How to Write a Lighting Specification: Luminaire Clauses and Equivalence Criteria

Without a specification, lighting quotes cannot be compared: one company offers a 30 W luminaire at 2,400 lm, another at 3,600 lm, and both look "compliant". A specification states in numbers what the luminaire must achieve, which clarifies both the quotation and acceptance on site.

What are the sections of a specification?

1. Scope and standards: description of the work and the standards to follow.
2. Light targets per room: illuminance, UGR, uniformity, Ra.
3. Luminaire types: wattage, luminous flux, optics, colour and mechanical values for each type.
4. Electrical and control: supply, driver, protocols such as DALI or 1-10V, emergency lighting.
5. Environment and mounting: IP and IK rating, ambient temperature, mounting type.
6. Documents and tests: datasheet, photometric file, test reports, CE declaration.
7. Equivalence and approval: how equivalence is measured and sample approval.
8. Warranty and delivery: warranty period, acceptance and handover documents.

How should standards be stated?

Stating the edition year next to the standard number is recommended. For example, the 2024 edition of EN 1838 has been published and escape route conditions changed compared with the previous edition; if the applicable edition is not stated, quotes may be prepared against different values.

Light targets per room

EN 12464-1 gives the required maintained illuminance (Ēm), glare limit (UGR), uniformity (Uo) and colour rendering (Ra) for each task. In the specification these four values are written for every area on the room schedule.

For other areas, see office lighting lux levels and the sector guides. The values in the table are typical targets from EN 12464-1; in a project, the table in the current edition of the standard and the specific conditions of the space should be used.

The 2021 edition of EN 12464-1 adds a "modified" value next to the "required" value. If one or two context factors apply, such as a critical task, costly errors, small or low-contrast details, unusually long tasks, little daylight or below-normal eyesight, illuminance rises by one step; if more than two apply, by two steps. If illuminance is raised, wall, ceiling and cylindrical illuminance values rise by the same number of steps. The specification should state clearly which value applies.

Clauses per luminaire type

The numbers in this table are examples; project values come from the calculation. For the meaning of lifetime figures, see the L70, L80 and B10 guide. Under EU Regulation 2019/2020, the flicker limits apply to mains-connected LED light sources at full load: PstLM ≤ 1.0 and, from 1 September 2024, SVM ≤ 0.4; SVM does not apply to outdoor and industrial applications or products below CRI 80.

Control and emergency lighting clauses

• Control: distinguish between DALI, 1-10V, Triac and on/off; on DALI, one line supports 64 addresses, and grouping and scene needs are added to the specification.
• Emergency lighting: state which luminaire types need an emergency kit, the duration (1 or 3 hours) and the escape route targets.
• EN 1838 values: under EN 1838:2013, escape routes up to 2 m wide need at least 1 lux on the centre line and open areas 0.5 lux; the current edition applies to the project.

Which documents are requested?

• Datasheet: wattage, luminous flux, CCT, CRI, beam angle, IP, electrical class, dimensions, dimming.
• Photometric file: LDT or IES; the wattage and lumens in the file must match the luminaire.
• CE declaration of conformity and luminaire safety test information.
• Test reports for lifetime and luminous flux (IES LM-79, LM-80, TM-21).
• Warranty document and scope.
• Mounting details and wiring diagrams.

How is an equivalence clause written?

"Brand X or equivalent" alone causes disputes because what counts as equivalent is undefined. The clause should list the values to compare. For the evaluation steps, see the equivalent luminaire guide.

1. Numerical values must meet the thresholds in the specification.
2. The illuminance calculation must be repeated with the proposed luminaire's LDT or IES file; Ēm, Uo and UGR targets must be met.
3. Dimensions, cut-out and mounting detail must fit the ceiling.
4. Control protocol and dimming range must be the same.
5. Where necessary, approval is given after seeing a sample.

Sample specification clause

Type A1 (linear pendant): Extruded aluminium housing, RAL 9005. Luminaire output ≥ 3,600 lm, system power ≤ 36 W, 3000K, Ra ≥ 80, UGR ≤ 19, opal diffuser. DALI (IEC 62386) driver. L80B10 50,000 h. IP20. LDT file, datasheet and CE declaration of conformity are submitted with the quotation. For a proposed equivalent, the illuminance calculation is repeated; targets of Ēm 500 lx, Uo 0.60 and UGR 19 are met.

Common mistakes

• Writing only the wattage; a luminaire is not defined without luminous flux and optics.
• Writing LED chip lumens as luminaire lumens.
• Not stating the control protocol, so an on/off luminaire is quoted for a DALI project.
• Not stating the edition of the standard.
• Not defining how equivalence is measured.

Conclusion

A good specification makes quotes comparable on the same values and simplifies acceptance on site. For luminaire data see technical documents, and for design-stage support see lighting support for architects.