Bat Friendly Lighting for Dark Skies

November 3, 2022
Mars and Milky Way from Herbert Lake by Alan Dyer

Following on from last week’s Bat Week & also Bat Appreciation Month, we wanted to expand on what Bat Friendly Lighting means, so we have generated a quick Q&A.

Bat Friendly Lighting Logo, Compliant with Dark Sky Approved
Image above shows Gemma Lighting’s approved Insect and Bat-Friendly Lighting logo.

Bat Friendly Lighting: Questions and Answers

Bat Friendly Lighting – What Is It? And What Does It Mean?

‘Bat Friendly Lighting’ is our way of self-certifying that our products meet the requirements set out by the International Dark-Sky Association, meaning that our lights are compliant with the Dark Sky Approved criteria.

Dark Sky Approved Criteria – What Is It?

The Dark Sky Approved Criteria is a list of requirements which when assessed by the International Dark-Sky Association (IDA), will grant you the ‘Dark Sky Approved’ fixture seal of approval.

What Are The Specific Requirements?

The requirements to be Dark Sky Approved are:

1) Approved fixtures shall employ warm-toned (3000K and lower) white light sources or may employ amber light sources or filtered LED light sources. (If other CCTs or mounting options are available for the luminaire, a notation needs to be made on the web page, spec sheets, and order forms).

NB: Gemma Lighting offer 3000K as a CCT option, and also have 2700K, 2200K and Red LEDs available as special order. Gemma Lighting note on their datasheets to refer to the 3000K CCT option or lower to be compliant.

2) Photometric files are needed to validate performance characteristics.

NB: Gemma Lighting have LDT files for all our luminaires to support this, and are also readily available for download in the Lighting Reality software.

3) There is an uplight allowance of 0.5% of total output or 50 lumens; whichever is lower, with no more than 10 lumens in 90-100 degree UL zone. Allowable uplight as a by product of the structure and not the source.

NB: The selected range of Gemma Lighting compliant luminaires have 0% uplight. They have internal and external photometric tests which support this.

4) Street and area lights must have a pre or post-installation shielding option.

NB: Spill shields are available from Gemma Lighting for the compliant luminaires.

5) Luminaires are required to have fixed mounts to ensure they are mounted as photometered. There can be up to + or- 10-degree adjustment for levelling if needed.

NB: Gemma Lighting’s compliant luminaires are required to be installed on columns or fixing plates, which is the same way they are mounted photometered in the photometric labs.

6) Luminaires must have dimming capability to 10% of full rating.

NB: Gemma Lighting’s compliant luminaires have DALI dimmable driver options, supplied from Osram for increased reliability.

7) Luminaires must have Safety Certification by an independent laboratory.

NB: Gemma Lighting’s compliant luminaires are independently tested by the LIA.

Why Does The Colour Temperature Need To Be 3000K or Warmer?

This is to remove the blue light content from artificial light which has become disruptive to the ecosystem, including bats & insects which are nocturnal, but also other animals too. In addition to the colour temperature for bat friendly lighting, there must be no upwards light spill.

What Is ‘Bug U-0’?

Bug U-0 is an ‘Innovation’ requirement, which isn’t required for the Dark Sky Approved status, but more of a best in class status. It states no uplight allowance, and in doing so achieves the BUG rating U-0.

Any Other Requirements?

The ‘Innovation’ requirement, which isn’t required for the Dark Sky Approved status, also states dimmable to 1% of full rating. smart controls to meet the purpose, no more than 7% of visible emissions in spectrum range of 380-520nm.

Bracken Bat Cave by Ann Froschauer
Image above shows Bracken Bat Cave by Ann Froschauer.

Bat Friendly Lighting: A Guide to Considerate Outdoor Illumination


As human habitation expands, so does the reach of artificial lighting. While these lights can enhance safety and aesthetics, they can also have significant impacts on wildlife, particularly nocturnal creatures like bats and insects. Below we will explore the concept of ‘bat friendly lighting’, focusing on external lighting and the considerations necessary for bats, insects, and other nocturnal creatures.

The Impact of Artificial Lighting

Artificial lighting, particularly at night, disrupts natural patterns of light and dark, affecting the feeding, breeding, and movement of invertebrates. For instance, moths can become disoriented and exhausted, making them more susceptible to predation. Similarly, artificial lighting can delay or prevent bats from emerging from their roosts, reducing their foraging time.

Birds too can be affected. Some species extend their activity period in artificial light, feeding longer and singing in the middle of the night. Migrating birds can become disoriented by bright urban lights, leading to mass mortality as they strike lit buildings.

Bat Friendly Lighting: Key Considerations

  1. Avoidance
    Preventing light spill into sensitive areas such as dark corridors, roosts, woodlands, and hedgerows is crucial. The best solution is often no light beyond natural conditions.
  2. Colour Temperature
    Opting for warm tones (2700K or less) can minimize the impact of blue light, which is highly attractive to many insects.
  3. Efficiency
    Reducing energy consumption through smarter lighting can also contribute to a more bat-friendly environment.
  4. Fixture Design
    Outdoor lighting fixtures should be designed with shielding to minimize glare and prevent light spill / light pollution. The light source should be directional downwards, so zero upwards light emissions, optics should be used control and focus the light to where it is needed, and controls for dimming and presence detecting should be implemented to reduce the operating time and intensity. A fixture which incorporates these elements would be less disruptive to nocturnal wildlife and therefor considered bat friendly lighting.


While artificial lighting is an essential part of modern life, it’s crucial to balance its benefits with the potential harm it can cause to wildlife. By considering the needs of nocturnal creatures and implementing bat friendly lighting practices, we can help protect these vital members of our ecosystem.

Remember, every small step towards reducing light pollution can make a significant difference. So, let’s switch off unnecessary lights and embrace the beauty of natural darkness.