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CircadianLab — EML, Illuminance & Glare Calculator

CircadianLab is a free lighting analysis tool that calculates four key metrics: melanopic equivalent lux (EML) for circadian lighting design, illuminance in lux and foot-candles for general lighting analysis, UGR (Unified Glare Rating) for visual comfort assessment, and daylight through windows and skylights using NREL solar-position physics and a Perez sky model. Daylight and electric light are solved together in a single unified radiosity pass, so heatmaps reflect realistic combined illuminance from all sources.

Use it to design lighting layouts that meet WELL v2 Feature L03 requirements, verify illuminance levels against IES/CIE standards, evaluate glare comfort per CIE 117:1995, study daylight at any date, time, and location, compare fixture options, and generate professional reports — all in your browser with no signup required.

What is EML and Why Does It Matter?

Traditional lighting design focuses on photopic illuminance (lux) — how bright a space appears to the human visual system. But the non-visual effects of light on circadian rhythms depend on a different metric: melanopic equivalent daylight illuminance.

EML is calculated as: EML = Illuminance (lux) × Melanopic DER

The melanopic Daylight Equivalent Ratio (DER) depends on the spectral power distribution of the light source and varies with color temperature (CCT). At 6,000K (daylight), the DER is 1.0 by definition. Warm LEDs (2,700K) have a DER of ~0.44, meaning they produce less than half the melanopic stimulation per lux compared to daylight. High-CCT sources like Innerscene Circadian Sky at 200,000K achieve DER values of ~1.89.

WELL v2 Feature L03 — Circadian Lighting Design

The WELL Building Standard v2 requires spaces to provide adequate melanopic light at eye level for occupant health and wellbeing:

Tier 1: ≥150 melanopic EDI in at least one vertical direction at 1.2m (seated eye height)
Tier 2: ≥275 melanopic EDI in at least one vertical direction at 1.2m

This calculator checks compliance at every measurement grid point and reports the percentage that passes each tier. The vertical-direction requirement means ceiling-mounted downlights alone often fall short — wall-mounted fixtures at eye level can be far more effective for melanopic stimulation.

How the Simulation Works

Direct Illuminance

Each fixture's intensity toward every measurement point is computed using IES Type C photometry with inverse-square law attenuation and cosine incidence correction. Area sources use 12×12 subdivision integration.

Radiosity (Indirect Light)

A 3-bounce iterative radiosity solver computes form factors between all surface patches, then solves for inter-reflected light. This captures how walls, floors, and ceilings redirect light throughout the space.

Melanopic Conversion

Photopic illuminance is converted to EML using measured melanopic DER values. For Circadian Sky fixtures, a 22-point lookup table from real spectral measurements is used. Custom DER values can be provided for any fixture.

Directional Measurement

EML is computed in 5 directions at each grid point: horizontal (desk level) plus the 4 cardinal vertical directions (north, east, south, west) at eye height. WELL compliance requires only one vertical direction to pass.

Daylight Through Windows

Sun position uses the NREL Solar Position Algorithm; sky brightness uses a Perez clear/intermediate/overcast model. For each window aperture, direct sun and diffuse sky illuminance are added as initial flux on every radiosity patch and measurement point and bounced through the same form-factor network as the fixtures — daylight and electric light share one solve.

Validated Calculations

Every calculation in this tool is verified by an automated validation suite — 120+ tests covering inverse-square law, cosine incidence, radiosity energy conservation, IES lumen integration, melanopic DER accuracy, and WELL v2 compliance logic. Tests run against 20 IES photometric files from 8 manufacturers including BEGA, Philips, American Electric Lighting, and Innerscene.

Features

IES Photometry

Load real measured photometric data from IES files for accurate light distribution modeling

Circadian Sky Presets

All 5 Innerscene Circadian Sky sizes with measured melanopic DER data

Wall Fixtures

Mount fixtures on any wall with height and tilt control for eye-level melanopic stimulation

WELL Compliance

Automatic Tier 1/2 checking at every grid point with pass/fail statistics

CCT Control

2,200K to 200,000K with real-time EML recalculation using variable melanopic DER

PDF Reports

Professional reports with heatmaps for all directions, fixture schedule, and QR code

Share Links

Save and share your exact session — room, fixtures, camera angle, and results

Custom IES Upload

Upload any IES file with custom melanopic DER for third-party fixtures

3D Visualization

Interactive 3D room view with orbit controls, heatmap texture, and occupant models

Ceiling Grid Snap

Rotatable ceiling grid with fixture snap alignment for precise troffer placement

Illuminance (Lux/FC)

Calculate horizontal and directional illuminance in lux or foot-candles with inverse-square law and IES photometry

UGR Glare Analysis

Unified Glare Rating per CIE 117:1995 with directional heatmaps, Guth position index, and per-occupant evaluation

Floor Illuminance

Separate floor-level analysis for emergency egress and ambient light distribution

Daylight + Skylights

Add wall windows and skylights with configurable glazing; sun + sky at any date, time, and lat/lon are solved with the same radiosity engine as the electric fixtures

Lighting Term Glossary(78 terms — click to expand)

Airmass: The relative thickness of atmosphere the sun's beam passes through, approximately 1/sin(altitude). Airmass 1 = sun overhead; airmass 18 = sun about 2.5° above the horizon. Drives the attenuation of direct sun illuminance near sunrise and sunset.
ANSI/IES RP-46-25: 2025 recommended practice from the Illuminating Engineering Society for lighting's circadian, neuroendocrine, and neurobehavioral effects. Calls for a daytime minimum of 250 mel-EDI at the eye. Newer than the WELL Building Standard and increasingly cited by specifiers.
Artificial skylight: A luminaire that simulates a real skylight, typically combining a directional sun beam with a diffuse sky luminance and a depth illusion. Innerscene Virtual Sun is an example.
Artificial window: A luminaire that simulates a real window in a wall, providing a virtual exterior view in addition to circadian-active light.
ATMOS: Innerscene's 4-chip LED platform underlying the Circadian Sky product line. Enables a 2,200K–200,000K tunable CCT range while holding CRI ≥ 91 across the entire range.
Ballast factor: Multiplier in an IES file that scales reported candela values to account for the actual driver or ballast. CircadianLab applies the ballast factor when reading IES photometry.
Beam angle: The cone angle within which a directional luminaire's intensity is at least 50% of its peak value. Tighter beam angles concentrate light into a narrower cone — important for spots, accents, and high bays.
Bollard: Short outdoor pedestal luminaire, typically 3–4 ft tall, used for path and perimeter lighting.
Candela (cd): SI unit of luminous intensity — the strength of a light source in a specific direction. The numeric values in an IES file are candela values for each angle pair.
CCT (correlated color temperature): Color appearance of a white light source in kelvins (K). 2,700K is warm, 4,000K is neutral, 6,500K is daylight white. Higher CCT generally means a higher melanopic DER and more circadian effect per lux.
CIE 117:1995: International standard from the Commission Internationale de l'Éclairage defining the Unified Glare Rating (UGR) formula and methodology for indoor discomfort glare assessment.
CIE S 026:2018: International standard defining the α-opic metrics — including melanopic equivalent daylight illuminance (mel-EDI) — for measuring light's effects on the human non-visual system.
Circadian rhythm: The ~24-hour biological cycle that governs sleep, alertness, hormone release, and core body temperature. Synchronized day-to-day primarily by ipRGC light exposure.
Circadian Sky: Innerscene's tunable artificial-sky luminaire family. Five sizes, CCT range 2,200K–200,000K, CRI ≥ 91, and a melanopic DER up to about 1.89 — about 3.5× the melanopic stimulation per lux of a 2,700K LED.
Cosine incidence: Illuminance on a surface is reduced by cos(angle) when light strikes the surface off-normal. CircadianLab applies the cosine factor for every fixture-to-measurement-point pair.
CRI (color rendering index): How accurately a light source renders eight reference colors versus a reference illuminant of the same CCT, on a 0–100 scale. CRI ≥ 80 is office grade; CRI ≥ 90 is preferred for skin tones and art.
D65 (daylight reference): Standard daylight illuminant (~6,500K) used as the reference point for the melanopic DER. By definition, D65 has a melanopic DER of 1.0.
Daylight: In CircadianLab, the combined sun + sky contribution through windows and skylights. Solved in the same radiosity pass as electric fixtures, so heatmaps show realistic combined illuminance from all sources.
Diffuse sky: Light scattered by the atmosphere reaching the workplane from across the sky dome (rather than directly from the solar disc). Dominant under overcast skies and in shaded zones; modeled by the Perez sky model.
Direct beam: Light coming straight from the solar disc, attenuated only by atmospheric airmass. Strongest at solar noon and falls off rapidly near sunrise and sunset.
Discomfort glare: Visual discomfort caused by excessive luminance contrast in the field of view. Doesn't necessarily impair visibility (that would be disability glare). UGR is the discomfort-glare metric.
DNI (direct normal illuminance): Sunlight measured on a surface perpendicular to the sun, before accounting for surface tilt. Roughly 100,000 lux at solar noon under a clear sky; collapses to a few hundred lux near the horizon due to airmass.
Downlight: Ceiling-recessed luminaire that directs light primarily downward. Effective for desk illuminance but typically poor for vertical mel-EDI at eye level.
EML (equivalent melanopic lux): Legacy name for mel-EDI from the WELL v2 standard. Mathematically equivalent when both reference D65 daylight. See mel-EDI.
Eye height: Vertical height at which mel-EDI is evaluated for WELL L03 compliance: 1.2 m for seated occupants, 1.5 m for standing. Vertical direction matters as much as height — light must arrive at the eye, not just the desk.
Fixture schedule: Standard lighting-design deliverable listing every luminaire in a project with manufacturer, model, lamp/driver specs, wattage, mounting, and quantity. Auto-generated as part of the CircadianLab PDF report.
Flat panel: Edge-lit luminaire with a thin, evenly illuminated face. Often replaces troffers as a lower-profile option.
Foot-candle (fc): North American illuminance unit, equal to 1 lumen per square foot. 1 fc = 10.764 lux. Typical office workplane target is 30–50 fc (300–500 lux).
Form factor: The geometric fraction of light leaving radiosity patch A that arrives at patch B, accounting for orientation, distance, and visibility. The expensive step of any radiosity solver.
Gauss-Seidel solver: Iterative numerical method used to solve the radiosity equation system. CircadianLab uses a 3-bounce Gauss-Seidel solver to converge on a steady-state energy distribution.
Glazing transmittance: Fraction of incident light that a window or skylight transmits, typically 0.5–0.9 for clear glass. Paired with reflectance and diffusion to fully describe a glazing in CircadianLab.
Guth position index: Multiplier in the UGR formula that increases the glare penalty for luminaires near the center of the field of view and reduces it for those at the periphery. Encodes the human eye's sensitivity to where glare sources sit.
High bay: Pendant or surface luminaire designed for spaces with 20+ ft ceilings (warehouses, gyms, big-box retail). Uses tight beam optics to deliver intensity from height.
IES file: Industry-standard text file (.ies) containing the measured candela distribution of a luminaire. Used by every major lighting design tool. CircadianLab ships with 250,000+ IES files and supports uploading custom ones.
IES Type C photometry: The most common IES distribution format, defining intensities on a sphere oriented with the luminaire's axis vertical. Used for most indoor luminaires. Types A and B are used for automotive and floodlight applications.
Illuminance: Light arriving on a surface, in lumens per unit area. SI unit lux; North American unit foot-candles. The standard work-plane lighting metric.
Inter-reflection (bounce): Light that has reflected off at least one surface before reaching the measurement point. Captures the "indirect" or "ambient" component of room illumination. CircadianLab models three bounces.
Inverse-square law: Illuminance from a point source falls off with 1/r² of distance. Doubling the distance quarters the light. Fundamental to direct illuminance calculation.
ipRGC (intrinsically photosensitive retinal ganglion cell): Retinal cell that uses melanopsin to signal light directly to the brain's circadian and alerting centers. Distinct from the rods and cones that drive vision.
Linear / strip: Long, narrow luminaires designed to be mounted in continuous rows. Pendant, surface, or recessed; popular in offices and retail.
Lumen (lm): SI unit of total light output from a source. A 60-watt incandescent lamp produces about 800 lumens. Total fixture output is the integral of luminous intensity over the sphere.
Luminaire: A complete lighting fixture — lamp, optics, housing, and driver. The unit referenced by IES files and by the lighting industry.
Luminance: Light leaving a surface in a given direction, in candela per square meter. Determines perceived brightness and is the key input to UGR glare calculation.
Luminous intensity: Light emitted by a point source in a specific direction, in candela. Reported per direction in IES files.
Lux: SI unit of illuminance, equal to 1 lumen per square meter. 1 fc = 10.764 lux. Typical office workplane target is 300–500 lux.
Measurement grid: A grid of points across the working plane where illuminance and mel-EDI are evaluated. Also called the working plane. Typically set at desk height (0.76 m) or floor.
mel-EDI (melanopic equivalent daylight illuminance): Illuminance weighted by the melanopsin spectral response, normalized to D65 daylight. The CIE S 026:2018 metric for circadian-effective light. Same units as lux. Formerly known as EML.
Melanopic DER (daylight equivalent ratio): Multiplier that converts photopic lux to mel-EDI for a given light source. Determined entirely by the SPD. Examples: 2,700K LED ≈ 0.44, 4,000K LED ≈ 0.61, D65 daylight = 1.0, Circadian Sky at 200,000K ≈ 1.89.
Melanopic light: Light weighted by its ability to stimulate melanopsin in ipRGCs, regardless of how bright it appears to the visual system.
Melanopsin: Photopigment in the retina (peak sensitivity ~480 nm, blue-ish) that drives the body's circadian, alerting, and pupillary responses to light independently of vision.
Mounting (sconce, pendant, recessed): Mounting categories: sconce = wall; pendant = hanging from ceiling on stems or cables; recessed = inset into ceiling. Wall-mounted fixtures are often the easiest path to vertical mel-EDI compliance.
Non-visual effect: Effects of light on the body — alertness, melatonin suppression, sleep timing, mood — that operate through ipRGCs and don't depend on conscious visual perception.
NREL Solar Position Algorithm (SPA): High-precision algorithm published by the U.S. National Renewable Energy Laboratory that computes the sun's altitude and azimuth for any date, time, latitude, and longitude. CircadianLab uses NREL SPA to position the sun for daylight calculations.
PAR (parabolic aluminized reflector): Lamp shape combining lamp and reflector in one sealed unit. Used in spot, track, and recessed downlight applications. Beam angles typically marked on the lamp itself (e.g., PAR30 NFL = narrow flood).
Perez sky model: Mathematical sky-luminance model that smoothly adapts between clear, intermediate, and overcast conditions. Drives the diffuse-sky contribution in CircadianLab's daylight calculations.
Photometric distribution: The shape of how a luminaire emits light into space, expressed as candela by horizontal and vertical angle. Captured in an IES file and visualized as a polar plot.
Photometric symmetry: Whether a luminaire's intensity pattern is symmetric (axial = rotationally symmetric, bilateral = mirror-symmetric, full = symmetric in both axes) or fully asymmetric. Affects how the IES file stores its candela values.
Photopic illuminance: Illuminance weighted by the human eye's daytime brightness response (CIE 1931 V(λ) curve). What a standard lux meter measures.
Radiosity: Physically-based global illumination method that solves for the steady-state inter-reflection of diffuse light between surfaces. Used by CircadianLab and most architectural lighting tools (AGi32, DIALux, ElumTools).
Radiosity patch: A small subdivision of a room surface (wall, floor, ceiling) used as the unit of energy exchange in the radiosity solver. Form factors connect every patch pair.
Reflectance: Fraction of incident light that a surface diffusely reflects, 0–1. Typical values: white ceiling 0.80, light walls 0.50, mid-tone floor 0.20. CircadianLab uses per-surface reflectance for wall, floor, ceiling, and obstructions.
Sky type: Discrete sky condition selected for the Perez model — clear, intermediate, or overcast. Determines how diffuse the sky luminance is and how strong the direct sun beam is.
Skylight: Roof aperture that admits sun and sky illumination from above. Modeled in CircadianLab with configurable glazing transmittance, reflectance, and diffusion.
Solar altitude: The sun's angle above the horizon. 0° at sunrise and sunset, 90° at the zenith. Combined with azimuth to fully locate the sun.
Solar azimuth: The sun's compass direction, measured clockwise from north (0° = north, 90° = east, 180° = south, 270° = west).
Solar zenith angle: The sun's angle from straight up — equal to 90° minus the solar altitude. Drives the cos(zenith) factor when projecting direct sun onto a horizontal surface.
Solid angle: The three-dimensional angle subtended by a luminaire at the observer's eye, measured in steradians. A physically larger or closer fixture occupies more solid angle and contributes more glare per unit luminance.
SPD (spectral power distribution): How much power a light source emits at each wavelength of visible light. Determines color rendering, perceived color, and melanopic DER all at once.
Spot / track: Adjustable directional luminaires mounted on a track. Used for accent and display lighting; aim-able after install.
Troffer: Recessed rectangular ceiling luminaire, typically 2×2 ft or 2×4 ft. The dominant office-fixture format.
Tunable CCT: A luminaire whose CCT can be electronically adjusted across a range. Standard tunable white LED tops out around 6,500K; Innerscene Circadian Sky tunes from 2,200K to 200,000K while holding CRI ≥ 91.
UGR (Unified Glare Rating): Discomfort glare metric for indoor luminaires, per CIE 117:1995. Scale: ≤16 very comfortable, ≤19 typical office target, ≤22 industrial, ≤25 corridor maximum. Lower is better.
Virtual Sun: Innerscene's artificial-skylight product line. Combines a directional sun beam with a diffuse sky and a parallax-correct depth illusion that responds to the viewer's position.
Wall wash: Luminaire optimized to deliver an even sheet of light onto a vertical wall surface. Usually positioned 2–4 ft from the wall.
Wall-mounted fixture: Luminaire fixed to a vertical wall surface, typically at or above eye level. Particularly effective for vertical mel-EDI because the light is directed horizontally toward eye level — often the easiest path to WELL L03 compliance.
WELL Tier 1: WELL v2 L03 base requirement: mel-EDI ≥ 150 in at least one vertical direction at 1.2 m seated eye height, met at ≥ 75% of workstations.
WELL Tier 2: WELL v2 L03 enhanced requirement: mel-EDI ≥ 275 in at least one vertical direction at 1.2 m seated eye height, met at ≥ 75% of workstations.
WELL v2 Feature L03: "Circadian Lighting Design" feature in the WELL Building Standard v2. Requires minimum melanopic light levels at occupant eye level to support healthy circadian function. See Tier 1 and Tier 2.

Frequently Asked Questions

What is EML (melanopic equivalent lux)?

EML (Equivalent Melanopic Lux), formally known as melanopic EDI (Equivalent Daylight Illuminance), measures how effectively a light source stimulates the melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs) in the human eye. These cells regulate circadian rhythms, alertness, and sleep-wake cycles. EML is calculated by multiplying photopic illuminance by the melanopic Daylight Equivalent Ratio (DER), which depends on the spectral power distribution of the light source.

What is the WELL v2 requirement for melanopic light?

WELL v2 Feature L03 (Circadian Lighting Design) requires melanopic EDI of at least 150 lux (Tier 1) or 275 lux (Tier 2) measured vertically at eye level (1.2m for seated occupants) in at least one cardinal direction. At least 75% of workstations must meet this threshold for compliance.

What CCT produces the highest EML?

Higher color temperatures produce more melanopic light per lumen. At 200,000K, the melanopic DER reaches approximately 1.89 for Circadian Sky fixtures. Standard LEDs at 6,000K have a DER of 1.0 (the daylight reference), while warm 2,700K LEDs have a DER of only 0.44. This means a 200,000K fixture produces roughly 3.5× more EML per lux than a 2,700K fixture.

How does the Circadian Sky melanopic DER compare to standard LEDs?

Standard phosphor-converted white LEDs are commercially available up to about 6,500K, where they achieve a melanopic DER of approximately 1.10. Above that, standard LEDs become harsh, bluish, and lose color rendering quality — so most offices use 3,500–4,000K (DER 0.61–0.69) or at best 5,000K (DER 0.87). Fluorescent lamps perform even worse: a T8 at 4,000K achieves only DER 0.56. Innerscene Circadian Sky uses a 4-chip ATMOS platform with a tunable CCT range of 2,200K to 200,000K while maintaining CRI 91+ throughout. This means it can operate at CCTs far beyond what standard LEDs offer — for example, at 10,000K (DER 1.23), 15,000K (DER 1.37), or 200,000K (DER 1.89) — delivering 2–3.5× more melanopic stimulation per lux than a typical office LED, without any additional glare penalty since UGR depends on luminance, not spectral content. At the same CCT, Circadian Sky also slightly outperforms standard LEDs: 0.76 vs 0.69 at 4,000K and 0.89 vs 0.87 at 5,000K.

What is radiosity in lighting simulation?

Radiosity is a global illumination method that simulates how light bounces between surfaces in a room. Unlike direct illuminance calculation alone, radiosity accounts for inter-reflections — light that hits a wall, reflects off it, then illuminates other surfaces. This tool uses a 3-bounce iterative Gauss-Seidel radiosity solver with form factor computation, providing physically-based indirect lighting estimates.

What are IES files and why do they matter?

IES (Illuminating Engineering Society) files contain measured photometric data describing exactly how a luminaire distributes light in three dimensions. Using real IES data instead of simplified cosine distributions produces much more accurate illuminance predictions, especially for directional fixtures like troffers and wall washers. This tool supports IES Type C photometry with bilinear interpolation.

What fixtures are included in the built-in library?

CircadianLab includes a searchable library of over 250,000 photometric files from 70+ manufacturers including Innerscene, Acuity Brands (Lithonia, Juno, Aculux, Peerless, Gotham, Holophane), Cooper Lighting (Eaton), TCP Lighting, Luminii, BEGA, Thorn Lighting, LSI Industries, Artemide, Lightnet, GE Current, Planlicht, LIGMAN, ERCO, Lutron, Cree, ARRI, ETC, Signify (Philips), and more. Fixture types include downlights, area/flood lights, linear/strip, troffers, wall wash, spot/track, high bay, bollards, flat panels, film/studio lights, and theatre fixtures. You can also upload any IES file from any manufacturer not in the library.

How do wall-mounted fixtures affect EML?

Wall-mounted fixtures at eye level can dramatically increase vertical melanopic illuminance because they direct light horizontally toward the occupant's eyes. Ceiling-mounted downlights primarily illuminate horizontal surfaces, producing high desk-level lux but lower vertical EML. For WELL v2 compliance, wall-mounted fixtures at seated eye height (1.2m) are often more effective per lumen than ceiling fixtures.

How does the illuminance calculator work?

CircadianLab calculates photopic illuminance in both lux and foot-candles using IES photometric data and inverse-square law physics. It computes illuminance on horizontal surfaces (desk level) and in all four cardinal vertical directions at eye height. The radiosity engine adds inter-reflected (indirect) light from walls, floor, and ceiling for realistic total illuminance predictions. Switch between lux and foot-candles using the metric/imperial toggle.

What is UGR (Unified Glare Rating)?

UGR (Unified Glare Rating) per CIE 117:1995 is the international standard metric for assessing discomfort glare from luminaires. The formula accounts for luminaire luminance, solid angle, background luminance, and the Guth position index based on the source's elevation and horizontal angle relative to the observer's line of sight. UGR ≤16 is very comfortable, ≤19 is suitable for offices, ≤22 is acceptable for industrial settings, and ≤25 is the limit for corridors. This tool calculates UGR heatmaps across the entire room and per-occupant values based on viewing direction.

What is the difference between lux and foot-candles?

Lux and foot-candles both measure illuminance (luminous flux per unit area) but use different units. 1 foot-candle = 10.764 lux. Foot-candles are commonly used in North American lighting design (IES standards), while lux is the SI unit used internationally (CIE standards). Typical office lighting targets are 30–50 fc (300–500 lux) on the work plane. CircadianLab supports both units and automatically converts between them.

Can I share my lighting design with someone?

Yes. Click the Share button to save your current session (room, fixtures, camera angle, selections) to a unique URL. Anyone with the link sees exactly what you see, including the heatmap results. Each share generates a new UUID — the simulation state is stored server-side and can be reopened at any time.

Is this tool free to use?

Yes, CircadianLab is completely free with no signup required. All calculations run in your browser using a Web Worker. You can upload custom IES files, generate PDF reports, and share links without any account or payment.

Can CircadianLab calculate daylight through windows and skylights?

Yes. CircadianLab simulates daylight through wall windows and skylights using the NREL Solar Position Algorithm for sun position (any date, time, and geographic location) and a Perez sky model for diffuse and direct horizontal/normal illuminance. Direct sun and diffuse sky contributions are added as initial flux on every radiosity patch and measurement point, then bounced through the same form-factor network as electric fixtures — so daylight and electric light are solved together in one unified radiosity pass. Glazing transmittance, reflectance, and diffusion are configurable per window. The result: a single combined heatmap showing total photopic illuminance and melanopic EML from all sources.

Why does my winter sunbeam show only ~10 fc when the sun is just above the horizon?

That is correct physics. Atmospheric airmass — the column of air sunlight passes through — is roughly 1/sin(altitude). At sun altitude 25° the airmass is ~2.4 and clear-sky DNI is around 64,000 lux; at altitude 2.5° (15 minutes before sunset on the winter solstice in Chicago) the airmass jumps to ~18 and DNI collapses to ~770 lux. Combined with the small cos(zenith) factor on horizontal surfaces, the workplane sees only a few foot-candles of direct beam. Move the time slider toward solar noon to see thousands of foot-candles in the same beam.

Supported Fixtures & IES Photometric Library

CircadianLab ships with a built-in library of 8,000+ photometric files covering 14 fixture categories: Troffer, Downlight, High Bay, Linear/Strip, Wall Wash, Spot/Track, Bollard, Flat Panel, Area/Flood, PAR, Tube/Strip, Circadian Troffer, Artificial Skylight, Artificial Window. You can also upload any IES file from any manufacturer with optional custom melanopic DER override.

InnersceneArtificial Skylight, Artificial Window, Circadian Troffer

Product lines: Circadian Sky, Virtual Sun, A7

Lithonia LightingTroffer, Downlight, High Bay, Linear/Strip, Area/Flood

Product lines: AVante, STAKS, IBG, WL Series, KAD LED

GothamDownlight, High Bay, Linear/Strip, Wall Wash

Product lines: Incito, EVO, ICO, Squares Cylinder

MetaluxTroffer, Linear/Strip, Flat Panel, High Bay

Product lines: Cruze, Encounter, SkyRidge, WaveStream

IRISDownlight, Spot/Track, Wall Wash

Product lines: BioUp, P3 Series

Mark Architectural LightingTroffer, Linear/Strip

Product lines: FCL ARC, Slot 2, Slot 4

CoreliteLinear/Strip, Downlight, Wall Wash

Product lines: D3X, Surround, Class R

HALODownlight, Spot/Track, Wall Wash

Product lines: HL6, H2, PD6, RL5

Juno LightingDownlight, Spot/Track, PAR, Wall Wash

Product lines: Aculux, Trac-Master, JuLED

PeerlessLinear/Strip, Troffer

Product lines: Open, Tradition, BeamLED

BEGABollard, Wall Wash, Downlight

Product lines: Outdoor LED, Step Lights

HolophaneBollard, High Bay, Troffer

Product lines: Charleston LED, Predator LED, V-Max

FineliteLinear/Strip

Product lines: HP-2, HP-4, Series 1

ARTEMIDEDownlight, Linear/Strip, Spot/Track

Product lines: Tolomeo, Architectural

Other Supported Brands

Acuity Brands · Cooper Lighting · Cree Lighting · Eaton · GE Current · Hubbell · LSI Industries · Philips · Signify · WAC Lighting · Zumtobel · Erco · Bock Lighting · XAL · Modular Lighting · Selux · Louis Poulsen · iGuzzini · Targetti — and any IES file from any manufacturer via upload.

Related Tools & Resources

Validation Suite

120+ tests against 20 IES files from 8 manufacturers

DWG Viewer

View AutoCAD DWG files online

SKP Viewer

View SketchUp 3D models online

Circadian Sky

Innerscene circadian lighting fixtures

Virtual Sun

Artificial skylight technology

WELL Standards

WELL Building Standard resources

Research

Circadian lighting research library

This tool is for design guidance only. Actual field conditions may differ due to furniture, finishes, maintenance factors, and other variables not modeled. Melanopic calculations follow CIE S 026:2018. WELL compliance assessment is based on WELL v2 Feature L03 requirements.