There is a pleasant surprise buried in cold storage lighting, and then a series of unpleasant ones.
The pleasant surprise: LEDs work better cold. Lower junction temperature means higher efficacy and longer life, so the same fixture that produces its rated output in a 25°C warehouse produces slightly more of it in a chilled room, and its LEDs age more slowly doing it. Fluorescent tubes did the opposite — they dimmed badly in the cold and struck unreliably — which is why so much cold storage advice still carries assumptions that stopped being true a decade ago.
The unpleasant surprises are everything around the LED. The driver, the gasket, the lens, the mounting, and the plant that has to remove every watt the lighting produces.
This guide covers what actually fails in cold storage, how chilled and frozen rooms differ as lighting problems, and the specification questions that decide whether a fixture lasts a decade or a season.
Key Takeaways
- The LED is not the weak point. The driver, the seal and the thermal cycling are.
- Condensation damage happens during warm-up, not while the room is cold. A fixture that cools breathes moist air in through its own gasket.
- “Cold storage” covers at least four different environments, from a +5°C chill room to a -40°C blast freezer, and they are not one specification.
- Every watt of lighting is a heat load the refrigeration plant has to remove, which makes occupancy control worth more here than in an ambient warehouse.
- Maintenance access is the real cost driver. Changing a fixture at height in a -25°C room is a scheduled operation, not a job ticket.
Four Rooms, Not One
The phrase “cold storage” hides a wide range, and the lighting specification changes across it.
| Space | Typical temperature | The lighting problem |
|---|---|---|
| Dock and airlock | Ambient to +5°C, high humidity | The worst condensation environment on site — warm moist air meets cold surfaces every time a door opens |
| Chill room | 0 to +5°C | Close to a normal warehouse; humidity and washdown are the differences |
| Frozen store | -18 to -25°C | Sustained low temperature, frost, and access that requires planning |
| Blast freezer / spiral | -30 to -40°C | Rapid, repeated thermal cycling; the most demanding environment in the building |
Our standard fixtures — the sealed tri-proof range and the SJGK high bays — carry an operating range of -20°C to 45°C, which covers docks, chill rooms and the warmer part of frozen storage. Below -20°C, the answer is not a catalogue number: tell us the room temperature, the defrost regime and the mounting position, and we will confirm what the application needs rather than assume one fixture spans the whole building. A supplier who quotes the same part number for a chill room and a blast freezer has not asked enough questions.
Why the Driver Is the Limit, Not the LED
The LED driver is where cold storage claims are won and lost, and the ambient temperature rating on the fixture datasheet is really a statement about it.
Two distinct problems live there.
Starting is harder than running. Electrolytic capacitors lose capacitance and gain internal resistance as they get colder — the electrolyte becomes more viscous, and the part behaves differently from the one characterised at room temperature. A driver can run happily in a cold room it cannot reliably start in, which is why the failure so often appears after a power interruption rather than on day one. Ask specifically about cold-start temperature, not just operating temperature. They are different figures and only one of them is usually printed.
The self-heating that saves it also complicates it. A driver dissipates its own losses and sits above room temperature once running. That is helpful in a freezer and unhelpful in the reasoning: a fixture that survives because its own waste heat keeps the driver in range will behave differently at low output on a dimming profile than at full output. If the scheme dims to 10% on unoccupied aisles, say so at specification stage.
The LED package itself, meanwhile, is having an easy time. Lower junction temperature raises luminous efficacy and slows the degradation that L70 rated life describes. Where an ambient warehouse fixture is fighting heat, a cold store fixture is not — which is exactly why the driver, not the light source, sets the limit.
Condensation: The Failure That Happens on the Way Up
This is the mechanism most specifications miss, and it is worth being precise about because the intuition is backwards.
A sealed fixture is not a sealed volume. As a fixture cools, the air inside it contracts and the internal pressure drops, so air is drawn in — through the gasket line, the cable gland, the seam. As it warms, the air expands and is pushed out. This is often called breathing, and it happens on every thermal cycle whether or not the fixture is rated IP65.
The damage is done during warm-up. Cold air holds very little moisture, so a cold fixture that draws in cold air draws in almost nothing. But a fixture that has been cold and then warms — a defrost cycle, a door left open, a room brought up for cleaning, a unit moved to the dock — draws in comparatively warm, humid air, which then condenses on the coldest internal surface as the fixture cools again. Repeat that a few hundred times and water accumulates inside a fixture whose IP rating is entirely genuine.
Three consequences for a specification:
- IP65 is necessary and not sufficient. The rating is a test against water applied from outside at stable temperature. It says nothing about pressure-driven exchange across a thermal cycle. Both matter; only one appears on the datasheet.
- The gland is as important as the housing. Cable entries are the largest breathing path in most fixtures, and an incorrectly sized gland on a correctly sealed housing is the whole seal.
- Defrost regime belongs in the enquiry. How often a room is defrosted, and how far it warms, describes the thermal cycling the fixture will actually see. It is a more useful number than the room’s set point.
Two mitigations are worth naming. A breather membrane — a vent that passes air but not liquid water — gives the fixture a controlled path to equalise pressure instead of pulling humid air through the gasket line, and the tri-proof guide covers how that works across the sealed-fixture range generally. And gasket material matters at temperature: silicone stays compliant across the range, while an inferior gasket stiffens at -25°C and stops sealing at precisely the moment condensation is worst.
Frost, Ice and Light Loss
Frost forms on cold surfaces exposed to moving humid air, and a light fixture in an air-blast cold store is exactly that.
A layer of frost on a lens scatters and absorbs light, so delivered illuminance drops without anything having failed. That belongs in the maintenance factor rather than being discovered later: a cold store design that uses an ambient-warehouse depreciation figure will be optimistic in service.
Two practical mitigations, neither exotic. Keep fixtures out of the direct discharge of the evaporator fans, which is where frost accumulates fastest and where vibration is highest. And prefer a smooth, low-relief lens over deeply ribbed diffusers in frost-prone positions, because what forms easily also has to be cleaned off easily by someone in freezer PPE.
Lighting Heat Is a Refrigeration Load
Here is the argument that changes how cold store schemes get costed, and it is simple physics rather than a sales claim.
Every watt a light fixture consumes inside a refrigerated space ends up as heat inside that space. The refrigeration plant then has to remove it, and removing heat from a cold room costs energy on top of the energy the lighting already used. The lighting load therefore counts twice on the meter, and the colder the room, the less efficiently the plant does that work.
Three things follow:
- Efficacy matters more in a freezer than in an ambient warehouse. The same lumens delivered on fewer watts saves the lighting energy and the refrigeration energy that would have removed it.
- Occupancy control is unusually valuable. Cold stores are frequently unoccupied for long stretches, and a room lit only when someone is in it is a room that is not being heated by its own lighting. Confirm that any PIR sensor specified is itself rated for the ambient — sensors have their own temperature limits, and a sensor that fails cold takes the whole control scheme with it.
- Optical efficiency is not a detail. Light absorbed inside the fixture is heat delivered to the room. A fixture that puts its lumens on the aisle rather than into the ceiling structure is doing double duty here.
What none of this justifies is a specific savings figure, because it depends on the plant, the room, the duty and the tariff. The direction is certain; the number belongs to your energy model.
Where the Light Actually Needs to Go
Cold stores are usually racked densely, often to a greater height than an ambient warehouse of the same footprint, because volume is expensive to chill. That makes the lighting problem a vertical one.
The rack face matters more than the floor. Pickers read labels on product at height, not on the concrete. A scheme that hits its floor lux target with poor vertical illuminance on the rack face reads as badly lit no matter what the meter says at ground level. This is the same principle covered in our warehouse lighting requirements guide, sharpened by narrower aisles and taller racking.
Aisle-aligned distribution beats symmetric distribution. Where racking is fixed, a linear fixture running along the aisle typically delivers better uniformity down the run than round fixtures on a grid — the form-factor decision covered in UFO vs linear high bay. Mounting height and spacing follow the same ratios as any high-bay scheme; our high bay spacing guide covers the arithmetic.
Mobile racking changes the problem entirely. In a mobile-rack store the aisle moves, so a fixture cannot be positioned over a permanent aisle at all. Schemes for these rooms light the whole ceiling plane more evenly and accept the fixture count that requires — and the thermal load argument above makes efficacy matter even more.
Colour temperature is a preference, not a performance question. 4000K to 5000K is common in cold stores for perceived crispness; where product colour is assessed, colour rendering matters more than the colour temperature number. Neither changes how much light reaches the rack face.
Access: The Cost Nobody Quotes
A cold store fixture is one of the most expensive things on site to reach.
Work at height in a -25°C room is a planned operation with PPE, limited working time per person, and often a stock movement to get a platform into the aisle. Some rooms cannot be entered with a standard access platform at all. In the worst case a fixture change waits for a scheduled shutdown, which means a failed fixture is a dark aisle for weeks rather than days.
That asymmetry should drive the specification the same way it does on a port crane:
- Specify for life, not for unit price. The cheaper fixture is rarely cheaper once one visit is counted.
- Group replacement beats individual call-outs. If fixtures are going to be reached during a shutdown anyway, replacing the population is usually cheaper than three separate visits.
- Ask how the fixture is serviced, not just whether it fails. A driver that can be replaced without unsealing the optical chamber avoids re-introducing the condensation problem every time maintenance happens.
- Documented L70 behaviour is worth more than a headline lifetime. Predictable depreciation lets you schedule the visit; an optimistic number does not.
What to Send Us With an Enquiry
Cold store schemes go wrong through missing information more often than through bad products. Five things answer most of it:
- Room temperature and defrost regime — the set point plus how far and how often the room warms.
- Room dimensions, ceiling height and racking layout, including whether racking is fixed or mobile.
- Mounting positions available, and whether fixtures can avoid the evaporator discharge.
- Target level and where it is measured — floor, rack face, or both.
- Access arrangements — how a fixture is reached, and how often the room can be entered for maintenance.
With those, the photometric layout answers fixture count and positions, and the ambient figure answers which series belongs in which room. Our sealed tri-proof fixtures suit chill rooms, docks and racking aisles; the high bay range covers taller frozen stores; and where a room runs below the -20°C standard range, tell us the conditions and we will confirm what the application needs. Send us the room and the regime and we will return a DIALux layout with IES files rather than a part number.
The Bottom Line
Cold storage lighting inverts the usual failure story. The light source is in the best conditions it will ever see, and everything else is in the worst. Drivers fail on cold starts, seals fail through thermal cycling rather than water ingress, lenses lose output to frost that no one logged as a fault, and the whole installation quietly adds to the refrigeration bill.
Specify the driver’s cold-start figure, describe the defrost regime rather than just the set point, keep fixtures out of the fan discharge, and cost the scheme on access rather than on unit price. The fixture that survives a decade in a freezer is rarely the one that looked cheapest at tender — and in a room where changing it is a scheduled operation, that gap is the whole argument.
FAQ
Do LED lights work in a freezer? Yes, and generally better than in an ambient warehouse. Lower junction temperature raises efficacy and slows LED degradation, so a fixture in a cold room produces slightly more light per watt and ages more slowly than the same fixture at 25°C. The constraint is the driver rather than the LED — check the fixture’s rated operating range and, separately, its cold-start temperature. Our standard sealed fixtures are rated -20°C to 45°C; below that, tell us the room conditions.
Why do sealed light fixtures get water inside them in cold storage? Because a sealed fixture still breathes. As it cools, the air inside contracts and draws air in through the gasket and cable gland; as it warms, the air expands and pushes out. When a cold fixture warms — a defrost cycle, an open door, a room brought up for cleaning — it draws in comparatively warm, humid air that condenses inside as it cools again. This happens across thermal cycles regardless of the IP rating, which is tested at stable temperature against water applied from outside. The defrost regime is therefore a more useful specification input than the room’s set point.
What ambient temperature rating do I need for cold storage lighting? It depends which room. A dock or chill room at 0 to +5°C is within any normal industrial fixture’s range. A frozen store at -18 to -25°C needs a fixture rated for it — ours are rated to -20°C as standard. A blast freezer at -30 to -40°C is a separate conversation; send the temperature, the defrost regime and the mounting position rather than assuming one part number covers the building.
Does cold storage lighting affect refrigeration costs? Yes. Every watt consumed by a fixture inside a refrigerated space becomes heat that the plant has to remove, so the lighting load is paid for twice — once as lighting energy and again as refrigeration work. That makes efficacy and occupancy control worth more in a freezer than in an ambient warehouse. The direction is certain; the size of the saving depends on your plant, duty and tariff, so it belongs in your energy model rather than in a supplier’s brochure.
Should cold store lighting use high bays or linear fixtures? It follows the racking, as in any warehouse. Fixed racking with defined aisles usually favours linear fixtures running along the aisle for uniformity down the run and light on the rack face; open or mobile-racked rooms are better served by an even ceiling-plane scheme. Height and spacing follow the standard high-bay ratios. In every case, keep fixtures clear of the evaporator fan discharge, where frost builds fastest and vibration is highest.