Technical information

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The comprehensive method
This method permits an exact determination of the energy used
as the method is based on actual values for each room. Unlike
the quick method, the comprehensive method can be used for all
types of buildings, even at dierent geographical positions. As the
comprehensive method is based on actual values it gives a lower
LENI number than a calculation with the quick method. Calcula-
tions provided by Fagerhult, and those via DIALux, are based on the
comprehensive method.
Using the comprehensive method you can calculate for a selected
period (not only the whole year) under the condition that you can
get an estimation of the presence and availability of daylight. In the
examples on the coming pages we have used the comprehensive
method.
LENI=W
light
+ W
parasitic
/A (kWh/m², time*)LENI=W
light
+ W
parasitic
/A (kWh/m², year)
Energy Directive 2002/91/EC
The LENI number, the rating index for lighting’s specic annual energy usage
The standard EN 15193
Common standards are created to produce common calculation
methodology. Dierent standards are drawn up to calculate the dif-
ferent energy consumers in the building.
Naturally lighting is included as an important part of the energy
usage in a building. Standard EN 15193, Energy performance of
Buildings – Energy requirements for lighting, describes a harmo-
nised method of calculating energy usage for interior lighting. The
lighting's energy eciency in the building must be evaluated with
an index; Lighting Energy Numeric Indicator (LENI) and is expressed
in kWh/m² per year.
The LENI-number must be shown for the entire building and can
be used to compare the energy expended on lighting. The compari-
son can be made between dierent buildings with the same func-
tion but of a dierent size and design.
The standard will provide example values of the LENI number for
a number of common building types, thus shifting the focus from
the installed output to how the energy in used over time.
The calculation of the LENI number for the building is performed using
the formula: LENI
calculated
=W
total
/ A (kWh/m², year)
The indicator for the energy eciency of the
lighting
The energy consumption for lighting must be declared via the an
Lighting Energy Numeric Indicator (LENI) and is expressed in
kWh/m
2
, year.
LENI is calculated on the lighting for the entire building. At the
same time the lighting shall conform to current standards
and recommendations for indoor lighting (EN 12464-1).
W
total
is the total annual energy usage for lighting.
A is the building’s total interior area (m
2
).
The area is calculated inside the external walls excluding
non-used cellar areas and unlit rooms.
The LENI number can be calculated in two dierent ways, a quick and a comprehensive
The quick method
This method is used to give an estimate of the building’s annual
energy usage, applicable for just a number of common building
types. The standard includes tables where the annual standard data
for dierent types of buildings can be read to aid calculation via
the quick method. These are oces, buildings for tuition, hospitals,
hotel, restaurants, sports centres, department stores and retail shops
and manufacturing industries.
The quick method also includes a standard value for the parasitic
energy (W
parasitic
) which is stated as 6 kWh/m
2
a year and which
should be used when applicable. It is distributed over 1 kWh/m
2
year for charging emergency lighting and 5 kWh/m
2
year for standby
energy for the ballast.
* Using the comprehensive method you can calculate on an annual, monthly or time basis.
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