Conservatory Lighting: Fixings, Lumens and the Black Mirror After Dark

Conservatory lighting is fixed to the glazing bars or the house wall, never to the glass, and aimed down and inwards. After dark the glass sends almost nothing back and mirrors everything, so plan about 40% more lumens than for a closed room, spread over several low sources rather than one ceiling light.

A conservatory is furnished like a sitting room and lit like nowhere else in the house. Three things set it apart: you cannot drill the glass, the air under the roof gets far hotter in summer than anywhere else, and at night the panes stop showing the garden and start showing the room. This guide covers where to fix your lights, how many lumens to plan, which fittings cope with heat and damp, the UK wiring rules and the ideas that suit each use of the room.

Glass, polycarbonate or solid: start with your roof

Before choosing a style, look up. A glass roof takes no fixing at all. Toughened glass shatters if it is drilled after toughening, and a sealed double-glazed unit with a hole in it loses its seal and mists up between the panes. A polycarbonate roof can be drilled, but every hole becomes a leak at the first driving rain.

A solid roof changes everything. Many British conservatories have had their glass or polycarbonate replaced by a tiled roof with a plastered ceiling inside, and many orangeries have a solid band, the pelmet, around a glazed lantern. Under plaster, you light the room like any other: downlights in the pelmet, a ceiling light fixed to a joist. The rest of this guide is about the glazed part.

Where to fix a light in a conservatory

A glazed roof offers almost nothing you can drill, but four supports remain, and they are enough:

Support	What it takes	How it is fixed	Watch out for
Glazing bars	Spotlights, a spot bar, a light pendant	Self-tapping screws or rivet nuts into the aluminium core of the bar	The clip-on cap carries nothing: unclip it, fix beneath it, clip it back
Ring beam and corner posts	Wall lights, adjustable spots	As for the bars, cable hidden behind the cladding	Check that no sliding door runs behind
House wall	Anything, including the start of a pendant moved across	Ordinary wall plugs in the brickwork	The only solid wall: keep it for fittings that light the room
Floor and furniture	Table lamps, floor lamps, battery lamps	No fixing	A floor socket is planned at build stage, rarely afterwards

The glazing bars are the support you will use most, and their even spacing gives you a ready-made grid for spreading light points. A bar of six adjustable spots, 100 cm long, weighs 1.65 kg, the kind of load a glazing bar takes without argument. For anything heavier, such as a ceiling fan light, ask the maker of your roof before you fix it.

Under a lean-to or a Victorian roof, the height changes from one end of the room to the other, and so does the effect of the same fitting. The reasoning is the one in our guide to vaulted ceiling lighting: the higher the fixing point, the further you bring the light down, rather than turning up its power.

After dark, the glass becomes a black mirror

Nobody expects this when they buy a conservatory, yet it decides whether the lighting works. Each glass surface sends back about 4% of the light that hits it head on, more at an angle, and a double-glazed unit has four surfaces, which is why you often see every lamp twice. By day the garden outshines that reflection. At night the balance flips, and the glass shows you the room instead of the garden.

Three remedies, in this order.

Hide the bright point. What reflects is the lit surface, not the fitting. A shade that hides the bulb shows up as a soft patch; a bare filament bulb, a clear globe or an LED panel shows up as a sharp point, repeated in every pane. Under a slatted or woven shade that lets you see the bulb, swap a clear bulb for an opal one: the bright point goes and the fitting stays.

Light the outside. It is the only remedy that acts on the cause. A little light outdoors, on a hedge, a tree or the patio, raises the brightness on the dark side of the glass and makes it see-through again. The conservatory stops reflecting itself and seems to open onto a garden that still exists at night. Our guide to outdoor lighting gives the levels zone by zone; here, a small amount is enough, aimed at foliage and paving rather than back at the glass.

Turn it down. A fitting sold as dimmable, on a compatible dimmer, cuts the reflections along with the brightness.

How many lumens a conservatory needs

In an ordinary room, about half of what your bulbs give out ends up lighting something useful, because the walls and ceiling send back what reaches them. BS EN 12464-1, the lighting standard for indoor workplaces published by BSI, recommends walls with a reflectance of 0.50 to 0.80 and a ceiling of 0.70 to 0.90. At night a conservatory has neither: glass returns an image, not a spread of light, and whatever goes up to the roof goes out.

So we treat a conservatory as a room with dark walls, as in our guide to how many lumens you need: 40% more on the lumens to fit. For a 15 m² conservatory used for dining, at 150 lux, that gives 2,250 useful lumens, 4,500 lumens to fit in a closed room with pale walls, and about 6,300 here. Used as a sitting room at 100 lux, the same floor needs about 4,200 lumens.

That total does not belong in a single fitting. A diffusing ceiling light sends part of its output upwards, and under glass that part is lost. The useful sources work down and inwards: adjustable spots, low pendants, wall lights on the house wall.

Summer heat and winter damp: what the fittings must cope with

An indoor light fitting is designed for air at 25 °C. Under BS EN 60598-1, a fitting made for hotter air must say so with a ta marking followed by its temperature. A south-facing conservatory without blinds goes well past that in summer, and the hot air gathers under the roof, exactly where the ceiling lights are. Heat hardly harms a shade, but it shortens the life of the electronics: LED driver, transformer, dimmer.

• Shade the room, not the fitting. Roof blinds or solar control glass cool the whole conservatory.
• Choose replaceable bulbs. An E27, GU10 or G9 fitting is repaired by changing a bulb; an integrated LED that gives up after three summers is replaced whole. Our guide on how to change a spotlight bulb covers both cases, from the GU10 to the sealed LED downlight.
• Keep natural materials out of direct sun. Rattan, paper, fabric and natural fibre fade and dry out within a season or two, and plastic diffusers turn yellow. Our advice: natural materials against the house wall or under the shadiest part of the roof, metal, glass and ceramic elsewhere.

Winter brings damp, and damp decides the IP rating. A heated, well-sealed conservatory is a dry room, where an ordinary IP20 fitting is right. An unheated one is different: on cold nights the glass drops below the dew point, condensation runs down the panes into the bars, and a fitting under the roof can take drips. The IP code of BS EN 60529 rates exactly that: a second digit of 1 for drips falling straight down, 4 for splashes from any direction.

• Heated and used all year: IP20 throughout, as in the rest of the house.
• Unheated, or heated now and then: IP20 on the house wall and for lamps, IP44 for anything fixed under the glass roof. Our glass and aluminium globe ceiling light is rated IP44.
• Doors left open all summer: IP44 throughout, connections included.

Both digits are explained in our guide to IP ratings. One more point: a Class II fitting, double insulated, needs no earth, which helps on an older lighting circuit wired without one.

Wiring conservatory lights: what the UK rules say

Many roof systems leave room for cables under the internal cladding of the ridge and the bars, which is why lighting is best wired while the roof goes up. The work follows BS 7671, the IET Wiring Regulations, which call for 30 mA RCD protection on lighting circuits in homes. In England, Part P of the Building Regulations makes a new circuit notifiable, like a new consumer unit or work in the zones around a bath or shower. A registered electrician in a competent person scheme such as NICEIC or NAPIT can certify and register it; otherwise building control must be told before the work starts. A conservatory exempt from building regulations is no exception: regulation 9(3) applies Part P to it as soon as it takes its electricity from the house. Wales has similar rules, while Scotland and Northern Ireland have their own.

Adding a light point to an existing circuit is not notifiable, but it must still meet BS 7671. And when there is no power under the roof at all, three answers avoid both drilling and chasing:

• A pendant moved across. Start from an existing point on the house side, run the flex to a hook on a glazing bar and let it drop where you want the light. Our guide to the off centre ceiling light gives the length of flex to order and the slack to leave.
• Plug-in lights. A lamp on a console, a plug-in wall light with a switch on its cable: nothing is drilled, and the room gains the low sources it needs.
• Battery lamps. On the table or among the plants, they bring mood light where there is no supply, never the main light.

Conservatory lighting ideas for each use

Three uses cover almost every conservatory, and each puts the light somewhere else.

A dining room. The most common use, and the easiest to get right, because the table gives the space the pale surface it lacks. Hang the pendant with about 60 cm between the table top and the bottom of the shade: the light falls on the plates, well below the glass where the reflections are strongest. Wood, rattan or natural fibre pendant lights are at home here, but choose one that hangs low rather than a wide shade high up, and check its maximum height on the product page against your fixing point.

A sitting room. Here a central ceiling light is the worst reflex. Combine three or four low sources instead: a wall light on the house wall, a lamp by the armchair, one or two spots on a wall. Wall lights with an adjustable spot are the most useful, because you set them once they are up, when you see how the room reflects. How many lumens those low sources need, and how high to put them, is worked out in our guide to mood lighting.

A garden room for plants. If the plants are the point, light them, not the roof. A narrow beam aimed down onto foliage draws shadows on the floor and creates a depth that general light never does. Our spot ceiling lights with adjustable heads suit it, as long as you prefer narrow beams to wide ones, which mostly light the glass behind the plant.

One setting is shared by all three: colour temperature. A conservatory is always compared with the light outside, and cool light looks artificial there at once. Stay at 2,700 K, the warm white of most LED bulbs, with perhaps 3,000 K over the dining table. Our guide to cool white vs warm white explains why the difference shows so much at night.

Conservatory lighting: your questions answered

Sources

• BS EN 60598-1, Luminaires, general requirements and tests: rated ambient temperature ta, 25 °C unless the fitting is marked otherwise. BSI
• BS EN 12464-1, Light and lighting, lighting of work places, indoor work places: reflectance of 0.70 to 0.90 for the ceiling and 0.50 to 0.80 for the walls. BSI
• BS EN 60529, Degrees of protection provided by enclosures (IP code). BSI
• Lichtanwendungen Wohnen, Wintergarten and Esszimmer: glass surfaces act as mirrors after dark; the bottom of a dining pendant about 60 cm above the table. licht.de
• BS 7671, Requirements for Electrical Installations, the IET Wiring Regulations: 30 mA RCD protection for lighting circuits in dwellings. IET and BSI
• The Building Regulations 2010, regulation 9(3) and Schedule 2, Class 7 (conservatories), and Approved Document P, notifiable electrical work in England. legislation.gov.uk and GOV.UK