Light pollution is a serious problem today, having a negative impact on both the environment and human health, and even preventing astronomical observations. In response to the growing challenges of reality, regulations such as the Dark Sky Planning Guideline have been created, which define methods to reduce light emissions in undesirable directions. A measure of this is the Upward Light Ratio (ULR).
ULR is one indicator that determines the percentage of luminous flux emitted above the horizontal plane of a luminaire. Understanding its importance and role is key to effectively managing the problem of light pollution. Therefore, it is worth paying attention to ULR in lighting design and installation in order to create a human- and environmentally-friendly space.
Effective action against light pollution involves adapting light emission standards to the specific characteristics and requirements of different environments.The EN12464-2 standard introduces four environmental categories, which specify maximum ULR (Upward Light Ratio) values depending on the type of area.
Category E1:Areas with minimal artificial light, such as national parks. In these areas, the ULR allowed is 0%, meaning that upward light emission is completely prohibited.Category E2:Rural areas and small villages where the ULR limit is 2.5%. This restriction minimises the impact of artificial light on the natural environment.Category E3:Urban areas with medium light levels, such as small towns. The maximum ULR in these locations is 5%, allowing moderate upward light emission.Category E4:Large city centres with intense lighting. Here the allowable ULR is up to 15%, which takes into account the higher light levels in such areas.
The ULR (Upward Light Ratio) value is documented in many lighting reports, such as the IES and LM79 reports. These provide detailed data on the distribution of light emitted by luminaires, including the proportion of light directed upwards. For example, in road lighting simulations, street lamps are usually installed without an upward angle to maintain a ULR value of 0%. In addition, special shields are used to direct the light downwards, preventing unwanted shining into residential windows.Responsible lighting design taking into account the Upward Light Ratio (ULR) is an integral part of sustainability and environmental protection efforts. Reducing ULR values effectively reduces light pollution, significantly improving the comfort of people and their natural surroundings. The use of luminaires with low ULR and modern technologies, such as asymmetrical light distribution and precision shielding, allows light to be efficiently directed to where it is needed, without being lost or unnecessarily illuminating the night sky.
The ULR (Upward Light Ratio) is the percentage of luminous flux emitted above the horizontal plane of a luminaire. It is a key parameter in the fight against light pollution.
ULR is important because it minimises light emission in undesirable directions, which in turn reduces light pollution and protects the environment and human health.
According to the EN12464-2 standard, the maximum ULR values depend on the environmental category: E1 (0%), E2 (2.5%), E3 (5%) and E4 (15%).
To lower the ULR, use luminaires with suitable covers that direct light downwards, avoid mounting luminaires at an angle and use modern technologies such as asymmetrical light distribution.
Light pollution can adversely affect human health, biota and hinder astronomical observations by disrupting the natural rhythm of day and night.
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