Lighting Design Intent

Transcription

1 LIGHTING DESIGN INTENT & CRITERIA Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 1 Lighting Design Intent 1. A clear design intent should be evident in all elements of the visual field. William Lam: Perception and Lighting as Formgivers for Architecture from Some rules of thumb for good design Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 2 1

2 Design Process Flow general process flow iterations Design intent Design criteria System ideas/proposals initial Design methods (patterns, tools, ) System ideas/proposals refined Implementation methods (physical things) System ideas/proposals near final Design validation During design (internal quality control and commissioning) During construction (internal quality control and commissioning) During usage (via complaints or via POE) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 3 Lighting Design Process Design intent Design criteria Start ( problem ) *Design concepts *Design validation Stuff happens Lighting design methods* End ( solution ) * to be discussed more over the next weeks Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 4 2

3 Issues > Intent > Criteria ISSUES Intent Criteria Flow into design process Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 5 Design Intent Examples: The lighting will be energy efficient Daylighting will be utilized (is this truly intent or simply a method?) The lighting will be reasonably comfortable The lighting will increase sales The lighting will increase productivity The lighting will enhance wayfinding The lighting will contribute credits for LEED The lighting will win a design award Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 6 3

4 Design Criteria Examples: The lighting will be energy efficient [intent] Perhaps: will meet the requirements of ASHRAE Standard 90.1 Perhaps: will be 30% more efficient than ASHRAE 90.1 Daylighting will be utilized [intent] (confirm not just a method) All spaces will have a minimum daylight factor of 2% Daylighting will reduce annual electric lighting energy requirements by 60% The lighting will be reasonably comfortable [intent] 80% of occupants will rate the lighting as very comfortable The lighting will be aesthetically pleasing [intent] Appearance will match three selected precedents Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 7 Design Criteria More examples: The lighting will increase sales [intent] The lighting will increase sales by 20% compared to sales in existing stores The lighting will increase productivity [intent] The lighting will increase worker productivity by 10% compared to the productivity in existing offices The lighting will support wayfinding [intent] note that criteria can be quantitative (useful during design and amenable to calculations) and/or qualitative (typically amenable to judgment and POEs) 25% fewer requests for assistance in finding major functional spaces will be made at the Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 8 4

5 Methods Methods should never be put forward as intent or criteria (with a few exceptions) Fluorescent lamps are NOT an intent Fluorescent lamps are NOT a criterion Fluorescent lamps are a method (a means, not an end; a cause, not an effect) More on lighting design methods later a method, such as daylighting, may become an intent if it is so strongly held as to be non-negotiable (even then, good daylighting is likely the real intent) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 9 A Reminder A proposed design solution is a hypothesis The designer believes that IF I do this, such and such will THEN result A hypothesis is a prediction, a prognosis, a wish, a wild guess (depending upon experience and extent of project research) A hypothesis is NOT a fact Hypotheses must be tested and verified Thus, design moves must be verified (they will have consequences see image on first slide) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 10 5

6 Design Validation Validation of design moves during design is essential, otherwise it will be too late for the victims of a bad decision (the decision will have been built and occupied by real people) Many lighting design validation tools are available Precedents (case studies) General rules and patterns Hand calculations Computer simulations Physical models (difficulty in scaling electric light sources limits this tool this was not the case with daylighting) Full scale mock-ups (cost may limit this tool) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 11 Implementation Methods These are the objects and systems that can produce the desired effects in a completed building Implementation methods convert concepts into physical reality Clerestory apertures Indirect lighting fixtures Digital lighting controls Reflective wall surfaces and so on Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 12 6

7 Lighting Design Issues Quantitative issues Illuminance Luminance Energy performance Environmental performance First cost Life-cycle costs. issues become intent by assigning value/direction; and thence become criteria by assigning minimum acceptable performance benchmarks Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 13 Lighting Design Issues Qualitative issues Glare Brightness (and brightness patterns) Color rendering Aesthetics Appropriateness. Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 14 7

8 Design Issues qualitative quantitative source: space type Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 15 Some Context for Lighting Design There is no unified theory of visual comfort (as there is with thermal comfort) there is no visual comfort zone diagram no advice regarding how a bit less glare might trade off with a bit less illuminance or how color rendering might trade off with luminance. The lighting design process essentially involves addressing each issue of concern in sequence with conceptual coordination by the designer left to deal with the disaggregated nature of the process. We ll look at the issues of illuminance and glare in some detail in the following slides as these are usually important concerns for most projects Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 16 8

9 Illuminance* On horizontal surfaces Requirements are generally a function of the visual acuity required or expected for a task The purpose of illuminance is to provide adequate light for successful task completion Task is the key (the designer is usually addressing a defined visual task versus general space-rendering) Task location(s) are of concern Multiple tasks require providing for the worst task, or for flexibility over time or for flexibility over space Measured in lux (SI) or fc (footcandles, I-P) *the density of light falling on a surface; the human eye cannot detect illuminance, but can detect its result (brightness/luminance) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 17 Illuminance On vertical surfaces If there is a vertical task (pinup, bulletin board, artwork, signage, ), then design concerns are the same as with horizontal illuminance Without a defined task, vertical illuminance requirements are generally a function of spatial design intent To illuminate walls (to avoid the cave effect) To draw attention, provide focus To reduce contrast To support aesthetic design intents Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 18 9

10 Visual Acuity Factors Illuminance recommendations are generally based upon visual acuity the ability to see detail; this ability is affected by: Size of detail Typically there is only minor architectural control over this factor via establishment of viewing distances or through signage design; the architect has little or no control for most work tasks Luminance of detail A result of illuminance and reflectance; illuminance is fully within the realm of lighting system design, while reflectance is often a property of a non-architectural object (such as the page of a book) Contrast at detail A result of task-background luminance relationships and glare condition; these factors are partially in the realm of lighting design and partially a property of the task Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 19 Size Visual Acuity Factors Luminance E E E E E E E E B F Contrast E E E E E easier to see detail more difficult Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 20 10

11 Design Illuminances illuminance categories from the IESNA Lighting Handbook (9 th edition) which is a guideline (not a code or standard) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 21 Illuminance Adjustments The 8 th edition of the IESNA Lighting Handbook suggested increasing illuminance by 1 category for each clear instance of a mitigating factor (poor eye condition, poor contrast, high speed task) the current edition (9 th ) is less specific regarding such adjustments but the idea of adjustments is still valid (and recommended). Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 22 11

12 Glare A negative visual sensation resulting from excessive brightness or excessive contrast in the field of view. Glare can be categorized by: Degree of impact: blinding, disability, discomfort Source/receiver relationship: direct or reflected Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 23 Glare: Degree of Impact Blinding glare: vision is temporarily disrupted (zero visual acuity for some period of time) Example: oncoming car headlights at night (a result of excessive contrast) Example: looking at the sun through a window (a result of absolute brightness) Source may be direct or reflected (although most commonly it is direct) Blinding glare should never be encountered in a building (but occasionally it is) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 24 12

13 Glare: Degree of Impact Disability glare: visual acuity is reduced; the viewer is physically less able to effectively complete visual tasks Example: a reflected image of a light fixture seen in a computer screen (a reflected glare situation, often called a veiling reflection) Example: looking at a TV that is located in front of a window (a direct glare situation, due to excessive contrast) Source may be direct or reflected (either is likely) and the negative effect is often a result of contrast versus absolute brightness Disability glare is undesirable in a building, but budget constraints may make total elimination difficult Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 25 Glare: Degree of Impact Discomfort glare: visual acuity is not measurably reduced, but glare has intruded into the viewer s consciousness; a viewer may be psychologically less able to complete visual tasks Example: reflection of ambient light from a computer screen (no image is seen, just reduced contrast) Example: marginal brightness ratios in a room Source may be direct or reflected and the effect is usually a result of contrast versus absolute brightness; the key issue may be attention-diversion Discomfort glare is undesirable in a building, but is very difficult to totally eliminate (due to budget and the qualitative nature of problem) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 26 13

14 Glare: Source Direct glare: a too-bright object or too-great a contrast scene is in the line of sight of an observer (no intervening transmitter is involved) This should be readily predictable during design, and thus readily solvable simply: Ask yourself what s going to be too bright (more technically, too luminous) Then, reduce brightness (luminance) or block view to object Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 27 Glare: Source Reflected glare: a too-bright object (the most common situation) or too-great-a-contrast scene (less common) is brought into the line of sight of an observer by the intervention of a reflective surface This combination of factors is not necessarily obvious during design, thus some brainstorming is needed Ask yourself what s going to be too bright Ask yourself what s likely to be reflective Then, consider the possible geometries between the above elements and users of the space and take appropriate action Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 28 14

15 Glare Glare Summary Is a perception, not an object or a flow Requires a human receptor/evaluator There is no glare in an unoccupied room Perceptions may vary from person to person Design to mitigate glare often relies upon patterns or statistics Glare cannot be admitted through a window (light can be admitted) Glare cannot be measured by equipment (luminance can be measured) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 29 Glare? Do you know this person? Do you see the person with the knife? Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 30 15

16 Glare? nice lamp shade nice pickup truck Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 31 Glare? what street? what data? Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 32 16

17 Another Visual Phenomenon Sparkle A positive visual sensation resulting from excessive brightness or excessive contrast (in the field of view) Fireworks, a chandelier, a diamond, Sparkle can be introduced to a space (in moderation) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 33 Sparkle? someone thought so sparkle or glare? ball four (just a little bit off the plate) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 34 17