Chapter Lighting and human Fifteen failings

Artificial lighting is a major factor in deciding the quality of the internal environment of offices. It is also a serious contributor to carbon dioxide, (CO2) emissions accounting in the US, for example, for up to 30 per cent of total electricity use (ScientificAmerican, March 2001). For these reasons it is a subject that warrants special attention.

Design studies suggest that considerable energy savings can be made by maximising natural light, particularly if it is linked to automatic controls. Passive solar studies claim that efficient and well-controlled lighting would reduce energy/carbon dioxide costs by more than any other single item.

There is still reluctance to accept any additional capital cost to achieve sustainable design despite the prospect of significant revenue savings. Even in terms of capital cost alone energy efficiency can make savings. For example, high frequency lighting, good reflecting luminaires and infra-red controls can save money because fewer fittings are required with lower heat production, in turn leading to a reduced cooling load. At the same time there is the chance to install fewer switch drops reducing cabling and simplifying fitting-out. This lighting strategy could also reduce the contract period with obvious benefits in terms of an earlier occupancy date.

Post-occupancy analysis has thrown some doubt on these assumptions (Bordass, W., PROBE studies). Changes in office design and work routines has caused a reappraisal of the maximisation philosophy. In addition, a build-up of user appraisal has shown that, in many cases, the claimed benefits of maximising natural lighting have turned into clear dis-benefits. As a result, recent occupancy studies have shown that artificial lights are left on much more than predicted. There are many reasons for this, and this chapter will review some of the most prominent.

When the original research into alternatives to the permanently artificially lit office space was carried out, work in offices was largely paper based. At the same time, research and guidance in the past has been simplistic and inadequately focused on the real contexts in which people make decisions. For example, it is possible for a single decision by an individual to put a whole system into an energy wasting state. Insufficient consideration is given to the fact that anomalous situations are often difficult to correct and it is easier to adopt the 'inertia solution'.

Now computers are the universal office tool and excessive daylight can be a severe nuisance due to reflection from VDU screens. If lighting controls are not tuned to each individual workstation, this can result in greater energy use than in a conventional office. For example, it has been found that all lights can be on because one person has drawn the blinds to avoid glare. Even where lights are zoned according to daylight penetration, these often do not relate to workstations with the result that lights are on all day to compensate.

A lesson which is being gradually learnt is that individuals will always select the least cost option in terms of effort. It is not that people are inherently lazy, but that they will tend to resent expending effort on activities which they regard as the responsibility of management. For example, it is often easier to switch on lights than adjust blinds, and that is what happens when natural light levels fluctuate. The common 'inertia response' is to close the blinds and switch on the lights. Where daylight results in glare, individuals will adjust the blinds and artificial lighting to avoid discomfort and achieve an even distribution of lighting regardless of energy consumption.

In cellular offices individuals take more responsibility for adjusting their light levels and optimising the relationship between artificial and natural lighting. In open plan situations where no individual is responsible, blinds tend to be left closed if that was their position on the previous day, regardless of external conditions.

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