Attribute Schema Library
Attribute schemalighting

Downlights: Attribute Schema Reference

A downlight is a recessed ceiling luminaire with a controlled downward distribution. The category runs from 2 in canless wafers bought by the case, through 4–6 in new-construction housings with interchangeable trims, to retrofit kits that mount into existing cans and spec-grade 3 in adjustables sold against a lighting schedule. Buyers are electrical contractors matching a submittal, lighting designers running photometrics, and facility teams replacing one failed fixture in a hole that already exists.

The data is hard for three reasons. Nominal size, aperture, and ceiling cutout are three different numbers published under one label — a "4 in" downlight can have a 4.13 in aperture and a 4.5 in cutout. Selectable-CCT and selectable-wattage products fold five CCTs and three lumen packages into one MPN, so single-valued fields either drop data or detonate into variants. And most of what a buyer filters on — beam angle, SDCM, dimming protocol, IC/airtight rating — lives in a PDF cut sheet and an ordering-code matrix, not in the price file the distributor loads.

Core

Every SKU needs these. Without them the record is not a product, it is a row.

Manufacturer Part Number
identifier
M4-1250L-930-40D-WH-ICAT

The only stable key across supplier price file, submittal, and contractor PO. Ordering-code suffixes change the actual fixture, not just the label.

GTIN / UPC
identifier
00190348052341

Required for marketplace listing and for item sync into the electrical data pool. Case and each GTINs differ; wafers ship in 4- and 12-packs.

Aperture Size
enum · in
4 in

The nominal family a buyer shops by. Drives trim interchangeability and ceiling appearance. Standard steps only — this is not a free-text dimension.

Ceiling Cutout Diameter
number · in
4.5

The hole the installer cuts, or the hole that already exists on a replacement. Does not equal aperture size and is the field that prevents returns.

Housing Type
enum
Canless, integrated junction box

Canless, new-construction housing, remodel/old-work, or UL 1598C retrofit kit. Determines whether the buyer also needs a trim, a can, or nothing.

Delivered Lumens
number · lm
1250

Luminaire output per LM-79, not source lumens. What the lighting layout is calculated against. Selectable-wattage SKUs carry a set, not one value.

Input Wattage
number · W
14.3

Drives circuit loading, fixture count per 20 A branch, and rebate math. Must be system watts including driver, not LED module watts.

Correlated Color Temperature (CCT)
enum · K
Selectable 2700/3000/3500/4000/5000 K

Nominal CCT per ANSI C78.377. Field-selectable products must publish every selectable step, not just the factory default.

Input Voltage
enum · V
120–277 V

120 V residential vs 120–277 V commercial vs 277 V only. A 120 V-only wafer on a 277 V commercial circuit is a callback.

Differentiating

What buyers actually compare on. This is where catalogs win or lose the filter.

Color Rendering Index (CRI)
number · Ra
93

80 CRI for back-of-house, 90+ for retail and residential, 95+ for gallery and merchandising. A hard filter on most spec jobs.

Chromaticity Consistency (SDCM)
enum · MacAdam step
2-step

Whether a row of downlights looks like one row. 2-step vs 5-step is visible on a ceiling and separates spec grade from commodity.

Beam Angle
enum · °
40° flood

15° narrow spot through 90°+ general ambient. Sets spacing and vertical illuminance. Adjustables publish a range, not a point.

Dimming Protocol
enum
0–10 V to 1%

0–10 V, TRIAC/ELV phase-cut, DALI-2, or non-dim — plus the floor (1%, 0.1%). The single largest source of downlight returns.

Trim Style & Finish
enum
Round baffle, matte white

Baffle, reflector, pinhole, wall wash, flangeless, adjustable/gimbal; white, black, bronze. Architectural selection, and often the reason for the RFQ.

Compliance & identifiers

Standards, regulatory data, and the identifiers channels reject you for missing.

IC Rating
enum
IC / Air-Tight (ICAT)

IC vs Non-IC vs IC/Air-Tight. IECC requires IC-rated, air-tight luminaires in the insulated thermal envelope; Non-IC in insulation is a code violation.

Location Listing
enum
Wet location, IP66

Dry, damp, or wet location, plus IP rating per IEC 60529. A damp-only trim over a shower is rejected at inspection.

Listings & Certifications
text
cULus (UL 1598/UL 8750), ENERGY STAR, Title 24 JA8-E

cULus to UL 1598 / UL 8750 (or UL 1598C for kits), ENERGY STAR, Title 24 JA8-E, fire rating, Chicago Plenum. Gates the bid, not just the page.

Country of Origin
identifier
CN

Drives duty, and gates Buy American / BABA federal and municipal work. Missing COO removes the SKU from public-sector bids outright.

The fields that aren't in the schema at all

What most downlights catalogs are missing.

The table above is the schema most catalogs already have. These are the attributes that usually aren't in it — each one surfaced by a signal from the live market rather than by an audit of what's already there. This is what Anglera's Schema Foundry does on a real catalog, in this category.

Search signal
+ Ceiling Cutout Diameter

Replacement buyers search '4 inch downlight 4.5 inch hole' and get filtered by aperture family instead. Catalogs publish nominal 'Trim Size: 4 in'; the cutout exists only in the cut sheet drawing.

Fixture arrives, hole is wrong, drywall gets patched or the unit goes back. Retrofit-into-existing-can is the highest-return sub-segment in the category.

Competitor signal
+ Chromaticity Consistency (SDCM)

Spec-grade manufacturer sheets lead with '93 CRI, 2-step SDCM'. Distributor filter rails expose CRI and stop, so a 2-step fixture and a 5-step fixture look identical on the page at different prices.

The premium SKU cannot justify its price against a commodity wafer, so the buyer sorts by price and the margin SKU is never seen.

Marketplace signal
+ DLC QPL ID / ENERGY STAR ID

Contractors check the DLC Qualified Products List before quoting so the job clears a utility rebate. Catalogs carry a 'DLC Listed' checkbox at best, and no product ID to look up.

Rebate cannot be verified at quote time, so the contractor specs a competitor SKU that shows its QPL ID. The rebate decides the order, not the fixture.

Supplier signal
+ IES Photometric File

Designers running AGi32 or Visual need the .ies for the exact catalog number, CCT, and optic. Distributor pages link a cut sheet PDF and no photometrics, so the designer leaves for the maker's site.

The fixture never enters the lighting schedule. The layout is built around whoever published photometrics, and that brand wins every downlight on the job.

Review signal
+ Dimmer Compatibility / NEMA SSL 7A

Reviews on phase-cut downlights are dominated by flicker, buzz, and drop-out at low end. Sheets say 'TRIAC dimmable'; the tested dimmer list lives in a separate document, if it exists at all.

Fixture is blamed for the dimmer mismatch and returned as defective. Title 24 requires phase-control LED sold in California to be SSL-7A compliant.

How Schema Foundry finds these

Messy in, governed out.

The same value, spelled every way lighting suppliers spell it. A filter only works once they agree.

Correlated Color Temperature (CCT)
3000K3000 K3,000KWarm White830WW
3000 K

'Warm white' spans 2700–3000 K depending on supplier. '830' encodes 80 CRI + 3000 K and must be split into two fields.

IC Rating
ICIC RatedICATIC/ATIC AirtightInsulation Contact
IC / Air-Tight (ICAT)

IC and air-tight are two separate claims. Collapsing them loses the air-leakage rating the energy code checks in the thermal envelope.

Aperture Size
4"4 in4-inch4IN102mmFour Inch
4 in

Metric-sourced suppliers send the cutout in mm, not the aperture in inches. Converting the wrong number silently breaks the size facet.

Dimming Protocol
0-10V0/10V010VELV/TRIACPhase CutDimmable
0–10 V

'Dimmable' is not a protocol. 0–10 V and phase-cut need different wiring and different dimmers; the merged value is unusable as a filter.

What buyers ask

Every one of these should be answerable from the attributes above. If it isn't, that's a gap.

  • Will this drop into the 4-inch hole I already have, or do I have to cut it bigger?
  • How many can I put on one 20-amp circuit?
  • Is this IC rated? It's going in an insulated attic.
  • Can I use it over a shower or on a covered porch?
  • Does it work with the Lutron dimmers already on the wall?
  • Do I need a housing and trim, or is this the whole fixture?
  • Is it on the DLC list? The job needs the utility rebate.
  • Will all twelve of these actually look the same color on the ceiling?

What channels require

The same SKU, different mandatory fields per destination.

Distributor's own faceted catalog
Aperture SizeCeiling Cutout DiameterDelivered LumensCorrelated Color Temperature (CCT)IC RatingTrim Style & Finish
IDEA Connector / Industry Data Warehouse (IDW)
GTIN / UPCManufacturer Part NumberUNSPSC codeCountry of OriginPack hierarchy and unit of measureMarketing description
DLC Qualified Products List (utility rebates)
Delivered LumensInput WattageLuminaire efficacy (lm/W)Correlated Color Temperature (CCT)Color Rendering Index (CRI)LM-79 test report
Amazon Business
GTIN / UPCManufacturer Part NumberInput WattageDelivered LumensCorrelated Color Temperature (CCT)Country of Origin

Downlights data, in practice

What's the difference between aperture size and ceiling cutout diameter?

Aperture size is the nominal family — 2, 3, 4, 5, 6, 8 in — and it governs trim interchangeability and how the fixture is shopped. Ceiling cutout diameter is the hole the installer actually cuts, and it is usually larger than nominal: a 4 in downlight commonly needs a 4.25–4.5 in cutout, and the visible aperture may be 4.13 in. All three get published under the label 'size' by different suppliers. Carry them as separate fields. Cutout is the one that matters on any replacement or retrofit, which is where the returns come from.

How should selectable-CCT and selectable-wattage downlights be modelled?

One MPN can ship five CCTs and three lumen packages behind a DIP switch. Do not pick the factory default and drop the rest — a buyer filtering 3500 K will never see a fixture that does 3500 K. Model CCT and lumens as multi-valued on the SKU, add a boolean for field-selectable, and enumerate the selectable steps (2700/3000/3500/4000/5000 K). Splitting into fifteen variants is worse: it inflates the catalog, breaks the price file mapping, and none of the variants are separately orderable.

Which standards genuinely apply to a downlight record?

Safety: UL 1598 for the luminaire, UL 8750 for the LED driver and module, UL 1598C for retrofit conversion kits — listed cULus or ETL. Colour: ANSI C78.377 defines the nominal CCT quadrangles. Performance: IES LM-79 for output and efficacy, LM-80 with TM-21 for lumen maintenance and L70. Ingress: IEC 60529 for IP. Dimming: NEMA SSL 7A for phase-cut compatibility, which California Title 24 requires. Programs: ENERGY STAR, Title 24 JA8-E, and the DLC QPL. Air leakage for air-tight claims is tested per ASTM E283.

Why carry SDCM if the record already has CRI?

They measure different things and buyers use them differently. CRI says how accurately the light renders colour against a reference. SDCM says how tightly a production run holds its chromaticity — how far one fixture can drift from the next. Two fixtures can both be 90 CRI 3000 K and be visibly different colours on the same ceiling if one is binned at 5-step and the other at 2-step. On a corridor of twelve downlights that mismatch is the complaint. It is also the field that explains a price gap the buyer would otherwise read as arbitrary.

More lighting schemas

Emergency LightingHigh Bay FixturesLamps & BulbsLED FixturesLighting Controls

Run this against your own downlights.

Bring the category. We'll show you which of these attributes your catalog is missing — and the ones we find that aren't on this page yet.

Book a demo