Is the use of daylight as the principal source of illumination in a given space.

Modern design of commercial buildings with a focus on sustainability, places importance on ‘day-lighting’ as an important feature of mainstream construction. Backed up by numerous studies attesting to the importance of daylight in design for improved user satisfaction/performance and retail sales, buildings with day-lighting can be more valuable and marketable.

Daylight harvesting

Involves programming your lighting control system to choose natural light first whenever available, and to top up with artificial lighting only when necessary.

Are the luminaires dimmable?

The first thing to consider when looking at lux control is the luminaires – are they dimmable. If they are not, the parameters for your daylight sensing will need to be set at a specific lux level to switch the luminaires either ‘on’ or ‘off’, or possibly for bi-level switching, perhaps ‘on’, ‘50%’ and ‘off’.

While such a system will provide energy savings, this on/off function could become somewhat annoying, especially on days where there is intermittent cloud cover. As well as ensuring that ‘nuisance switching’ is not an issue, the programming will also need to ensure that the life of the light fittings and the lamps is not compromised by too frequent switching.

Where dimming luminaires are installed, the daylight harvesting will dim up / or dim down continuously over the dimmable ballast’s range, allowing whatever range of light output necessary to augment the available daylight in order to keep the lux levels within a predetermined range. Light harvesting when programmed well with dimming luminaires, should pass almost unnoticed by those using the space.

Do note however, not all dimmable fittings behave in the same way, or fit the same criteria. Many ballasts can be dimmed between 1% and 100%. Recently however we have heard of one manufacturer who is rejecting warranty claims if their fittings are dimmed below a set percentage e.g. 20%. Intelligent Environments are happy to provide advice in this area if required.