ISO/CIE TR 3092

TECHNICAL ISO/CIE TR
REPORT 3092
First edition
2023-08
Light and lighting – Energy
performance of lighting in buildings –
Explanation and justification of ISO/
CIE 20086
PROOF/ÉPREUVE
Reference number
ISO/CIE TR 3092:2023(E)
© ISO/CIE 2023

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ISO/CIE TR 3092:2023(E)
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© ISO/CIE 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
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ISO/CIE TR 3092:2023(E)
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviations .1
4.1 General . 1
4.2 Symbols and abbreviations . 1
5 Description of the methods . 3
5.1 General . 3
5.2 Method 1 – Comprehensive method . 4
5.3 Optional methods . 5
5.3.1 Method 2 – Quick calculation method . 5
5.3.2 Method 3 – Direct metering method . 5
6 Method 1 — Calculation of the energy required for lighting. 5
6.1 Output data . 5
6.2 Calculation time steps . 5
6.3 Input data . 6
6.3.1 Lighting system data . 6
6.3.2 Product data . 9
6.3.3 System design data . 10
6.3.4 Operating conditions . 10
6.3.5 Constants and physical data . 11
6.4 Calculation procedure . . 11
6.4.1 Applicable time step . 11
6.4.2 Operating conditions calculation . 11
6.4.3 Energy calculation . 11
7 Method 2 – Quick calculation of the energy required for lighting .29
7.1 General .29
7.2 Output data .29
7.3 Calculation time steps . 29
7.4 Input data .30
7.5 Calculation procedure . .30
7.5.1 Applicable time step .30
7.5.2 Operating conditions calculation .30
7.5.3 Energy calculation . 30
7.6 Expenditure factors for lighting systems .48
8 Method 3 — Metered energy used for lighting .48
8.1 General .48
8.2 Output data .48
8.3 Calculation time steps .49
8.4 Input data .49
8.5 Calculation procedure of annual energy .49
8.5.1 General .49
8.5.2 Calculation information .49
8.5.3 Calculation procedure of annual energy . 51
9 Quality control .51
9.1 Method 1 . 51
9.2 Method 2 . 52
9.3 Method 3 . 52
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ISO/CIE TR 3092:2023(E)
10 Compliance check .52
Annex A (informative) Calculation example for a new design retail store .53
Bibliography .83
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ISO/CIE TR 3092:2023(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received
notice of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 274, Light and lighting, in cooperation
with CIE Joint Technical Committee 6.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
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ISO/CIE TR 3092:2023(E)
Introduction
It is important that lighting schemes are designed appropriately to provide the right light in the right
place at the right time, while being energy efficient and conforming to local, regional, and/or national
regulations. It is also important that the lighting systems are operated energy efficiently and managed
by suitable lighting control systems.
Carrying out a comprehensive lighting design (daylight and electric lighting) for new or refurbished
buildings will yield both effective and energy efficient lighting solutions that fulfil the lighting criteria
specified in the lighting application standards. The lighting design process will show how much daylight
will be available and how much electric lighting is needed and what scheme solutions will satisfy the
required lighting conditions during the occupied and unoccupied periods.
ISO/CIE 20086 gives a procedure to estimate the required energy and the energy efficiency of the
electric lighting scheme.
There is a risk that the purpose and limitations of ISO/CIE 20086 will be misunderstood, unless the
background and context to its content is explained in some detail to users. If this information would
have been placed in ISO/CIE 20086, the standard would be overloaded with informative content; and
the result is likely to be confusing and cumbersome, especially if ISO/CIE 20086 is referenced in local,
regional, or national building codes.
Therefore, this technical report accompanies ISO/CIE 20086 and provides informative content to
support the correct understanding, use and national implementation of the lighting standard. It also
provides explanation of the lighting energy calculation methodology, working examples and descriptions
of integrated lighting control options. ISO/CIE 20086 defines the methods for estimating or measuring
the amount of energy required or used for lighting in buildings. The method of separate metering of the
energy used for lighting will also give regular feedback on the effectiveness of the lighting control. The
methodology of energy estimation not only provides values for the Lighting Energy Numeric Indicator
(LENI) but it will also provide input for the heating and cooling load estimations for the combined total
energy performance of building indicator.
LENI represents the absolute amount of energy required for a lighting scheme and does not directly
provide indications on the efficiency of the lighting technology employed. Therefore, a concept
of expenditure factors intending to render energy flows in lighting systems more transparent is
introduced in ISO/CIE 20086:2019, 6.5 and Annex E to complement LENI.
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TECHNICAL REPORT ISO/CIE TR 3092:2023(E)
Light and lighting – Energy performance of lighting in
buildings – Explanation and justification of ISO/CIE 20086
1 Scope
This document is a technical report supporting ISO/CIE 20086.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
CIE S 017, ILV: International Lighting Vocabulary
ISO/CIE 20086:2019, Light and lighting — Energy performance of lighting in buildings
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/CIE 20086, CIE S 017 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
CIE maintains a terminology database for use in standardization at the following address:
— e-ILV: available at https:// cie .co .at/ e -ilv
3.1
useful floor area
total gross floor area of all enclosed spaces, measured to the internal face of the external walls
Note 1 to entry: The total useful floor area can have a different value than the total floor area in the building.
4 Symbols and abbreviations
4.1 General
As given in CIE S 017, considering that LED technology has mostly replaced the conventional form of
lamps, the term “lamp” should be replaced with the more general term “light source” to follow changes
already introduced in some definitions of terms. However, as this document intends to accompany
ISO/CIE 20086, the terms and definitions used in this document are consistent with ISO/CIE 20086 by
using the term “lamp”. Still, whenever the term “lamp” is used in this document, it also refers to the
term “light source”.
4.2 Symbols and abbreviations
For the purposes of this document, the symbols given in ISO/CIE 20086 and the specific symbols listed
in Table 1 apply.
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ISO/CIE TR 3092:2023(E)
Table 1 — Symbols and units
Symbol Name of quantity Unit
2
A Total useful floor area in the building m
a Depth of daylight area m
D
b Width of the daylight area m
D
2
A Total useful floor area of the relevant zone or area m
i
2
A Sum of task areas within the room or zone m
s
b Daylight width m
D
D Daylight factor %
D Daylight factor of the raw building carcass opening %
CA
E Maintained illuminance on immediate surround of task area lx
sur
E Maintained illuminance on the task area lx
task
F Absence factor 1
A
F Constant illuminance dependency factor 1
c
F Correction factor for reduced power of area 1
CA
F Factor for the efficiency of the constant illuminance control 1
cc
F Daylight dependency factor 1
D
F Lighting control factor 1
D,C
F Daylight supply factor 1
D,S
F Correction factor for the light source efficiency 1
L
f Maintenance factor 1
m
F Correction factor for maintenance factor 1
CMF
f a Lamp luminous flux maintenance factor 1
LLM
a
f Lamp survival factor 1
LS
a
f Luminaire maintenance factor 1
LM
a
f Room surface maintenance factor 1
RSM
F Occupancy dependency factor 1
O
F Controls function factor 1
OC
h Height of the window lintel above the floor m
Li
h Mounting height of luminaire m
m
H /H Luminous exposure ratio 1
dir glob
h Height of the task area above the floor m
Ta
I Room depth index 1
RD
I Shading index 1
Sh
I Transparency index 1
Tr
K Room index 1
L Time period at which x % of the measured initial luminous flux value is main- h
x
tained
L Length of room m
R
n Number of lamps in the luminaire 1
La
P Control standby power of luminaire i W
c,i
P Total emergency standby power W
em
P Emergency charging power of luminaire i W
e,i
P Power of luminaire i W
i
a
The symbols for lamp luminous flux maintenance factor, lamp survival factor, luminaire maintenance factor and room
surface maintenance factor have changed according to CIE S 017 ILV and differ from ISO/CIE 20086.
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ISO/CIE TR 3092:2023(E)
TTaabblle 1 e 1 ((ccoonnttiinnueuedd))
Symbol Name of quantity Unit
2
P Power density of area j W/m
j
2
P Illuminance-normalized power density of area j W/(m lx)
j,lx
P Total power of n luminaires W
n
P Total standby power for automatic lighting controls W
pc
P Declared (marked) lamp rated power W
r
2
Q Lighting energy numeric indicator (LENI) for a building kWh/m
LENI
2
Q Lighting energy numeric indicator for an area or relevant zone kWh/m
LENI,sub
t Battery charge time h
e
t Daylight time h
D
t Daylight absence time h
N
t Specified time step hour, month,
s
year
t Total operating hours h
tot
t Number of hours in a standard year h
y
W Total annual energy used for lighting kWh
W Annual energy required for lighting for an area or a zone kWh
az
W Total energy for illumination kWh
L,t
W Total metered energy used for electric lighting kWh
mt
W Total energy for standby kWh
P,t
W Energy used for lighting per time step kWh
t
2
W Standby energy density for automatic lighting controls per year kWh/m
pc
2
W Standby energy density for battery charging of emergency luminaires per year kWh/m
pe
W Width of the room or zone m
R
a
The symbols for lamp luminous flux maintenance factor, lamp survival factor, luminaire maintenance factor and room
surface maintenance factor have changed according to CIE S 017 ILV and differ from ISO/CIE 20086.
For the purposes of this document, the specific subscripts listed in Table 2 apply.
Table 2 — Subscripts
i Relevant element under consideration
or Month number, 1-12
j Relevant area under consideration
5 Description of the methods
5.1 General
ISO/CIE 20086 provides three methods for the assessment of the energy required for electric lighting
within buildings:
a) Method (1): comprehensive;
b) Method (2): quick calculation;
c) Method (3): direct metering (see figure 1).
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ISO/CIE TR 3092:2023(E)
These methods can provide the information on the electric energy required for lighting in the selected
time steps and the Lighting Energy Numeric Indicator (LENI) for the whole building, individual room
or zones. LENI can be used for comparison of similar buildings and as a measure of the lighting energy
performance of the building.
Methods (1) and (2) are based on calculations, and Method (3) is based on the direct metering of the
lighting circuit. The calculation methods [(1) and (2)] can be used during feasibility studies or detailed
design of new or refurbished buildings, and for the assessment of energy use in existing buildings by
first performing a lighting installation audit [(1)]. The metered Method (3) can only be used in existing
buildings that have segregated lighting circuits that include meters to facilitate direct metering of the
energy used for lighting only or a building management system that can measure lighting energy use.
Figure 1 — Flow chart illustrating alternative routes to determine energy use
In terms of the outcome for the installed power, occupancy estimation and daylight availability,
Method 1, which relies upon a comprehensive lighting design, is a more accurate calculation procedure
than Method 2, which provides a quick estimation based on default values used during pre-design.
Method 3 provides the actual energy use for lighting information; however, it can only be used for
existing buildings that are lighting end-use metered, commissioned and occupied.
5.2 Method 1 – Comprehensive method
Method 1 provides the most accurate calculation procedure as it relies upon a comprehensive lighting
scheme design that is based on real data of the specified products as the main input to the energy
calculation. This method can be used for new and refurbished buildings and for assessing existing
buildings where it involves a detailed audit of the existing lighting system to establish the installed
lighting load. The lighting energy (kWh) per time step (month or hour) normalized to an area unit
2
(m ) of the useful applicable zone area provides a sub-LENI value for the building zone. In a case of the
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ISO/CIE TR 3092:2023(E)
yearly time step, and for total useful building area, this is the total annual Lighting Energy Numeric
Indicator (LENI).
5.3 Optional methods
5.3.1 Method 2 – Quick calculation method
Method 2 is a simplified method that calculates the required lighting load and evaluates an impact of the
control's features using an approximation approach and a set of default data for new and refurbished
buildings at the conceptual project stage where no comprehensive lighting design has been completed.
Therefore, the calculation results in a preliminary lighting energy (kWh) per time step (year)
2
normalized to an area unit (m ) of the useful applicable building or zone area and gives the budget LENI
or sub-LENI value, respectively. This estimated energy budget in general is likely to be higher than
those obtained from the comprehensive design process and is recalculated for more accurate results
with real data when the more detailed and comprehensive lighting system design has been completed.
5.3.2 Method 3 – Direct metering method
Method 3 relies on the direct measurement of the energy used for lighting in buildings. It is ideal for
buildings where segregated lighting power circuits exist and separate energy meter has been installed.
This method gives true values of the energy used for lighting at any time intervals and the annual
value can also be used to calculate the LENI for the building. This method can be used to verify the
values obtained by calculations and to continuously monitor the energy used for lighting. It can also be
used where a building management system (BMS) allows energy use for lighting to be measured. It is
important that the segregated energy meters only record the energy used for lighting in any parts of
the building.
6 Method 1 — Calculation of the energy required for lighting
6.1 Output data
For the purposes of this document, the output data of Method 1 listed in Table 3 apply.
Table 3 — Output data of Method 1
Description Symbol Unit
Specified time step, e.g. hourly, monthly or annually t hour, month, year
s
Energy used for lighting (kWh) per time step (e.g. hourly,
W kWh
t
monthly or yearly) within rooms or zones
2
LENI is the area normalized annual energy used for lighting within the building [kWh/m ]. Method 3
(direct metering) provides the most accurate value of Q , while Method 1 (comprehensive) assesses
LENI
Q more accurate than Method 2 (quick calculation).
LENI
6.2 Calculation time steps
The time step for calculations is chosen consistently for the input and output data and can be:
— yearly – 8 760 h/year,
— monthly – 730 h/month, or
— hourly – 1 h, derived from the monthly calculated value divided by 730,
— with accordance to the time step of the input data.
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ISO/CIE TR 3092:2023(E)
The provided method for the estimation of the lighting energy demand is based on an annual approach.
Seasonal impacts can be considered with monthly correction factors, if available. Hourly values cannot
be derived in any correct correlation with climatic data. Accurate hourly calculation of the energy
required for lighting is not practical as there is no robust method for the prediction of the values of the
dependency factors.
This document takes an alternative way to link into the hourly calculation scheme of other parts of
the energy balance, such as internal loads for heat load calculation, by the average hourly value. The
average hourly value is obtained from the monthly calculated value divided by the hours (730) in the
month. For each month a constant (not variable) term will therefore be added as lighting energy to the
other hourly variable parts of the energy balance.
The reason for this restriction lies in modelling the impact of daylight. This requires a photometrically
correct three-dimensional calculation scheme of the light distribution outside entering through the
façades into the adjacent indoor spaces. Early simple approaches have been based on the determination
of the daylight factor (D) at a given inside position and an hourly multiplication with an estimate of the
outside illuminance to obtain the indoor illumination which then serves as the basis for estimating the
electric ligh
...