Sustainable lighting for healthcare facilities: More than just lumens per watt

Sustainability is, as the name implies, a movement to ensure long-term, efficient utilization of resources. Sustain-ability does not imply that resources should be restricted nor that resource utilization should be subsidized. Bill McDonough (McDonough and Braungart 2002) has described sustainability in terms of the three E's: environment, equity, and economy. In the last quarter century the lighting industry has dramatically improved the energy efficiency (environment E) and life-cycle cost of lighting (economy E). Much less attention has been given to the equity E. Lighting standards are still set primarily in terms of illuminances (lumens per square meter) and lumens per watt, both of which are based upon the implicit assumption that the value of lighting can be characterized by the lumen. The lumen is, however, unrelated to other non-visual effects of light, such as the circadian system, and is only indirectly related to our perceptual system. In particular, our current architectural practices do not adequately support the most fragile segments of the population. And no matter how much energy is conserved or how much value engineering is applied, we are not designing or implementing sustainable lighting because we are not supporting many of the people in our built environments. In fact, the role of lighting as it affects human perceptual and circadian functions is almost completely ignored in standards. Arguably, the failure to consider these two human domain functions can be ignored in many modern applications because of the inherent flexibility and robustness of the human species. One segment of construction where the equity E should always be more seriously considered, however, is healthcare applications. These applications contain our most fragile humans, and lighting has been shown, for example, to demonstrably affect the lives of seniors and premature infants. But there are no standards to assist architects and engineers in supporting the well-being of these fragile people. To illustrate this assertion, this article focuses on sustainable lighting for healthcare applications where good lighting in all three human domains, visual, perceptual, and circadian, can be best documented.