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BUILDING (SCOTLAND) ACT 2003 CONSULTATION ON BUILDING REGULATIONS
AND GUIDANCE DOCUMENT: NON DOMESTIC
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Annex 6.K Example lighting calculations
6.K.0 Introduction
6.K.1 Example following guidance in 6.5.1 a.
6.K.2 Example following guidance in 6.5.1 b.
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annex 6.K
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Example lighting calculations
[Appendix J]
6.K.0 Introduction
The examples in this annex show two ways of providing
energy efficient lighting to buildings. The first is for an extension
to an existing building and the second is for a new building. These approaches
are not however exclusive to the type of building work referred to in
this annex, i.e. the first example could be adopted for new build and
the second, for an extension. Where the work consists of an alteration
or replacement these methods can be used, but only where a completely
new system of lighting is to be provided.
6.K.1 Lighting calculation to show that 95% of
installed circuit power is comprised of lamps listed in the table to 6.5.1a.
A new hall and changing rooms are to be added to an existing
community centre. The proposed lighting scheme incorporates lamps that
are listed in the table to 6.5.1 a. except for some low voltage tungsten
halogen downlighters which are to be installed in the entrance area with
local controls. A check therefore has to be made to show that the low
voltage tungsten halogen lamps comprise less than 5% of the overall installed
capacity of the lighting installation.
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Main hall specification
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Twenty wall mounted uplighters with 250 W
high pressure Sodium lamps are to provide general lighting needs. The uplighters
are to be mounted 7 metres above the floor. On plan, the furthest light
is 20.5 metres from its switch, which is less than three times the
height of the light above the floor. It is also proposed to provide twenty
18 W compact fluorescent lights as an additional system enabling instant
background lighting whenever needed. |
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Specification for changing rooms, corridors and entrance
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Ten 58 W, high frequency fluorescent light fittings
are to be provided in the changing rooms and controlled by occupancy detectors.
Six more 58 W fluorescent light fittings are to be located in the
corridors and the entrance areas and switched locally. Additionally, in
the entrance area there are to be the six 50 W tungsten halogen downlighters
noted above.
A schedule of light fittings is prepared as follows:
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Position
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Number
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Description of light source
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Circuit Watts per lamp
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Total circuit Watts (W)
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Main hall
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20
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250 W SON
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286 W
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5720
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Main hall
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20
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18 W compact fluorescent
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23 W
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460
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Entrance, changing rooms and corridors
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16
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58 W HF fluorescent
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64 W
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1024
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Entrance
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6
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50 W low voltage tungsten halogen
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55 W
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330
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Total =
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7534 W
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Calculation
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From the schedule of light fittings above, the total
circuit Watts of the lamps in the installation is 7534 W.
The percentage of circuit Watts consumed by lamps not
listed in the table to 6.5.1a.:
Therefore, more than 95% of the installed lighting capacity,
in circuit Watts, is from light sources listed in the table to 6.5.1a.
The switching arrangements follow the guidance in 6.5.3. The lighting
scheme can therefore be considered as following the guidance in Section
6.
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General specification
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6.K.2 Lighting calculation to show average circuit
efficacy follows the guidance in 6.5.1b.
A lighting scheme is proposed for a new public house
comprising a mixture of concealed perimeter lighting using high frequency
fluorescent fittings and supplementary compact fluorescent lamps in the
dining area. Lights in the dining and lounge areas are to be switched
locally from behind the bar. Lighting to kitchens and toilets is to be
switched locally.
The table below shows a schedule of the light sources
proposed.
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Position
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Number
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Description
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Circuit Watts (W) per lamp
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Lumen output (lm) per lamp
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Total circuit Watts (W)
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Total lamp lumen output (lm)
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Over tables
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20
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11 W compact fluorescent
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16
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900
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320
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18,000
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Concealed perimeter and bar lighting
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24
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32 W T8 fluorescent high frequency ballast
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36
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3300
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864
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79,200
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Toilets and circulation
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6
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18 W compact fluorescent with mains frequency ballast
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23
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1200
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138
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7,200
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Kitchens
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6
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50 W, 1500 T8 fluorescent with high frequency ballast
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56
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5200
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336
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31,200
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Totals
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1658
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135,600
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Calculation
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From the schedule of light fittings above, the total
lumen output of the lamps in the installation is 135,600 lumens.
The total circuit Watts of the installation is 1658 Watts.
Therefore, the average circuit efficacy is:
The proposed lighting scheme can be considered as following
the guidance in Section 6.
Note: If 60 W tungsten lamps were used in the dining
area instead of the 11 W compact fluorescent lamps actually proposed,
the average circuit efficacy would drop to 51.9 lumens/W, which would
not be following the guidance in 6.5.2b.
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