In short
How to specify lower-carbon, more circular recessed downlights using CIBSE TM65, TM66 and EPDs, ahead of the SLL and LIA Sustainability Unfiltered event.
On Tuesday 3 November 2026 the Society of Light and Lighting (SLL) and the Lighting Industry Association (LIA) bring their Sustainability Unfiltered series to CIBSE in London, running from 12:30 to 20:00 (CIBSE). The organisers describe it as a chance for designers and specifiers to move "beyond sustainability statements and into meaningful action".
Earlier in October, Recolight's Circular Lighting Live event in the City of London also covered embodied carbon, Environmental Product Declarations (EPDs) and updates to the TM66 circularity metric (Recolight). So what does this mean for the humble downlight? This guide sets out the documents to ask for and the questions to put to manufacturers when you specify recessed lighting.
The three documents to know
| Document | What it is | How it helps a downlight specification |
|---|---|---|
| CIBSE TM65 | A calculation methodology for the embodied carbon of building services products, published in January 2021 | Explains how to use EPDs, and how to estimate embodied carbon where there is no EPD |
| CIBSE TM65.2 | A lighting-specific companion: embodied carbon in building services: lighting | Applies the embodied carbon approach to luminaires |
| CIBSE TM66 | Creating a circular economy in the lighting industry, published in October 2021 | Includes a checklist and a method of assessing a product's circular economy performance |
| EPD | A verified declaration of a product's environmental impacts | Gives the most reliable embodied carbon figures for comparison |
CIBSE says TM65 provides guidance on how to use EPDs to assess the embodied carbon of building services equipment and, where EPDs are not available, how to estimate it (CIBSE TM65). The lighting document, TM65.2, is listed on CIBSE's TM65 page (CIBSE).
TM66 includes the Circular Economy Assessment Method (CEAM). CIBSE describes CEAM-Specify as a triage tool that lets designers, specifiers and engineers quickly compare two or more products (CIBSE TM66).
What to ask a downlight manufacturer
Most of a downlight's circularity is decided at the design stage. Use these questions when you compare options:
- Is there an EPD? If not, is there a TM65 calculation, and which method was used?
- Can the LED module and driver be replaced? A downlight with a replaceable engine and a remote or plug-in driver can be repaired rather than thrown away.
- Are fixings standard? Screws and clips are easier to take apart than glued assemblies.
- What is the CEAM-Specify result? Ask for it if you are comparing similar products.
- Are spares available? Ask how long modules, drivers, reflectors and trims will be supported.
- What about packaging? Ask about bulk packaging on large orders and how it can be recycled.
Design choices that reduce carbon
Specifying a lower-carbon product is only part of the picture. Layout and design choices matter just as much.
Use fewer, better downlights
A good lighting calculation often shows that fewer fittings with the right optic meet the brief. Our guides to beam angles and multi-optic downlights explain how optics affect spacing. For layouts, see cut-out sizes and setting out.
Specify sensible light output and efficacy
Over-lighting wastes energy over the whole life of the building. Check lumen output, efficacy and lifetime on the data sheet. Linear-led.com's guide to lumens per metre and efficacy covers how to read these figures.
Add controls
Presence detection, daylight dimming and scene setting reduce operational energy. See controls for recessed lighting.
Plan for change
Standard cut-outs make future upgrades easier. A downlight that fits a common cut-out can be replaced later without cutting new holes in the ceiling.
Existing buildings: keep before you replace
In refurbishment, the lowest-carbon downlight is often the one already in the ceiling. Where housings are sound, a retrofit can replace the LED engine and driver and keep the rest. Read relumen8.com on whether a housing is worth keeping and TM66 and circular retrofit. Our own guide to recessed lighting in refurbishments covers the practical side, and value engineering recessed lighting explains how to make savings without losing quality.
A simple specification checklist
| Stage | Action |
|---|---|
| Brief | Agree lighting levels, glare limits and any sustainability targets, such as BREEAM |
| Concept | Run calculations to keep the number of fittings sensible |
| Specification | Ask for EPDs or TM65 calculations and TM66 or CEAM-Specify information |
| Tender | Compare like with like, and do not swap products without the same information |
| Handover | Keep data sheets, spares lists and maintenance information for the building manager |
How 299 Lighting can help
299 Lighting has supplied architectural lighting since 2009 and can help with layouts and specification. Browse our products, read about our services or send us your drawings for a lighting layout. For plaster-in details, see trimless downlights, and for decorative fittings in residential areas, browse recessed lights on decorativelighting.shop.
Further reading at 299 Lighting
Next steps on recessedlighting.co.uk
Planning a recessed scheme?
Send us your reflected ceiling plan. We'll come back with a product shortlist, ceiling cut-out details and lighting calculations.
Start a project →Frequently asked questions
When is Sustainability Unfiltered in London?
Tuesday 3 November 2026, from 12:30 to 20:00 at CIBSE in London. It is presented by the Society of Light and Lighting and the Lighting Industry Association.
What is CIBSE TM65?
A methodology for calculating the embodied carbon of building services products. It explains how to use EPDs and how to estimate embodied carbon where no EPD exists.
What is TM66?
CIBSE's guide to creating a circular economy in the lighting industry. It includes a checklist and the Circular Economy Assessment Method (CEAM).
What makes a downlight more circular?
Features such as a replaceable LED module and driver, standard fixings and available spares, so the fitting can be repaired or upgraded instead of replaced.
