Where To Obtain Light Reflectance Values

One of the most searched topics on the LightNOW website is “sources for reflectances.” This article is intended as an introduction on where to locate light reflectance values (LRVs) for different building materials / surfaces.

Room-surface reflectance should be based first on the specified product—not a generic “ceiling/wall/floor” default. The most defensible sources are manufacturer-published light-reflectance data, standardized color-system data, and project-specific measurement when finishes are unusual, critical, or not yet reliably documented.

Lighting calculations are only as credible as their room-surface assumptions. Yet ceiling, wall and floor reflectances are often entered as a familiar 80/50/20 combination and left unchallenged—even when the architectural concept includes charcoal acoustic ceilings, exposed concrete, dark carpet, wood slats, glass partitions or highly textured finishes.

Those default values are useful starting points, but they are not a substitute for material-specific data. In a building where reflected light contributes substantially to perceived brightness, vertical illuminance, uniformity and the performance of indirect lighting, the best source of reflectance information is usually the project’s actual finish specification.

For paint, the first stop should be the paint manufacturer’s published Light Reflectance Value (LRV). Major paint suppliers commonly list LRV in color decks, technical data, online product pages and digital specification tools. LRV generally expresses the amount of visible light reflected by a surface on a 0-to-100 scale: higher numbers indicate lighter, more reflective colors. Because paint color may change late in design, lighting teams should obtain the final color code and sheen—not merely a description such as “white” or “light gray.”

Sheen deserves attention. A paint’s LRV can be useful for a diffuse-reflectance assumption, but a glossy or semigloss coating may introduce directional, or specular, reflections that a simple room reflectance input cannot fully capture. In spaces with video displays, visual-task requirements, glare-sensitive workstations or prominent indirect lighting, the finish’s gloss level should be documented alongside its LRV.

For ceilings, walls and specialty interior products, request technical literature directly from the product manufacturer. Ceiling-system suppliers, acoustic-panel manufacturers, wallcovering firms, flooring suppliers, tile companies and furniture manufacturers may publish light-reflectance, luminous-reflectance-factor or spectral-reflectance data. These manufacturer declarations are usually more valuable than a generic material table because they relate to a defined product, colorway, texture and finish. Ecophon, for example, publishes ceiling light-reflectance information and describes measurement using a recognized British Standard and CIE viewing and illuminant conditions.

When project documents are incomplete, standard color systems can provide a useful secondary source. Systems such as RAL publish color information that can support preliminary LRV assumptions, while paint brands’ color libraries often provide equivalent data for their proprietary palettes. However, a nominal color match should not be treated as proof that two materials have identical optical behavior. A cream-colored carpet, matte wall paint and textured acoustic panel may look similar under one light source while producing materially different reflectance and scatter characteristics.

Published reference tables remain helpful for early design, budgeting and sensitivity analysis. Typical guidance commonly uses reflectances near 80% for ceilings, 50% for walls and 20% for floors; ANSI/ASHRAE/IES Standard 90.1 has historically used that 80/50/20 convention as a representative baseline. Tables can also establish plausible ranges: light veneers may be around 40%, medium wood around 20%, dark carpet around 10%, and cement around 40%, but these should be treated as approximations rather than design facts.

A practical source hierarchy

Use this hierarchy when building a calculation model:

1. Measured installed sample or in-situ measurement for critical projects, unusual finishes, renovations and high-consequence spaces.
2. Manufacturer technical data for the exact specified product, color and finish.
3. Paint-brand or standardized color-system LRV data for identified colors where product-specific optical data is unavailable.
4. Published technical reference tables for preliminary assumptions and generic materials.
5. Documented default assumptions only when no better information exists.

Measurement becomes especially valuable when the surface is aged, dirty, porous, patterned or heavily textured. A clean white acoustic tile, for example, cannot be assumed to retain its initial reflectance after years of airborne soil accumulation. Likewise, exposed concrete can vary significantly with aggregate, sealing, moisture, formwork pattern and finish.

Model the room, not the label

The central lesson is simple: “white ceiling,” “gray wall” and “dark floor” are not optical specifications. A white plasterboard ceiling may have a reflectance near 0.80, while a white acoustic tile, open-cell ceiling or textured concrete surface may behave differently. Published tables show similarly wide spreads among common finishes, including light-gray carpet, timber, tile, brick and concrete.

For lighting designers, the workflow should be to obtain the finish schedule early, identify the largest and most influential visible surfaces, request LRV or reflectance documentation, and record every assumption in the calculation report. When exact values remain uncertain, model a reasonable range—such as a nominal case and a darker-case sensitivity test—rather than presenting a single optimistic reflectance input as fact.

That discipline improves more than photometric accuracy. It helps project teams understand whether lighting performance depends on a bright ceiling, pale walls or a floor finish that may later change. In an era of tighter energy targets and increasingly architectural interiors, reflectance data should be treated as a design input with the same importance as luminaire output, optics and controls.

More information is available here and here.

Top image is AI-generated.

David Shiller

David Shiller is the Publisher of LightNOW, and Senior Business Development Consultant at Capacity Consulting, a North American consulting firm providing business development services to advanced lighting manufacturers. The ALA awarded David the Pillar of the Industry Award. David has been co-chair of the ALA’s Engineering Committee since 2010. David established MaxLite’s OEM component sales into a multi-million dollar division. He invented GU24 lamps while leading ENERGY STAR lighting programs for the US EPA. David has been published in leading lighting publications, including LD+A, enLIGHTenment Magazine, LEDs Magazine, and more.

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