This post is about standards relating to brightness.
As part of our energy saving measures after the earthquake in March, I think that our efforts at switching off unnecessary lights were a little patchy. Since we started to try and save energy in July last year, we removed some of the tubes from the ceiling fixtures, and we’ve got by with lighting at about half the usual levels. It does seem dark and a few people are occasionally turning on their own desk lights to compensate, but in the main everyone got used to it.
So, while we really want to save energy we are not too happy at being stuck in the dark, and people likely hesitated to complain as they don’t really like to. But, how do we decide the necessary levels of brightness in the first place?
1．Several standards
Brightness is indicated using an index of luminance in Lux (lx) units. Here in Japan the most commonly used standards are the domestic JIS standards, and in general office spaces the standard lighting level is 750lx. In addition to this, under Japan’s Industrial Health and Safety Law, lighting levels of over 300lx are necessary in offices where precision work is carried out. However, looking overseas the standard range in the United States is from 200 to 300lx. Compared to this the JIS standards levels are very high at 750lx.
2. Reviewing the JIS standards
JIS lighting standards were finally, after a period of 30 years revised in 2010. Until then the standard for offices was given as a range of between 500 and 1000lx however, an easily understandable representative value of 750lx was usually specified.
However with the recent power shortages, the range of 500 to 1000lx was restored under the JIS lighting standards in May 2011. Under this review, appropriate lighting levels were set depending on the actual conditions, with the intention of promoting energy conservation. I would venture to say that this reflects the opinion that the levels specified under the 2010 revisions were excessive. There is a tendency in the design of new buildings to increase lighting levels in competition with other buildings and also above the JIS standards. A situation which is not conducive to energy saving.
3．Future brightness levels
When lighting designs are implemented, there are seldom complaints that it is too bright, but there are bound to be complaints if it is too dark. There are not a few lighting designers who will install excessive lighting in order to avoid dark spots. There are likely facility managers who have the same tendency when planning new offices.
Incidentally, we managed to cut our ceiling lighting from 800 to about 400lx however, by using desk lights occasionally there were hardly any complaints. Actually, we have been working on detailed drawings in a 400lx lighting environment however, personally I felt it was no hindrance at all.
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| Desktop luminance 389lx |
I think those who are concerned with lighting environments may feel a further study is necessary to ensure there is no excess or insufficiency in lighting levels. So rather than disabling light fixtures, we need to reduce the number of fixtures installed from the very beginning.
Recently, this proposal is being accepted here and there, and seeing this makes me really feel that things are changing.
Kaoru Maeyama, Environmental Grouphttp://www.ptmtokyo.co.jp/
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