Defining Daylight White|
Article - January 16, 2016 By LarsonElectronics.com
Defining Daylight White
When optimizing lighting conditions for a specific location, one must take intensity and light color into consideration. One of these options is daylight white, or the natural lighting conditions of outdoor environments during a sunny day.
Daylight white can be used to improve visual clarity in the target area, boost productivity and reduce workplace accidents. These days, there are several ways to mimic natural daylight conditions, such as the use of LEDs or tubular daylight devices. In addition to incorporating bright luminaries that are capable of daylight-like illumination, the building’s design must be closely scrutinized for daylighting practices.
Definition of Daylight White
The characteristics of daylight white includes a pure white, bluish color with a color temperature rating range between 4,500K and 6,000K. By comparison, lighting conditions around sunrise or sunset is warm-yellow with a slight red tint, which is closer to low color temperature ratings between 2,200K and 3,000K. On the high end of the color temperature scale, clear skies during full sunlight at noon supports 10,000K (or higher) ratings.
In professional locations, such as offices, factories and other commercial buildings, daylight white light is used to support daytime and nighttime operations. For example, a building may incorporate large windows around the establishment to guide natural daylight into the facility. In areas without access to natural lighting (including businesses that conduct nighttime operations), artificial luminaries can be used to mimic daylight conditions indoors or in low light environments.
Applications of Daylighting
Daylighting involves the practice of creating daylight-like conditions in a specified location. In most cases, the target area lacks the support of bright fixtures and access to natural sunlight via windows or skylight panels. Furthermore, the building could be located next to massive establishments, such as tall buildings, towers and trees; or the facility could be located underground. When setting up lighting systems that incorporate daylight conditions, one must take several factors into consideration, such as the following:
• Reflectance of surfaces
• Type of work being conducted in the area
• Visual capabilities of employees
• Location of windows and skylight panels
• Glazing or tints on windows and panels
• Furniture or positioning of desks, workstations, machinery and computer monitors
• Amount of natural daylight entering the facility during different times of the day
Based on the factors above, one should carefully consider that some influential daylighting elements originate from the building’s initial design. Therefore, the fixed or permanent nature of such components must be taken into account, when carrying out a retrofit project. For instance, the reflectance of surfaces inside the facility is a factor that lighting specialists do not have direct control over during retrofit projects. Ideally, buildings should adhere to specific reflectance values of room surfaces to maximize daylight performance. These figures include up to 80 percent reflectance for ceilings, 50 percent for walls and 20 percent for floors.
To allow natural daylight to enter the facility, building designers may apply side-lighting strategies, which may also improve the location’s ventilation and scenic features. A daylight penetration depth of roughly 2.5 times the distance between the top part of the window and the sill is recommended to cater to side-lighting applications.
Light Dimming and Daylighting
Robust dimming controls are highly favored in buildings that require daylighting. This feature can help facilities create a consistent lighting environment for workers. During optimal daylight white conditions, operators may keep artificial light output to a minimum. As the day progresses and natural sunlight shifts to lower color temperature ratings and intensity levels, individuals may increase artificial light output. Buildings in areas with shifting sunlight patterns (summer solstice, autumn equinox and winter solstice- just to name a few) and facilities that are prone to extreme seasonal weather may find dimming controls beneficial.
Businesses may deploy a handful of dimming features to maximize control over the lighting system. Switching controls are applied to turn the fixture on/off when natural daylight exposure is at its peak. Stepped controls offer preset brightness or intensity levels in the building, while dimming controls provide fine-tuning options with gradual changes in the overall brightness of the lighting system. Such features can be applied in tandem with occupancy controls and timers for a cost effective approach.
LEDs and Tubular Daylight Devices
Light-emitting diodes (LEDs) are often used to mimic daylight white. The fixtures can reach the desired color temperature ratings needed to generate such conditions. Moreover, the lighting technology supports optimal Color Rendering Index ratings between 80 and 92 (for high-quality variants). This is relevant because natural daylight conditions are used by researchers as the benchmark for color rendering comparison with artificial fixtures. In 1948, PJ Bouma, author of Physical Aspects of Color (Philips technical library), helped establish the use of daylight as the standard for exceptional color rendering based on the following characteristics: wide variety of colors, aids in distinguishing different shades of color and promotes the natural color of objects.
A developing trend in harnessing daylight-white level conditions includes the installation of tubular daylight devices. The units are large prismatic tubes with built-in reflective surfaces. When installed properly, the devices harvest natural sunlight during the day, and a diffuser is applied to ensure that light is allocated generously in the space. For hard-to-reach locations, such as lower floors, the tubes can be extended up to 100 feet in length. This type of tubular lighting system was installed in a Macy’s Distribution Center warehouse located in Goodyear, Arizona. The 600,000-square-foot facility handles the company’s order fulfillments and customer shipments in the region.
Applying best daylighting practices requires observing recommendations in building design and artificial lighting systems. For smooth lighting transitions, luminaries should be grouped accordingly, in relation to the amount of natural daylight distributed over the target area. Most buildings incorporate around 10-15 feet of daylight illumination in spaces near windows and skylights. Grouped luminaries over this naturally well-lit area can easily be dimmed or controlled to match the lighting conditions of the room.
Daylight penetration from high points in the space, such as roof monitors and sky lights, decreases the risk of excessive brightness. If sunlight penetration is limited, the application of reflective surfaces may help improve daylight conditions in the building. Lastly, if natural daylight is excessive and contributing to visual strain, filters, such as plants, curtains and large decorative ornaments may be used to block or diffuse the light.