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archived articles Cooking Light Okay, boiling down lighting design to a simple "recipe" is impossible, impracticable, and maybe is dangerous. Every project is different, every client has different desires, and every designer has his or her own theory for lighting design. However, is there a simple recipe that everyone can use that will result in an energy efficient lighting design? First and foremost, any "energy efficient recipe" must always provide a better lighting environment than the standard lighting design that would normally be used. Why, you may ask, for years, have energy efficiency / conservation been synonymous with sacrificing comfort for the common good? I still remember Jimmy Carter from the White House telling us to turn down the thermostat while wearing a sweater. The mind set for energy efficient lighting should be getting more for less. Better color, better comfort, higher light levels, lower utility bills, higher worker productivity -- now that's energy efficient lighting! We need to realize that the electric energy yearly cost is a miniscule part of the operating budget of most companies. Let's assume that an existing building uses 2 watts per square foot for the lighting; the lighting system operates for 3120 hours per year, and the utility charges $0.08 per kWh. That equates to $0.50 per square foot per year for the lighting system. New buildings that meet state energy codes or ASHRE/IESNA 90.1 will be even lower on lighting energy usage, and fewer dollars per square foot per year. If the average workers salary and benefits are $30,000 per year and they occupy 300 square feet (including shared spaces). That's $100 per square foot per year. Therefore the cost of the worker is 200 times greater than the energy used per year! I'm not saying that saving electrical energy costs should not be considered. Being "Green" is in. In areas where gas, oil, and coal are burned to create energy, fewer pollutants are released into the atmosphere. Greenhouse gases are reduced, slowing the effects of global warming. In the Pacific Northwest, where I live, our electric generation is predominantly hydro. By being energy efficient, more water can move through the rivers, helping endangered salmon reach the ocean. In the above example, electricity used by the lighting system will average less than 0.5% of the total per square foot yearly costs. Lets say that I can save 20% of the energy cost by using a energy efficient lighting system (20% of $0.50 = $0.10), but in doing so I produce a 1% decrease in worker productivity (1% of $100 = $1.00). The savings per square foot per year are -$0.90, not a very good return on investment! You are probably asking, "how could an energy efficient lighting system produce a decrease in worker productivity?" Easy. Switch out existing Mercury Vapor lighting in a warehouse or factory to high efficient High Pressure Sodium. The decrease in Color Rendering will obviously slow down some workers who find it harder to read labels, or inspect the products . Or, how about the office that was de-lamped from four-lamp troffers to two-lamp troffers. Ninety percent of the workers were okay with the change, but 10% are still complaining. How productive are those 10%? Or, occupancy sensors that false trigger and shut off the light on office workers, causing the sensors to be disabled. Never happen you say, I've seen it. Therefore, an energy efficient lighting design must provide a better lighting environment than the existing lighting system. Some of the factors that can influence the final lighting environment, and how the end user accepts, or rejects the system are the following: color of the lamps; color rendering of the lamps; glare from the lamps/lighting system; flickering of the lamps/ballasts; noise from the luminaires; heat produced by the lighting system; surfaces lighted by the lighting system; user interaction with controls; color of the surface materials; andlight levels produced. Here is my basic recipe for energy efficient lighting:
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