Daylighting Accident or Technology Marc Schiler Associates University

Daylighting: Accident or Technology? Marc Schiler & Associates / University of Southern California

Technical Approach to Natural Lighting w Provide the light: • Building plan, section and orientation • Fenestration location and sizing w Lighting circuits and controls • Balance the availability of natural light • Shutoff in stages w Sensors • Occupancy sensors • Photosensors

Aesthetic Approach to Natural Lighting w Provide the space: • Building plan, section and orientation • Fenestration location and sizing w Colors, reflective forms and gradation • Show the sensuous nature of the space • Reinforce the design concept and parti w Reinforce the function • Avoid glare • Provide visual terminus(humans are phototropic)

Five Topics: w Topic One: Technical – Concepts and Strategies w Topic Two: Aesthetic – Examples and Images w Topic Three: Models – Simulating Daylight with Physical Models w Topic Four: Calculations – Rules of Thumb and Calculations w Topic Five: Equipment – Sensors and Controls

Topic One w Technical: Concepts and Strategies

Agenda for Topic One w Benefits w Strategies and Elements w Definition of Terms w Design Guidelines

Benefits w Quantitative – Cost savings for user – Peak Reduction – Sustainability w Qualitative – Color Rendering – Productivity – Connection

Prototype Strategies w Foot Prints w Clerestories w Sawtooth w Skylights w Light Shelves w Atria w Exotica

Foot Prints

Clerestories

Sawtooth

Skylights w Caveat: – Lower winter angles = less light – Higher summer angles = more heat

Light Shelves

Light Pipes

Atria / Light Wells

Fresnel Lenses and Holographic Films

Design Guidelines w Basic Principles – illuminance vs. luminance w Glare – discomfort glare vs. veiling reflections w Vertical vs. Horizontal w Tips – Bring it in high – Bounce it or filter it – Control it – Harvest it

Vertical vs. Horizontal w Solar Control vs. Lighting per glazing area – more light from horizontal glazing, more heat gain in summer, less heat gain in winter – less light from vertical, better distribution, overhang controls for southern orientations, fins for eastern and western orientations (and northern)

Single Story w Warehouses w Supermarkets Bldgs. w Light Industrial w Suburban sites

Multiple Story w Offices w City Bldgs. w Urban sites

Summary (of Topic One) w Strategies and design elements w Design “Tips”

Break w Take a break – Stretch your legs – Get some coffee – Get rid of some coffee – Call home

Daylighting: Accident or Technology? Marc Schiler & Associates / University of Southern California

Topic Two: Aesthetics w Classics – Older buildings with natural lighting often stand the test of time very well. w Current Examples – Newer buildings enjoy the technique and the technical.

Good Examples, Old to New w St. Gallen Abbey Library, Peter Thumb w Bradbury Building w Ventura Coastal Building by Scott Ellinwood w Mt. Airy Library by Ed Mazria w Boy’s / Ralph’s Supermarket w Lyons School of Architecture by Jourda and Peroudin

Examples for Varying Functions and Climates w Arab Center, Paris, Jean Nouvel w Episcopal Church, Phoenix w MIT Chapel, Boston, Aero Saarinen w Wells Branch Bank, Minnesota w BRF Office Building, Copenhagen

More Examples w Crystal Cathedral, Philip Johnson w North Jutland Art Museum, Alvar Aalto w Menil by Renzo Piano w Kimbell Museum, Louis Kahn w Ronchamps, Le Corbusier w La Tourette, Le Corbusier

Note - w The preceding three pages refer to 35 mm slide collections of each building.

Summary of Part Two w The greatest designs include natural lighting. – Natural light saves energy – Natural light can project in dramatic fashion – Natural light can be bounced and diffused to fill a space w This has proven true throughout history – Rather than fight the architecture, we wish to work with the architecture in the designing the natural and “artificial” lighting to work together.

Daylighting: Accident or Technology? Marc Schiler & Associates / University of Southern California

Topic Three: Models w Using Scale Models to Study Light Distribution

Daylight Harvesting w Provide the light: – Building plan and orientation – Fenestration location and sizing w Test the design – Physical models – Computer simulations w Lighting circuits and controls – Balance the availability of natural light – Occupancy sensors, Photosensors

Agenda for Topic Three w Scales w Examples w Model Craft w Measurement w Photography w Computations

Scale #1 - Quick and Dirty w Simple question: – skylight in middle or by the wall? – horizontal skylight or monitor? – eyeball assessment of question w Small Scale: – 1/16”=1’-0” to 1/2” = 1’-0” or about 1: 200 to 1: 20

Quick and Dirty (cont’d) w Construction – time: one hour or less – foamcore or chipboard, approximate reflectances – tacky glue, masking tape or even pins – scissors, scrap materials at hand w Time and cost – 1/2 hour, $0 - $20

Scale #2 - Developmental w Developmental issues: – Sizing issues: “How big should the skylight be? ” – Placement/Light distribution: “How close to the wall? ” – Details: “How wide or deep should the light well be? ” – Actual measurements taken at different times and seasons w Middle Scale: – 1” = 1’-0” or about 1: 10

Developmental (cont’d) w Construction – Correct reflectances, some details like baseboards – simple furniture, critical objects to be lit – more detail, such as mullions to show shadow patterns – specular and diffuse surfaces are differentiated w Time and cost – 2 to 4 hours, $30 - $100

Scale #3 - Presentation w Qualitative issues: – Calibration against existing space to test proposed renovations – Color interaction, mood, ambience, personal reactions – Search for glare sources, veiling reflections – Photographs taken at different times and seasons w Large Scale: – 2” = 1’-0” or about 1: 5 or larger

Presentation (cont’d) w Construction – Correct colors, complete details like return air grills, blackboards – Complete furniture, with simulated textures – Ceiling treatments, light fixtures, ducts – Dirty surfaces, where appropriate w Time and cost – 20 to 100+ hours, $100+

Review - Solar Angles w Altitude w Azimuth

Solar Gnomons w One for each latitude, gnomon at correct height w Glued to model in relation to model compass w Manipulated to get shadow in the correct position – Azimuth first – Altitude second

Solar Gnomon Example 1

Model Craft w Joints must be sealed – electrical tape, or aluminum foil taped over all corners and seams w Walls must be opaque – construction paper, opaque internal surface treatments glued to internal surfaces – aluminum foil covering all exterior surfaces (exception: any surface which might reflect light into the model, such as a roof adjacent to a roof monitor or sawtooth)

Model Craft (cont’d) w Replaceable parts or oversized parts – Whatever is being tested should fit into a light-leak -proof slot – Prepare modules for each variation in developmental or presentation models – In some cases, testing skylight placement can be done by making an oversize roof, and then sliding it around so that the skylight sits over different areas. One roof and skylight can then simulate many positions without any cutting.

Model Craft (cont’d) w Portholes for measurement – allow access for meters and wires, if necessary, and cover the hole if it is possible to read the meter from somewhere else. – if necessary, cut holes in the floor to allow the meter surface to be at the workplane height in the scale of the model

Model Craft (cont’d) w Portholes for photography – plan the access for the camera from the desired viewpoints – place portholes at in scale eye position, e. g. 5’-3” in model scale – if multiple views are desired, cover portholes with scale blackboards or paintings so that one porthole is not visible from the other camera angle

Review - Measurement w Footcandle or Lux w Suggested Daylight Factors (DF) – What the heck is a daylight factor? Ein / Eext hor

Measurement Procedures w Grid Record Sheet – Draw a grid of expected measurement points on a sheet of paper, along with headers recording actual time of day and simulated time of day – Xerox enough copies of the sheet for different date or design variations – Record each set of readings onto separate sheets

Measurement (cont’d) w Don’t let light in over your shoulder – shade the meters from direct beam for DF values – Don’t let light in through the measurement port (it screws up the measurement) – put a shroud over your head, and tape it to the model, if necessary (black plastic trash bag, double thick, is usually sufficient)

Measurement (cont’d) w Do let light in over your shoulder! – when measuring through the active window, be sure that your body stays below the field of view of the window and the meter – don’t shade the meters from direct beam for absolute values

Photography w Record date and time – Include the date and time you are simulating within the image itself

Photography (cont’d) w Provide a porthole w Don’t let light in over your shoulder – again, put a shroud over your head, and tape it to the model, if necessary (a black plastic trash bag, double thick, is usually sufficient)

Slides w Note. At this point the presentation proceeds to proof that this can be done at each scale in the form of a series of 35 mm slides of the interiors of real buildings followed by models of the same space, generally indistinguishable.

Summary of Topic Three w Scales, costs and functions w Examples w Model Craft w Measurement w Photography

Break w Take a break – Stretch your legs – Get some coffee – Get rid of some coffee – Call home

Daylighting: Accident or Technology? Marc Schiler & Associates / University of Southern California

Topic Four: Calculations Rules of Thumb and Calculations

Agenda for Topic Four w Rule of Thumb Computations – Width to Depth – Percentage Glazing w IES calculation methods – sidelighting – toplighting

Design Guidelines (Reminder) w Basic Principles – illuminance vs luminance w Glare – discomfort glare vs veiling reflections w Vertical vs. Horizontal w Tips – Bring it in high – Bounce it or filter it – Control it – Harvest it

Reminder of Application Guidelines w Different functions and building forms will require different calculation methods.

Vertical vs. Horizontal w Solar Control vs. Lighting per glazing area – more light from horizontal glazing, more heat gain in summer, less heat gain in winter – less light from vertical, better distribution, overhang controls for southern orientations, fins for eastern and western orientations (and northern)

Single Story w Warehouses w Supermarkets Bldgs. w Light Industrial w Suburban sites

Multiple Story w Offices w City Bldgs. w Urban sites

Rules of Thumb for Aperture Sizing w Suggested Daylight Factors (DF) – What the heck is a daylight factor? w Sizing to obtain the suggested DF – What glazing area in which kind of element w Computer Programs – If the client’s got money

Suggested Daylight Factors Function DF Comment Circulation Public Spaces Warehouse Office area Detailed office work Factory work Detailed manf’g Manual drafting, color comparison 1% >1% 1. 5% 2 -4% 5% vertical surfaces are important more light, more drama higher for tightly packed shelves filing, reception, general area focus on work surface dependent on function and danger tasks requiring high visual acuity 6% provide one area within the space

Sizing From Sidelighting (d < 2. 5 x h) near the front of the space at the middle of the space near the back of the space Suggested Glazing Area DF x Af / 0. 5 Tg DF x Af / 0. 2 Tg DF x Af / 0. 1 Tg From Toplighting Vertical monitors North facing sawtooth Horizontal Skylights* Suggested Glazing Area DF x Af / 0. 2 Tg DF x Af / 0. 33 Tg DF x Af / 0. 5 Tg

Example #1 w 2, 000 sf of warehouse, toplighting – – forklift access, generous aisles suggested DF = 1. 5% Transmissivity of glazing = 62% Horizontal skylights w Go for uniform 1. 5% – Ag = DF x Af / 0. 5 Tg – =. 015 x 2, 000 sf / (0. 5 x. 62) – = 96 sf

Example # 2 w 2, 000 sf of simple office space, sidelighting – – non strenous tasks, filing, some computer terminals suggested DF = 2 -4% depth within 2. 5 h of window (20 ft of 8 ft window) Transmissivity of glazing = 75% w Do layout, decide desired daylit depth l Go for 3% at middle –Ag = DF x Af / 0. 2 Tg – =. 03 x 2, 000 sf / (0. 2 x. 75) – = 400 sf l Go for 3% at back –Ag = DF x Af / 0. 2 Tg – =. 03 x 2, 000 sf / (0. 1 x. 75) – = 800 sf

IES Lumen Method w Tracks light from sky and sun separately w Applies form and reflectance factors to light from ground w Assumes a strip window for the entire length of one wall (as might be found in an office. )

IES Lumen Method (cont’d) w Calculates a Coefficient of Utilization (CU) for five locations within the cross section of the space

Basic Equation w Ei = Ex NT CU w where w Ei = interior illuminance in lx, Ex = exterior illuminance in lx, NT = net transmittance, CU = coefficient of utilization.

Sidelighting w Ei = Exv τ CU w where w Ei = interior horizontal illuminance on a reference point from sidelighting, in lx, Exv = exterior vertical illuminance on the window wall in lx, τ = net transmittance of the window wall, CU = coefficient of utilization.

Ground Exitance w Mg = ρg (Exh sky + Exh sun) w where w Mg = exitance from the ground in lm/m 2, ρg = reflectance of the ground, Exh sky = horizontal illuminance from the sky in lx, Exh sun = horizontal illuminance from the sun in lx.

Illuminance from Overcast Sky w Refer to IESNA Lighting Handbook, Ninth Edition for complete tables

Illuminance from Clear Sky w Refer to IESNA Lighting Handbook, Ninth Edition for complete tables

Illuminance from Sun w Refer to IESNA Lighting Handbook, Ninth Edition for complete tables

Net Transmittance w τ = T Ra Tc LLF w τ = net transmittance of window LLF = light loss factor representing dirt accumulation Ra = the net-to-gross window area ratio representing such elements as mullions and glazing bars; Tc = other elements such as shades and drapes

Light Loss Tables (used to be slide 87) w Refer to IESNA Lighting Handbook, Ninth Edition for complete tables

CU Sky Component = 0. 75 w Refer to IESNA Lighting Handbook, Ninth Edition for complete tables

CU Ground Component w Refer to IESNA Lighting Handbook, Ninth Edition for complete tables

Clear Window Illuminance w Ei = τ (Exv sky CUsky + Exv g CUg) w Ei = interior illuminance at a reference point in lx, τ = net transmittance of the window wall, Exv sky = exterior vertical illuminance from the sky on the window in lx, CUsky = coefficient of utilization from the sky, Exv g = exterior vertical illuminance from the ground on the window in lx, CUg = coefficient of utilization from the ground.

Diffusing Window Illuminance w Ei = 0. 5 τ (Exv sky + Exv g ) ( CUsky + CUg) w Ei = interior illuminance at a reference point in lx, τ = net transmittance of the window wall, Exv sky = exterior vertical illuminance from the sky on the window in lx, CUsky = coefficient of utilization from the sky, Exv g = exterior vertical illuminance from the ground on the window in lx, CUg = coefficient of utilization from the ground.

Toplighting w Ei = Exh τ As / Aw w Ei = average incident illuminance on the workplane from skylights in lx, Exh = horizontal exterior illuminance on the skylights in lx, As = gross projected horizontal area of all the skylights in m 2 Aw = area of the workplane in m 2, τ = net transmittance of the skylights and light well, including losses because of solar control devices and maintenance factors, CU = coefficient of utilization.

Toplighting (cont’d) w TDM = 1. 25 TFS (1. 18 - 0. 416 TFS) w TDM = dome transmittance, TFS = flatsheet transmittance.

Toplighting (cont’d) w T = (T 1 T 2) / (1 - ρ1 ρ2) w T 1, T 2 =diffuse transmittances of the individual domes, ρ1 = reflectance from the bottom side of the upper dome, ρ2 = reflectance from the top side of the lower dome.

Light Well Equation w WCR = 5 h(w +l) / wl w WCR is the well cavity ratio, used to look up the well efficiency Nw w h is the well height, w is the well width, l is the well length. (The dimensions h, w, and l must be expressed in the same units. )

Light Well Cavity Ratio w Table from IESNA Lighting Handbook, Ninth Edition

Diffuse Transmittance w τd = Td Nw Ra Tc LLF w Td is equal to the diffuse transmittance w Nw is the well efficiency w Ra = ratio of net to gross skylight area Tc = transmittances of diffusers, lenses, louvers, or other controls LLF = the light loss factor from IES tables.

Direct Transmittance w τD = TD NW Ra Tc LLF w TD is equal to the direct transmittance of the dome w Nw is the well efficiency Ra = ratio of net to gross skylight area Tc = transmittances of diffusers, lenses, louvers, or other controls LLF = the light loss factor from IES tables.

Room Cavity Ratio w RCR = 5 hc (l + W) / lw w hc is the height from the workplane to the bottom of the skylight well, l is the length of the room, w is the width of the room. (All three parameters must have the same units. )

Room Cavity CU Tables w Refer to IESNA Lighting Handbook, Ninth Edition for complete tables

Overcast Sky w Ei = Exh sky τd CU N (A / Aw) w Exh sky = exterior horizontal illuminance due to the sky only, in lx, τd = net diffuse transmittance, τD = net direct transmittance, CU = coefficient of utilization, N = number of skylights, A = area of each skylight in m 2, Aw = area of the workplane in m 2.

Clear Sky w Ei = (Exh sky τd + Exh sun τD) CU N (A / Aw) w Exh sky = exterior horizontal illuminance due to the sky only, in lx, Exh sun = exterior horizontal illuminance due to the sun only, in lx, τd = net diffuse transmittance, τD = net direct transmittance, CU = coefficient of utilization, N = number of skylights, A = area of each skylight in m 2, Aw = area of the workplane in m 2.

Daylight Factor w CIE (European) methods w Less accurate, more flexible, in allowing asymmetrical window placement w PSALI w Some methods only account for overcast conditions

Computer Programs w More accurate predictions or renderings – – Lightscape Radiance Lumen Micro (et al) Superlite w Payback period, including effect of HVAC – DOE 2. 1 E – Micro. DOE, Power. DOE, CECDOE, etc. – HEED, Solar 5

Summary of Topic Four w Computational Rules of Thumb w IES Lumen Method – sidelighting – toplighting w Daylight Factor w Computer programs

Break w Take a break – Stretch your legs – Get some coffee – Get rid of some coffee – Call home

Daylighting: Accident or Technology? Marc Schiler & Associates / University of Southern California

Part Five: Equipment Natural Lighting: Control Devices and Systems

Daylight Harvesting w Provide the light: – Building plan and orientation – Fenestration location and sizing w Test the design – Computer simulations – Physical models w Lighting circuits and controls – Balance the availability of natural light – Occupancy sensors, Photosensors

Agenda for Topic Five w Controls w California Codes w Typical Circuits w Demonstration w Possible Savings w Dangers and Pitfalls w Walkthrough

Review - Terms w Design Level w Circuits w Devices – sensors – power packs – switches

Basic Strategy w Circuit layout and sensor placement, daytime

Basic Strategy w Circuit layout and sensor placement, nighttime

California Code w Must provide possibility for 50% reduction in any room over 100 sq. ft. w Provide separate switching for daylit areas, to allow harvesting w Allowable Lighting Power Density and Actual Lighting Power Density – Credits for daylight sensors – Credits for occupancy sensors – Credits for automatic time controls, etc.

California Code (cont’d) w Credit factors for occupancy sensors

California Code Required Layouts

Control types w Occupancy Sensors w Photosensors w Continuous Dimming vs. Step Dimming w Occupancy and Photosensor Interaction

Occupancy Sensors w Ultrasonic – – sees around corners quartz crystal oscillator multiple receivers sees inanimate movement, sometimes vibrations w Infrared – line of sight only – ignores movement of same temperature objects – can be aimed and masked

Comparison

Ultrasonic

Infrared

Photosensors w Ceiling mounted, viewing workplane

Continuous Dimming vs. Step Dimming w Low natural light + single step = no savings w (single step is never activated, light too low)

Continuous Dimming vs. Step Dimming w Continuous dimming harvests immediately w (begins @ 100%, reduces to 30%*)

Continuous Dimming vs. Step Dimming w Large natural light + single step = big savings w (single step is activated, goes to zero)

Continuous Dimming vs. Step Dimming w Plentiful daylight + single step = best value w Lower natural light levels require continuous dimming

Typical circuits w Power Pack w Separate low voltage signal w RS-232, EPROM, Carrier Wave and X-10

Power Pack w Switches, sensors and outside sources

Staged Signals w Interim logic box collects signal data

“Intelligent Ballasts” w Separate low voltage signal from sensor to ballasts

Possible savings w DOE 2. 1 E – – – STEPPED vs. CONTINUOUS LT-REF-PT-1 ( x, y, z) LT-FRACTION-1 DESIGN LEVEL Lighting ->HVAC -> plant -> Economics w HEED, DAYLIT – STEPPED vs. CONTINUOUS – 3 zones – DESIGN LEVEL

Dangers and Pitfalls w Users – Sensitivity and Time Delay – Incorrect Placement – “Know it All” w Contractors – Upside Down – Wrong Voltage – Passive Circuit to Active Circuit – No Calibration

Summary w Controls – Occupancy Sensors – Photosensors – Continuous Dimming vs. Step Dimming – Occupancy and Photosensor Interaction w Code Requirements and Benefits

Summary (cont’d) w Typical Wiring Diagrams – Power pack vs. “intelligent ballasts” w Typical Pitfalls w Energy saved w Quality Environment!

Overall Summary w Natural Light in Buildings – Provide the light: • Building plan, orientation and section • Fenestration location and sizing – Lighting circuits and controls • Balance the availability of natural light • Shutoff in stages – Sensors • Occupancy sensors • Photosensors

Sources for further study w Books: – Ander, Gregg; Daylighting Performance and Design, Van Nostrand Reinhold, New York 1995 – Kaufman, John, et al; IES Handbook; Illuminating Engineering Society (IESNA), New York – Schiler: Simplified Design of Building Lighting, Wiley & Sons, New York 1992 – Schiler et al: Simulating Daylight with Architectural Models, DNNA report

Sources for further study (cont’d) w Monographs: – ____; RP-5 Recommended Practice of Daylighting; Illuminating Engineering , Society (IESNA), New York – ____; RP-21 Calculation of Daylight Availability; Illuminating Engineering Society (IESNA), New York – ____; RP-23 Calculation of Daylight; Illuminating Engineering Society (IESNA), New York

Finis w Daylighting: Accident or Technology? w Marc Schiler & Associates / University of Southern California