Are outdoor pendant lights suitable for a cold-frame or greenhouse?

Yes, and the specification matters more than the style. A greenhouse is a damp location under BS 7671, so the fitting must carry a minimum IP44 rating and be fed from a circuit protected by an RCD at the consumer unit. Most quality outdoor pendant lights already meet this threshold, which is precisely why they suit glazed growing spaces better than interior fittings. Mount the pendant from a treated timber batten fixed to a ridge beam, or use a sealed cable gland where the supply enters the aluminium frame. Keep any driver or connection box outside the growing zone, ideally in a weatherproof enclosure on the outside wall. Hang the fitting high enough that watering cans, misting lines and tomato foliage cannot reach it — 2.1 metres clear height is a sensible minimum. Glass glazing amplifies UV and heat, so choose a fitting with a UV-stable powder-coated or marine-grade finish rather than bare mild steel, which will corrode within a season in a humid, fertiliser-laden atmosphere.

A closed greenhouse routinely sits at 80–90% relative humidity overnight, and condensation runs down the glazing every morning as the sun heats the glass. That moisture finds every unsealed joint in a light fitting. An IP44 enclosure resists splashing water from any direction, which covers condensation drip and stray spray from a hose. IP65 is better still if the pendant sits directly above a bench where misting irrigation operates. Cable entries deserve as much attention as the fitting itself: use glands with compression seals, not bare flex through a drilled hole, and drip-loop the cable so water runs off rather than wicking into the luminaire. Corrosion is the second failure mode — fertiliser salts and damp air attack untreated metal quickly. Powder-coated aluminium or 316 stainless hardware survives; plated steel does not. The same logic applies to any automated setup: the Energy Saving Trust notes that smart controls and sensors in damp environments need properly rated equipment, and a greenhouse is no exception to that principle.

A pendant in a greenhouse is supplementary lighting, not a substitute for a dedicated grow light, so specify it accordingly. An LED lamp at 3000K delivers useful ambient illumination for evening tasks and extends effective daylight at the margins of the season without the heat load of halogen. Keep total wattage modest — 10–15W of LED per fitting is ample in a typical 2m x 3m cold frame, where the glass already maximises natural daylight. Put the circuit on a photocell or smart plug with a schedule so the fitting runs only when needed; lighting left on through daylight hours is wasted money, and the Energy Saving Trust's guidance on energy at home puts lighting among the easiest wins for cutting household consumption. Check the lamp's temperature rating too, because a sunny greenhouse can reach 40°C internally and cheap LEDs degrade faster at those temperatures. Finally, position the pendant so it lights the path and staging rather than shining directly into seed trays, where intense close-range light does more harm than good.