Evidence brief: commissioning LED height with a PPFD map
What evidence is needed to choose a useful mounting height rather than repeat a generic distance recommendation?
Scope of this review
Canopy-level measurement, spatial distribution and daily exposure under horticultural LED fixtures. No crop yield trial or comparison of lamp brands.
How we assessed the evidence
We reviewed the cited sources, separated published observations from our operating recommendations, and checked the units and assumptions of any calculations. This is a literature-based technical analysis, not an on-site experiment.
What the evidence supports
Distance is a system variable
Published lighting guidance supports checking layout and delivered light together. Our recommendation is to compare the same measurement grid after each change.
The example is reproducible
The nine explicitly hypothetical values sum to 2280. Dividing by nine gives 253.3; 200 divided by the unrounded mean gives 0.79 after rounding.
DLI needs a time assumption
The 14.4 example assumes constant PPFD throughout the specified lighting period. Changing daylight requires time integration.
What this review does not establish
- The example values are invented for explanation and contain no crop performance evidence.
- Nine points may miss small hotspots or gradients in a large installation.
- We do not establish a universal distance, PPFD or DLI target for all crops.
Hamfy’s proposed next step
Use a repeatable spatial map to commission a lighting installation, then verify it again as canopy height and operating settings change.
Evidence to collect for a real project
- A measured map for the actual fixture layout and canopy
- The crop objective and photoperiod
- Sensor specifications, calibration status and a record of adjustments
Source notes
- Technical source · 2017Lighting Plans: Their Generation and ImportanceMichigan State University
Explains how fixture geometry, output and placement affect a lighting plan and why delivered light should be measured.
- Technical source · n.d.Quantum PAR Sensor Spectral Error Estimation ToolApogee Instruments
Manufacturer guidance on quantum-sensor spectral mismatch; used for measurement limitations, not a product ranking.
- Technical source · n.d.Lighting for indoor plantsUniversity of Minnesota Extension
Basic horticultural lighting context. Household mounting examples are not transferred to commercial fixtures.