LIGHTING DESIGN PROCESS

Transcription

1 LIGHTING DESIGN PROCESS illustration by James Benya Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 1 Lighting Design Process: IESNA Lighting design is the creative process for developing safe, productive, and enjoyable lighting solutions within the built environment. In the past, emphasis was placed on simply delivering an appropriate quantity of light. The quality of light was considered mainly in terms of controlling direct or reflected glare. But as this Design Guide reveals, lighting design now extends far beyond these basic factors. This Guide explains that many factors influence the quantity and quality of light. Thus there is no one perfect solution to a single lighting problem. Instead there are multiple solutions, each more or less successful depending on the judging criteria. The judging criteria would ideally be the OPR Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 2 1

2 Lighting Design Process: IESNA continued And the design must also be appropriate in terms of cost, energy, maintenance, style, availability, and a dozen other considerations. Though not a predictable, linear process, lighting design as revealed by this Guide begins with a concept selected from a myriad of alternatives. Then, as the process proceeds, it is filled with cross-checking. Like many architectural projects, most lighting designs can be circumscribed by the following seven-step process: Programming, Schematic Design, Design Development, Contract Documents, Bidding and Negotiation, Construction, and Post-occupancy Evaluation. These elements are discussed in full detail in this Guide. Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 3 Lighting Design Process: Lam A new process of design This is the diametric opposite of the typical engineered approach, which starts with the selection of light fixtures and then, taking them as givens, places them in patterns to achieve predetermined illumination levels. William Lam Perception and Lighting as Formgivers for Architecture Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 4 2

3 A Holistic (Lam-like) Lighting Design Process Would be entered into with a big picture view: The designer would clearly understand the desired overall result (the collective lighting effect) and work iteratively to make it happen The designer essentially envisions an effect and works backward to institute appropriate causes The designer cycles through possible methods and validations The designer selects the best (or at least an acceptable) solution This design process requires experience and confidence Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 5 An Incremental (IES?) Lighting Design Process Would be entered into sequentially: The designer would establish OPR (intent and criteria) The designer (through observation/precedent/intuition) would establish some aspects of the proposed system (perhaps lighting fixture types) The designer addresses specific design issues (illuminance, glare, energy, color, ) individually The designer selects the best (or acceptable) solutions for each of the individual issues The designer integrates potential solutions to the various design problems into a good overall solution This process can succeed in the face of limited experience and confidence Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 6 3

4 Some Design Issues to Consider issues considered very important in an office with computers are flagged IESNA Lighting Design Guide Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 7 Some Design Issues cont d IESNA Lighting Design Guide Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 8 4

5 Following the Incremental Trail Let s look, in more detail, first at: Illuminance (a quantity ) and then Glare (a quality ) Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 9 Illuminances to be Considered Design illuminance (DI) The design criterion (a target; defines success) Initial illuminance (II) Illuminance at the time the lighting system is first used (at the start of owner occupancy) Maintained illuminance (MI) Illuminance after some defined time (typically several years) of usage; after wear and tear takes a toll on the system MI must be >= DI II will be > DI Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 10 5

6 Sources for Illuminance Values Codes = formal, mandatory, governmentenforced (not much help in fact, close to useless in the US) Standards = formal, voluntary (contractenforced, or lawyer-enforced) (rare in the US) Guidelines = less formal than a standard (in the US, this source would commonly be the IESNA Lighting Design Guide) Recommendations = even less formal (perhaps coming from an owner or a colleague) General practice = real informal ( everybody does this use with caution) Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 11 Design Illuminance Code (an example) 2014 Florida Building Code Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 12 6

7 Design Illuminance Code Florida Building Code (2014) SECTION 1205: LIGHTING Comments: although compliance with codes is mandatory, there is not much in this code section to truly inform design beyond a specific minimum illuminance for emergency conditions; Terminology is awkward: natural and artificial The specified minimum non-emergency illuminance (107 lux or 10 fc) would be quite unacceptable to most owners/users in many common space types Codes are not written to ensure satisfaction but to ensure life safety Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 13 Design Illuminance Guideline room/task-specific illuminance values; generally above the 107 lux code minimum see next slide Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 14 7

8 Design Illuminances Guideline Illuminance categories From IESNA Lighting Handbook (9 th edition) codes may control performance needs will control Note: the 10 th (current) edition of the IES Lighting Handbook substantially revised the design illuminance selection information; this older table is shown here because the concept is similar and the information is easier to digest. Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 15 Design Illuminances Addressing based upon visual acuity tempered by project specifics contrast and task size with judgment eye condition (age)? task speed? validation? and judgment Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 16 8

9 A Comment on Illuminances UK and European lighting standards generally require substantially lower design illuminances than the IESNA guidelines. This does not reflect a lack of concern across the ocean for human health and comfort. This does not reflect a difference in human physiology. It does reflect a difference in culture and history. We ll see where this difference leads the US in the future (perhaps for green or carbon-neutral projects). Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 17 Direct Glare Guidance* Design Patterns** Maximum luminance rule Maximum contrast rule * there are no known US code requirements regarding glare mitigation ** these are simple patterns to help guide design decisions toward direct glare avoidance Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 18 9

10 Maximum Luminance Rule 2500 cd/sq m Is the maximum luminance recommended for large light sources (such as a fluorescent fixture, window, or skylight) that may be seen 7500 cd/sq m Is the maximum luminance recommended for small light sources (such as a recessed downlight fixture) that may be seen although glare is a perception associated with brightness, luminance is measurable and therefore easily verifiable and specifiable Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 19 Maximum Contrast Rule Recommended Maximum LUMINANCE RATIOS** 3 : 1 Between task and surround 10 : 1 Between task and more distant surroundings 20 : 1 Between light sources and surroundings 40 : 1 Anywhere in field of view ** with opaque surfaces under equal illuminance, this becomes simply the ratio of surface reflectances Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 20 10

11 A Numeric Index for Direct Glare Visual Comfort Probability (VCP) VCP represents the percentage of occupants who, when using a space as intended, would say that they do NOT sense direct glare 70 or greater is considered a good value VCP varies from lighting design to lighting design; and from location to location within a given space Can be measured in an occupied space (as a POE tool) or simulated using computers (as a design tool) Generic data are provided by some electric luminaire manufacturers for typical room layouts (but not by window manufacturers for daylighting) Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 21 Direct Glare and Daylighting occupant s response designer s approach recod.net/daylighting/ Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 22 11

12 Reflected Glare Rules The common sense geometry rule (which involves identifying the offending zone ) Look at the geometry of tasks and lighting elements during design and avoid potentially poor design decisions involving reflective surfaces (see next slide) Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 23 The Offending Zone bottom line: to avoid introducing the potential for reflected glare, do not place lighting fixtures (electric or daylighting luminaires) in this zone; or limit fixture brightness (luminance) if you do so locate fixtures Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 24 12

13 Light Sources and Glare Potential ceiling potential for direct glare if high luminance potential for reflected glare if high luminance less potential for glare if high luminance Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 25 Two Numeric Indices for Reflected Glare Contrast rendition factor (CRF) Equivalent spherical illuminance (ESI) Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 26 13

14 Contrast Rendition Factor (CRF) CRF is the ratio of contrast at a task under a proposed (or given) lighting system to the contrast under a reference spherical ( glarefree ) lighting system C prop /C ref CRF could possibly range from 1.0 to 0.0 The higher the CRF the better (with respect to reducing reflected glare potential) No generally-accepted design standards or guidelines for appropriate CRF values are currently available Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 27 Equivalent Spherical Illuminance (ESI) ESI = (E) (CRF) where E = raw illuminance (as in, just dumping some light on a surface) ESI = equivalent spherical illuminance (as in good without much reflected glare potential light) CRF = contrast rendition factor ESI was briefly the basis for design criteria published by IESNA, but the concept was dropped at the time there was no ESI meter, so design criteria could not be readily verified in the field ESI is still an interesting and valid concept Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 28 14

15 Illuminance and Glare are not the only Lighting Issues color rendering: four pieces of the same cloth; on the left under four different lamp types, on the right under the same lamp which color is real? Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 29 Energy and Environmental Impact are also Lighting Design Issues energy use for lighting: in residences (left) and offices (right) the first best design moves are building-type specific Ball State Architecture ENVIRONMENTAL SYSTEMS 1 Grondzik 30 15