(Continued)

Visit the EDR website at:www.energydesignresources.com

In the world of leading-edgecommercialbuilding design,acoustical ceilingtile hasn’texactly been anexciting topic.It’s been doingits job, reducingnoise levelswithin a spacewhile allowingaccess to theplenum. Recentadvances help buildingdesigners to use this formerly ho-hum building material as a keyelement in an energy-saving, environmentally friendly lightingdesign. High light reflectance ceiling panels can benefit alllighting schemes, although the greatest energy and capital costsavings come with the use of indirect lighting.

The ability of an acoustical ceiling tile to reflect light isindicated by its Light Reflectance value (LR), or the percentageof light striking the panel that is reflected. LRs range from 0.00to 1.00, so an LR of 0.75 means the panel reflects 75 percent ofthe light striking it. Commonly used acoustical ceilings have anLR of 0.70 to 0.81, but high light reflectance ceilings have anLR of 0.82 or higher.

Benefits for Indirect Electric LightingHigh light reflectance ceilings can increase a designer's abilityto use indirect lighting more efficiently. Indirect lighting systemsprovide a brighter, more evenly distributed light with fewershadows and less glare than direct systems. To complementthese features, high light reflectance ceilings provide balanced

Some Strategies to Maximize

Daylighting Systems

• Use light shelves combined with higher, morereflective ceilings to control glare and excessivecontrast, as well as to bring natural light deeperinto perimeter spaces.

• Shape the architectural plan and section to maximize the amount of useful, controlled daylightthat penetrates into occupied spaces through roofmonitors, clerestories, atriums, and courtyards.

• Use shading devices such as overhangs on southelevations, vertical fins on east and west elevations,and/or vegetation to let in natural light but reduceglare and overheating.

• Select glazing with the highest possible visibletransmittance to increase daylighting.

• Use appropriate photocontrols to adjust electriclighting in response to available daylight.

From the Sustainable Design Guide of theUniversity of Minnesota www.sustainabledesignguide.umn.edu

A Reflection on Your Expertise:New Ceiling Materials that Enhance the Efficiency of Your Lighting Design

energydesignresources.com e-News Issue 33 May 27, 2001

Photo credit: Lawrence Berkeley National Laboratory

High reflectance ceilings can increase light levels and

save energy in most lighting strategies.

lighting diffusion due to their consistent surface finish and lower lighting loss factor because their soil-resistant surfacesremain reflective. In addition, high reflectance ceilings provide a significant increase in light level, according to a lightingeconomic study prepared by The Weidt Group, an independentbuilding industry consulting firm. For example, when comparedto a ceiling with a 0.75 LR, a 0.89 LR ceiling can increase light levels up to 25 percent with indirect lighting, up to 18percent with direct/indirect lighting, and up to four percent with direct lighting.

The Weidt study also found that upgrading ceilings from thetypical 0.75 LR to 0.89 LR in spaces lit with indirect fixturescan result in 18 percent reductions in both initial costs andongoing operating costs. The savings in initial costs are possiblebecause the increase in light level per fixture allows for theinstallation of fewer fixtures in a space for any given requiredfootcandle level. In the case of indirect systems, up to 18 percentfewer fixtures are needed. Savings on building operating costscontinue because when fewer fixtures are installed, less energyis needed to power them and remove the heat they generate, andless money is spent on replacement parts and labor.

Benefits for DaylightingHigh reflectance ceilings also increased the benefits ofdaylighting because the principal light distribution mechanism is the ceiling. Technological advances in fenestrationconfigurations have improved the lighting levels available withenergy-saving passive daylighting techniques. Features such as louvers, prisms, or light-transmitting fibers placed inside the airspace can direct daylight up to the ceiling surface where it may be reflected into the workspace. The angle of reflection can be adjusted to account for building geographic location and orientation of the particular side of the building. Passivesolutions offer the advantage of flexibility, effectiveness,energy savings, and virtually no maintenance for the owner.

Ceilings are an important part of that light distribution system. If the ceiling is highly reflective, it increases the effectiveness of the daylighting strategy. These surfaces increase the lightlevel within the space and the penetration of the light into the space. For example, the Weidt study showed that a 0.89 LR ceiling increased daylight levels 15-20 percent at adistance of 12-22 feet from a window when compared to a 0.75 LR ceiling.

Ceilings and Indoor Air Quality

Ceilings have strong impacts on the indoor airquality. Along with upholstery and carpet, ceilingshave the most potential to absorb hazardouschemicals and release them into the environment. The most environmentally sound ceilings are made of natural materials that do not release volatileorganic compounds. Perlite, ceramic clay, andinorganic binders are categorized as natural materials.All of these materials are non-flammable so they willnot burn or emit toxins nor will they encourage mold,mildew, or bacteria. Highly reflective ceilings workwith the climate control in the area because they helpto distribute heat throughout the area.

The leading manufacturers of ceiling materials arenow including a significant proportion of recycledcontent in their product lines, including the energy-saving high reflectance products.

Benefits in a High Performance Integrated Building DesignFollowing an integrated design approach using a raised floorsystem, high reflectance ceilings have an even greater impact. In addition to maximizing electrical/teledata flexibility, thecavity between the structural slab and the raised floor planecreates a supply air plenum. Relocatable floor-mounted diffusersin every workspace allow for individual air volume andtemperature control.

Using this approach, the ceiling is free of supply air diffusersand acts as an uninterrupted reflecting surface for pendantmounted indirect illumination, a system of split task/ambientlighting. By utilizing state-of-the-art high reflectance ceilingtiles, ambient lighting can be reduced from 100 footcandles atthe work surface to only 30 footcandles. This reduces thenumber of required light fixtures, lowering lighting energyconsumption by 20 to 30 percent. It also decreases the heat loadgenerated by these lights, which in turn further reduces requiredchiller capacity. Task lighting can be controlled by motionsensors to further reduce energy consumption.

As a result, these integrated technologies also dramaticallyimprove light and air quality. This translates directly intopositive impacts on the comfort and productivity of officeworkers while reducing energy consumption.

For more information on high reflectance ceilings, see “Look Up to Bring Down Lighting Costs” by William Beakes,a research scientist with Armstrong World Industries, atwww.isdesignet.com/Magazine/Oct'96/Lightingcosts.html

You can also request a free copy of the Weidt Group study,“Performance Benefits of High Reflectance Ceilings,” by calling(800) 448-1405.

For a case study of an integrated building design using highreflectance ceiling design, seewww.gggc.state.pa.us/building/scrobhpis.html

Energy User News 2001 Efficient

Building Awards

Energy User Newsis soliciting nominations for itsannual energy efficiency and building awards.Winning installations will be announced and profiledin the December issue. Awards will be presented at abreakfast held in Atlanta in October, concurrent withthe World Energy Engineering Congress.

The awards recognize innovations in building management and energy efficiency–in either retrofitsor new construction throughout North America–thatprovide unique building solutions and also achieve significant energy and cost savings. To be eligible forthe 2001 competition, projects must have entered service no earlier than May 1, 2000, and have actualoperating data from at least three consecutive months.Nominations are due by August 15, 2001.

The nomination form is available at www. energyusernews.comor by calling Nikki Smithat (248) 244-6479. For more information, contactKevin Heslin, (518) 731-7311,kevineun@earthlink.net.

U.S. Green Building Council

Fourth Annual Member Summit

"Green Building University"Loews Ventana Canyon Resort, Tucson, ArizonaAugust 20-21, 2001Pre-Summit Events: August 18-19Post-Summit LEED Workshop: August 22 For more information, see www.usgbc.org.