shall comply with the residential or non-residential conditioned space
requirements.
NOTE 4 For semi-heated spaces, the building envelope includes any roofs, walls, floors, doors, fenestration, etc. that
separate the semi-heated space from conditioned or unconditioned spaces (as well as from the exterior). These elements
shall comply with the semi-heated space requirements, as shall elements separating conditioned space from
unconditioned space.
3.29
building exit
any doorway, set of doors, or other form of portal that is ordinarily used for emergency egress or convenience
exit
3.30
building grounds lighting
lighting provided through a building's electrical service for parking lot, site, roadway, pedestrian pathway,
loading dock, exterior architectural lighting and security applications
3.31
building official
official authorized to act on behalf of the authority having jurisdiction
3.32
building type
classification of a building by usage
3.33
check metering
measurement instrumentation for the supplementary monitoring of energy consumption (electric, gas, oil, etc.)
to isolate the various categories of energy use to permit conservation and control, in addition to the revenue
metering furnished by the utility
3.34
clerestory
part of a building that rises clear of the roofs or other parts and whose walls contain windows for lighting the
interior
3.35
coefficient of performance
COP
〈cooling mode〉 ratio of the rate of heat removal to the rate of energy input in consistent units, for a complete
cooling system or factory assembled equipment, as tested under a nationally recognized standard or
designated operating conditions
© ISO 2008 – All rights reserved 5

---------------------- Page: 10 ----------------------
ISO 16818:2008(E)
3.36
coefficient of performance
COP
〈heat pump — heating mode〉 ratio of the rate of heat delivered to the rate of energy input, in consistent units,
for a complete heat pump system under designated operating conditions
NOTE Supplemental heat shall not be considered when checking compliance with the heat pump equipment COPs.
3.37
coefficient of utilization
CU
ratio of lumens from a luminaire calculated as received on the work plane to the lumens emitted by the
luminaire's lamps alone factored by room surface reflectances and room dimensions
See room cavity ratio (3.202).
3.38
conditioned space
treated space
enclosure served by an air distribution system
3.39
connected lighting power
power required to energize luminaries and lamps connected to the building electrical service
NOTE The connected lighting power is expressed in units of watts.
3.40
continuous insulation
insulation that is continuous across all structural members without any thermal bridges, excluding fasteners
and service openings
NOTE It is installed on the interior of, exterior of or integral with any opaque surface of the building envelope.
3.41
control
regulation of the operation of equipment
3.42
control device
specialized device used to regulate the operation of equipment
3.43
control loop, local
control system consisting of a sensor, controller and controlled device
3.44
control point
quantity of equivalent ON or OFF switches ascribed to a device used for controlling the light output of a
luminaire(s) or lamp(s)
3.45
cool down
reduction of space temperature down to occupied set point after a period of shutdown or setup
3.46
cooled space
See space (3.217).
6 © ISO 2008 – All rights reserved

---------------------- Page: 11 ----------------------
ISO 16818:2008(E)
3.47
cooling
removal of latent and/or sensible heat
3.48
cooling degree-day
See degree-day (3.58).
3.49
cooling design temperature
outdoor dry-bulb temperature for sizing cooling systems, equal to the temperature that is exceeded 2,5 % of
the number of hours during the nominal cooling season (June through September in northern hemisphere) in
a typical weather year
3.50
cooling design wet-bulb temperature
outdoor wet-bulb temperature for sizing cooling systems and evaporative heat rejection systems, such as
cooling towers
3.51
daylit area
area under horizontal fenestration (skylight) or adjacent to vertical fenestration (window) as described in
3.51.1 and 3.51.2
3.51.1
daylit area, horizontal
area under horizontal fenestration (skylight) with a horizontal dimension in each direction equal to the skylight
dimension in that direction plus either the floor-to-ceiling height, the distance to the nearest 1 m or higher
opaque partition, or one-half the distance to an adjacent skylight or vertical glazing clerestory, whichever is
least
See Figure 1.
3.51.2
daylit area, vertical
area adjacent to vertical fenestration (window) with one horizontal dimension that extends into the space
either a distance of 4,5 m, or to the nearest 1 m or higher opaque partition, whichever is less; and another
horizontal dimension equal to the width of the window plus either 0,6 m on each side, the distance to an
opaque partition, or one-half the distance to an adjacent skylight or window, whichever is least
See Figure 2.
© ISO 2008 – All rights reserved 7

---------------------- Page: 12 ----------------------
ISO 16818:2008(E)

Key
1 skylight width
2 full height partition
3 outline of skylight above
4 daylit area
5 non-daylit area
H floor-to-ceiling height
a
45°.
b
Daylit area beneath conventional skylight.
c
Daylit area includes the floor of the atrium and the top floor next to the atrium.
Figure 1 — Horizontal daylit area
8 © ISO 2008 – All rights reserved

---------------------- Page: 13 ----------------------
ISO 16818:2008(E)

Key
1 daylit area
a
Daylit area cut short by full-height partition.
b
Daylit area extends 610 mm (2 ft) or to nearest wall.
Figure 2 — Vertical daylit area
3.52
daylit space
space bounded by vertical planes rising from the boundaries of the daylit area on the floor to the above floor
or roof
3.53
daylit zone
types of daylit zones as defined in 3.53.1 and 3.53.2
3.53.1
daylit zone, under skylights
area under each skylight whose horizontal dimension in each direction is equal to the skylight dimension in
that direction plus either the floor-to-ceiling height or the dimension to an opaque partition, or one-half the
distance to an adjacent skylight or vertical glazing, whichever is least
3.53.2
daylit zone, at vertical glazing
area adjacent to vertical glazing that receives daylighting from the glazing
NOTE For purposes of this definition and unless more detailed daylighting analysis is provided, the daylit zone depth is
assumed to extend into the space a distance of 4,5 m or to the nearest opaque partition, whichever is less. The daylighting
zone width is assumed to be the width of the window plus either 0,6 m on each side, the distance to an opaque partition,
or one half the distance to an adjacent skylight or vertical glazing, whichever is least.
© ISO 2008 – All rights reserved 9

---------------------- Page: 14 ----------------------
ISO 16818:2008(E)
3.54
daylight sensing control
DS
device that automatically regulates the power input to electric lighting near the fenestration to maintain the
desired workplace illumination, thus taking advantage of direct or indirect sunlight
3.55
dead band
dead zone
range of values within which an input variable can be varied without initiating any noticeable change in the
output variable
3.56
decorative lighting
See lighting, decorative (3.138).
3.57
default assumption
value of an input used in a calculation procedure when a value is not entered by the designer
3.58
degree-day
difference in temperature between the outdoor mean temperature over a 24-h period and a given base
temperature
NOTE For the purposes of determining building envelope requirements, the classifications are defined in 3.58.1 and
3.58.2.
3.58.1
degree-day, cooling
for any one day, when the mean temperature is more than the base temperature, there are as many degree-
days as degrees Celsius temperature difference between the mean temperature for the day and the base
temperature
NOTE Annual cooling degree-days (CDDs) are the sum of the cooling degree-days over a calendar year.
3.58.2
degree-day, heating
for any one day, when the mean temperature is less than the base temperature, there are as many degree-
days as degrees Celsius temperature difference between the mean temperature for the day and base
temperature
NOTE Annual heating degree-days (HDDs) are the sum of the heating degree-days over a calendar year.
3.59
dehumidification
controlled reduction of water vapour from the air
3.60
demand, electric
rate at which electric energy is delivered to or by a system, a part of a system, or a piece of equipment
NOTE The electric demand is expressed in kilowatts, kilovolt amperes or other suitable units, at a given instant or
averaged over any designated period.
3.61
demand energy
energy to be delivered to provide the required service with an ideal system to the end user
10 © ISO 2008 – All rights reserved

---------------------- Page: 15 ----------------------
ISO 16818:2008(E)
3.62
design capacity
output capacity of a system or piece of equipment at design conditions
3.63
design conditions
specified indoor environmental conditions, such as temperature, relative humidity, lighting level, etc., required
to be produced and maintained by a system and under which the system must operate
3.64
design energy consumption
estimated annual energy usage of a proposed building design
3.65
design energy costs
estimated annual energy expenditure of proposed building design
3.66
direct digital control
DDC
type of control where controlled and monitored analogue or binary data (e.g. temperature, contact closures)
are converted to digital format for manipulation and calculations by a digital computer or microprocessor, then
converted back to analogue or binary form to control physical devices
3.67
distribution system
conveying means, such as ducts, pipes and wires, to bring substances or energy from a source to the point of
use
NOTE The distribution system includes auxiliary equipment, such as fans, pumps and transformers.
3.68
efficiency
performance at specified rating conditions
3.69
efficiency, HVAC system
ratio of the useful energy output (at the point of use) to the energy input in consistent units for a designated
time period, expressed in percent
3.70
electric meter
mechanical/electrical device that can measure electric power
3.71
electric supplier
agency that sells and/or distributes electric power
3.72
emittance
ratio of the radiant heat flux emitted by a specimen to that emitted by a blackbody at the same temperature
and under the same conditions
3.73
enclosed space
volume substantially surrounded by solid surfaces, such as walls, floors, roofs, and “open-able” devices such
as doors and operable windows
© ISO 2008 – All rights reserved 11

---------------------- Page: 16 ----------------------
ISO 16818:2008(E)
3.74
energy
capacity for doing work; having several forms that may be transformed from one to another, such as thermal
(heat), mechanical (work), electrical or chemical
3.75
energy carrier
substance of phenomena that can be used to produce mechanical work or heat, or to operate chemical or
physical processes
3.76
energy cost
cost of energy by unit and type of energy as proposed to be supplied to the building at the site including
variations such as time of day, seasonal and rate of usage
3.77
energy cost budget
maximum allowable estimated annual energy expenditure for a proposed building
3.78
energy efficiency ratio
EER
ratio of net equipment (cooling or heating) capacity to total rate of electric input under designated operating
conditions
NOTE When consistent units are used, this ratio becomes equal to COP.
See also coefficient of performance (3.35).
3.79
energy efficiency ratio for buildings
EERB
ratio of energy required (ER) and energy used (EU)
3.80
energy factor for water heater
EF
measure of the overall efficiency of a water heater
3.81
energy management system
control system designed to monitor the environment and the use of energy in a facility and to adjust the
parameters of local control loops to conserve energy while maintaining a suitable environment
3.82
energy need for heating or cooling
heat required for delivery to or extracted from a conditioned space by a heating or cooling system to maintain
the intended temperature during a given period of time
3.83
energy need for domestic hot water
heat required for delivery to the domestic water to raise its temperature from the cold network temperature to
the prefixed delivery temperature at the delivery point
3.84
energy performance of a building
calculated or measured amount of energy actually used or estimated to meet the different needs associated
with a standard use of the building, which may include, inter alia, energy use for heating, cooling, ventilation,
domestic hot water and lighting
12 © ISO 2008 – All rights reserved

---------------------- Page: 17 ----------------------
ISO 16818:2008(E)
3.85
energy, recovered
See recovered energy (3.193).
3.86
energy resource
energy taken from a source that is depleted by extraction (e.g. fossil fuels) and which is required to achieve
the building performance and comfort over a given period of time including HVAC, lighting, occupancy,
domestic hot water, etc.
3.87
energy use for space heating and cooling
energy input to the heating or cooling system to satisfy the energy need for heating or cooling, respectively
3.88
envelope performance factor
trade-off value for the building envelope performance compliance option calculated using the procedures
specified in the systems performance trade-off
3.89
envelope performance factor, base
building envelope performance factor for the base design
3.90
envelope performance factor, proposed
building envelope performance factor for the proposed design
3.91
enthalpy
thermodynamic property of a substance defined as the sum of its thermodynamic energy plus the quantity PV,
where P is the pressure, V is its volume
NOTE Formerly called total heat and heat content.
3.92
equipment
devices for comfort conditioning, electric power, lighting, transportation or service water heating, including, but
not limited to, furnaces, boilers, air conditioners, heat pumps, chillers, water heaters, lamps, luminaries,
ballasts, elevators, escalators, or other devices or installations
3.93
exfiltration
uncontrolled outward air leakage from inside a building, including leakage through cracks and interstices
around windows and doors and through any other exterior partition or penetration
3.94
exterior building envelope
See building envelope (3.28).
3.95
exterior envelope
See building envelope (3.28).
3.96
exterior lighting power allowance
calculated maximum allowance of lighting power for an exterior area of a building or facility
NOTE The exterior lighting power allowance is expressed in units of watts.
© ISO 2008 – All rights reserved 13

---------------------- Page: 18 ----------------------
ISO 16818:2008(E)
3.97
external air
controlled air entering the system or opening from outdoors before
...