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BEAM P
LUS FOR
N
EW
B
UILDINGS
I
NDOOR
E
NVIRONMENTAL
Q
UALITY
(I
EQ
)
V
ERSION
1.2
I
EQ
15 N
ATURAL
L
IGHTING
Copyright © 2012 BEAM Society Limited. All rights reserved.
Page 173
6
IEQ
6.6
L
IGHTING
Q
UALITY
I
EQ
15 N
ATURAL
L
IGHTING
E
XCLUSIONS
None.
O
BJECTIVE
Encourage a holistic examination of site layout, building design, and
fenestration design, such as to maximise access to daylight for the
purposes of improved health and comfort.
C
REDITS ATTAINABLE
2
P
REREQUISITES
None.
C
REDIT REQUIREMENT
1 credit where at least 80% of the floor area in all normally occupied
spaces is adequately lit with an average daylight factor of 1%.
2 credits where at least 95% of the floor area in all normally occupied
spaces is adequately lit with an average daylight factor of 1%.
A
SSESSMENT
The Client shall submit evidence in form of a report prepared by a
suitably qualified person demonstrating compliance with the assessment
criteria. Daylight availability, based on ‘worst case’ scenarios, i.e., the
most obstructed windows, shall be demonstrated by either one of the
following methods:
a) Measurement of DF
Measurement of average daylight factor (DF) shall be by the methods
recommended by CIBSE [1], or equivalent.
Given that the specified sky condition can be difficult to obtain in practice
the following modelling methods are acceptable alternatives.
b) Estimation of DF
The average daylight factor (DF) shall be estimated according to the
preferred method [ 2 ], that given in the CIBSE design guide [ 3 ], or
equivalent method. Alternatively, daylighting design software such as
Radiance [4] can be used to calculate the average DF provided it can be
demonstrated that the method of computation employed by the software
used is not inconsistent with the preferred calculation method.
The report submitted shall identify the key parameters used in the
computations/modelling, especially with regard to glazing transmittance,
and the reflectances of external and internal surfaces; and the suitable
daylight glare control. The values of the parameters shall reflect the
nature and type of surfaces on the external vertical obstructions and
horizontal surfaces, and likely internal finishes.
The room dimensions shall be taken to be a typical perimeter room for
the building, such as a habitable room, office, classroom, etc.
Where at least 80% of floor area in all normally occupied spaces is
adequately lit with an average daylight factor of 1% or more the credit
shall be awarded. The second credit shall be awarded where at least
95% of floor area in all normally occupied spaces is adequately lit with an
average daylight factor of 1% or more.
In addition, to ensure a realistic result that reflects the urban density of
1
The Chartered Institution of Building Services Engineers. Applications Manual – Window design.
2
Cheung H D, Chung T M. Calculation of Mean Daylight Factor in a Building Interior Within a Dense Urban Environment.
Department of Building Services Engineering, Hong Kong Polytechnic University.
3
The Chartered Institution of Building Services Engineers. Lighting Guide LG10. daylighting and window design. CIBSE.
4
Ward Larson, G. and Shakespeare, R. Rendering with RADIANCE. Morgan Kaufmann. San Francisco.