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BS 8206-2:2008

BS 8206-2:2008

$152.82

Lighting for buildings – Code of practice for daylighting

Published By Publication Date Number of Pages
BSI 2008 56
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This part of BS 8206 gives recommendations regarding design for daylight in buildings. It includes recommendations on the design of electric lighting when used in conjunction with daylight.

NOTE Data for daylight and sunlight calculations are given in Annex A.

PDF Catalog

PDF Pages PDF Title
3 Contents
Section 1: General 1
1 Scope 1
2 Terms and definitions 1
Section 2: Aims and criteria for design 4
3 The contribution of daylight 4
4 Windows and view 5
5 Daylight and room brightness 8
6 Daylight for task lighting 11
Section 3: Further design issues 14
7 Electric lighting used in conjunction with daylight 14
8 Sunlight shading 16
9 Energy efficiency 18
10 Conservation of materials inside buildings 20
11 Statutory and legal requirements affecting the provision of daylight 21
Section 4: Methods of calculation 23
12 Sunlight 23
13 Calculation of average daylight factor 29
14 Calculation of daylight illuminance 31
15 Examples of the calculation of window transmittance 32
Annexes
Annex A (informative) Data for daylight and sunlight calculations 33
Annex B (informative) Climate-based daylight modelling 40
Bibliography 44
List of figures
Figure 1 – Solar altitude and solar azimuth 3
Figure 2 – Views from windows of different shapes and sizes 7
Figure 3 – Window reveal drawn on a sunpath diagram for London 26
Figure 4 – Obstructing building superimposed on the sunpath diagram 27
Figure 5 – Use of sunlight probability diagram to determine sunlight reaching window reference point 27
Figure 6 – Angle of visible sky used in calculating average daylight factor 30
Figure 7 – Limiting depth of a side-lit room 31
Figure A.1 – Sunpath diagram for London (latitude 51° N) 36
Figure A.2 – Sunpath diagram for Edinburgh (latitude 56° N) 37
Figure A.3 – Sunlight probability diagram 38
Figure A.4 – Diffuse illuminance (Eh) availability for London 39
Figure A.5 – Diffuse illuminance (Eh) availability for Edinburgh 39
Figure A.6 – Mean horizontal diffuse illuminances at London (Kew) 40
List of tables
Table 1 – Minimum glazed areas for view when windows are restricted to one wall 6
Table 2 – Minimum average daylight factor 10
Table A.1 – Approximate values of the reflectance of light 33
Table A.2 – Mean light transmittance of glazing materials 34
4 Table A.3 – Percentage losses of light in particular types of buildings 35
Table A.4 – Exposure multiplying factors 35
Table A.5 – Special exposure multiplying factors 35
Table A.6 – Correction factors for frames and glazing bars 36
Table A.7 – Diffuse orientation factors for an 09.00 to 17.00 working day 38
5 Foreword
7 Section 1: General
1 Scope
2 Terms and definitions
2.1 daylight
2.2 window
2.3 rooflight
2.4 transom
2.5 obstruction
2.6 no-sky line
2.7 working plane
2.8 window reference point
2.9 supplementary electric lighting
8 2.10 sunlight
2.11 skylight
9 Figure 1 Solar altitude and solar azimuth
10 Section 2: Aims and criteria for design
3 The contribution of daylight
3.1 General
a) for view;
b) to enhance the overall appearance of interiors, using sunlight (the direct beam) and skylight (diffuse daylight);
c) for lighting of visual tasks.
3.2 Daylight and health
3.2.1 Regulation of the circadian system
3.2.2 Mood
11 3.2.3 Seasonal affective disorder (SAD)
3.2.4 Ultraviolet (UV) radiation
4 Windows and view
4.1 Principle
4.2 Analysis of view
a) Most people prefer a view of a natural scene: trees, grass, plants and open space.
b) In densely built-up areas, a view of the natural scene may not be available. When only buildings, sky and street can be seen,…
c) A specific close view may be essential, particularly for security and supervision of the space around dwellings.
d) There is often a need for privacy. This varies with the building type and with the expectations of the users. The view into a building should be considered when the view outwards is determined.
12 1) upper (distant), being the sky and its boundary with the natural or man-made scene;
2) middle, being the natural or man-made objects themselves;
3) lower (close), being the nearby ground.
4.3 Size and proportion of windows
Table 1 Minimum glazed areas for view when windows are restricted to one wall
13 Figure 2 Views from windows of different shapes and sizes
a) Large window providing a view containing all three layers.
b) Smaller window of horizontal proportions providing a view with some sky visible.
c) Smaller window of vertical proportions showing all three layers, but with a restricted view.
14 5 Daylight and room brightness
5.1 General
5.2 Sunlight: principle
15 5.3 Sunlight duration
5.4 Skylight: principle
5.5 Average daylight factor
16 5.6 Minimum values of average daylight factor in dwellings
Table 2 Minimum average daylight factor
5.7 Uniformity of daylight
a) a significant part of the working plane (normally more than 20%) lies behind the no-sky line; or
b) in a room lit by windows in one wall only, the depth of the room is too large in comparison with the height and the width of the windows. (A procedure for calculating this is given in 13.3.)
17 5.8 Contrast between the interior and the view outside
a) providing additional illumination on the window wall from other windows;
b) reducing the luminance of the sky as seen from the interior with translucent blinds, curtains or tinted/solar-control glazing, if adequate illumination can be provided by other sources;
c) splaying window reveals, to give a larger area of intermediate brightness between the exterior view and the window wall.
6 Daylight for task lighting
6.1 General
18 a) A constant illuminance on the task cannot be maintained. When the sky becomes brighter, the interior illuminance increases; a…
b) The direction of light from windows, which act as large diffuse light sources to the side of a worker, gives good three-dimen…
c) The spectral distribution of daylight varies significantly during the course of a day, but the colour rendering is usually considered to be excellent.
6.2 Quantity of daylight
6.2.1 Illuminance
6.2.2 Uniformity
6.3 Quality of daylight
6.3.1 General
6.3.2 Glare
19 6.3.3 Specular reflection
20 Section 3: Further design issues
7 Electric lighting used in conjunction with daylight
7.1 Functions of supplementary electric lighting design
a) to enhance the overall appearance of the room, by improving the distribution of illuminance and by reducing the luminance contrast between the interior and the view outside;
b) to achieve satisfactory illuminance on visual tasks.
7.2 Lighting quality
7.2.1 Balance of daylight and electric light
7.2.2 Modelling
7.2.3 Contrast between interior and exterior
21 7.2.4 Colour appearance of lamps
a) using lamps of cool or intermediate class correlated colour temperature (see BS EN 12464-1:2002, Table 3);
b) screening lamps from the view of occupants (see BS EN 12464-1:2002).
7.2.5 Sequences of spaces
7.3 Task lighting
7.3.1 Illuminance
7.3.2 Direction and modelling
7.3.3 Colour
22 7.4 Change in lighting at dusk
8 Sunlight shading
8.1 General
23 8.2 Overshadowing
8.2.1 Loss of daylight to existing buildings
a) If the vertical sky component at the centre of the existing window would exceed 27% with the new development in place, then enough skylight would still be reaching the existing window.
b) If the vertical sky component with the new development in place would be both less than 27% and less than 0.8 times its forme…
24 8.2.2 Loss of sunlight to existing buildings
8.2.3 Overshadowing of an open space by a proposed development
9 Energy efficiency
9.1 Energy consumption in lighting
25 9.2 Window design and energy efficiency
9.3 Passive solar design
26 9.4 Lighting controls
a) manual;
b) timed switch-off with optional manual reset;
c) photoelectric switching on/off;
d) photoelectric dimming.
10 Conservation of materials inside buildings
10.1 General
10.2 Factors affecting degradation
a) spectral composition of the light;
b) illuminance;
c) period of exposure.
27 10.3 Improving conservation
10.3.1 Spectral composition
10.3.2 Illuminance
10.3.3 Exposure period
11 Statutory and legal requirements affecting the provision of daylight
29 Section 4: Methods of calculation
12 Sunlight
12.1 Sunpath diagrams
12.1.1 General
12.1.2 Day angle
12.1.3 Solar declination
12.1.4 Equation of time
30 12.1.5 True solar time
12.1.6 Hour angle
12.1.7 Solar altitude
12.1.8 Solar azimuth
31 12.1.9 Stereographic sunpath diagrams
12.2 Probable sunlight hours
32 Figure 3 Window reveal drawn on a sunpath diagram for London
33 Figure 4 Obstructing building superimposed on the sunpath diagram
Figure 5 Use of sunlight probability diagram to determine sunlight reaching window reference point
34 12.3 Use of physical models
12.4 Use of computer models
35 13 Calculation of average daylight factor
13.1 Windows and rooflights with continuous obstructions of uniform height
36 Figure 6 Angle of visible sky used in calculating average daylight factor
13.2 Limitations of the formula
13.3 Room depth
37 Figure 7 Limiting depth of a side-lit room
14 Calculation of daylight illuminance
38 15 Examples of the calculation of window transmittance
15.1 Average daylight factor
15.2 Overall aperture and net glazed area
39 Annex A (informative) Data for daylight and sunlight calculations
A.1 Values of reflectance and transmittance
A.1.1 Reflectances
Table A.1 Approximate values of the reflectance of light
40 Table A.1 Approximate values of the reflectance of light (continued)
A.1.2 Transmittances
Table A.2 Mean light transmittance of glazing materials
41 A.1.3 Maintenance factors
Table A.3 Percentage losses of light in particular types of buildings
Table A.4 Exposure multiplying factors
Table A.5 Special exposure multiplying factors
42 A.1.4 Correction for frames and glazing bars
Table A.6 Correction factors for frames and glazing bars
A.2 Availability of sunlight
Figure A.1 Sunpath diagram for London (latitude 51° N)
43 Figure A.2 Sunpath diagram for Edinburgh (latitude 56° N)
44 Figure A.3 Sunlight probability diagram
A.3 Availability of skylight
Table A.7 Diffuse orientation factors for an 09.00 to 17.00 working day (factor fo in equation 3 in Clause 14)
45 Figure A.4 Diffuse illuminance (Eh) availability for London (see Clause 14 for factor Eh in equation 3)
Figure A.5 Diffuse illuminance (Eh) availability for Edinburgh (see Clause 14 for factor Eh in equation 3)
46 Figure A.6 Mean horizontal diffuse illuminances at London (Kew)
Annex B (informative) Climate-based daylight modelling
B.1 General
47 B.2 Use of climate data
B.3 Applications
48 B.4 Methodology
49 a) arithmetic aggregation of the time-series values derived from a daylight coefficient approach; and
b) synthesizing sky and sun descriptions that contain the aggregated luminance (or radiance) of many “instantaneous” sky and sun configurations.
50 Bibliography
[1] CHARTERED INSTITUTION OF BUILDING SERVICES ENGINEERS. Lighting Guide LG10 Daylighting and window design. 1999.
[2] NHS ESTATES. Windows. Health Technical Memorandum 55. London: The Stationery Office, 1998.
[3] SOCIETY OF LIGHT AND LIGHTING. The code for lighting.
[4] BUILDING RESEARCH ESTABLISHMENT. Report Site layout planning for daylight and sunlight: a guide to good practice. 1991.
[5] KASABOV, G., ed. Buildings, the key to energy conservation. RIBA Energy Group, 1979.
51 [6] CRISP, V.H.C., LITTLEFAIR, P.J., COOPER, I. and G. McKENNAN. BRE Report Daylighting as a passive solar energy option: an assessment of its potential in non-domestic buildings. Building Research Establishment, 1988.
[7] BUILDING RESEARCH ESTABLISHMENT. Selecting lighting controls and daylight use. BRE Digest 498. Building Research Establishment, 2006.
[8] CHARTERED INSTITUTION OF BUILDING SERVICES ENGINEERS. Lighting Guide LG8 Lighting for museums and art galleries. 1994.
[9] GREAT BRITAIN. Approved Documents for the Building Regulations.
[10] GREAT BRITAIN. Workplace (Health, Safety and Welfare) Regulations 1992 (as amended). London: The Stationery Office.
[11] GREAT BRITAIN. Health and Safety (Display Screen Equipment) Regulations 1992 (as amended). London: The Stationery Office.
[12] TREGENZA, P.R. Modification of the split-flux formulae for mean daylight factor and internal reflected component with large external obstructions. Lighting Research and Technology. 1989, 21, 125-128.
[13] LITTLEFAIR, P.J. BRE Information paper IP 15/88 Average daylight factor: a simple basis for daylight design. Building Research Establishment, 1988.
52 [14] CHARTERED INSTITUTION OF BUILDING SERVICES ENGINEERS. Guide J Weather, solar and illuminance data.
[15] CLARKE, J.A. Energy simulation in building design. 2nd Edition. Butterworth-Heinemann, 2001.
[16] LITTLEFAIR, P. The luminous efficacy of daylight: a review. Lighting Research and Technology. 1985, 17(4), 162-182.
[17] MARDALJEVIC, J. The simulation of annual daylighting profiles for internal illuminance. Lighting Research and Technology. 2000, 32(3).
[18] REINHART, C.F. and S. HERKEL. The simulation of annual illuminance distributions – a state-of-the-art comparison of six radiance-based methods. Energy and Buildings. 2000, 32(2), 167-187.
[19] NABIL, A. and J. MARDALJEVIC. Useful daylight illuminances: A replacement for daylight factors. Energy and Buildings. 2006, 38(7), 905-913.
[20] REINHART, C.F., MARDALJEVIC, J. and Z. ROGERS. Dynamic daylight performance metrics for sustainable building design. Leukos. 2006, 3(1).
[21] MARDALJEVIC, J. Time to see the light. Building Services Journal. 2006, September, 59-62.
[22] TREGENZA, P. and I.M. WATERS. Daylight coefficients. Lighting Research and Technology. 1983, 15(2), 65-71.
[23] MARDALJEVIC, J. Daylight simulation: Validation, sky models and daylight coefficients. PhD thesis. 2000, De Montfort University, Leicester, UK.
[24] LI, D.H.W., LAU, C.C.S. and J.C. LAM. Predicting daylight illuminance by computer simulation techniques. Lighting Research and Technology. 2004, 36(2), 113-128.

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BS 8206-2:2008
$152.82