Industry Application
Vertical farming lighting must balance crop light requirements, shelf spacing, light uniformity, fixture efficiency and heat management across every growing level. Because each tier is a separate lighting zone stacked in one conditioned room, the design is driven by layer height and photons per kilogram of produce — not by a single room-level PPFD target.
Illustrative image of a typical vertical farming environment — not a customer installation photograph.
Technical focus on this page
Multi-layer geometry, layer height, uniformity and energy per kilogram
How this application works
In a vertical farm the lighting system is no longer one installation; it is repeated dozens of times, once per tier, and every design decision multiplies. A fixture that is 8 mm too deep can cost a layer in a rack. A layout that is 10% less uniform produces a harvest that varies by tier, which complicates grading and packing more than a lower average yield would.
The tight constraint is vertical space. Typical leaf-greens racks run with 300–450 mm between the tray surface and the underside of the fixture, which limits heat-sink volume, driver placement and beam clearance. Slim linear bars with remote or top-entry drivers exist precisely because the geometry, not the wattage, decides what fits.
The second constraint is heat. Nearly all input power is rejected inside the growing envelope, and in a sealed multi-tier room that heat has to be removed by the HVAC system before it reaches the crop. Energy cost per kilogram is therefore a function of fixture efficacy, layer geometry, airflow and cooling — all four together. A published comparison of plant factories and greenhouses illustrates the scale: producing one kilogram of lettuce dry weight took around 247 kWh of electricity in a plant factory, against 70 to 211 kWh in greenhouses depending on location and whether supplemental lighting was used (Graamans et al. 2018).
Application challenges
These are the constraints that decide whether a lighting plan survives contact with an operating facility.
With 300–450 mm of clearance, a fixture with a deep heat sink or a bulky driver reduces the usable growing height or forces a wider tier pitch. Every millimetre of fixture depth is paid for across the whole rack footprint.
Uneven light within one tier produces uneven plants; repeated across twenty tiers it produces systematic differences by shelf position, which complicates harvest scheduling and packing specification.
Lighting heat must be removed by refrigeration in most sealed vertical farms, and cooling energy can be a substantial share of the total. Lower fixture wattage for the same PPF reduces both lighting energy and cooling energy.
Hundreds of small fixtures mean hundreds of connections. Daisy-chain ports, per-tier circuits and a single control protocol per zone reduce installation labour and maintenance visits; poorly planned wiring becomes the limiting factor in scaling a design.
Fixtures must be cleanable and serviceable without dismantling a tier. Tool-free mounting, accessible drivers and consistent bar lengths matter more here than in any other application.
Lighting requirements
Each metric below has to be set from the crop, structure and operating practice — not from a generic watts-per-square-metre rule.
| Parameter | Planning target | Why it matters |
|---|---|---|
| PPFD at tray level | Leafy greens commonly 150–300 µmol/m²/s depending on cultivar and cycle | Tray-level PPFD, measured at the crop surface, is the only intensity that matters in a rack. |
| DLI | About 12–17 mol/m²/day for lettuce and many leafy greens; higher for herbs | Short cycles and long photoperiods can reach the same DLI at lower intensity, which reduces heat near the canopy. |
| Uniformity within a tier | Minimum-to-average of about 0.85 is a reasonable design aim for rack lighting | Tray edges and rack ends are the first places to fall short; a single low corner changes the whole tier’s harvest date. |
| Fixture depth and beam | Slim linear profile with a beam that covers the tier width at the installed height | Layer height is fixed by the rack; the fixture must fit inside it and still light the full tray width. |
| Efficacy | Compare µmol/J within the same power class; higher efficacy cuts both lighting and cooling energy | In vertical farming the lighting system runs long hours every day of the year, so efficacy compounds. It is also finite: published analysis puts the practical ceiling for LED fixtures at about 3.4 µmol/J for white-plus-red and 4.1 µmol/J for blue-plus-red (Kusuma et al. 2020). |
| Heat rejected to the room | Account for essentially all input wattage as internal load | Cooling capacity, not fixture count, often limits how many tiers can be installed in a room. |
| Control granularity | Per-tier or per-bank dimming and scheduling | Different crops and transplant schedules share the same room; per-tier control preserves recipe flexibility. |
Reference data
Planning references compiled from horticultural lighting literature and standards. They are starting points for your own trials, not guarantees of performance.
| Crop | PPFD (µmol/m²/s) | Photoperiod | DLI (mol/m²/day) | Rack note |
|---|---|---|---|---|
| Lettuce (butterhead, romaine) | 150 – 250 | 16 – 18 h | 10 – 16 | Tipburn risk rises with intensity and low airflow; keep uniformity tight |
| Baby leaf / rocket | 180 – 300 | 16 – 18 h | 12 – 18 | Short cycles amplify any tier-to-tier variation |
| Basil | 200 – 350 | 14 – 16 h | 12 – 20 | Responds strongly to DLI; leaf colour and aroma affected by spectrum |
| Microgreens | 100 – 200 | 12 – 16 h | 6 – 11 | Tray density and airflow usually limit before light does |
| Kale / chard transplants | 200 – 300 | 16 h | 11 – 17 | Stockier plants at higher DLI; watch leaf temperature near bars |
| Strawberry (rack) | 250 – 400 | 14 – 16 h | 13 – 23 | Higher cooling load; verify cultivar response before committing |
Planning references compiled from controlled-environment horticulture literature. Recipes must be validated on your own cultivar, substrate and airflow — vertical farms differ enough that published ranges are starting points only.
| Layer clearance | Fixture consequence | PPFD consequence | Practical check |
|---|---|---|---|
| 300 – 350 mm | Slim bar only; remote or top-entry driver | Very close mounting; risk of hot spots and leaf scorch | Measure PPFD and leaf temperature at tray level, not at 300 mm |
| 350 – 450 mm | Standard slim bar with shallow heat sink | Good coverage with wide beam; watch bar-to-bar banding | Check a grid across the tier width and at the tray edge |
| 450 – 600 mm | Bar or compact board possible | Higher intensity per fixture; fewer bars per tier | Confirm beam overlap before reducing bar count |
| 600 mm+ | Board or bar; more driver placement freedom | Higher mounting gives better uniformity but needs more PPF | Recalculate PPF per tier rather than reusing a lower-tier layout |
Geometry is usually fixed by the rack and the building, not by the lighting. The design must work within it, so these constraints should be settled before fixture selection.
Lighting system design
The order matters: geometry and targets first, fixture count second, verification and control last.
Tier pitch, tray width, aisle access and the number of layers determine almost everything else. Settle these before comparing fixtures, because a fixture that does not fit the clearance cannot be rescued by a better spectrum.
Decide PPFD, photoperiod and DLI for the crop on each tier. If tiers will carry different crops, plan separate control zones; otherwise the whole rack runs at the most demanding recipe.
Multiply tray-level PPFD by tray area, apply a utilisation factor for edge and end losses, and divide by the PPF of one bar. Round to whole bars so the layout stays symmetrical across the tray width.
Bar spacing and mounting height together set the banding pattern. Ask for a PPFD grid across a full tier — centre, mid and edge — and check the minimum, because the tray edge is where grading problems appear.
Add the lighting wattage per tier to the room heat balance and confirm the HVAC can hold the target VPD. In sealed rooms the cooling limit is often reached before the electrical limit.
Daisy-chain ports, per-tier circuits and one control protocol reduce installation and maintenance cost. Confirm that a technician can reach and clean every fixture without removing a tray.
Worked example
Illustrative example — assumptions stated below, not client data
| Step | Calculation | Result |
|---|---|---|
| DLI check | 250 × 16 × 0.0036 | 14.4 mol/m²/day — within the lettuce planning range |
| Total PPF at canopy level | 250 µmol/m²/s × 120 m² | 30,000 µmol/s |
| Installed PPF including losses | 30,000 ÷ 0.85 | 35,294 µmol/s (reported as ≈ 35,300) |
| Bars required (photon budget) | 35,294 ÷ 250 µmol/s per bar | 141.2 → round up to 142 bars |
| Bars after tier symmetry | 142 ÷ 6 tiers = 23.7 → 24 bars per tier | 24 × 6 = 144 bars installed (regular structure beats a 142-bar odd layout) |
| Delivered PPFD check | 144 × 250 × 0.85 ÷ 120 m² | ≈ 255 µmol/m²/s — target met with a small margin |
| Installed load | 144 × 100 W | 14.4 kW for the rack |
| Daily lighting energy | 14.4 kW × 16 h | 230.4 kWh/day, all of which becomes internal heat load |
| Energy intensity indicator | 230.4 kWh ÷ expected daily harvest (kg) | kWh per kg — the number to optimise when comparing fixture options |
Bars per tier come from canopy PPFD, tray area and bar PPF, then round up twice: once for the photon budget (142) and once for tier symmetry (144). Every input above is an assumption you should replace with your own rack dimensions and measured PPFD; the arithmetic is the method, not a quotation.
Three different kinds of number
The worked example above is an initial estimate. It is not a lighting layout, and it is not a verified PPFD. Keeping the three apart is what stops a photon budget from being quoted as delivered performance.
Tray-level PPFD × tray area ÷ utilisation allowance ÷ bar PPF, expressed as bars per tier and kilowatts for the rack.
Arithmetic only. It tells you what the rack will draw and roughly how many bars to quote for — nothing about the pattern of light on the tray.
Bar spacing across the tier width, mounting height inside the available clearance, beam overlap, and the edge and end rows.
A per-tier PPFD grid at tray level, with the minimum value at the tray edge reported alongside the average — plus a leaf-temperature check at the closest clearance.
Measured PPFD across a full tier, top tier and bottom tier, at the documented clearance and dim level.
Measurement data only. Tiers are not interchangeable: the top tier and the bottom tier must be measured separately, because airflow and temperature differ between them.
Fixture selection
Selected from the six fixture categories we manufacture; the right mix depends on ceiling height, canopy structure and control requirements.
Primary lighting for every tier
Slim linear profiles fit 300–450 mm clearances, spread light across the tray width and can be daisy-chained, which keeps wiring density manageable.
Gentle, uniform light close to the tray
Short-cycle crops need lower intensity and better uniformity than high-output fixtures provide; lower wattage also reduces heat next to the canopy.
Higher tiers, mother stock and taller crops
Where clearance allows, a board concentrates more PPF in a smaller footprint and reduces the number of connection points per tier.
Real products
Specifications shown are the confirmed values from each product record. Where a parameter is not confirmed by the source material, it is not displayed here.
100W / 120W seedling bar, 1100 mm, 36,000 lm at 240 lm/W, IP65, WiFi and RJ14.
View product details
120W to 300W waterproof tube, 1156 mm, 14,400 lm at 120 lm/W, IP65, PC cover.
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100W rack bar, 1045 mm, 14,946 lm, 281B diodes, IP54, knob dimming.
View product detailsOEM & ODM
We build fixtures to a specification, document what was built, and support the certification and packaging work that a private-label programme needs.
Common mistakes
Each of these shows up after installation, when the layout is already fixed and the circuits are already run.
| Mistake | What to do instead |
|---|---|
| Treating a vertical farm as one big room | Design per tier: each layer has its own height, uniformity pattern, heat load and control zone. A room-level average hides exactly the variation that ruins a harvest. |
| Choosing fixtures before fixing rack geometry | Settle tier pitch, tray width and clearance first; then select a fixture depth and beam that fit inside those constraints. |
| Optimising peak PPFD instead of uniformity | A tier with a bright centre and dim edges grades unevenly. Check minimum-to-average across the tray width, including the edge row. |
| Ignoring cooling energy in the business case | Lighting wattage becomes internal heat that refrigeration must remove. Compare fixtures on total energy — lighting plus cooling — not lighting alone. |
| Under-planning wiring and access | Hundreds of fixtures need planned circuits, connectors and service access. Retrofitting cable routing into an operating rack is expensive and disruptive. |
Related technical guides
Published articles that explain the measurement and selection logic used on this page.
Buying Guide
A commercial buyer’s framework for choosing LED grow lights: match crop PPFD and DLI targets, fixture efficacy (µmol/J), uniformity, spectrum, dimming, IP rating and total cost of ownership.
Read the guideTechnology
PPF and PPFD are the two most quoted numbers on a grow light spec sheet — and the two most commonly confused. Here is what each one measures and how to use them.
Read the guideTechnology
PPF is total photon output (µmol/s), PPFD is canopy intensity (µmol/m²/s), and PPE is efficacy (µmol/J). Learn the exact units, formulas and how to use each when specifying LED grow lights.
Read the guideRelated articles
In-depth guides written for this application — planning, spectrum, DLI and layout.
Vertical Farming
Design lighting for a vertical farm: layer spacing, PPFD per tier, rack layout and uniformity, with a worked example that ties shelf count to photon delivery.
Read Article
Vertical Farming
Spectrum strategy for vertical farm leafy greens and herbs: which bands matter, when a fixed recipe beats tunable, and how to keep spectrum consistent tier-to-tier.
Read Article
Vertical Farming
The economics of vertical farming under LED come down to photons per joule and yield per photon. A framework for comparing efficacy, density and cost — with worked numbers.
Read ArticleEvery technical figure on this page is traceable to one of the sources below. Each entry gives the publication, its author or issuing body and year, a resolvable link, and the specific claim on this page that it supports — an institution name on its own is not evidence, and no manufacturer marketing material is used here as independent research. All links were checked and resolved on 19 October 2026.
Graamans L., Baeza E., van den Dobbelsteen A., Tsafaras I. & Stanghellini C., Agricultural Systems 160: 31–43 (2018)
Supports on this page: The energy-intensity comparison used in the overview: about 247 kWh of electricity per kilogram of lettuce dry weight in a plant factory, against 70–211 kWh in greenhouses by location and supplemental-lighting regime.
Kusuma P., Pattison P.M. & Bugbee B., Horticulture Research 7:56 (2020)
Supports on this page: The ceiling on fixture efficacy (3.4 µmol/J white + red, 4.1 µmol/J blue + red, roughly 10% lower with optical protection), which is what makes an efficacy-based comparison between rack fixtures meaningful rather than open-ended.
Faust J.E. & Logan J., HortScience 53(9): 1250–1257 (2018)
Supports on this page: The DLI figures in the crop table and the note that a rack recipe is a DLI target delivered through a PPFD and photoperiod pair, not a PPFD target on its own.
DesignLights Consortium, technical requirements effective 18 April 2025
Supports on this page: Comparing rack fixtures at a defined class and test configuration, including efficacy and quality metrics, rather than on a headline wattage or a single-point PPFD reading.
American Society of Agricultural and Biological Engineers, standard S640 JUL2017 (reaffirmed 2022)
Supports on this page: The units the per-tier calculation depends on: PPF in µmol/s per bar, PPFD in µmol/m²/s at tray level, DLI in mol/m²/day and PPE in µmol/J.
Where a source could not be confirmed as publicly accessible, the claim it would have supported has been written as a lower-certainty statement rather than given a citation. Planning ranges remain starting points for your own trials — they are not guarantees of performance, and no figure on this page is a quotation.
Industry FAQ
Specific follow-up questions about this application, answered directly and then explained.
Send the growing area, crop and stage, target PPFD or DLI, ceiling or layer height and your market requirements. We will come back with a fixture proposal, a layout suggestion and the documentation you need to evaluate it.
