Commercial Lighting Glossary

A plain-language guide for property managers, facilities management, and purchasing departments.

Light Measurement & Quality

Color Rendering Index (CRI)

CRI is a scale from 0 to 100 that measures a light source's ability to accurately reveal the colors of objects. A value of 80 or higher is standard for most commercial applications. Retail, healthcare, and food service environments typically require CRI 90+. FSG's guide to CRI and color temperature covers both metrics side by side.

Color Temperature

Color temperature is the general term for how warm or cool a light source appears, measured in Kelvins. It is often used interchangeably with CCT. The right color temperature for a given space has meaningful implications for productivity, safety, and how the space presents to occupants and visitors.

Correlated Color Temperature (CCT)

CCT describes the color appearance of light emitted by a fixture, measured in Kelvins (K). The range of 2700K to 3000K produces warm, amber-toned light. The range of 3500K to 4000K is neutral white, common in offices and retail. The range of 5000K to 6500K produces cool, daylight-like light used in warehouses and industrial spaces. FSG's CRI and color temperature guide covers both CCT and CRI together.

Foot-Candle

A unit of light measurement that represents the amount of light that actually hits a surface. One foot-candle represents the light produced by one candle on a surface that is one foot away. Foot-candle is the most common unit of measurement for determining the level of brightness required in a commercial environment. To learn more, see FSG's full breakdown of foot-candle measurements.

Glare

Glare is excessive brightness within a person's field of view that causes discomfort or reduces visibility. In commercial environments, uncontrolled glare from improperly aimed or unshielded fixtures can cause eye strain and safety issues. Glare is managed through fixture shielding, optical design, and proper mounting height.

Lumen

A unit of measurement that represents the total amount of visible light emitted from a light source. The higher the lumen rating, the more light the source produces. When comparing LED fixtures to older fluorescent and HID fixtures, lumens, not watts, indicate the actual level of brightness.

Lumen Output

Lumen output represents the total amount of light emitted by a fixture under real-world operating conditions. This may differ from the manufacturer's initial rated lumens. When comparing fixtures, always compare lumen output, not just the lumens rating of individual lamps.

Luminous Efficacy

Luminous efficacy measures how efficiently a fixture converts electrical power into visible light, expressed in lumens per watt (lm/W). The higher the lm/W value, the more efficient the fixture. Modern LED fixtures typically range from 100 to 160+ lm/W, compared to 50 to 80 lm/W for traditional fluorescent fixtures.

Lux

Lux is the metric system equivalent of the foot-candle. It represents the amount of light, measured in lumens, distributed over one square meter. To convert foot-candles to lux, multiply the foot-candle value by 10.76.

Uniformity Ratio

Uniformity ratio measures how evenly light is distributed across a surface. It is expressed as the ratio of minimum illuminance to average illuminance (min/avg). A ratio close to 1.0 indicates consistent, even illumination. Low uniformity is a concern in parking lots, warehouses, and sports facilities, where bright and dark patches create safety hazards.

LED Technology

Ballast

A ballast is the power control device used in older fluorescent and HID fixtures, performing a similar function to an LED driver. Many LED retrofit projects involve bypassing or removing the existing ballast rather than replacing it. Ballast-compatible LED lamps (Type A) do not require rewiring, while ballast-bypass lamps (Type B) require minor electrical modifications.

DLC (DesignLights Consortium)

The DesignLights Consortium (DLC) is a nonprofit organization that maintains a qualified products list (QPL) of energy-efficient commercial lighting. DLC listing is required by most utility rebate programs in the United States. Products are listed at Standard or Premium tiers, with Premium products qualifying for higher rebate amounts. FSG's utility incentives team can identify which DLC-qualified products maximize rebate eligibility for your project.

ENERGY STAR (Lighting)

ENERGY STAR is a U.S. EPA certification mark for products that meet specific energy efficiency and quality standards. While DLC is the more commonly referenced standard in commercial retrofit projects, ENERGY STAR certification can also qualify products for certain utility incentive programs.

High-Bay Fixture

A high-bay fixture is designed for spaces with ceiling heights of 20 feet or more, such as warehouses, manufacturing facilities, and large retail environments. High-bays generate focused, high-intensity light to illuminate large vertical distances effectively. LED high-bays have replaced traditional metal halide and fluorescent fixtures due to substantial energy savings. FSG's industrial lighting division specializes in high-bay applications.

Lamp vs. Fixture (Luminaire)

A lamp is the light source itself, while a fixture (also called a luminaire) is the complete assembly that houses the lamp, driver, and optics. In commercial LED systems, the lamp and driver are often integrated into the fixture and are not separately replaceable components.

LED (Light Emitting Diode)

LED is a semiconductor light source and the dominant technology in commercial lighting today. LEDs are energy-efficient, long-lasting, and versatile. Most commercial LED products have a rated lifespan of 50,000 to 100,000 hours, significantly longer than fluorescent or HID alternatives. See how the LED investment stacks up for commercial facilities.

LED Driver

An LED driver is the electrical supply unit that controls the flow of current into an LED fixture. It converts AC power to the DC power LEDs require. Driver quality is a critical factor in fixture lifespan and dimming performance. FSG supplies a full range of commercial lighting products, including drivers, fixtures, and controls.

Linear Fluorescent

Linear fluorescent lamps are long, tube-style lights that were formerly standard in commercial environments. Common formats include T8 (1-inch diameter) and T5 (5/8-inch diameter). Most linear fluorescent products are being phased out in favor of LED alternatives due to federal efficiency regulations and significantly better LED performance. FSG covers the fluorescent ban and what it means for your facility.

Low-Bay Fixture

A low-bay fixture is designed for spaces with ceiling heights between 12 and 20 feet. Low-bays are commonly used in smaller warehouse environments, maintenance facilities, and smaller retail environments. They produce a wider beam spread than high-bays to ensure even coverage at lower mounting heights.

Lumen Depreciation

Lumen depreciation is the gradual reduction in light output that occurs over the life of an LED fixture. All light sources depreciate over time; the rate at which they do so is what matters. High-quality LED fixtures typically retain 90% or more of their original output for the first several years before depreciation begins. Lumen depreciation is what the L70 rating is designed to measure.

Luminaire

A luminaire is the complete, functional lighting unit including the light source, housing, optics, and driver. The term is commonly used in engineering, specifications, and building code documents. When a lighting proposal references luminaires, it refers to complete fixture assemblies, not individual lamps or components. FSG offers a broad range of commercial lighting fixtures and products.

Rated Life / L70

Rated life is the expected lifespan of a light source under normal operating conditions. For LED products, this is expressed as L70: the point at which light output has declined to 70% of its original output. A fixture rated at L70/50,000 hours will maintain at least 70% of its original brightness through 50,000 hours of operation.

Retrofit Kit

Retrofit kits are upgrade packages used to convert an existing fixture to LED without full fixture replacement. They preserve the existing housing while replacing the light source, driver, and optics, with minimal installation time and labor. Retrofit kits are commonly used in commercial spaces where removing existing fixtures is not practical. Learn about FSG's commercial lighting retrofit services.

T8 / T5 Lamp

T8 and T5 refer to the diameter of fluorescent tube lamps, measured in eighths of an inch (T8 = 1 inch diameter, T5 = 5/8 inch diameter). These were the most common commercial fluorescent formats. LED replacements are available in both direct-fit and retrofit-kit formats and typically deliver 40 to 60% energy savings compared to their fluorescent counterparts.

Lighting Controls

0-10V Dimming

0-10V is the most widely used dimming protocol in commercial LED lighting. A low-voltage control signal between 0 and 10 volts tells the driver how much to reduce its output: 10V equals full brightness, 0V equals minimum output. It is straightforward to implement and compatible with a wide range of fixtures and control systems. FSG's guide to commercial lighting controls explains dimming protocols and how to choose between them.

DALI (Digital Addressable Lighting Interface)

DALI is a two-way digital communication protocol for commercial lighting control. Unlike 0-10V, DALI allows each individual fixture to be addressed, monitored, and adjusted independently. It is used in facilities that require sophisticated control, such as individual fixture feedback, group zoning, and fault reporting. DALI adds cost and complexity but provides significantly greater flexibility. See FSG's lighting controls capabilities for more on advanced control options.

Daylight Harvesting

Daylight harvesting is a lighting control strategy that automatically dims or adjusts electric light levels based on available natural light. Sensors measure ambient light and reduce fixture output accordingly, maintaining target illuminance while reducing energy use. It is commonly used near windows, skylights, and roof monitors. FSG's lighting controls page covers daylight harvesting as part of a broader controls strategy.

Dimming

Dimming allows lighting output to be adjusted to any level between full brightness and minimum output, rather than simply turning lights on or off. In commercial applications, dimming reduces energy consumption, extends fixture life, and enables scene control in multi-use spaces. Dimmable LED systems require compatible drivers and control equipment.

Lighting Control System

A lighting control system is any combination of hardware and software used to manage how, when, and at what level lights operate. Systems range from simple occupancy sensors to fully networked platforms that integrate with building management systems. The right system depends on facility size, complexity, and operational goals. Explore FSG's commercial lighting controls offerings.

Networked Lighting Controls

Networked lighting controls connect individual fixtures or groups of fixtures to a centralized software platform, enabling facility-wide monitoring, scheduling, and adjustment from a single interface. These systems can track energy use, report faults, and integrate with building automation systems. They are most cost-effective in large facilities with complex operational needs. FSG's lighting controls team can assess whether networked controls are a fit for your facility.

Occupancy Sensor

An occupancy sensor turns lights on when it detects movement in a space and off after a set period of inactivity. Occupancy sensors are one of the most cost-effective controls for commercial spaces with intermittent use, such as restrooms, conference rooms, storage areas, and stairwells. They can reduce lighting energy use by 30 to 60% in applicable spaces. FSG's lighting controls services include occupancy sensor specification, installation, and commissioning.

Photocell / Daylight Sensor

A photocell is a sensor that responds to ambient natural light levels and adjusts or switches lighting accordingly. In exterior applications such as parking lots, photocells turn lights on at dusk and off at dawn. In interior applications, they work alongside daylight harvesting systems to reduce output when sufficient natural light is present. FSG's parking lot lighting services include photocell and control integration.

Time Clock / Scheduling

A time clock or scheduling system automates lighting based on time of day and day of week. Scheduling is the simplest and lowest-cost form of lighting control. It is commonly used in parking lots, exterior applications, lobbies, and facilities with predictable occupancy patterns.

Energy & Financial

DLC-Qualified Product

A DLC-qualified product appears on the DesignLights Consortium's Qualified Products List (QPL) and meets established efficiency and performance standards. Most utility rebate programs in the U.S. require DLC listing as a condition of eligibility. Products at the DLC Premium tier meet higher efficacy thresholds and typically qualify for larger rebate amounts. FSG's utility incentives page explains how DLC qualification affects rebate amounts by market.

Energy Savings Guarantee

An energy savings guarantee is a contractual commitment that a lighting or energy upgrade will deliver a specified level of savings. If savings fall short, the contractor covers the difference. This model reduces financial risk for facility owners and is commonly used in large-scale projects funded through Energy as a Service arrangements.

kWh (Kilowatt-Hour)

A kilowatt-hour (kWh) is the standard unit used to measure electricity consumption and the basis for commercial utility billing. One kWh equals 1,000 watts of power used for one hour. Lighting energy savings are typically calculated and reported in kWh per year, then converted to dollar savings using the local utility rate.

Lighting Audit

A lighting audit is a systematic assessment of an existing lighting system that documents fixture types, quantities, wattages, operating hours, and current energy costs. The audit output is used as the basis for a retrofit proposal and ROI analysis. A professional audit also identifies code compliance gaps, maintenance issues, and control opportunities. FSG's guide to conducting a lighting audit walks through the process step by step.

Lighting Retrofit

A lighting retrofit is the process of replacing existing lighting with a more efficient system, most commonly upgrading fluorescent or HID systems to LED. Retrofits range from simple lamp swaps to full fixture replacements and can include control upgrades. Most commercial retrofits pay back the project cost through energy savings within 2 to 5 years. Read about the benefits of a commercial lighting retrofit, or explore FSG's retrofit services.

Simple Payback Period

Simple payback period is the amount of time required for the energy savings from a lighting upgrade to equal the upfront project cost. It is calculated by dividing the total project cost by the annual energy savings. For most commercial properties, the payback period on a lighting retrofit falls between 2 and 4 years, depending on operating hours, utility rates, and available rebates.

Utility Rebate

A utility rebate is a financial incentive offered by a utility company to customers who upgrade to more energy-efficient equipment. For commercial properties, rebates can offset 20 to 50% of total project costs in many markets. Most programs require DLC-listed products and documentation of the system being replaced. FSG's utility incentives team manages the rebate application process on behalf of clients.

Watts vs. Lumens

Watts measure how much power a light source consumes, not how much light it produces. For many years, wattage was used as a proxy for brightness because higher-wattage bulbs were brighter. With LED technology that relationship no longer holds: a 25-watt LED fixture can produce more light than a 100-watt fluorescent. Lumens are the correct unit for comparing brightness between light sources.

Project & Process

Fixture Layout

A fixture layout is a plan showing the proposed placement, spacing, and aiming of light fixtures within a space or on a site. It is developed alongside the photometric plan and is used for permitting and installation coordination. A well-developed fixture layout is critical to achieving target foot-candle levels and uniformity ratios across the project.

Lighting as a Service (LaaS)

Lighting as a Service is a model in which a facility pays a fixed monthly fee for a fully upgraded lighting system rather than a large upfront capital expenditure. The provider funds the installation and retains ownership of the equipment, delivering the benefits of a modern lighting system without capital budget impact. FSG's Energy as a Service program applies a similar model to broader facility energy upgrades.

Lighting Design / Photometric Plan

A photometric plan is a technical drawing produced using lighting simulation software that models how light from proposed fixtures will distribute across a space. It shows predicted foot-candle levels and is used to verify that the design will meet specified targets before installation. Photometric plans are a standard deliverable in commercial lighting proposals. FSG's commercial lighting design services include photometric planning for new construction and retrofits.

Lighting Specification

A lighting specification, or lighting spec, is a formal document that defines the technical requirements for a lighting project, including fixture types, performance standards, mounting requirements, control integration, and warranty expectations. Specifications are used in bidding, procurement, and construction documentation to align all parties on what is being installed.

Maintained Illuminance

Maintained illuminance is the average light level across a surface after accounting for lumen depreciation, dirt accumulation, and other real-world factors over time. Lighting standards and specifications are written around the expected maintained illuminance level, not the initial output of new fixtures.

National Account Program

A national account program is a service structure that allows a single contractor to manage lighting or electrical projects across multiple locations under a consistent pricing, scope, and reporting framework. It is particularly beneficial for organizations with multiple locations, such as retail chains, property management firms, and healthcare systems. FSG's national lighting program serves clients with 5 to 500+ locations.

Photometric Study

A photometric study is a more in-depth analysis of a lighting system's performance, often evaluating multiple design alternatives. It may examine tradeoffs between fixture spacing, mounting height, and target illuminance levels. Photometric studies are common during the design phase of new construction, major renovations, and large outdoor lighting projects.

Turnkey Installation

Turnkey installation means the contractor manages the entire scope of work: procurement, installation, controls programming, and commissioning. The client receives a fully operational system without needing to coordinate individual vendors or trades. Turnkey delivery simplifies project management and consolidates accountability for the facility operator.

Facility-Specific Standards & Requirements

ASHRAE 90.1

ASHRAE 90.1 is the primary commercial building energy efficiency standard in the United States, published by the American Society of Heating, Refrigerating and Air-Conditioning Engineers. It establishes maximum lighting power density (LPD) limits by building type and space category. Most U.S. commercial building energy codes are based on or reference ASHRAE 90.1, making compliance a baseline requirement for new construction and major renovation projects.

Dark Sky Compliant / Full Cutoff

Dark sky compliant fixtures direct light downward to prevent it from escaping upward into the night sky. Full cutoff is the technical classification for a fixture that emits no light at or above the horizontal plane. Many municipalities require full cutoff fixtures for parking lots, street lighting, and other exterior installations to reduce light pollution and comply with local ordinances. FSG's parking lot lighting services include full cutoff and dark sky compliant fixture options.

Emergency Lighting

Emergency lighting refers to fixtures that automatically activate during a power failure to provide minimum illumination for safe egress. Commercial buildings are required by the NEC and local fire codes to maintain emergency lighting in corridors, stairwells, and exit paths. Systems include both battery backup fixtures and central emergency power solutions.

Exit Sign / Egress Lighting

Exit signs are illuminated signs that mark emergency egress routes and are required in virtually all commercial occupancies. Modern LED exit signs consume 2 to 5 watts, compared to 20 to 40 watts for older incandescent models. Egress lighting refers to the broader system of emergency lighting and exit signage that ensures occupants can evacuate safely during a power failure or emergency.

Hazardous Location Lighting

Hazardous location fixtures are engineered and certified for environments where flammable gases, vapors, dust, or fibers may be present, such as chemical plants, oil refineries, grain storage facilities, and paint booths. These fixtures must meet NEC classification requirements and carry appropriate UL or CSA certifications. FSG's industrial lighting division handles hazardous location lighting projects nationwide.

IES (Illuminating Engineering Society) Standards

The Illuminating Engineering Society (IES) publishes illuminance recommendations and lighting quality standards for virtually every commercial space type, from offices and classrooms to warehouses and sports fields. IES standards are the most frequently referenced benchmarks in commercial lighting design. FSG's industrial lighting standards guide applies IES recommendations to warehouse and manufacturing environments.

IP Rating (Ingress Protection)

An IP rating is a two-digit code that defines a fixture's level of protection against solid particles and liquids. For example, an IP65 rating indicates the fixture is fully dust-tight and protected against direct water jets. IP ratings are critical when selecting fixtures for food processing facilities, car washes, industrial environments, and covered outdoor spaces.

Parking Lot Lighting Standards

Parking lot lighting standards define minimum foot-candle levels for vehicle driving areas, pedestrian walkways, and building entrances. IES RP-20 is the primary reference standard for parking facility lighting. Key metrics include average horizontal illuminance, uniformity ratio, and vertical illuminance. Vertical illuminance is particularly important for facial recognition and security camera performance. FSG's parking lot lighting services include photometric planning to IES RP-20 standards.

Sports Lighting (Foot-Candle Requirements)

Sports lighting is governed by IES standards and sport-specific regulatory bodies. Foot-candle requirements vary by sport, level of play (recreational or competitive), and whether the venue supports broadcast. Achieving proper uniformity ratios, not just average foot-candle levels, is critical for player visibility and camera performance. FSG's sports field lighting standards guide covers IES-recommended levels for football, baseball, soccer, tennis, and more.

Wet / Damp Location Rating

Lighting fixtures are rated for the environmental conditions in which they are approved to operate. A wet location rating applies to fixtures exposed directly to water, such as outdoor signage, covered walkways, and some parking structures. A damp location rating applies to fixtures exposed to moisture but not direct water contact. Installing an under-rated fixture in a wet environment creates safety hazards and voids the product warranty.