The document provides an overview of daylighting buildings, including potential benefits such as reduced energy loads and improved occupant satisfaction. It discusses concepts like daylight factor, useful daylight illuminance, and daylight autonomy. Rules of thumb are presented for factors like building orientation, external shading, and typical light levels. Software for daylighting analysis is reviewed, including Radiance and Daysim for static and dynamic simulations. Metrics and options for achieving LEED credits related to daylighting are also covered.

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. Agenda:
 Introduction
 Rules of Thumb
 Metrics
 Case Study Using Metrics
 Software Overview
 Daylighting and LEED
Daylighting Buildings
Nexus | November 12, 2009

3. What is daylighting?
Introduction

4. What are some of the potential benefits of
daylighting?
Introduction

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. What are some of the potential drawbacks of
daylighting?
Introduction

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. 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. For other Rules of Thumb and Tutorials Go to:
www.gsd.harvard.edu/research/gsdsquare/tutorials.html
Rules of Thumb

10. Rules of Thumb
Daylighting Buildings
Nexus | November 12, 2009

11. Sun angles
Rules of Thumb

12. Sun angles
Opinion poll: Would you rather have your office
window facing north, south, east, or west?
Rules of Thumb

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. 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. Sun angles
Rules of Thumb

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. Sun angles
Rules of Thumb

18. Sun angles
south
VS.
Rules of Thumb

19. Building orientation: north/south +/- 15 degrees
Carmax Headquarters by ADD Inc
Rules of Thumb

20. Façade Design and Building Massing
Carmax Headquarters by ADD Inc
Rules of Thumb

21. External Shading
Why is EXTERNAL shading so important?
Rules of Thumb

22. External Shading
Why is EXTERNAL shading so important?
Rules of Thumb

23. Lighting Controls and Interior Design
Rules of Thumb

24. Lighting Controls and Interior Design
 Interior light shelf
 photosensors
 zoning of electric
lighting
 reflective colors
 low/translucent
partitions
Rules of Thumb

25. Some definitions
Luminance
Illuminance
Rules of Thumb

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. Falsecolor Luminance Image from Radiance
Rules of Thumb

28. Illuminance Image from Ecotect
(calculations performed in Radiance)
Rules of Thumb

29. What are some typical light levels?
Office:
Classroom:
Parking lot at night:
Overcast day outside:
Sunny day outside:
Rules of Thumb

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. Illuminance meter
$60 to $500 +/-
Rules of Thumb

32. Glare
 direct glare
discomfort glare -
physical discomfort
disability glare – reduced
visual performance
 indirect glare
 veiling reflections
Rules of Thumb

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. 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. A Glare Study
Classroom renderings from Radiance
Rules of Thumb

36. A Study of Contrast Ratios in a Daylit Space
Rules of Thumb

37. A Study of Contrast Ratios in a Daylit Space
Rules of Thumb

38. Daylight Penetration
How far can daylight
X
penetrate into a space?
Rules of Thumb

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. 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. Daylighting Metrics
Daylighting Buildings
Nexus | November 12, 2009

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. 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. Daylight Factor Image in Ecotect
(Calculations Performed in Radiance)
Daylighting Metrics

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. 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. 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. A Case Study Using Daylighting Metrics
Daylighting Buildings
Nexus | November 12, 2009

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. 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. 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. 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. 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. 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. Software Overview
Daylighting Buildings
Nexus | November 12, 2009

56. Software Overview:
Direct Shading
Solar Position
Static Simulations
Dynamic Simulations
Glare Probability

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. Solar Position:
 Climate Consultant (freeware)
http://www.energy-design-tools.aud.ucla.edu/
Software Overview

59. Solar Position:
 Ecotect / Ecotect Weather Tool
Software Overview

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. Radiance Rendering
From: www.artifice.com/radiance.html
Software Overview

62. Radiance Illuminance Images
Software Overview

63. Exporting to Radiance in Ecotect
Software Overview

64. Radiance Calculations Visualized in Ecotect
Software Overview

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. The Daysim GUI
Software Overview

67. Evalglare: For Calculating Glare Probability
A classroom rendering A glare study in
in Radiance Evalglare
Software Overview

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. Daylighting and LEED
Daylighting Buildings
Nexus | November 12, 2009

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. 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. 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. Option 2 Prescriptive
0.150 > VLT X WFR < 0.180
Daylighting and LEED

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. 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. Questions?
Daylighting Buildings
Nexus | November 12, 2009