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Lighting Assessments

This is simplified page discussing lighting assessment, and we hope you enjoy reading it. If you require a Lighting Assessment Report for a planning application please pick up the telephone and call, and we can talk you through the process (free of course), or send over some plans via email, and we'll quote for the work required. Thanks.

The Basics of Lighting Assessment 

There are three primary things to consider when undertaking a lighting assessment:

1 - Light Everything Properly

A light bulb (by example) will light a given area adequately. For example a small light bulb might light a small room to the point where the light level is adequate for use as a . . . kitchen. . . but it would not produce enough light, to light the same room for use as a  . . . laboratory.

So when we write a lighting assessment report we have to carefully work out how an area is illuminated, and whether it will be adequately illuminated given the intended use. So like the example below we might use a computer model to mapping light levels.

Below Image (click to enlarge): lighting contours shown within a rectangular area

lighting contours shown within a rectangular area

2 - Don't Splash Light All Over the Place

Light above the horizon is considered bad. It gives rise to light pollution, and is in most cases is a sign of waste, and a badly designed lighting system. Light pollution, also known as photo-pollution, is the presence of anthropogenic and artificial light in the night environment. It is exacerbated by excessive, misdirected or obtrusive use of light, but even carefully used light fundamentally alters natural conditions.

Image result for light pollution creative commonsThis picture (from space station: creative commons license) is of Paris. Look at how much light is spilling upwards. That is mostly "wasted" energy. Mon dieu!

Some of this light will come from up-lighting of building exteriors, signposts or trees. Some may be reflected from the ground surface.

In some cases light may spill upwards from roof lights or glazed roofs, such as the glass pyramid at the Louvre Art Gallery.

3- Use as Little Energy as Possible

In just 10 years we have gone through 3 commonly used bulb types. It is hard to keep up. Even technology such as LED is improving year on year with emitters becoming more and more efficient. The problem as always to choose lights which provide the best possible output for the least amount of energy used. Just looking at LED technology the least efficient emitters can use 10 times more energy than the most efficient. So it is not just a case of choosing LEDS, there are choices to be made beyond that.

3.1 - A Note on Choose LEDs

What ever type of LEDs you choose be sure to choose "driverless". This is not so much to do with he emitter themselves but how they are powered.  Many LED fittings such as bulbs, surface mounted fittings, recessed fitting will include a "driver" this is in affect a power adaptor (much like a phone charger - converting 240v AC current to 6v DC or 12v DC). This adaptor is a common failure point, and can result in mountains if e-waste.

In our waste management work we regularly see 100's of LED compound fittings that have failed, and as the emitters themselves are so reliable we can only assume a fault with the driver, or rectifier. It is unlikely to be the rectifier. So please choose driverless.

Lighting Assessments for Ecology

 Over the last 2 or 3 years (as of 2022) it has become more common for Lighting Assessments to have an ecological angle. This is particularly true when considering bats.

For bats, artificial lighting is thought to increase the chances of predation, and therefore bats may modify their behavior to respond to this threat. Many avian predators will hunt bats which may be one reason why bats avoid flying in the day.

The target figure for dark areas, and buffer zones is typically set at 0.2 lux. This is easily achieved on most sites, provided the light fittings are set at appropriate height, are of low power, and the beam pattern is not too splashy.

However, lighting that is good for ecology, is often very subtle. Features common in the 2000's such as flood lit exterior facades and perimeter lighting will be  unimplementable, where ecological buffer zones are to be maintained. 

Below image (click to enlarge): a plan showing lighting contours or iso-lines drawn over a site layout plan

a plan showing lighting contours or iso lines drawn over a site layout plan

Modelling Light Spill

 Creating a computer model to show lighting spill can be a time consuming affair. It is not overly onerous for small sites with 1 or 2 dwellings, but for larger sites, with 50 plus houses the level of detail required can be very labor intensive.

That being said given enough time, a very detailed design can be provided with a great variety of solutions for avoiding light spill. For example to protect ecological features on a site boundary directional cut off fittings can be used to direct light spill away from ecological features. This does however require that each fitting be painstakingly rotated so as to achieve optimum beam angle.

Below image (click to enlarge): screen shot from light spill model, used to inform lighting assessment

screen shot of lighting spill model


Lighting Assessments in Dark Sky Areas

For lighting assessments in dark sky areas it is important to reduce light that is directed upwards, and reduce reflectivity of surfaces. The aim is to reduce or maintain lumens "emitted above the horizon". Recessed down lighting is good. Upward facing flood lights (as below image) are considered less favorable.

Below image (click to enlarge): Example of poor up-lighting.