Acoustic ceiling tile, or ACT, buffers sound transmission in thin-walled, hard-floored buildings. Common in college dormitories, business and hospital settings, acoustic ceiling tile allows students to concentrate more fully, business meetings to flow without distraction, and patients to sleep uninterrupted. When installed to suspend from a ceiling, these tiles also mask wiring and ductwork. An often-overlooked benefit of these tiles is the light-reflecting property that brightens rooms and reduces electric bills.
Acoustical Ceiling Tile Materials
The most common materials used in the impact-resistant tiles are mineral wool and fiberglass wool. Mineral, or stone, wool comes from melted slag and basalt. Fiberglass wool comes from melted sand, limestone and soda ash. Both substances are spun into fibers and injected with binders. Acoustical ceiling tiles of either material typically have off-white, white or black matte finishes. The light-reflecting tiles may be smooth or fissured.
Measuring ACT Light Reflectance
ASTM International, formerly the American Society for the Testing of Materials, has developed a standardized method for testing light reflectance. It applies to a range of different materials, including those used in ACT. The test, ASTM E-1477, measures the tiles' light reflectance against the light reflectance from a perfect reflecting diffuser. This is a nonabsorbent, non-transmissive surface. It reflects equal intensities of light in every direction. A single number, or luminance reflectance factor, expresses each tested tile's light-reflectance level compared to that of the PRD. It also predicts how much a tile will increase a room's illumination.
Degrees of ACT Light Reflectance
Most white ACT ceilings have light reflectance values between 0.75 and 0.90, according to a 2008 Armstrong Building Products study presented at Acoustics '08 Paris. Armstrong's research states that white ceilings with a 0.90 LR value reflect 90 percent and absorb 10 percent of incident light. Those with a 0.75 LR value reflect 75 percent of the light. Factors affecting light reflectance include texture and paint. Most ceilings with LR values exceeding 0.85 pair smooth textures with high-quality, refractive paint. White paint containing titanium oxide pigment provides high light reflectance. Fissured, dark-colored ceilings reflect the least amount of light.
ACT Light Reflectance by Material
Many ACT ceilings have fiberglass-mat backings. These mats, or veils, support the tiles and create a smooth surface for painting. The Armstrong Building Products study lists the varying LR values of veiled and non-veiled ACTs. The highest measured LR values, between 0.81 and 0.90, belong to white, veiled fiberglass, mineral or mixed wool tiles. Smooth, veiled slag wool tiles earned the lowest LR measurements, between 0.70 and 0.90 percent. The values of similar products vary widely, depending on their manufacturers. The study indicates that advertised LR values for all ACTs are in their higher ranges.
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