- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 15 Feb 2020
Illuminance is ‘The level of light on a surface; measured in lux (lx). Previously called the illumination value. It can be used as a reference measurement of the performance of a lighting system as related to the activity.'
It is measured in lux (lx), the ‘...SI unit (the International System of Units) of illuminance or amount of light on a surface. One lux is equal to one lumen per square metre (lm/m^2)’ where a lumen (lm) is the ‘...SI unit of luminous flux, describing the quantity of light emitted by a lamp or received at a surface.’
Average illuminance is ‘The illuminance averaged over a specific area. In practice, this may be derived either from an average of the illuminances at a representative number fo points on the surface, or from the total luminous flux falling on the surface divided by the total area of the surface’
Maintained illuminance is ‘Illuminance at the time when maintenance is expected to take place. Most values of illuminance that are quoted as applicable to a store, eg 500-1000 lx, refer to this value. The time taken to reach the maintained illuminance level would depend on the lamp types and application’.
 Related articles on Designing Buildings Wiki
- Ballast or control gear.
- Colour appearance.
- Commercial lighting.
- Daylight benefits in healthcare buildings.
- Daylight factor.
- Daylight lighting systems.
- Dichroic reflector.
- Discharge lamp.
- Extra-low voltage lamps.
- General lighting v task lighting.
- Lamp efficacy.
- Light pollution.
- Lighting designer.
- Lighting energy numeric indicator LENI.
- Lighting of construction sites.
- Luminaire efficacy.
- Rights to light.
- Uniformity of illuminance.
Featured articles and news
Civil engineers can lead the way.
Cutting-edge tech pairs with building management systems.
BSRIA updates its assessment of the industry.
What happens when it all goes wrong?
Input being gathered by CIOB.
Changes proposed for MHCLG consultation on house building statistics.
Full of passion and acerbic wit. 1 min book review.
Reminding us what is possible.
Five signs you are at risk.
Biotechnology as it applies to the built environment.
Stopping sound coming through windows.
Government response to the Building a Safer Future consultation.
Energy savings quickly payback any small additional capital investment.