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The client has speci ed Level B for humidity comfort.
For Level B, the minimum value in the case of humidi cation is raised to 40% to take account of the requirements of Article 57 of the General Regulations for Work Protection which stipulates a relative humidity level of 40-70%.
VISuaL COmFORt – LIGHtING
Visual comfort is dependent on various parameters:
– the level of lighting for visual tasks;
– the uniformity of luminance in the visual eld (glare); – the availability of natural lighting;
– correct colour rendering;
– outside views.
For people to be able to carry out visual tasks effectively and accu- rately, adequate lighting has to be provided, without undesirable effects such as glare or blinding.The lighting required for a task
is de ned in detail in standard NBN EN 12464-1: 2011 (Light and lighting – Lighting of workplaces. Part 1: Indoor work places).This standard de nes comfort and performance criteria needing to be met by the arti cial lighting system.The standard speci es the mean lighting level, glare (CIE ‘Uni ed Glare Rating’, or UGR) and the colour rendering for different tasks.The Belgian best-practice document ‘Code de bonne pratique en éclairage intérieur’, pub- lished by Group B of the Belgian Lighting Institute IBE-BIV, rounds off the standard.
On the other hand, standard NBN EN 15251: 20072 speci es three levels of lighting quality based on natural light, light uniformity, UGR and colour rendering.
Performance
De-humidi cation (%)
humidi cation (%)
Level a High quality
50
40
Level B Normal quality
60
30 (40: see note))
Level C acceptable quality
70
20
NatuRaL LIGHt
Design levels of lighting can be made available by daylight, arti cial lighting, or a combination of both. For health, comfort and energy ef ciency reasons, preference is given to daylight (possible with spot lighting) rather than arti cial lighting.
To ensure the availability of a reasonable quantity of daylight during working hours, standard EN 15251: 2007 recommends setting requirements with regard to daylight penetration in spaces devoted to human occupation.
Natural light is characterized by the daylight factor, specifying the relation between the illuminance due to daylight at a point on the indoor working plane and the simultaneous outdoor illuminance on a horizontal plane from an unobstructed hemisphere of over- cast sky.
Levels (NBN eN 15251: 2007)
Level A
Level B
Level C
Daylight factor in the middle of the space
5%
3%
1%
table 5. Classi cation relative to air humidity
table 7. Levels of daylight availability under NBN eN 15193: 20083
The of ces correspond to Levels B (EN 15251) and ‘Strong daylight
penetration’ (EN 15193) in the middle of the of ces.
table 6. Levels of daylight availability under NBN eN 15251: 2007
Levels (NBN eN 15193: 2008)
Strong daylight penetration
Medium daylight penetration
Weak daylight penetration
No daylight penetration
Daylight factor (DF) in the middle of the space
FLJ ≥ 3%
2 ≤ FLJ < 3%
1 ≤ FLJ < 2%
FLJ < 1%
16 14 12 10
8 6 4 2 0
Meeting rooms
Restaurant
Offices on floor 1
Offices on floor 2
Building (including the kitchen)
Fig. 1. Overall breakdown of the daylight factor (by function and for the whole of the building)
0 20 40 60 80 100 Percentage of the surface concerned (%)
Daylight factor (DF) exceeded