Wasted light

Part of the efforts to improve the energy efficiency of buildings is to set air tightness requirements. At the same time natural ventilation is being considered as a viable option to mechanical air conditioning.

There is a parallel with lighting where the use of daylight has benefits for both energy consumption and occupant well-being. The past age of cheap electricity however encouraged architecture to ignore daylight and to assume electric lighting to be available at all times. This magnanimous use of light continues today, demonstrated by the national press regularly showing large office blocks with all their lights blazing long after the workers have gone home.

This presents two opportunities to save energy. The first is to optimise the use of lighting controls coupled with the education of building users and occupants. If people do not understand the need to switch off when vacating a space then it is likely that any lighting controls installed will change this behaviour.

The second aspect is the amount of now expensively produced electric light that simply goes out the window. After dark this loss could be reduced by blinds provided they are drawn. Perhaps there is a photochromic sensitive glass that becomes opaque and highly reflecting when there is an absence of daylight.

So how about a campaign for “light-tight” buildings? Something to consider for the 2013 edition of Part L?

Richard Forster is a Lighting Expert with over 40 years experience in lighting, both as an engineer and consultant. As a well-respected author and lecturer, his wealth of knowledge is continually used by BSRIA.