Insights

Avoiding light immissions

Causes, effects and solutions

02.04.2026

Artificial light characterises the image of our cities, increases the feeling of safety and provides orientation. But the fact that the night is losing its natural darkness also has undesirable consequences for people, animals, plants and the environment. For this reason, lighting immissions are increasingly becoming the focus of those who plan, use or are responsible for lighting. The aim is to develop solutions that are functional and targeted in order to minimise light pollution through well thought-out and adapted lighting design.

What are light immissions? Definition and delimitation

Light immissions (also known as light pollution or light smog) are the undesirable effects of artificial, man-made lighting on humans, animals, plants and the environment. Unlike light emission, which simply refers to the light emitted by a source, immission refers to the actual negative effect of light on the surroundings. It becomes particularly relevant when lighting has an effect outside the intended area of use, is perceived as disruptive or impairs natural processes.

Effects of artificial, man-made lighting

Light immissions increase significantly, especially at night, when excess light is emitted without functional benefit into areas that should actually remain dark. They are usually caused by incorrectly planned, inadequately shielded or excessively bright lighting systems.

Typical examples of the disruptive brightening caused by artificial lighting include:

Lighting that radiates upwards without benefit, brightens the night sky and thus displaces the natural darkness (skyglow),
widely scattered light that unintentionally illuminates neighbouring properties, residential or natural areas,
unnecessarily high luminous intensities that cause glare and annoyance.

Possible consequences of excess light and lack of darkness

Light is a central biological clock to which almost all living organisms orientate themselves consciously or unconsciously. The natural day-night rhythm (also known as the circadian rhythm) controls sleep, activity phases, metabolism and hormone balance.

Light immissions are often perceived as a comfort or design problem. Under certain conditions, they can also contribute as a relevant environmental factor to the impairment of human, animal and plant health, ecology or society:

Effects on people

Sleep disorders due to impairment of the day-night rhythm,
…and the resulting secondary diseases such as high blood pressure,
Impairment of performance and concentration,
Increased stress load and reduced ability to recover,
Reduction in quality of living and quality of life.

Effects on animals

Disorientation, especially in nocturnal animals, birds and insects,
Disturbance of orientation during reproduction and foraging,
Insect mortality due to attraction to artificial light sources (leads to exhaustion due to permanent circling and increased conspicuousness as prey for predators).

Effects on plants

Impairment of the natural growth and rest cycle,
Changes in flowering times and vegetation phases,
Disruption of photosynthesis and regeneration processes,
Long-term effects on the ecological balance.

Legal regulations, guidelines and standards

In Germany, the handling of light immissions is regulated by a combination of federal laws, technical guidelines and specific industry standards.

According to Section 3 of the Federal Immission Control Act (BimSchG), light immissions are one of the most harmful environmental impacts alongside noise, vibrations and air pollution. The law centres on avoiding exposure to artificial light or limiting it to a necessary level. The precautionary principle applies here: possible negative effects should be taken into account at the planning stage. This primarily affects plant operators, local authorities, companies and those responsible for planning.

These guidelines for the measurement, assessment and reduction of (light) immissions specify the requirements of the Federal Immission Control Act (BImSchG) and serve as a recognised technical basis for assessment throughout Germany. They define specific guideline values for assessing room illumination and psychological glare (disturbing but not impairing visual performance), taking into account the respective type of area as well as the time of day and night and the duration of use. Authorities often use the assessment criteria as a definitive set of rules.

In addition to the statutory regulations and the LAI instructions, there are a number of technical standards that play a role in the planning of outdoor lighting installations. They provide specific, practical recommendations on how light pollution can be minimised. Relevant standards in lighting design include

DIN EN 12464-2 for the lighting of outdoor workplaces
DIN EN 13201-(1-5) for street lighting

Measurement and assessment of light immissions

Light is considered a harmful environmental impact if it is perceived as a significant burden for an averagely sensitive person, taking into account the type of area, time of use and duration of use. The basis for the legally compliant assessment are the LAI guidelines, which are used in practice in the context of immission reports. These are usually drawn up by lighting designers, specialised engineering firms or environmental consultants. Frequent reasons for commissioning us are neighbourhood disputes, approval procedures or complaints to environmental or building authorities.

Measurable values of the report are

The amount of incident light on a surface (e.g. at windows or on balconies) is important when assessing disturbances in the living space.

This describes the brightness of a luminous surface and is often relevant for highly luminous advertising systems or LED walls.

This refers to the subjectively disturbing sensation (psychological glare) caused by light sources.

Light containing blue in particular (cool white) has a glaring and disturbing effect. The review is therefore important for LED lighting and nature conservation issues.

In addition, there are various factors that determine the assessment criteria of the circumstances and effects and thus also the measured values more precisely:

Duration of lighting (all night or only at dusk?),
Directional effect (direct illumination, e.g. of windows),
moving or flashing light,
sudden changes in brightness,
Location of the immission impact (e.g. differentiation between nature conservation areas, residential areas or industrial areas).

Solutions for avoidance

Street and outdoor lighting conveys a sense of security, especially in densely populated areas, but is also the most frequent cause of light pollution. Professional, strategic lighting design therefore brings both needs together: functional lighting that only shines where it is needed.

In the best case scenario, appropriate measures are taken into account from the outset during planning. However, existing systems can also be effectively optimised retrospectively using simple means. These include, for example:

Shields to prevent stray light,
energy-efficient lighting solutions,
LEDs with low luminance,
needs-based activation (e.g. smart, timed or by movement),
targeted, punctual alignment of the light sources,
Choice of dimmable light sources (e.g. with Tunable White outdoor lights).

Light immissions

Act now and illuminate wisely

Intelligent lighting design makes an important contribution to protecting people, animals and the environment. But it also benefits the implementing organisations, because: Using appropriate light sources reduces energy consumption and therefore also ongoing operating costs. Adapting your lighting is therefore also a sensible step from an economic point of view.

Modern, low-emission luminaires and lighting systems already take the problem of light immissions into account. They enable you to use light specifically where it is actually needed. This allows you to invest in efficient technology and sustainable solutions that increase convenience, acceptance in the neighbourhood and long-term planning security.

TRILUX supports you with smart solutions such as outdoor light management (LiveLink Outdoor) and a wide range of low-emission outdoor luminaires, including models such as Lumega IQ N, Jovie IQ, ConStela, Publisca and Lumantix.

Editors

Ann-Christin Blum

Online-Marketing
TRILUX

Avoiding light immissions

Causes, effects and solutions