(4 credits)
Aim
To ensure appropriate lighting is provided to enable residents to perform visual tasks efficiently and accurately.
Question
Do internal and external lighting levels meet best practice illuminance (lux) levels?
| Credits | Answer | Select either B, C or D, Answer E can be selected independently |
| 0 | A | Question not answered |
| 0 | B | No |
| 1 | C | Yes, ≥50% of occupied communal spaces meets best practice illuminance (lux) levels for internal lighting |
| 2 | D | Yes, ≥80% of occupied communal spaces meets best practice illuminance (lux) levels for internal lighting |
| 2 | E | Yes, ≥80% of relevant external space meets best practice illuminance (lux) levels for external lighting |
Assessment criteria
| Criterion | Assessment criteria | Applicable answer |
| 1 |
Filtering The external lighting credits can be filtered out in the following circumstances:
|
C,D |
| 2 |
For the purposes of this assessment issue, the following standards are considered to contain best practice illuminance (lux) levels:
Alternatively, where local standards have similar requirements to any of the above standards, the local standard may be used to demonstrate compliance with this criterion. |
C,D |
| 3 | Illuminance levels are measured in occupied spaces by a suitably qualified person in accordance with the procedure(s) in the relevant best practice standard (criterion 2). Where the best practice standard does not stipulate procedures for measuring illuminance, the procedure in the Methodology section must be followed. If during measurement light fittings need to be added or removed, or covered, in an occupied space to achieve the best practice illuminance levels, the occupied space would not comply with the criteria. | C,D |
| 4 |
External spaces within the scope of the external lighting requirements include, but are not limited to, the following:
|
E |
Methodology
Procedure for measuring illuminance
The suitably qualified person must confirm that they have used either the illuminance verification procedure(s) stipulated within the relevant best practice standard (criterion 2) or where the best practice standard does not stipulate procedures for measuring illuminance, the following procedure:
- Illuminance measurements should be undertaken using calibrated illuminance meters with a photocell that is both colour/spectrally and cosine corrected. The deviation of the calibration values as per the calibration certificate should be applied when analysing the measurement results. Additionally, it should be checked that the ambient temperature during the measurements does not depart markedly from the ambient temperature for which the photocell had been calibrated (typically, this is 25°C); if this is the case, then the measured values should also be corrected for ambient temperature.
- Illuminance meters with an integrated photocell should be checked for the correct levelling on the measurement surface. In case of illuminance meters that have a detachable photocell, the photocell should be secured inside a specially designed holder and the holder should be checked for the correct levelling on the measurement surface.
- The mains voltage supply in the test areas should be stable during measurements.
- It should be checked that there are no unusual temperature differences between different zones of the test areas. The artificial lighting should also be kept on long enough so that its light output stabilises (e.g. at least 20 minutes for fluorescent, discharge or LED lighting).
- Indoor illuminance measurements should be carried out so that daylight penetration is avoided completely whilst taking the readings. In spaces with windows, illuminance measurements would ideally be undertaken after dusk; if blinds are fitted, these should be closed in order to minimise any potential stray light from buildings nearby and external lighting. Measurements of outdoor illuminance should be carried out when it is fully dark and in good weather conditions.
- Items within the measurement areas should be kept to a level that would be expected during normal use. Additionally, the Assessor should be far enough away from the photocell, ideally below its height if possible, to avoid casting shadows or preventing light from being reflected onto the photocell.
- Illuminance measurements are normally required to assess average illuminance or illuminance uniformity on the working plane or other task areas that can be horizontal, vertical or inclined. In existing buildings, task areas, e.g. kitchen work surfaces, are generally known. In an open task area, a grid of measurement points should be set out. The distance between the measurement points p is calculated using the formula:
- Where d is the length of the longer dimension of the area being measured, and thus the number of points in the relevant dimension is given by the nearest whole number of d/p. The resulting spacing between the grid points is used to calculate the nearest whole number of grid points in the other dimension. Once illuminance is measured at each grid point, average illuminance can be determined as the arithmetic mean of the measured values. Illuminance uniformity can be calculated as the ratio of the minimum illuminance (as measured) to the average illuminance (as calculated).
- A perimeter zone of 0.5 m from the walls can be excluded from the measurement area except when a task area is in or extends into this perimeter zone.
- An appropriate grid size for walls and ceilings can be calculated similarly, and a band of 0.5 m can also be used.
- Alternatively, spot readings of illuminance may be taken. This is acceptable practice where measurement grids cannot be defined due to the presence of obstructions in the measured areas.
Evidence
| Criteria | Evidence requirement |
| - | The evidence below is not exhaustive, please also refer to the ‘BREEAM evidential requirements’ section in the scope of the Guidance for appropriate evidence types which can be used to demonstrate compliance. |
| 1-4 | Documentation confirming the illuminance levels in occupied space meet the best practice levels and have been measured in accordance with the ‘Procedure for measuring illuminance’ (see Methodology). |
Definitions
Illuminance
The amount of light falling on a surface per unit area, measured in lux.
Occupied space
A room or space within the asset that is likely to be continuously occupied for 30 minutes or more per day by an asset user.
Suitably qualified person
Someone that has demonstrable experience in undertaking lighting measurements in internal and external spaces.
© Copyright Building Research Establishment Ltd 2021
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