Daylighting Buildings Nexus November 12, 2009

Transcription

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 reduced internal gains reduced cooling loads improved lighting conditions color rendition color temperature sparkle occupant satisfaction occupant comfort reduced cooling loads connection to nature time orientation health: circadian rhythms 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, Lighting Norbert Lechner Sun, Wind & Light Brown and DeKay Environmental Control Systems Fuller Moore Green Studio Handbook - Kwok and Grondzik Introduction

9 For other Rules of Thumb and Tutorials Go to: 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/m 2 (SI), candela/ft 2 (IP) (1 candela/ft 2 = about 11 candela/m 2 )* Illuminance Units: lux (SI), footcandles (IP) (1 fc = about 11 lux)* *Use a conversion factor of 10 today, for 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 Lighting 1 Ratio Areas Example 3:1 Task to immediate surroundings 5:1 Task to general surroundings 10:1 Task to remote surroundings 20:1 Light source to large adjacent area 1 From Heating, Cooling, Lighting, Lechner 2009 Book to desk top Book to nearby partitions Book to remote wall Window to adjacent wall Rules of Thumb

34 Maximum Recommended Luminance Ratios for Indoor Lighting 1 Ratio Areas Example 3:1 Task to immediate surroundings 5:1 Task to general surroundings 10:1 Task to remote surroundings 20:1 Light source to large adjacent area 1 From Heating, Cooling, Lighting, Lechner 2009 Book to desk top Book to nearby partitions Book to remote wall Window to adjacent wall 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 X How far can daylight penetrate into a space? Rules of Thumb

39 Daylight Penetration 1 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-headheight. If a space does not require the use of a shading device the ratio can increase up to X 2 X 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: 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: 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 B C D E Variant D: Interior/Exterior Shelf 24 exterior shelf plus 36 interior shelf at 10 Variant E: As Designed 3 or 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) 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: Software Overview

61 Radiance Rendering From: 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: Software Overview

66 The Daysim GUI Software Overview

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

68 Evalglare: For Calculating Glare Probability Freeware (Site in German. Look for evalglare v0.9f Windows Version in lower right) Software Overview

69 Daylighting and LEED Daylighting Buildings Nexus November 12, 2009

70 LEED 2009 IEQ Credit % 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 and And the space must meet this ceiling height requirement < VLT X WFR < Daylighting and LEED

73 Option 2 Prescriptive > VLT X WFR < 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