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Thursday
Oct032013

Daylighting and LEED v4: What this means for design and allied professionals

As of July 2013 the USGBC voting body overwhelmingly approved the new LEED v4 rating system.  In November the new rating system will be launched at the Greenbuild Conference in Philadelphia.  Introducing the system will be Scot Horst, Vice-President of LEED at the USGBC.  At the conference LEED will present updated v4 exam information, reference guides, and educational resources.  More information about the conference and its schedule can be found on the Greenbuild website listed below.  With change there comes dire speculation about how the new rating system will be implemented.  Beginning in November, LEED v4 and LEED 2009 will concurrently accept applications for project certification.  LEED 2009 will accept applications until June 1, 2015, at which time LEED v4 will become the exclusive certification rating system.  Most importantly, however, the major question most design professionals and members of the allied professions are asking themselves is, “What does this mean for me?”  In response the Bozeman Integrated Design Lab is examining the new Daylighting credit structure.  Provided is a basic summary of what has changed in the Daylighting credit for those professionals seeking LEED v4 certified projects.

 

The changes to the daylighting credit are, for the most part, relatively simple.  Most obviously is that the daylighting and view credits previously known as IEQ Credit 8.1: Daylight and Views-Daylight, has become simply EQ Credit: Daylight.  “Views” is now a separate credit.  Within this v4 credit, there are a few structural changes.  First, the illuminance units have been switched from the English unit “footcandles” (fc) to the SI-unit “lux”.  Additionally, the acceptable illuminance value range has been narrowed to 300-3000 lux (approximately 28 fc to 280 fc).  Another important change is the elimination of “Option 2. Prescriptive” as a choice for the verification of daylighting values.  This option has been replaced by a new simulation called “Spatial Daylight Autonomy and Annual Sunlight Exposure.”  Spatial daylight autonomy (sDA) is a standard requiring 50% of occupiable hours during the year be adequately daylit in a project (between 300-3000 lux).  The caveat, however, is controlling Annual Sunlight Exposure (ASE), which is the percentage of square footage in regularly occupied spaces that has direct sunlight during the year.  LEED v4 will require that illuminance values of 1000 lux and above must not exceed 250 occupied hours during the year, and must not exist in more than 10% of the occupiable floor area.  Occupiable hours will be typically considered between 8 a.m. and 6 p.m.  Two points can be gained if the sDA value is achievable in 55% of regularly occupied space, and three points can be gained if the sDA value is achievable in 75% of occupied space.  The hierarchy of points has been carried through to the other two traditional LEED 2009 verification options: “Illuminance Calculations” and “Measurement.” 

 

While these changes are topical, they will certainly require familiarization.  In order to help mitigate confusion, Figure 1.illustrates some of the new terminology in the daylighting credit, and Figure 2.breaks down the new hierarchy of points.  The Integrated Design Lab in Bozeman is committed to aiding design and allied professionals understand the possibilities for designing with daylight regardless of LEED certification.  However, the lab welcomes your questions and advice on the new LEED v4 rating system.  In future e-news sections, the lab will be addressing changes to the views credit in v4 as well as following up on information that emerges from v4’s implementation.

 

TERM

DEFINITION

Spatial Daylight Autonomy

     LEED v4 Abbreviation: sDA 300, 50%

*Standard that requires 50% of occupiable hours during the year be adequately daylit

 

*In the LEED v4 abbreviation “sDA 300, 50%” the “300” is the lux value and the “50%” percentage of occupiable hours.  Therefore sDA 300 lux, 50% of occupiable hours

Annual Sunlight Exposure

     LEED v4 Abbreviation: ASE 1000, 250

*Standard that requires regularly occupied spaces to not have too much direct sunlight, which causes glare and can increase cooling loads

 

*In the LEED v4 abbreviation “ASE 1000, 250” the “1000” is the lux value considered direct sunlight and the “250” is the maximum number of occupiable hours direct sunlight can be present in an area.  Therefore ASE 1000 lux, 250 hours

Figure 1. Terminology of Option 1: Simulation

 

TYPE OF PROJECT

NC, CS, Schools Retail, Data Centers, Warehouses and Distribution Centers, Hospitality

sDA (regularly occupied floor area)

Points Possible

55 %

2

75 %

3

 

 

Calculation: Regularly Occupied, Daylit Floor Area

 

75 %

1

90 %

2

 

 

Measurement: Regularly Occupied, Daylit Floor Area

 

75 %

2

90 %

3

Figure 2. Revised Hierarchy of Points Possible

 

Greenbuild International Conference and Expo 2013

http://www.greenbuildexpo.org/home.aspx