In short
What the Future Buildings Standard's 105 luminaire lumens per circuit watt means for linear lighting in new non-domestic buildings, and how to check it.
The Future Homes and Buildings Standards were published on 24 March 2026 and generally come into force on 24 March 2027, with transitional arrangements for non-higher-risk work that starts before 24 March 2028 (GOV.UK Building Circular 01/2026). With the start date now under six months away, projects at stage 3 and 4 are already being designed against it.
For lighting, the headline is a higher efficacy baseline. Under the new Approved Document L, internal general lighting in new non-domestic buildings must achieve an average of more than 105 luminaire lumens per circuit watt, measured at the luminaire rather than at the LED chip (Future Buildings Standard guide). This guide explains what that means for linear lighting and how to check a specification.
What has changed
| Part L 2021 | Future Buildings Standard | |
|---|---|---|
| Notional general lighting efficacy | 95 lm/W, light-source level | 105 lm/W, luminaire level |
| What is measured | The lamp or light source | The whole luminaire, including optical and driver losses |
| Consultation proposal | n/a | 150 lm/W, later reduced to 105 lm/W after industry feedback |
The same guide notes that the government originally consulted on 150 lm/W before settling on 105 lm/W. The shift to luminaire level matters more than the number: losses in the diffuser, optic and driver now count.
Luminaire lumens, not chip lumens
Many datasheets still lead with source or chip lumens. For compliance you need the luminaire output divided by the circuit watts, including the driver. A linear fitting with an opal diffuser can lose a noticeable share of its source output in the optic, so two fittings built on the same LED board can have very different luminaire efficacy.
- Ask for luminaire lumens and circuit watts from a photometric test.
- Check the figure is for the exact diffuser, length and colour temperature specified.
- Compare like with like: the same CCT, CRI and output setting.
Our guides to lumens per metre and efficacy and how to read a linear LED datasheet go into the detail.
Choices that move the number
Optics and diffusers
Microprismatic optics are usually more efficient than deep opal diffusers, as well as controlling glare. If the design calls for a soft opal look, check the luminaire efficacy of that version rather than assuming the family figure. See microprismatic vs opal diffusers.
Colour temperature and colour rendering
Warmer colour temperatures and higher CRI typically reduce efficacy slightly. That does not rule out 3000K or CRI 90 in client-facing areas, but it should be checked area by area. See colour temperature for linear lighting.
Direct or direct/indirect
Direct/indirect pendants help meet CIBSE LG7 ceiling and wall brightness guidance, and they can still be highly efficient. The trade-off is with the design intent, not compliance alone; read direct vs direct/indirect.
Drivers and controls
Driver losses now count. Dimmable DALI drivers with good efficiency at the operating point help, and controls reduce energy in use. See daylight dimming and presence detection.
A specification checklist
- State the minimum luminaire efficacy for general lighting in the specification.
- Ask suppliers for test-based luminaire lumens and circuit watts for each type.
- Calculate the average across the general lighting, as the standard requires an average.
- Keep feature and display lighting separate from general lighting in the calculation, following the Approved Document.
- Record the figures in the BRUKL or SBEM inputs and keep the data for handover.
- Re-check if a substitute is offered during value engineering.
Glare, quality and LG7 still apply
Efficacy is only one target. Offices still need UGR 19 or lower for screen work, appropriate illuminance and good room brightness. A very efficient luminaire that causes glare is not a good result. Our guides to UGR19 and CIBSE LG7 explain how linear schemes meet both.
Existing buildings and refurbishments
The 105 lm/W figure applies to new non-domestic buildings. Refurbishments follow the requirements for work to existing buildings, but many owners now ask for new-build performance anyway, for EPCs and ESG reporting. Where existing housings are sound, a retrofit can be the lower-carbon route; see lighting, EPCs and minimum energy standards on relumen8.com.
How 299 Lighting can help
299 Lighting can provide photometric files, luminaire efficacy data and lighting design support for linear schemes, and our suspended and recessed ranges include versions for open-plan offices and education. For pendants without the linear brief, see suspended lighting for offices, and for downlights in the same scheme, recessed lighting for offices.
Send us your luminaire schedule and we will check the luminaire efficacy of each type.
Further reading at 299 Lighting
Next steps on linear-led.com
Specifying a linear scheme?
Send us your drawings or brief. We'll come back with a shortlist, photometrics and LG7 calculations.
Start a project →Frequently asked questions
What is the lighting efficacy requirement in the Future Buildings Standard?
Internal general lighting in new non-domestic buildings must achieve an average efficacy of more than 105 luminaire lumens per circuit watt.
When does the Future Buildings Standard come into force?
Generally on 24 March 2027, with transitional arrangements for non-higher-risk work where notice was given before that date and work starts before 24 March 2028.
Is 105 lm/W measured at the LED or the luminaire?
At the luminaire. It includes losses in the optic, diffuser and driver, so ask suppliers for tested luminaire lumens and circuit watts.
Does the 105 lm/W figure apply to refurbishments?
It applies to new non-domestic buildings. Work to existing buildings follows separate requirements, although many owners ask for similar performance.
