Traditionally, building managers review lighting design with a focus on improving energy efficiency and thus reducing energy costs for your facility. It is now well known that lighting controls in combination with the use of day lighting in offices can cut costs by up to 50% in commercial buildings.

The danger of this approach can be that your gains made in energy savings may be large in total dollars, but even a 1% increase in productivity will be worth more than twice this potential saving, due to the relative high cost of labour. Therefore, you must consider lighting reviews and design in the context of the overall cost-effectiveness of your operation.

We know that employees tend to work longer and more effectively when they are comfortable. Lighting can affect your occupants' level of comfort, so lighting designs are very important in providing effective illumination and therefore maximising productivity and safety.

The physiological advantage of improving access to daylight is that daylight is an effective stimulant to the human visual system and the circadian system. (The body's circadian system regulates the body's sleep/wake cycle, and can mean the difference between an alert worker and a sleepy one.) There is growing evidence that the light intensities and spectra adequate for the visual system, typically supplied by electric sources, are different to those required to activate the circadian systems. This lack of bright light exposure during the day may result in disruption of the circadian system and can lead to feelings of depression; poor sleep quality, lethargy and even illness.

It has been hypothesized that people working in interior offices would spend less time in their offices and would be less productive than a matched group of people in windowed offices. An overseas study looked into the occupancy rates (windowed versus interior offices) and the amount of time subjects spent on work related tasks. The results showed no difference in occupancy, but people in windowed offices spent significantly more time (15%) on work-related tasks compared to people in interior offices. What this study couldn’t prove directly was the exact cause of this difference in time spent on work-related tasks.

Psychologically, access to daylight and views through windows have a positive impact, as long as they do not cause thermal discomfort or visual distractions, including glare. Allowing employees to have individual control of their own lighting also tends to increase productivity.

The key message is do not ignore the impact of lighting on productivity. Small changes in productivity can easily outweigh the savings from inadequate designs that focus alone on cutting costs. Also, consider the measurement of productivity, at some level, preferably using a mixture of measures. Productivity is not easy to measure and assign cause. However, consider a 1% increase in productivity can easily be achieved by any one of the following - two less sick days per year, 5 minutes extra time spent at work per day, ten less headaches per year, or slightly less eye strain. Furthermore 1% of an $50,000/year salary cost is $500 per year, which for a company with 200 employees on site, could reap a benefit of $1,000,000 over ten years with this improvement in productivity. Not exactly chicken-feed!

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