When light strikes a surface, some of the light is absorbed. Because of lower reflectance, absorption is higher. Lighter-colored stone and surfaces can reflect light better than darker surfaces. The color of the surface is a trade-off between visual and environmental impact.
When it comes to making lighting choices for a specific project, a practical definition of sustainability helps: “Sustainable lighting meets human needs with the least impact on the natural environment.”
Thus, the prerequisite for sustainable lighting is meeting human needs. Lighting that fails to provide adequate illumination for safe passage, task performance, and overall well-being is inherently wasteful and therefore not sustainable, regardless if little carbon is released into the atmosphere.
What about lighting for beauty and image?
An extravagant kitchen may not sit atop the hierarchy of human needs, but it still serves an important human desire, one that is inextricably tied to our social relations.
Meeting human needs is necessary—but not sufficient—for sustainability. Sustainable lighting must meet human needs with the least impact on the natural environment.
Environmental impacts of lighting
Indoor lighting, such as that in kitchens and baths, affects the natural environment in three principal ways:
1. Impact of electricity consumption
2. Quantity of material used initially over time
3. Potentially harmful material content
Sustainable lighting strategies
The environmental impact of lighting consists of three basic components: emissions from electricity generation powered by fossil fuels, material used (and disposed of) in the lighting equipment, and any potentially hazardous content in that material.
The financial cost of lighting includes both installed and operating cost and includes material, electricity, labor, and disposal.
Electricity represents the single largest environmental and financial cost of lighting.
The environmental and financial cost of electricity both depend on the electrical power in the lighting and the hours it is used.
These points lead directly to practical strategies for sustainable lighting. But first you should consider the client’s perspective.
Clients use sustainable lighting for three reasons: they value the environment; they expect financial savings; and they have no choice due to regulations. In simple terms, these are known as the Want to, Pays to, and Got to.
Regardless of your client’s wishes, your design must conform to applicable codes, even when those codes add cost. That’s the Got to.
Some clients will ask (even demand) that your design minimize environmental impact, as a priority. That’s the Want to.
Other clients only wish to adopt cost-saving technologies. If those technologies also reduce environmental impact, so much the better. That’s the Pays to.
Still others—perhaps most clients—look for a reasonable balance, lighting that both reduces environmental impact and lowers financial cost. That’s common sense.
The strategies you adopt for your design will ultimately depend on your client’s values. Those strategies include energy efficiency, long life equipment, and clean material content.
Because energy usage—electricity consumption—imposes the highest cost on the environment, energy efficiency is the most important strategy for sustainable lighting. When it comes to lighting, energy efficiency is more important than material usage or content—by far. As a sustainable strategy, energy-efficient lighting applies three basic techniques.
The strategy begins by using only what you need. That is, minimizing the use of light when tasks do not require it, or when daylight provides the necessary illumination, or when no one is around to use it. Because you are only preventing waste, this aspect of energy efficiency does not limit lighting’s ability to meet client needs.
- A layered lighting design with task-specific illumination uses less electricity than a uniform level of illumination.
- Windows provide the critical amenity of view; they can also reduce lighting energy consumption. To accomplish this, the lighting design combines daylight with controls to reduce illumination when daylight is present.
- Lighting controls can reduce electricity still further: switching lights off when no is present, or dimming them down when users—or occasional tasks—require less than full output.
The second technique is using reflective finishes. When light strikes a surface, some is absorbed. The lower the reflectance, the higher the absorption, and the less light ultimately reaches its target. Dark stone and highly textured surfaces, for example, can be light traps. Because these low-reflectance materials can be an important part of the interior design, you face a potential trade-off between visual and environmental impact. Careful design—limiting the use of dark finishes and locating them so they are not important reflecting surfaces—can address the issue.
The third technique and perhaps the most familiar is using efficient lighting equipment—light sources and luminaires. The measure used to evaluate lighting equipment is called luminous efficacy—the amount of light produced per unit of power, technically, lumens per watt. Lumens per watt is sometimes shown as LPW.
Light sources differ considerably in their ability to convert electricity into light. Similar looking fixtures may perform quite differently. The better lighting choice will emit more light than the other.
However, some efficient fixtures are simply glary. Some efficient light sources distribute light inappropriately or with poor color. It is important to establish lighting needs—quantity and quality—so the pursuit of efficiency does not come at their expense.
Long equipment life
Reducing the number of luminaires in order to lower material consumption is not generally a satisfactory approach to sustainable lighting. Remember, the first priority is meeting lighting needs. The luminaire location contributes directly to the effectiveness of the lighting design. Spacing luminaires farther apart may leave undesirable dark areas, while using fewer brighter luminaires often produces glare.
Using long-life light sources, on the other hand, is a good sustainable lighting strategy provided the source produces the lighting needed. Because today’s energy-efficient light sources—LED and fluorescent—also enjoy relatively long life, this strategy dovetails well with using energy-efficient equipment, where it serves lighting needs well.
Sustainability and cost
The direct association of environmental impact and financial cost should be clear. On a life cycle basis, sustainable lighting—efficient, long lasting, and clean—costs less than lighting with a heavier environmental footprint.
The environmental impacts of lighting include the emissions from fossil-fuel fired electric power plants, material usage, and potentially toxic elements in the material. Sustainable lighting therefore is energy efficient, lasts a long time, and uses clean materials. The financial cost of lighting includes initial and operating costs, comprising material, electricity, labor, and disposal. As with environmental impact, energy dominates financial cost. PR
This article is excerpted from the NKBA Professional Resource Library volume: Kitchen & Bath Lighting to be published in 2014. Daniel Blitzer, with Tammy MacKay, AKBD and Vince Butler, CGR, GMB, CAPS. Copyright: 2014 National Kitchen & Bath Association; published by John Wiley & Sons Inc. Reproduced with the permission of John Wiley & Sons Inc.