Lighting : Lighting August 2015 - Vol 35 Issue 4
32 LIGHTING MAGAZINE | August/September 2015 Ph: + 612 9502 1161 Fax: + 612 9502 1154 Email: firstname.lastname@example.org READ MORE AT EVOLT.COM.AU LEDFIREIIIPROCODE:1694 The Ektor Generation III platform introduces you to a new era of emergency lighting control. With years in the making, the third generation platform builds on the Ektor product range increasing quality, reliability and performance. GEnERATIOn III A nEW ERA FOR EMERGEnCy MOnITORInG AnD TEsTInG FEATUREs • Recessed • Dueldish85/140mm • Best in class energy consumption • Lithium batteries (LiFePO4) and smart charger • Selectabledischargerating1/2/3/4/8hour Ektor_Aug_app.indd 1 09-Jul-15 4:49:28 PM sufficient to ensure that the space does not appear dull, gloomy, or under-lit, then this extent of provision would be defined by the perceived adequacy of illumination (PAI) criterion. Providing the standard ambient illumination specified for the location and the activity it houses could be expected to ensure PAI satisfaction. The proposed metric for ambient illumination is mean room surface exitance (MRSE), which relates to the overall density of inter-reflected luminous flux within an enclosed space. MRSE could be used in standards (or lighting codes or recommended practice documents) to define standard ambient illumination levels to satisfy the PAI criterion for different types of activities and locations. Alternatively, it could be used by designers to achieve chosen design objectives, such as providing for an overall brightness of illumination appearance within a space, or variation of appearance as people pass from one space to another. Before we move on, take a look at the nearby café space shown in Figure 2. This is a space of very different character, and the illumination is only one factor in that difference. It should be clear that not every space needs to be governed by a standard ambient illumination. This is an example of space where designers should have free reign to apply low ambient illumination levels (providing at least that safety is not compromised) enabling high contrasts to be achieved, and as in this case, drawing attention to the view-out. The standard ambient illumination would set the minimum level, whereas the designer’s chosen design ambient illumination would become the first component of the lighting design concept. A higher level could be opted for, or for locations where no standard value is specified, the lighting designer has free range to introduce design objectives that depend on low ambient illumination levels. Lighting design objectives for a space may be described in terms such as ‘a bright and lively overall appearance’, or ‘a subdued and restful appearance’, or even ‘a dim and intriguing space’. In this way, the design ambient illumination is a design objective that is chosen for a particular location, and it forms the foundation for the illumination hierarchy. ILLUMINATION HIERARCHY At this point we need to take a thoughtful pause. What we see is a distribution of reflected flux, and what the light sources, whether luminaires or windows, provide is a distribution of direct flux. An effective distribution of direct flux is one that creates a scene of reflected light for the space, directing attention to objects of interest, giving emphasis to forms, colours, and textures that have visual significance, whether as furnishings, work tasks, art objects, or whatever identifies the function of the space. This is what is meant by an illumination hierarchy, being a distribution of flux that creates a structured pattern of brightness that is related to the space and the activities to that it houses. It needs to be understood at the outset that this does not need to be an elaborate or fanciful pattern, but rather that for every location, the pattern of light is sensibly and appropriately related to the space and whatever goes on within it. The process of planning such a distribution is greatly facilitated by use of the illumination hierarchy spreadsheet, an example of which is shown in Table 1. We will use it to devise a lighting layout for a hotel foyer, and if the spreadsheet looks a trifle formidable, keep in mind that only the bits shown in red are entered by the user: all the rest is generated automatically. The first three columns are pretty straightforward – room surfaces, their areas, and their reflectances – but keep in mind that the reflectance values do matter and you need to be confident that the values you enter are realistic. Now you are ready for the first insight. As has been explained, the first component of the design concept is the design ambient illumination, for which the metric is mean room surface exitance, MRSE, and the lm/m2 value is entered as shown. It will take designers a little while to become accustomed Figure 2. Quite close to the entrance foyer is this café where lighting standards would not have been a design concern. It can be seen that the ambient illumination is distinctly lower and a quite different light distribution has been opted for, with a different sense of ambience and the emphasis on connecting visitors to the outdoors. It should be clear that not every space needs to be governed by a standard ambient illumination.
Lighting June 2015 - Vol 35 Issue 3
Lighting October 2015 - Vol 35 Issue 5