Daylighting Buildings

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Program Level: This is a level 200 program. Intended for individuals familiar with green building principles and practices.

Who Should Come: Individuals involved in the building design, construction and renovation industries, especially those who are interested in optimizing daylighting to reduce energy consumption and enhance occupant comfort and productivity.

"When properly designed and effectively integrated with the electric lighting system, daylighting can offer significant energy savings by offsetting a portion of the electric lighting load. A related benefit is the reduction in cooling capacity and use by lowering a significant component of internal gains. In addition to energy savings, daylighting generally improves occupant satisfaction and comfort. Windows also provide visual relief, a contact with nature, time orientation, the possibility of ventilation, and emergency egress."

-US Department of Energy

Daylighting has the potential to significantly reduce energy consumption, improve life-cycle cost, and increase occupant productivity and wellbeing. In light of the inherent value of strategic daylighting design, dont miss the opportunity to join GRTs own Holly Wasilowski as she presents a 2.0-hour intro-level training on the principles of daylighting for buildings.

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Daylighting Buildings

  1. 1. Daylighting Buildings Nexus | November 12, 2009 Holly Wasilowski, Registered Architect, LEED AP Doctor of Design Student in Sustainable Design Harvard Graduate School of Design
  2. 2. Agenda:  Introduction  Rules of Thumb  Metrics  Case Study Using Metrics  Software Overview  Daylighting and LEED Daylighting Buildings Nexus | November 12, 2009
  3. 3. What is daylighting? Introduction
  4. 4. What are some of the potential benefits of daylighting? Introduction
  5. 5. What are some of the potential benefits of daylighting?  reduced electric lighting load  occupant satisfaction  reduced internal gains  occupant comfort  reduced cooling loads  reduced cooling loads  improved lighting conditions  connection to nature color rendition  time orientation color temperature health: circadian rhythms… “sparkle”  etc. Introduction
  6. 6. What are some of the potential drawbacks of daylighting? Introduction
  7. 7. What are some of the potential drawbacks of daylighting?  increased heat gains  increased cooling loads  glare!  increased electric lighting load – how?  functional interference (example: projectors) More is not always better. Introduction
  8. 8. Some Resources Heating, Cooling, Sun, Wind & Environmental Green Studio Lighting – Light – Brown Control Systems Handbook Norbert Lechner and DeKay – Fuller Moore - Kwok and Grondzik Introduction
  9. 9. For other Rules of Thumb and Tutorials Go to: www.gsd.harvard.edu/research/gsdsquare/tutorials.html Rules of Thumb
  10. 10. Rules of Thumb Daylighting Buildings Nexus | November 12, 2009
  11. 11. Sun angles Rules of Thumb
  12. 12. Sun angles Opinion poll: Would you rather have your office window facing north, south, east, or west? Rules of Thumb
  13. 13. Sun angles Opinion poll: Would you rather have your office window facing north, south, east, or west? What about your bedroom? Rules of Thumb
  14. 14. Sun angles Opinion poll: Would you rather have your office window facing north, south, east, or west? What about your bedroom? Would you rather have your outdoor swimming pool on the north, south, east, or west of your Boston apartment building? Rules of Thumb
  15. 15. Sun angles Rules of Thumb
  16. 16. Sun angles Quiz question: Does an east-facing surface in Boston receive more solar radiation in the summer or the winter? A horizontal surface? A south-facing surface? Rules of Thumb
  17. 17. Sun angles Rules of Thumb
  18. 18. Sun angles south VS. Rules of Thumb
  19. 19. Building orientation: north/south +/- 15 degrees Carmax Headquarters by ADD Inc Rules of Thumb
  20. 20. Façade Design and Building Massing Carmax Headquarters by ADD Inc Rules of Thumb
  21. 21. External Shading Why is EXTERNAL shading so important? Rules of Thumb
  22. 22. External Shading Why is EXTERNAL shading so important? Rules of Thumb
  23. 23. Lighting Controls and Interior Design Rules of Thumb
  24. 24. Lighting Controls and Interior Design  Interior light shelf  photosensors  zoning of electric lighting  reflective colors  low/translucent partitions Rules of Thumb
  25. 25. Some definitions Luminance Illuminance Rules of Thumb
  26. 26. Some definitions Luminance Units: candela/m2 (SI), candela/ft2 (IP) (1 candela/ft2 = about 11 candela/m2)* Illuminance Units: lux *Use a conversion (SI), footcandles (IP) factor of 10 today, for (1 fc = about 11 lux)* convenience. Rules of Thumb
  27. 27. Falsecolor Luminance Image from Radiance Rules of Thumb
  28. 28. Illuminance Image from Ecotect (calculations performed in Radiance) Rules of Thumb
  29. 29. What are some typical light levels? Office: Classroom: Parking lot at night: Overcast day outside: Sunny day outside: Rules of Thumb
  30. 30. What are some typical light levels? Office: 50 fc, 500 lux Classroom: 30 fc, 300 lux Parking lot at night: 1 fc, 10 lux Overcast day outside: 1500 fc, 15,000 lux Sunny day outside: 8000 fc, 80,000 lux Rules of Thumb
  31. 31. Illuminance meter $60 to $500 +/- Rules of Thumb
  32. 32. Glare  direct glare discomfort glare - physical discomfort disability glare – reduced visual performance  indirect glare  veiling reflections Rules of Thumb
  33. 33. Maximum Recommended Brightness Ratios for Indoor Lighting1 Ratio Areas Example 3:1 Task to immediate Book to desk top surroundings 5:1 Task to general Book to nearby surroundings partitions 10:1 Task to remote Book to remote wall surroundings 20:1 Light source to large Window to adjacent adjacent area wall 1 From Heating, Cooling, Lighting, Lechner 2009 Rules of Thumb
  34. 34. Maximum Recommended Luminance Ratios for Indoor Lighting1 Ratio Areas Example 3:1 Task to immediate Book to desk top surroundings 5:1 Task to general Book to nearby surroundings partitions 10:1 Task to remote Book to remote wall surroundings 20:1 Light source to large Window to adjacent adjacent area wall 1 From Heating, Cooling, Lighting, Lechner 2009 What is wrong with these rules of thumb for daylighting? Rules of Thumb
  35. 35. A Glare Study Classroom renderings from Radiance Rules of Thumb
  36. 36. A Study of Contrast Ratios in a Daylit Space Rules of Thumb
  37. 37. A Study of Contrast Ratios in a Daylit Space Rules of Thumb
  38. 38. Daylight Penetration How far can daylight X penetrate into a space? Rules of Thumb
  39. 39. Daylight Penetration1 In a sidelit space with a standard window and venetian blinds, the depth of the daylit area usually X lies between 1.5 and 2 time the window-head- height. If a space does not require the use of a shading device the ratio can increase up to 2.5. 1.5X 2X 2.5 X 1 From Christoph Reinhart, Harvard Graduate School of Design 2009 Rules of Thumb
  40. 40. For other Rules of Thumb and Tutorials Go to: www.gsd.harvard.edu/research/gsdsquare/tutorials.html Current Tutorials:  Daylighting Rules of Thumb  Getting Started with Ecotect/Radiance/Daysim  From Rhinoceros to Ecotect Getting Started with DesignBuilder/EnergyPlus Rules of Thumb
  41. 41. Daylighting Metrics Daylighting Buildings Nexus | November 12, 2009
  42. 42. Daylight Factor (DF)  Ratio of Outside Illuminance to Inside Illuminance  DF = 100 * Ein / Eext From: www.learn.londonmet.ac.uk/packages/clear/visual/daylight/analysis/hand/daylight_factor.html Daylighting Metrics
  43. 43. Daylight Factor (DF)  Widely used metric  Easy to understand  2% or 5% DF are 2 common thresholds for daylighting  Limitations:  Overcast sky only!!!  More is not always better Daylighting Metrics
  44. 44. Daylight Factor Image in Ecotect (Calculations Performed in Radiance) Daylighting Metrics
  45. 45. Dynamic Climate Responsive Daylight Metrics  Consider daylight over a period of time, such as a year  Use actual occupied hours  Use actual climate conditions  TMY weather files Daylighting Metrics
  46. 46. Daylight Autonomy (DA)  Percentage of working hours when a minimum work plane illuminance (example, 300 lux or 28 fc) is maintained by daylight alone Daylighting Metrics
  47. 47. Useful Daylight Illuminance (UDI)  Divides working hours into three bins:  % < 100 lux (insufficient daylight)  % between 100 lux (9.2 fc) and 2000 lux (186 fc) (useful daylight)  % > 2000 lux (186 fc) (too much daylight) Daylighting Metrics
  48. 48. A Case Study Using Daylighting Metrics Daylighting Buildings Nexus | November 12, 2009
  49. 49. Case Study  Academic Building in Northern Kentucky  West-facing Laboratories  South-facing Classrooms  East-facing Offices  Comparing Design Alternatives for Each Case Study Using Daylight Metrics
  50. 50. Case Study Variant A: “No Shade” Same as E but without sun shelf. Variant B: “Different Glass” 60% visible transmittance rather than 72% Variant C: “Horizontal Louvers” 6” deep louvers at 6” O.C. for portion of windows above 7’ A Variant D: “Interior/Exterior B Shelf” 24” exterior shelf plus 36” C interior shelf at 10’ D Variant E: “As Designed” 3’ or E 7’ sill, 12’-6” head, 24” deep exterior sun shelf at 10’ Case Study Using Daylight Metrics
  51. 51. Case Study: Daylight Autonomy (DA) Here all the variants show that there is plenty of daylight in the space. A B C D Case Study Using Daylight Metrics E
  52. 52. Case Study: Useful Daylight Index (UDI) The UDI for all 5 variants indicates that glare control near the windows is a concern. Variant B shows that glass with less visible transmittance is actually beneficial from a daylighting perspective. This would allow for a lower solar heat gain coefficient, which would be beneficial from an energy stand-point as well. A B C D Case Study Using Daylight Metrics E
  53. 53. Case Study: Direct Shading Studies South-Facing Classroom: June 21, noon South-Facing Classroom: Dec 21, noon The louvers of variant C and the deep lightshelf of variant D help control glare; however, interior blinds will be needed during low sun-angles for each of the current variants. South-Facing Classroom: March 21, noon Case Study Using Daylight Metrics
  54. 54. Case Study: Conclusions The classroom receives plenty of daylight. If the window sizes could be reduced it would likely be beneficial from an energy stand-point as well as cost. The lower glazing provides the least lighting benefit but the best view. Use photo-controlled dimmers throughout the space. Zone perimeter space separately if possible. A glass that provides more shade is recommended for this space. Consider 0.6 visible transmittance or higher and 0.35 shading coefficient or lower (instead of 0.7 and 0.43 respectively.) Add an interior sun shelf if possible or consider horizontal louvers. Provide as much depth as feasible for the shading devices. Case Study Using Daylight Metrics
  55. 55. Software Overview Daylighting Buildings Nexus | November 12, 2009
  56. 56. Software Overview: Direct Shading Solar Position Static Simulations Dynamic Simulations Glare Probability
  57. 57. Direct Shading:  SketchUp, Ecotect…  Any other 3D modeling program in which you can accurately set:  Your location (longitude/latitude or city)  Your orientation (face your building the right direction)  And the time of day and year  And which accurately positions the sun Software Overview
  58. 58. Solar Position:  Climate Consultant (freeware) http://www.energy-design-tools.aud.ucla.edu/ Software Overview
  59. 59. Solar Position:  Ecotect / Ecotect Weather Tool Software Overview
  60. 60. Radiance:  Accurate, physically-based renderings  Static (one moment in time) Calculations  Luminance values  Illuminance values  Freeware: http://radsite.lbl.gov/radiance/download.html Software Overview
  61. 61. Radiance Rendering From: www.artifice.com/radiance.html Software Overview
  62. 62. Radiance Illuminance Images Software Overview
  63. 63. Exporting to Radiance in Ecotect Software Overview
  64. 64. Radiance Calculations Visualized in Ecotect Software Overview
  65. 65. Daysim:  Dynamic, Climate-Based Calculations  UDI  DA  Uses Radiance Engine  Can Model Blind Operations Freeware: http://www.nrc- cnrc.gc.ca/eng/projects/irc/daysim/versions.html Software Overview
  66. 66. The Daysim GUI Software Overview
  67. 67. Evalglare: For Calculating Glare Probability A classroom rendering A glare study in in Radiance Evalglare Software Overview
  68. 68. Evalglare: For Calculating Glare Probability  http://www.sbi.dk/download/pdf/Evalglare.pdf Freeware (Site in German. Look for evalglare v0.9f – Windows Version in lower right)  http://www.ise.fhg.de/radiance Software Overview
  69. 69. Daylighting and LEED Daylighting Buildings Nexus | November 12, 2009
  70. 70. LEED 2009 IEQ Credit 8.1  75% of Occupied Spaces Daylit = 1 point  90% of Occupied Spaces Daylit = 2 points  Option 1: Simulation  Option 2: Prescriptive  Option 3: Measurement  Option 4: Combination Daylighting and LEED
  71. 71. Option 1 Simulation  To qualify as daylit, space must meet a minimum of 25 fc and max of 500 fc on September 21 at 9am and 3pm under clear skies  Automated shades exempt you from the maximum illuminance limitations Daylighting and LEED
  72. 72. Option 2 Prescriptive  To qualify as daylit, the visible light transmittance (VLT) times the window-to-floor area ratio (WFR) must be between 0.150 and 0.180 0.150 < VLT X WFR < 0.180  And the space must meet this ceiling height requirement… Daylighting and LEED
  73. 73. Option 2 Prescriptive 0.150 > VLT X WFR < 0.180 Daylighting and LEED
  74. 74. Option 3 Measurement  To qualify as daylit, space must meet a minimum of 25 fc measured on a 10 foot grid Daylighting and LEED
  75. 75. Option 3 Combination  To qualify as daylit, each space must meet one of the methods described above  In all cases (Options 1-4) provide glare control Daylighting and LEED
  76. 76. Questions? Daylighting Buildings Nexus | November 12, 2009

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