Lighting a garden is the opposite of lighting an office. In an office you start from a level to be reached; in a garden you start from darkness, which is the normal condition of the place, and you add only the light needed to walk, to recognise a face and to see what is worth seeing. At night the eye is dark adapted: a few lux are enough to make a surface look bright.
The design therefore balances three constraints pulling in different directions: how much light is really needed, how much is wasted towards the sky — the reason projects get rejected by local authorities — and how much disturbance is caused to what lives in the garden, night insects and animals included.
1. How many lux: far fewer than expected
The reference for public outdoor areas is EN 12464-2; for roads and driveways EN 13201 applies. Private gardens have no binding level, but sensible values are these.
| Area | Average illuminance | Note |
|---|---|---|
| Private footpath | 5 – 10 lux | uniformity matters more than peak value |
| Steps, level changes, ramps | 20 lux | grazing light, never into the eyes |
| Seating area, outdoor table | 20 – 50 lux | several soft points beat one strong one |
| Driveway entrance, gate | 10 – 20 lux | at road level |
| Facade or boundary wall | 2 – 5 cd/m² | expressed as luminance, not lux |
| Tree canopy | 15 – 30 lux | on the foliage, from below or above |
Peak value matters less than the ratio between areas. A path at 40 lux next to a dark lawn reads worse than one at 8 lux in a uniformly dim garden, because the eye adapts to the brightest point and everything else disappears. Practical rule: keep the ratio between adjacent areas below 1 to 5.
2. Light pollution: the constraint that rejects projects
In Italy there is no national law: the matter is ruled by regional laws, nearly all derived from Lombardy law 17/2000. The recurring requirement is sharp and easy to check:
(ULOR = 0, in the installed position)
Two phrases deserve attention. Above the horizontal plane: what counts is not the luminaire but the way it is mounted — a compliant luminaire tilted by 20° is no longer compliant. In the installed position: verification happens on site, not in the catalogue.
The technical standard defining quantities and methods is UNI 10819. Beyond ULOR, most regions also require night switch off or dimming, forbid beams aimed at the sky except for monuments, set minimum efficiency for road installations and forbid lighting areas outside the property boundary.
3. Glare: you should see what is lit, not the lamp
- the source must never be visible from the usual viewpoints: recessed, shielded or above eye line;
- ground luminaires are aimed along the direction of travel, not towards people arriving;
- on stairs, light comes from the side or from the riser, never head on;
- pole luminaires with cut-off optics must stay horizontal;
- shiny surfaces — water, wet paving, glass — mirror the source: aiming should be checked at night after rain.
4. Light and nature: why colour matters
Artificial light at night is now recognised as an environmental pressure, and the measured effects depend mostly on the blue content of the spectrum, below 500 nm: night insects are attracted, bats lose flight corridors, migrating birds are disoriented by vertical beams, and trees near luminaires shift their phenology. Hence the colour temperature choice is technical, not aesthetic: 3000 K maximum, 2700 K where green must stay alive, 2200 K amber in natural areas or near watercourses.
Greens and browns are saturated colours: a LED with Ra ≥ 90 and decent R9 renders foliage as seen by day, while a cheap LED turns it grey-blue.
5. Designing in layers, not in luminaires
- safety — paths, steps, entrances: few lux, high uniformity, always on;
- orientation — low luminous marks showing the way: bollards, wall recessed units, grazing light on low walls;
- scene — trees, sculptures, water: narrow beam floodlights, on during use hours;
- living — table, outdoor kitchen, relax area: warm and dimmable light.
6. Durability: what actually kills outdoor installations
Outdoor systems die of water and corrosion, not of light: IP65 on walls and poles, IP67 in the ground, IP68 underwater; IK08 where a mower passes; marine grade anodised aluminium or AISI 316 near the sea; buried grade cable with resin joints or inspection pits; drainage under every ground recessed unit; drivers kept out of the soil. On voltage, 24 V SELV simplifies trenching and is almost mandatory near pools, but beyond 20-25 m of cable the voltage drop becomes visible.
7. What to write in a specification
- ULOR = 0 % in the installed position, with declaration of compliance to the applicable regional law and to UNI 10819;
- colour temperature ≤ 3000 K (≤ 2200 K in sensitive areas), within 3 SDCM;
- Ra ≥ 90 where vegetation is in view;
- maintained average illuminance and uniformity per area, with a maximum ratio between adjacent areas;
- IP and IK rating per mounting position, with material and surface treatment declared;
- night dimming profile and control system;
- on site verification with the installation running, measured rather than quoted.
8. Frequently asked questions
Far fewer than people assume, because at night the eye is dark adapted. A private footpath is safe with 5-10 average lux, a step or a level change with 20 lux, a seating area or outdoor table with 20-50 lux, a driveway entrance with 10-20 lux. Above those values you do not see better: you see worse, because unlit areas turn black and the eye can no longer adapt.
There is no national law: the matter is ruled by regional laws, nearly all modelled on Lombardy law 17/2000. The common requirement is zero luminous flux emitted above the horizontal plane in the installed position, that is ULOR equal to zero per cent, with few exemptions for monuments. Many regions also impose switch off or dimming at night and forbid beams aimed at the sky. The technical reference standard is UNI 10819.
It depends on shielding and on where the light that misses the canopy ends up. A ground floodlight firing upwards emits flux above the horizon and in many regions is allowed only for monumental heritage, with power and curfew limits. In practice compliance comes from narrow optics aimed into the canopy, glare shields and a switch off time: the foliage intercepts the light and what passes beyond must be negligible.
Low. Wildlife guidance and recent regulations ask for 3000 K maximum, dropping to 2200 K amber in natural areas or near watercourses. The reason is blue content: the component below 500 nm attracts night insects, disorients bats and alters plant rhythms. At 2200 K lawn green looks dull, so 2700 K is often the compromise in ornamental gardens.
IP65 for wall or pole luminaires, IP67 for ground recessed units exposed to standing water, IP68 for underwater installation in pools and ponds. Mechanical strength matters too, IK08 or better where a mower passes, and so does corrosion: near the sea use marine grade anodised aluminium or AISI 316 stainless steel, since AISI 304 stains within a few seasons.
Extra low voltage 24 V simplifies trenching and maintenance, allows work on the system without electrical risk and is almost mandatory near pools. The limit is voltage drop: beyond 20-25 m of cable with ordinary cross sections the light visibly falls off, so either several drivers are distributed or the system moves to 230 V with class I or II luminaires.
9. From design to installation
Three choices decide the result: fewer lux than instinct suggests, because at night contrast matters more than level; no flux above the horizon, which is both the legal constraint and the measure of how much light is being thrown away; warm spectrum with high rendering, which protects wildlife and shows green as it should be. Poles, recessed units and floodlights come afterwards, and that is the easy part.