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Lighting Reflectance - Lumitron Lighting Compliance
Lighting Reflectance & Lighting Compliance
The reflectance of a surface can dramatically alter
both the levels achieved in an area and more importantly the likelihood
of LG7 compliance. The result of applying arbitrary
figures can often be that the areas appear excessively ‘bright’ or
surprisingly ‘dark’. In table 1.0 below we have used a
standard type recessed luminaire with an LOR of 65%. This is
representative of many fittings in use today. This
table has a dual purpose since it shows that if the ‘typical’ or
‘assumed’ reflectances were applied as opposed to the real percentages,
then not only are the levels achieved distorted but also if the client
is seeking LG7 compliance, there is a temptation to ‘pour’ more light
onto the walls by the use of wall washing downlights.
These, whilst beneficial if applied correctly, can if viewed against a
‘brighter’ than anticipated surface, appear overpowering.
Figure 1.0
This scheme illustrates the problem with reflectances
and their effects on LG7 compliance. Based on information to hand (70%,
50%, 20% reflectances) the scheme theoretically needed additional
wallwash downlights to supplement the wall and ceiling levels.
In reality the reflectances were 82%, 81% and 23% for ceiling, wall and
floor respectively. Figure 2.0 (Shown right)
At proposal stage this scheme was deemed to fail to meet LG7. The client
accepted this and after discussion decided against supplementary
wallwash downlights, instead preferring to sell the building on its
merits. When designed initially with 70%, 50% and 20%
reflectances the scheme showed levels of 435lux average, 43% walls /
working plane and 20% ceiling / working plane. After
attending site with Dulux® colour swatches we determined the real
reflectance values. Without going into detail, the scheme now fully
complies with LG7 and the maintained levels are well over 500lux.
Ceiling
70% = Typical lighting industry ceiling reflectance
80% = Notional reflectance assumed where it is known that the
reflectance factor is greater than 70%
86% = RAL 9010 20% gloss ceiling
Wall
50% = Typical lighting industry wall reflectance
70% = Notional reflectance assumed where it is known that the
reflectance factor is greater than 50%
83% = Actual reflectance of Magnolia colour paint in matt (Dulux®)
Floor
20% = Typical industry floor reflectance
10% = Notional reflectance of a floor based on assumption that floor
finishes are very dark
30% = Actual reflectance of a light coloured carpet
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Lumitron Lighting Reflectance & Compliance
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