Can Lights in Garage: What to Watch For After They Go In

Can lights work in a garage, and they will almost certainly leave it dimmer than you pictured. Nine 6-inch LED wafer downlights in a 20-by-20-foot two-car garage deliver about 16 initial footcandles at bench height, against the 30 to 50 footcandles the U.S. Department of Energy's Energy Saver guidance calls sufficient for most home and office work. What decides the result is published photometry — delivered lumens, beam angle, spacing criterion — measured against your ceiling height and the spots where you look at things closely. Fixture count follows from that arithmetic; it does not lead it. Afterwards, the three problems that surface most are ambient heat, insulation added later, and the open door panel occupying the front two-fifths of the ceiling.

I have cataloged photographs of weather-damaged parked cars for more than a decade. The most common reason I hand one back without a verdict is that the garage was lit on a grid: even coverage, no shadow control, a rocker panel that reads gray whether it is dirty or blooming with rust.

Map the garage before you map the ceiling

Municipal codes publish the dimensions worth starting from. Oxnard's city code, Sec. 16-638(E), sets a single-car garage at not less than 10 feet 6 inches wide by 20 feet long measured from the interior, a two-car garage at 20 by 20 feet, and the interior height of all garages at not less than seven feet. The same section allows storage cabinets four feet high within four feet of the rear wall, so your zoning code already assumes a cabinet run at the back — and a downlight centered over it lights cabinet tops.

Ceiling height is where the assumption breaks. The International Residential Code sets minimum heights in Section R305.1: seven feet for habitable space, hallways and portions of basements containing them, as reproduced in the City of Boise's IRC handout #434. Garages are not on that list. Yours may be seven feet, eight, or a scissor-trussed nine, and every photometric number below moves with it.

Then the door. Clopay's measuring guide requires 10 inches of headroom for a standard extension spring system and 12 for a torsion spring, more with an opener, and backroom equal to the door height plus 18 inches. For a seven-foot door that is 8 feet 6 inches of horizontal track running back from the header — 42 percent of a 20-foot depth, in the ceiling plane, with a steel panel parked under it whenever the door is open.

Record five things before drawing anything: joist direction and depth, the track footprint above, the height and depth of the bench top, where you stand while working, and which wall the cabinets claim.

How many can lights a 20-by-20 garage actually needs

Lithonia Lighting's spec sheet for the WF6 wafer downlight lists 1,020 delivered lumens at 13 input watts, 78.5 lumens per watt, 3000 K, 80 CRI, test number ISF 30024. Its candela summary gives 381 candelas straight down, a 50 percent beam of 63.3 degrees, a 10 percent beam of 108 degrees, and a spacing-to-mounting-height ratio of 1.2. That ratio is the manufacturer's own spacing rule, and it beats any generic four-and-a-half-foot recommendation because it comes from this fixture's measured distribution.

The same sheet publishes illuminance for one luminaire at a plane 30 inches above the floor:

| Mounting height | Center footcandles | 50% beam diameter | 10% beam diameter | |---|---|---|---| | 8 ft | 12.6 fc | 6.8 ft | 15.1 ft | | 10 ft | 6.8 fc | 9.2 ft | 20.6 ft | | 12 ft | 4.2 fc | 11.7 ft | 26.1 ft |

Raising the ceiling two feet costs nearly half the light directly under the fixture. That is inverse-square law, and no fixture choice repeals it.

Turning that into a garage answer takes five steps:

1. Measure the room and the plane you care about. A 20-by-20-foot bay with an 8-foot ceiling and a 30-inch bench gives 400 square feet and 5.5 feet of cavity above the workplane.
2. Compute the room cavity ratio: five times cavity height times perimeter, divided by floor area. Here that is 2.75, so read row 3 of the coefficient table.
3. Pick honest reflectances. An unpainted garage runs roughly 50 percent ceiling and 30 percent walls against the table's assumed 20 percent floor, putting the coefficient of utilization at 0.69.
4. Multiply fixture count by delivered lumens by the coefficient, divided by floor area.
5. Compare against a published target, then subtract for dirt and lumen depreciation.

Nine WF6s on a three-by-three grid at 6 feet 8 inches — inside the 6.6-foot maximum the 1.2 spacing criterion allows — give 15.8 footcandles initially, about 13.5 after a realistic 0.85 light loss factor. Reaching 30 footcandles takes 17 of them, 221 watts, and 17 holes.

Two published figures frame that. DOE's Energy Saver glossary states that 30 to 50 footcandles is sufficient for most home and office work, that detailed work wants 200 or more, and that 5 to 20 may serve for finding your way at night. OSHA's construction illumination table, 29 CFR 1926.56 Table D-3, requires 10 footcandles in general construction plant and shops, including carpenter shops. That OSHA number is a legal floor for a construction workplace rather than a design target, and it does not reach a private garage.

The gap is worth naming: no residential code I could find sets a light level for a garage. The Illuminating Engineering Society's residential recommended practice, RP-11, is the governing document and sits behind a paywall — I did not open it, so I will not quote a number from it. The only interior illuminance figure I found in a residential code is California Residential Code R303.7, cited in the City of Milpitas building safety handout, requiring not less than 1 footcandle at the center of stair treads. Your garage has no number to meet, which is why the arithmetic matters.

Can lights versus linear shop lights over a work area

| | Lithonia WF6 (recessed) | Halo HLB6 (recessed) | Lithonia FMLWL 48 (linear) | |---|---|---|---| | Delivered lumens | 1,020 | 1,061 (tested) | 4,492 | | Input watts | 13 | 16 (tested) | 42 | | Efficacy | 78.5 lm/W | 66.3 lm/W | 111 lm/W | | CRI | 80 | 90+ (Ra 94.1, R9 68.5) | >85 | | Location listing | Wet | Wet, IP44 | Damp | | L70 rating | 36,000 hrs | 50,000 hrs | 60,000 hrs | | Emitting surface | 4.9 in aperture | 6 in round | 47⅜ × 5½ in |

For the same 30 footcandles across that 400-square-foot bay, the arithmetic gives 17 recessed cans at 221 watts and 17 ceiling penetrations, or four 4-foot wraparounds at 168 watts and none. The linear fixtures do it on 24 percent less power, because the wrap runs at 111 lumens per watt against the wafer's 78.5.

One thing I expected to find and did not: the beam shapes are nearly identical. The zonal summaries put 79.8 percent of the WF6's output within 60 degrees of straight down, 80.2 percent for the HLB6, and 78.6 percent for the wraparound. Whatever advantage a shop light holds over a work area, a wider beam is not it. The difference is emitting geometry — a 47⅜-inch line of light against a 4.9-inch aperture — which softens the shadow edge your own shoulders throw.

My position, and it is arguable: in a garage you work in rather than merely park in, recessed cans are the wrong primary layer. Use them for the clean ceiling and the parking bay, and let linear or task fixtures carry the bench.

Where the shadows land, and how far you can move a can

Roughly four-fifths of a recessed downlight's output arrives within 60 degrees of vertical, landing on horizontal surfaces: the floor, the bench top, the closed hood. Open the hood and the engine bay becomes a box lit from directly above, the fender line shading its own walls, the person leaning in shading whatever the fender missed.

The published beam angle tells you how far you can offset a fixture to get around your own body. At 5.5 feet above a 30-inch plane, the WF6's 63.3-degree 50 percent beam reaches 3 feet 5 inches horizontally before intensity falls below half. The HLB6's 110-degree beam angle reaches 7 feet 10 inches. Same nominal aperture, more than double the useful offset. Read the beam angle before you buy, not the wattage.

Glare works the same way. The DOE glossary is blunt: glare is primarily the result of the relative placement of light sources and the objects being viewed. A bare wafer lens 5 feet in front of your eyes while you sight down a fender is a light source in the visual field rather than illumination on the panel.

Four ceiling conditions reliably ruin a can layout. Open joists give the fixture nothing to clip to. Insulation in the cavity dictates housing rating before anything else. The door track band across the front 8 feet 6 inches leaves no usable plenum and, when the door is up, no line of sight. Cabinet runs turn any fixture within about three feet of the back wall into cabinet-top lighting.

The ratings, wiring, and code questions to settle before the hole saw

Two clearances govern. Under IRC Section E4004.8, corresponding to NEC 410.116(A)(1) and (A)(2), a recessed luminaire not identified for contact with insulation must have all recessed parts spaced at least half an inch from combustible materials. Under E4004.9, corresponding to NEC 410.116(B), thermal insulation must not be installed above a recessed luminaire or within 3 inches of its enclosure, wiring compartment, ballast, transformer, LED driver or power supply, unless the luminaire is identified as Type IC. Both appear in DOE's Building America Solution Center brief on recessed lighting, which also notes the IECC requirement that recessed luminaires in the thermal envelope be IC-rated and labeled at not more than 2.0 cfm of air leakage tested to ASTM E283 at 75 pascals.

Both fixtures I looked at clear that bar. The WF6 is listed IC and air-tight certified to ASTM E283-2004; the HLB6 is cULus certified Type IC and airtight per ASTM E283-04. The HLB6 sheet then adds a caveat almost nobody reads: it is not recommended for direct contact with spray foam insulation, referencing NEMA LSD 57-2013. Type IC does not mean any insulation.

That caveat is enforceable. The Milpitas handout cites CEC 110.3(B) — listed or labeled equipment shall be installed in accordance with any instructions included in the listing. The instruction sheet is code. The same handout gives the damp-versus-wet rule from CEC 410.10(A): luminaires marked "Suitable for Damp Locations" may go in damp locations, while those marked "Suitable for Wet Locations" may go in either. A garage that takes a wet car in February earns the wet-listed fixture.

Miami-Dade County's electrical inspection guidelines confirm that boxes must sit in accessible locations for all junctions and outlets under NEC 300.15 and 314.29, which is why canless driver boxes come out through the aperture. St. Paul's 2020 NEC garage checklist adds a wall-switched lighting outlet in any powered garage under 210.70(A)(2)(a), and a detached garage served by only one branch circuit or feeder under 225.30. It also carries a local interpretation worth knowing, since local amendments are where projects fail inspection — the department reads horizontally wired exposed NM cable below 8 feet as subject to physical damage under NEC 334.15.

Circuit load is the worry that turns out to be nothing. Twelve HLB6 fixtures draw 0.092 amps each at 120 volts: 132 watts, about 1.3 amps, under 10 percent of a 15-amp circuit. That detached-garage single-circuit limit is the real constraint. Milpitas also requires an electrical permit for lighting work, with rough inspection before power is supplied and before anything is covered.

Already dim? What you can fix without recutting the ceiling

Start with paint, the cheapest coefficient you own. Moving from a bare garage at 50 percent ceiling and 30 percent wall reflectance to a white-painted 80 and 50 lifts the WF6's coefficient of utilization from 0.69 to 0.80 at the same room cavity ratio. Those nine fixtures go from 15.8 to 18.4 footcandles with no electrical work at all.

Then add rather than replace. The arithmetic scales linearly, so three fixtures placed at measured dark spots buy the same light as three anywhere, at three holes instead of nine. Put them where your body blocks, offset toward the room from the bench edge, inside the beam distances above.

Change the light before you change the fixture. Both wafers ship with field-selectable color temperature, and the DOE glossary is worth quoting against the reflex 5000 K choice: color rendition is generally considered a more important lighting quality than color temperature, and 2700 to 3600 K is generally recommended for most indoor general and task lighting. The same page notes that cool light produces higher contrast for visual tasks, so there is a genuine trade here rather than a right answer. For judging corrosion I would take the HLB6's measured Ra of 94.1 and R9 of 68.5 over a higher Kelvin number every time. Rust bloom is red.

A ceiling cannot do detailed work. DOE's 200-footcandle figure is roughly seven times what nine cans deliver, and that gap closes at the bench, not overhead.

What to watch for in the first year

Heat catches people, which is why I lead with it. The WF6 is rated for ambient operation from −40 °F to 104 °F. The HLB6 lists −30 to 40 °C, the same 104 °F ceiling. Even Lithonia's CSVT vapor-tight commercial fixture stops at 40 °C. An unconditioned garage in a hot climate puts its ceiling plane above that in August, and the sheets say plainly that actual performance may vary with the ambient temperature of the installed location. Early lumen depreciation and year-two driver failure usually trace back here rather than to a bad fixture.

Watch the insulation. If anyone blows in an attic above that garage after the lights are in, the 3-inch clearance rule applies retroactively to non-IC housings, and the spray-foam caveat applies even to IC ones.

Watch the rodents, where my own ground overlaps this topic. Open-joist garage ceilings run NM cable through exactly the void mice prefer, and a nest against a driver box is a fire question as much as an electrical one. Light that reaches vertical surfaces and cavity edges makes nesting visible in month two. A flat downlight grid hides it until the harness is chewed.

Watch the light age. The three fixtures here carry L70 ratings of 36,000, 50,000 and 60,000 hours, meaning 70 percent of initial output at that point. A layout designed with no headroom above your target arrives below it.

The plan that survives all this is layered and circuited for change: a recessed general layer sized with the arithmetic above, linear or task fixtures over the current work zone, and a switched circuit with spare capacity so the second layer can move when the bench moves. Garages change use every few years. Ceiling holes do not move.

Frequently asked questions

How many can lights do I need in a 2 car garage?

For a 20-by-20-foot bay with an 8-foot ceiling, nine 1,020-lumen 6-inch wafers on a 6-foot-8 grid give about 16 initial footcandles at bench height. Reaching the 30 footcandles DOE calls sufficient for most home work takes about 17 fixtures and 221 watts.

Do can lights in a garage have to be IC rated?

Only if insulation contacts them. NEC 410.116(B) prohibits thermal insulation above a recessed luminaire or within 3 inches of its enclosure or driver unless it is identified as Type IC. Energy codes separately require IC-rated, air-tight-labeled fixtures in the building thermal envelope, which includes garage ceilings under conditioned space.

Can I install can lights in a garage with an unfinished ceiling?

Not directly. Canless wafers clip to a finished ceiling — the Halo HLB6 is listed for ceilings half an inch to 1¼ inches thick — so open joists give the spring clips nothing to grip. You must drywall first, or choose surface-mounted fixtures that fasten to the framing instead.

Will garage heat damage recessed LED lights?

It can. Both wafer downlights I checked are rated to a maximum ambient of 40 °C, which is 104 °F, and a commercial vapor-tight fixture stops at the same point. An unconditioned garage ceiling can exceed that in summer, and manufacturers state that performance varies with installed ambient temperature.

Are can lights or shop lights better over a workbench?

Shop lights, for bench work. A 4-foot LED wraparound delivers 4,492 lumens at 42 watts against a wafer's 1,020 at 13, and its 47-inch emitting surface softens the shadow your own shoulders cast. Their beam distributions are nearly identical, so the advantage is source size, not spread.

What code applies to recessed lights in a garage?

NEC 410.116 governs clearance from combustibles and insulation, and 410.10(A) governs damp versus wet location marking. NEC 210.70(A)(2)(a) requires a wall-switched lighting outlet in a powered garage. Local amendments and permit rules vary, so confirm the adopted edition with your building department before cutting.