Lighting guidelines

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Dark sky best practice

Environmental zones | Preventing light pollution

To reduce the problems of obtrusive light:

A1 Switch off lights when not required for safety, security or enhancement of the night-time scene. For example, limitation on lighting levels between agreed hours (off between 11pm and dawn)

A2 Direct light downwards wherever possible to illuminate a target, not upwards. If there is no alternative to up-lighting, then the use of shields and baffles will help to reduce spill light to a minimum.

A3 Use specifically designed lighting equipment that minimizes the spread of light above the horizontal plane.

A4 Do not 'over' light. It is a cause of light pollution and a waste of money.

A5 Ensure that the main beam angle of all lights directed towards any potential observer is kept below 70 degrees. The higher the mounting height, the lower the main beam angle. In places with low ambient light, extra care should be taken in positioning and aiming.

A6 Wherever possible, use floodlights with asymmetrical beams that permit the front glazing to be kept at or near parallel to the surface being lit.

A7 For domestic and small-scale lighting, there are two solutions:

passive infrared detectors can be used to good effect, if correctly aligned and installed. A 150W (2000 lumen) tungsten halogen lamp is more than adequate. 300/500W lamps create too much light, more glare and darker shadows
all-night lighting at low brightness is equally acceptable. For a porch light a 9W (600 lumen) compact fluorescent lamp is more than adequate in most locations.

Environmental zones

Obtrusive Light Limitations for Exterior Lighting Installations
Environmental Zones	Sky Glow UWLR (max. per cent) Glow UWLR (max. per cent)	Light into Windows Ev (lux)		Source Intensity 1 (kcd)
		Before curfew	After curfew	Before curfew	After curfew
E5	0	0	0	0	0
E4	0	2	1*	0	0
E3	5	5	1	50	0.5
E2	15	10	5	100	1.0
E1	25	15	10	100	2.5


E5:	in "national parks" or other "dark landscapes" (e.g. where protection of flora/fauna/wildlife is paramount)
E4:	areas of "very low district brightness" (e.g. in an urban location, but outside a Zone E1)
E3:	areas of "low district brightness" (e.g. in an urban location Remuera or similar, but outside a Zone E1)
E2:	areas of "medium district brightness" (e.g. in an urban location, Newmarket or similar)
E1:	areas of "high district brightness" (e.g. in an urban centre with high night-time activity Queen Street or similar)

Where: UWLR (Upward Waste Light Ratio) = Maximum permitted percentage of luminaire flux that goes directly into the sky.
Ev = Vertical illuminance in Lux
I = Light intensity in candelas
L = Luminance in candelas per square metre
* Acceptable from public road lighting installations only
** Source intensity - this applies to each source in the potentially intrusive direction, outside of the area lit. The figures given are for general guidance only and for some medium to large sports lighting applications with limited mounting heights, may be difficult to achieve. However, if the aforementioned recommendations are followed then it should be possible to lower these figures to fewer than 10 kcd (kilo-candela).
*** Building luminance - this should be limited to avoid over-lighting, and relate to the general district brightness.

Preventing light pollution

Three point plan

Urban sky glow (light pollution) arises from a combination of artificial light emitted directly into the sky from light fittings and light reflected up into the sky from buildings and the ground. The International Dark-sky Association recommends that:

Wherever possible lights should be installed in full cut-off or ultra low-profile housings to prevent the emission of light above the horizontal.
'Over-lighting' must be avoided. Using only the correct amount of light for the task in hand, according to accepted standards, will reduce the amount of reflected light contributing to sky glow.
Unnecessary night-time lighting, particularly decorative floodlighting, merchandising and advertising lighting and sports floodlighting, should be switched off at 11pm or midnight to reduce the total sky glow in the early morning, pre-dawn hours.

Published December 2008