When a space is designed, we usually assume that the lighting will properly illuminate the area evenly. However, have you ever thought about what type of light source should actually be used? What the color temperature (Kelvin) rating of the bulbs is? Or what is the color-rendering index (CRI) that determines if colors in a room are truly the colors your eye thinks it sees?
Look up at the lighting in your surrounding space. See anything that looks strange?
• Different colored lamps.
• Lamps that are burned out.
• Bugs, dust, and debris in the lenses.
• Reflectors that aren’t clean.
• Fixtures that are switched on when no one is around.
Each one of these factors contributes to an environment where the lighting is not ideal. Not only can these eventually put a strain on your eyes, they can also affect the mood of an employee.So where do you start in regards to providing a good lighting design? The basics. Know your options in regards to what types of lighting fixtures and lamp sources are available. By planning your design for illumination up front, you’ll have a better understanding of what the space is going to look like when the design progresses.
Lumen output, color temperatures, CRI ratings, beam spread, lamp life depreciation, and rated lamp life can all dramatically affect your design. However, with the help of photometric software, you can visualize what a proposed design will look like even before it’s started.
• Lumen – Is the total amount of visible light emitted from a source in a particular direction. The higher the lumens are, the brighter the light source will be. Typically one lumen equals one candela (or foot-candle). A candela is equivalent to the light emitted from a single candle burning.
• Color Temperature (Kelvin) – Determines the “warmness” or “coolness” of a particular lamp measured in Kelvin’s. The lower Kelvin ratings give a warmer appearance of a lamp. The higher Kelvin ratings give a cooler appearance of a lamp. Warmer colors typically emit a more orange to yellow appearance while cooler colors typically emit a more blue to pink appearance. Daylight is a mixture of both cool and warm colors.
• Color Rendering Index (CRI) – The ability of a lamp to render the color of an object in a normal and natural way. Typically measured from 0-100. The higher the rating, the better the color appearance of an object. Lower ratings may give an object a false color appearance (a beige wall may look gray under certain lighting, for example)
• Beam Spread – The total angle of a projected beam of light.
• Lamp Life Depreciation – Measures the overall lumen depreciation level over the life of a particular lamp.
• Rated Lamp Life – The actual number of hours a particular lamp will burn before failing
• Photometrics – Actual candela (foot-candle) plots that can be placed on a floor plan for a particular light fixture. There are thousands of different types of photometric files that are specific to a particular fixture. These files are called .IES files, which are certified by the Illuminating Engineering Society of North America (IESNA) and are entered into lighting calculation software.
Types of Light Sources
There are a wide variety of light sources available to illuminate a particular space. However, there is no “one size fits all” category. Some sources are better suited for certain environments rather than others.
• Fluorescent – The most commonly and widely used light source available today. They can be found in a wide variety of different types of fixtures: 2×2, 1×4, 2×4, 4×4, 4’ strips, downlighting, undercabinet and decorative lighting.
• Incandescent – Commonly found in floor and table lamps, downlighting, and flood lighting. Very inefficient in regards to power consumption. This particular light source is being phased out.
• Halogen – Commonly found in small, decorative fixtures, smaller downlights, landscape lighting, house lighting for theaters and sanctuaries and some floor lamps.
• High Intensity Discharge (HID) – Commonly found in exterior fixtures consisting of Metal Halide, Low Pressure Sodium or High Pressure Sodium light sources.
• Light Emitting Diode (LED) Have become a viable alternative to fluorescent light sources as the technology continues to improve and prices drop. Commonly found in a wide variety of interior and exterior fixtures due to the best “bang for the buck” in regards to energy consumption versus lumen output.
• Induction – This source is similar to fluorescent lamp, except it doesn’t have electrodes as part of the fixture. Therefore, these sources have a much longer lamp life than any other source available. However, they’re cost prohibitive and limited in applications and lamp wattage.
You don’t have to be limited to just on/off switching to control light levels in a space. Dimming or dual level switching is a common practice to control different light levels. Daylight harvesting can be used to switch off or dim lighting near windows. When they’re not in use, occupancy/vacancy sensors switch off lights. And Building Automation Systems (BAS) can be tied into lighting systems for seamless building wide control, even remotely!
Providing control to automatically switch off lighting when it isn’t needed saves the owner money on their energy bill. Control devices are also eligible for incentives and rebates from many different power companies from around the country.
One of the best and most abundant sources of illumination is daylight. Bringing more daylight into a space will reduce the amount of artificial illumination needed. Roof penetrating “Solar Tubes” with internal mirrors and lensed reflectors bring in a surprising amount of daylight from such a small footprint. Skylights and large windows are another great way to bring in large amounts of daylight. Building orientation and landscaping are also an important factor in regards to the amount of daylight that can be brought into a space.
Picking the right illumination source early in the design process is only part of the solution. Coordinating with the architect and interior designer in regards to the space design is critical. Determine who is going to use the space and what they’re going to use it for. Will it be occupied continuously or periodically? Will it be used during the day, at night, or both?
There is some up front research that must be completed before a lighting design takes place. But this is necessary in order to get a good idea of what the space is going to look like before the design is even started. This will help the architect, interior designer, and owner choose the proper design approach for the space.