Industrial lighting design basics come down to one sentence: a design is a calculated promise that a stated maintained illuminance will reach a stated working plane, evenly enough, without disabling glare, in the right colour, for the whole maintenance period. Fixtures, wattages and spacings are only the means of keeping that promise. A buyer who can read the promise can judge any quotation, whoever wrote it.
Quotations rarely state that promise. They quote lumens, watts and “equivalent to 400 W” and leave the rest to assumption. This guide maps the subject: the outputs, the units, where lux targets come from, the fixture’s photometry, the calculation with a worked example, and how to review a design report. Each section routes to the detailed article on that topic.
Key Takeaways
- A lighting design is judged on five outputs, not one: maintained illuminance, uniformity, glare, colour quality and maintenance assumptions. Average lux alone passes bad designs.
- Lux targets come from application standards (EN 12464-1/-2, EN 13201, EN 12193, or IES equivalents), and every figure only means something with its task area or class attached.
- The lumen method sizes a job in four lines: area × target lux ÷ (UF × MF) ÷ fixture lumens. At 200 lx, UF 0.8, MF 0.8 and 150 lm/W, a 1,500 m² hall needs about 469,000 installed lumens.
- The lumen method scopes; a point-by-point calculation with the real IES file decides. Racking, roads, sport, asymmetric optics and any uniformity or glare requirement make the full calculation mandatory.
- A design report without a stated maintenance factor, calculation grid and photometric file reference is not checkable, and should not be signed.
What an Industrial Lighting Design Must Deliver
Before any product is chosen, the design brief should name five outputs. Each one fails in its own way, and each has its own number.
| Output | The quantity | What goes wrong if it is ignored |
|---|---|---|
| Task illuminance | Maintained average illuminance in lux on a defined working plane | The space measures well on day one and falls below target within a few years |
| Uniformity | Uniformity ratio U0 = minimum ÷ average lux | Bright pools and dark troughs; the eye adapts to the pools and reads the troughs as darkness |
| Glare | UGR indoors, GR outdoors in sport and area lighting | Operators squint at fixtures, forklift drivers are dazzled at aisle ends |
| Colour | CCT and CRI (with R9 where reds matter) | Labels, cables and product condition misread; mismatched fixtures look like faults |
| Maintenance | Maintenance factor, cleaning interval, lumen maintenance data | The design is quietly sized for new, clean fixtures that will not exist for long |
The brief also needs the working plane (floor level for forklift traffic, 0.85 m for benches, vertical rack faces for picking), which fixes where the calculation grid sits, and the operating profile, which decides the controls. A quotation that answers only the first row of the table is a fixture count, not a design.
The Units: Lumens, Lux and Candela
Three quantities carry the whole subject, and confusing them is the most common way a quotation overpromises.
- Lumens are the total light a fixture emits. A property of the product.
- Lux is the light arriving on a surface, per square metre. A property of the installation.
- Candela is the intensity in one direction. A property of the beam.
Standards specify lux, catalogues quote lumens, and photometric files are written in candela. The inverse-square law (lux = candela ÷ distance²) bridges the last two. The full explanation, including chip lumens versus measured fixture lumens, is in lumens vs lux vs candela; everything below assumes it.
Where Lux Targets Come From
A lux figure without its source and condition is a vendor assertion. Targets come from application standards, and each standard governs a different kind of space and sometimes a different quantity altogether.
| Standard | Governs | Design quantity | Figures already published on this site |
|---|---|---|---|
| EN 12464-1 | Indoor workplaces | Maintained lux, U0, UGR limit and minimum CRI per task area | Warehouse practice: bulk storage 100–150 lx, general storage and aisles 150–200 lx, packing 300–500 lx, inspection 500 lx |
| EN 12464-2 | Outdoor workplaces: yards, terminals, loading areas | Maintained lux, uniformity, glare rating, obtrusive-light limits | Values per task area from the applicable edition |
| EN 13201 | Roads, footpaths, car parks | Road-surface luminance (cd/m²) for M classes; lux for C and P classes | M3 = 1.0 cd/m² average; P1 = 15 lx down to P6 = 2 lx |
| EN 12193 | Sports lighting | Horizontal lux and uniformity by sport and class; vertical lux for broadcast | Football: 500 lx (Class I), 200 lx (Class II), 75 lx (Class III) |
| ANSI/IES RP series | North American practice: RP-7 industrial facilities, RP-8 roadway, RP-6 sports | Recommended illuminance, often in foot-candles | 1 fc = 10.76 lx; same quantity, different unit |
The quantity can change, not just the number. Traffic routes under EN 13201 are designed in road-surface luminance, because the same lux looks different on concrete and dark asphalt; see the EN 13201 roadway design guide. Class matters more than venue: “stadium lighting” is not a specification, “Class II football” is; see the EN 12193 stadium lighting guide. Hazardous-area standards do not set lux. GB/T 3836 and IEC 60079 govern whether equipment may enter an explosive atmosphere, while the process area’s illuminance still comes from EN 12464; the equipment side is in GB/T 3836-2021 explained.
EN standards are paid documents, so work from the edition your project specification cites for any task area not listed above.
The Fixture’s Photometry: What the Product Contributes
Once the target is set, the design needs to know how the chosen fixture throws its light. That information lives in three places.
The photometric file
An IES file (LM-63 format) or LDT file (EULUMDAT) holds the fixture’s candela values on a grid of angles, and DIALux, Relux or AGi32 compute lux from it point by point. It should trace back to a measured test report, and its catalogue number must match the quoted SKU. The five-minute checks are in how to read an IES file.
Beam angle and distribution type
The beam angle is the cone within which intensity stays above half the peak. It decides how far apart fixtures can sit relative to their height:
| Beam | Spacing-to-mounting-height ratio (site rule) | Typical use |
|---|---|---|
| 60° | 0.8–1.0 | High mounting, racking aisles |
| 90° | 1.0–1.2 | General halls at medium height |
| 120° | 1.2–1.5 | Open floors at low height |
Beam angle is only a summary. The distribution type describes the shape: symmetric beams for high bays, aisle distributions for racking, forward-throw IES Type II and III optics for roads, and asymmetric flood optics that keep the fixture face near-horizontal to control glare and spill. Same beam angle, different distribution, different result, which is why the file goes into the calculation.
The datasheet
The datasheet carries what the file does not: measured input power, efficacy, CCT, CRI, power factor, ingress rating and the lumen maintenance claim. Whether those numbers are measured or summed from component data is the difference between a specification and an advertisement; how to read an LED lighting datasheet walks through each line. For a benchmark of measured evidence, our 200 W flood light measured 35,309 lm at 201.3 W (175.4 lm/W, 60° beam, 34,444 cd peak), and the measured goniophotometer reports are downloadable on the flood light pages.
The Calculation: Lumen Method and Point-by-Point
Lighting calculation basics rest on two methods. The lumen method sizes the job on paper in minutes. The point-by-point method, run in software, proves it.
The lumen method
Installed lumens = (area × target maintained lux) ÷ (UF × MF)
Fixture count = installed lumens ÷ lumens per fixture
- UF (utilisation factor) is the share of emitted light that reaches the working plane. It falls with dark surfaces, tall narrow rooms and racking.
- MF (maintenance factor) covers lumen depreciation and dirt over the maintenance cycle.
Worked example: a 50 × 30 m production hall
Inputs, all stated:
| Input | Value |
|---|---|
| Floor area | 50 m × 30 m = 1,500 m² |
| Mounting height | 10 m |
| Target | 200 lx maintained, horizontal, open floor |
| Utilisation factor | 0.8 (open hall, direct high bays, reasonably light surfaces) |
| Maintenance factor | 0.8 (clean, dry building, sealed fixtures) |
| Fixture | 200 W high bay at 150 lm/W = 30,000 lm, 90° optic |
Step 1: lumens needed on the working plane. 1,500 m² × 200 lx = 300,000 lm.
Step 2: correct for losses. 300,000 ÷ (0.8 × 0.8) = 300,000 ÷ 0.64 ≈ 468,750 lm installed. That is about 312 installed lumens per m² to hold 200 lx maintained.
Step 3: fixture count. 468,750 ÷ 30,000 = 15.6, so at least 16 fixtures.
Step 4: fit it to a grid and check the ratio. Sixteen fixtures do not grid neatly into a 50 × 30 m hall. The candidates:
| Grid | Count | Centres | S/MH at 10 m | Maintained average | Verdict |
|---|---|---|---|---|---|
| 4 × 4 | 16 | 12.5 m × 7.5 m | 1.25 / 0.75 | 205 lx | Uneven: too wide one way for 90° optics |
| 5 × 3 | 15 | 10 m × 10 m | 1.0 / 1.0 | 192 lx | Perfect geometry, below target |
| 6 × 3 | 18 | 8.3 m × 10 m | 0.83 / 1.0 | 230 lx | Meets target; tighter spacing only helps uniformity |
(Maintained average = count × 30,000 lm × 0.64 ÷ 1,500 m².) The scoping answer is 18 × 200 W in a 6 × 3 grid, outer rows at half spacing from the walls. That agrees with the site chart putting 8–12 m mounting at 200–300 W on the same basis, derived in high bay wattage by ceiling height; spacing and racking rules are in the high bay light spacing guide. What the example cannot tell you is the minimum lux between fixtures or the glare at a workstation. The lumen method knows only averages.
Point-by-point calculation
Software computes illuminance at every grid point from each fixture’s candela distribution. For one fixture, horizontal illuminance at a point is E = I(θ) × cos³θ ÷ h², where I(θ) is the intensity toward the point, θ the angle from straight down and h the mounting height. Directly beneath, θ = 0 and this becomes the inverse-square law: our 200 W flood’s measured 34,444 cd peak gives 34,444 ÷ 8² ≈ 538 lx at 8 m. Summing every fixture at every point is tedious by hand and trivial for DIALux.
The point-by-point calculation is mandatory when:
- The specification has any uniformity or glare requirement. The lumen method cannot produce U0 or UGR.
- There is racking or obstruction, where vertical illuminance on rack faces is the real target.
- The project is a road, car park or outdoor area, with luminance, threshold increment or obtrusive-light limits.
- It is sports lighting, including vertical illuminance toward cameras.
- The optics are asymmetric or aimed, or the room is irregular or has mixed mounting heights.
That covers almost every industrial project. Use the lumen method to budget and to check a quotation’s fixture count; accept only a point-by-point study as the design.
Maintenance Factor and Lumen Depreciation
The maintenance factor is the most consequential number in a design and the easiest to fudge, because it is invisible in a rendered layout.
Following the CIE approach, MF is the product of separate losses: lumen maintenance of the light source at the end of the period, light source survival, dirt on the luminaire and, indoors, dulling of room surfaces. MF 0.8 is only honest if those together stay within 20% over the period the design claims to cover. That is realistic for sealed fixtures in a clean building with a cleaning schedule, not for a foundry. Working values on this site: 0.8 for clean interiors, 0.7 for dusty or greasy buildings, 0.8–0.9 for sealed IP65 street lighting.
Sensitivity on the worked example: at MF 0.7, installed lumens rise from about 469,000 to about 536,000 and the minimum count from 16 to 18. A study run at 0.8 in a dusty building overpromises by more than 10%.
L70, LM-80 and TM-21
LEDs dim rather than fail, so lifetime is defined by lumen maintenance. L70 rated life is the operating time at which output is projected to fall to 70% of initial. Our range is rated at 50,000 h.
The evidence chain behind such a claim runs in two steps:
- IES LM-80 is the test method for measuring lumen maintenance of LED packages over thousands of hours at controlled temperatures.
- IES TM-21 is the method for projecting that data forward. It limits how far a projection may be reported beyond the test duration, so a capped “L70 >” figure reflects test length, not a measured failure.
Two consequences follow. The data is measured on the LED package, so the fixture’s thermal design decides whether the package runs at the tested temperature. And if the design period runs to full L70 life, lumen maintenance alone contributes 0.7, so MF with dirt included must be lower still. Designs therefore state a shorter maintenance period, or use L80 or L90 data at that period; the report should say which.
Light Quality: CCT, CRI, UGR and Flicker
Delivered lux is necessary and not sufficient. Four quality specifications decide whether people can actually work under the installation.
| Specification | What it controls | Site guidance |
|---|---|---|
| CCT (colour temperature) | Colour appearance of the light, not brightness | 4000K default for industrial interiors; 5000K for inspection zones; 3000K residential streets and sensitive areas, 4000K arterials, industrial areas and car parks |
| CRI (colour rendering) | How accurately object colours read | CRI ≥ 80 for labels, goods and cables; check R9 where reds matter |
| UGR (discomfort glare, indoors) | Glare from fixtures toward the observer A limit per task area from the standard (office work, including mezzanine offices, at UGR ≤ 19); confirm it in the calculation | |
| Flicker | Modulation of output from the driver | Ask for percent flicker or flicker index; IEEE 1789 gives recommended limits |
Cooler light is not more light. 5000K looks brighter at identical lux, but neither the meter nor the standard credits it, and batch consistency (SDCM) matters more than the choice between neighbouring values. UGR belongs to the installation: the same high bay can pass at 12 m and fail at 6 m, so demand UGR from the calculation at your geometry. Flicker is a safety item around machinery, because deep modulation can make rotating equipment appear slowed or stationary; ask for the driver data.
Controls: Designing When the Light Is On
Spacing decides where light can go; controls decide when it is delivered. The design should state the strategy, not leave it to the electrician.
| Strategy | Where it earns its place | What the design must specify |
|---|---|---|
| Occupancy zoning | Low-traffic aisles, stores, yards at night | Zones (per aisle, never per building), standby level, hold time |
| Daylight harvesting | Bays under rooflights, dock glazing | Photocell zones matched to the rooflight pattern |
| Time scheduling and photocells | Shift patterns, external areas, roads | The profile, and the lux level or class held in each period |
Order dimmable drivers (0–10V or DALI on our high bays, dimming and photocells configurable on our flood lights, depending on the series) at purchase, because retrofitting drivers into sealed IP65 bodies costs more than the option did. And record dimmed levels in the design file, so commissioning readings are compared against the level each zone should hold at that hour.
How to Review a Design Report You Have Been Sent
A photometric study is a document you are asked to rely on. This checklist catches most of what goes wrong.
| # | Check | What good looks like | Red flag |
|---|---|---|---|
| 1 | Target and source | Maintained lux per zone, with the standard, edition and task area named | One figure for the whole building, or no source |
| 2 | Maintenance factor | MF stated, with the maintenance period and environment it assumes | MF missing, or 0.8 assumed in a dusty or greasy building |
| 3 | Luminaire file | IES/LDT file name and catalogue number matching the quoted SKU, optic and wattage | Generic file, neighbouring model, or “similar product” |
| 4 | Calculation grid | Grid spacing, working-plane height and boundary stated; vertical planes where racking exists | Averages only, no grid, rack faces not calculated |
| 5 | Uniformity | U0 reported per zone against the requirement | Average reported, minimum missing |
| 6 | Glare | UGR at named observer positions indoors; GR or TI outdoors where applicable | No glare figure at all |
| 7 | Surfaces and UF | Reflectances stated (ceiling, walls, floor), obstructions modelled | Default reflectances in a dark, racked building |
| 8 | Colour | CCT, CRI minimum and SDCM tolerance per zone | CCT only |
| 9 | Fixture evidence | LM-79-based photometric report and LM-80/TM-21 lumen maintenance data referenced | Chip data or “up to” lumens |
| 10 | Controls, power, commissioning | Dimming protocol and zones, W/m² per zone, measurement grid for handover | Left “to be confirmed on site” |
A sanity pass first: rerun the lumen method backwards with the report’s own figures. Eighteen 30,000 lm fixtures holding 230 lx over 1,500 m² imply UF × MF = 230 × 1,500 ÷ 540,000 ≈ 0.64, which is consistent. If a racked warehouse implies 0.9, ask how.
The Illuminating Engineering Society publishes the LM, TM and RP documents referenced here, the International Commission on Illumination (CIE) the glare and maintenance methods European standards build on, and the US Department of Energy’s solid-state lighting programme independent background on LED performance.
Where to Go Next, by Application
The fundamentals stay the same; the governing standard, quantity and geometry change.
| Application | Governing reference | Starting point | Read next |
|---|---|---|---|
| Warehouses and factories | EN 12464-1 | 200 lx maintained basis; 8–12 m mounting → 200–300 W; S/MH by beam | High bay spacing guide · Wattage by ceiling height |
| Flood and area lighting, yards | EN 12464-2 | Throw distance → beam angle → lux → wattage | LED flood light selection guide |
| Car parks | EN 13201 P-classes | 4–6 m poles, 18–24 m spacing, 20–40 W, confirmed by calculation | Parking lot lighting guide |
| Roads and streets | EN 13201 M/C/P classes | Spacing ≈ 3.5–4 × pole height with a quality optic | Pole height and spacing chart · EN 13201 design guide |
| Ports, interchanges, large yards | EN 12464-2 / EN 13201 | 20–40 m masts, per study | High mast lighting guide |
| Sports | EN 12193 | Lux and uniformity by sport and class | Stadium lighting to EN 12193 |
| Hazardous areas | GB/T 3836 / IEC 60079 (equipment) + EN 12464 (levels) | Zone, gas group and temperature class first | GB/T 3836-2021 explained |
The Bottom Line
Industrial lighting design is a short chain of reasoning: name the maintained target and its source, know the fixture’s measured photometry, size with the lumen method, prove with a point-by-point calculation at a stated maintenance factor, then specify the quality and controls that let people work under it. Every weak quotation breaks one link in that chain, and the review checklist above shows you which.
The one next action: send us your floor plan or site drawing, mounting heights and target levels, and our engineers return a DIALux study with the calculation grid, maintenance factor, uniformity, glare and IES files stated, at no cost with the quotation. For interiors, the fixtures behind that study are our LED high bay lights, offered in several beam-angle options so the same calculation can iterate the optic without changing fixture family.
FAQ
What are the basics of industrial lighting design? Five outputs: maintained illuminance on a stated working plane, uniformity, glare control, colour quality, and the maintenance assumptions that keep the first four true over time. The lux target comes from an application standard such as EN 12464-1, the lumen method sizes the fixture count, and a point-by-point calculation with the fixture’s IES file verifies the result before ordering.
How do I calculate how many light fixtures I need? Floor area × target maintained lux ÷ (UF × MF) ÷ lumens per fixture. A 1,500 m² hall at 200 lx with UF 0.8, MF 0.8 and 30,000 lm fixtures gives 1,500 × 200 ÷ 0.64 ÷ 30,000 ≈ 16, rounded up to a grid that respects the beam’s spacing-to-height ratio (18 in a 50 × 30 m hall). Then confirm uniformity and glare in DIALux.
What is a maintenance factor in lighting design? The multiplier for light lost over the maintenance period to LED lumen depreciation, dirt on optics and dulling surfaces. A design at MF 0.8 installs 25% more initial light than the target. Clean, sealed installations commonly justify 0.8; dusty or greasy buildings 0.7 or lower. A study that does not state its MF cannot be checked.
When is a DIALux calculation necessary instead of the lumen method? Whenever there is a uniformity or glare requirement, racking or obstruction, a road, car park, yard or sports facility, aimed or asymmetric optics, or an irregular room. The lumen method only knows average lux: good for budgeting and plausibility checks, not for signing off a design.
What lux level does an industrial building need? It depends on the task area. EN 12464-1 practice for warehouses runs from 100–150 lx for bulk storage and 150–200 lx for general storage to 300–500 lx for packing and 500 lx for inspection. Outdoor workplaces fall under EN 12464-2, roads under EN 13201 and sport under EN 12193. Always quote a lux figure with its task area or class.
What is the difference between L70 and LM-80? L70 is the result: the projected operating time at which output falls to 70% of initial. LM-80 is the IES test method measuring lumen maintenance of LED packages, and TM-21 projects that data into an L70 figure within limits set by test duration. Ask for the LM-80/TM-21 data behind any lifetime claim.