For years, acoustical ceilings have been known primarily for their functional value. They reduce the noise level within a space while allowing access to the plenum.

Today, however, advancements in light reflectance technology allow a new generation of acoustical ceilings to not only perform their traditional functions, but also help designers save up to 18 percent on lighting costs. The catalyst behind this development: the advance of light reflectance ceilings.

The ability of an acoustical ceiling panel to reflect light is indicated by its light reflectance value or LR. LRs range from 0 to 1 and denote the percent of light striking the panel that is reflected. For example, a LR of .75 means the panel reflects 75 percent of the light striking it.

Most commonly used acoustical ceilings have an LR of .7 to .81. High light reflectance ceilings have an LR of .82 or higher. The LR of a particular ceiling panel can usually be found on the manufacturer's data sheet.

The performance benefits of high reflectance ceilings were recently documented in a lighting economic study prepared by The Weidt Group, an independent building industry consulting firm that specializes in architectural design, energy research and analysis and software development.

The study was conducted to determine how a new acoustical ceiling with an especially high LR of .89 performed with different types of light fixtures compared to other ceilings.

The study found that high reflectance ceilings provide a significant increase in light level for any type of fixture system. For example, when compared to a ceiling with a .75 LR, a .89 LR ceiling can increase light levels up to 25 percent when indirect lighting is installed, up to 18 percent with direct/indirect lighting and up to four percent with direct lighting.

According to Weidt researchers, the substantial improvement in light for indirect systems results from the ceiling performing as an integral part of the lighting distribution system.

Indirect lighting systems are those in which the lighting fixtures are positioned below the ceiling plane and directed up at it. Indirect systems are becoming increasingly popular because they provide a more evenly-distributed light with fewer shadows and less glare, thereby improving visual comfort. This is especially important in spaces such as open office plans where annoying reflections on computer screens can decrease productivity.

The study also found that upgrading ceilings from the typical .75 LR to .89 LR in spaces lit with indirect lighting fixtures can result in 18 percent reductions in both initial costs and ongoing operating costs.

The savings in initial costs is possible because the increase in light level per fixture allows for the installation of fewer fixtures in a space for any given required foot-candle level. In the case of indirect systems, up to 20 percent fewer fixtures are needed.

Every fixture that is not required to provide the specified light level reduces the cost of purchasing and installing the fixture, the cost of wiring the fixture, the cost of providing chiller and other HVAC capacity to remove the heat generated by the lights and the cost of wiring the HVAC components.

While first costs are a one-time affair, savings on building operating costs continue year after year. That's because when less fixtures are installed, less energy is needed to power them, less energy is needed to remove the heat they generate and less money is spent on replacement parts (such as lamps and ballasts) and less labor needed to maintain the system.

Even when the number of fixtures cannot be reduced, operating costs savings can still be realized through the use of dimming ballasts that reduce light output until it matches the required light level in the space. Reducing the light level reduces the energy needed to operate the system.

Study findings also show that higher reflectance ceilings increase the benefits of daylight by increasing both the light level within the space and the penetration of the light into the space. For example, a .89 LR ceiling increased daylight levels 15 to 20 percent at a distance of 12 to 22 feet from a window when compared to a .75 LR ceiling.

Finally, the study points out that the use of high light reflectance ceilings can help building owners and managers stay within energy budgets dictated by national and local codes, including both the current and soon-to-be-adapted versions of ASHRAE/IES 90.1. High light reflectance ceilings also are an environmentally responsible design solution because they help minimize energy consumption. Note: a copy of The Weidt Group study described in this article is available at no charge. Call (800) 448-1405 and ask for "Performance Benefits of High Reflectance Ceilings."

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