Exponation AIA Provider Number: 70119700

Tile 24 Series: Improving

Daylighting Performance

Prediction - New Metrics and

Tools LSW13-S9

Mudit Saxena 10.23.13

Credit(s) earned on completion of

this course will be reported to AIA

CES for AIA members.

Certificates of Completion for both

AIA members and non-AIA

members are available upon

request.

This course is registered with AIA

CES for continuing professional

education. As such, it does not

include content that may be

deemed or construed to be an

approval or endorsement by the

AIA of any material of construction

or any method or manner of

handling, using, distributing, or

dealing in any material or product. _______________________________________

Questions related to specific materials, methods,

and services will be addressed at the conclusion

of this presentation.

Daylighting is an essential strategy to

get to zero energy commercial

buildings. However, simplistic metrics

that cannot account for climate location,

orientation or advanced technologies

have made it difficult to design

programs that require daylighting,

promote optimized design or

technologies, or ensure occupant

comfort in day lit spaces. A new

method of calculating climate-based

performance metrics approved by the

IES and recent improvements in annual

simulation programs offer new power in

assessing daylighting design, and thus

improve prediction of the energy and

comfort performance of the resulting

buildings.

Course

Description

Learning

Objectives

The new IES approved method of calculating climate-based daylight metrics (Spatial Daylight

Autonomy and Annual sunlight Exposure)

The latest developments in simulation tools to predict daylighting in spaces

Variables that affect daylighting performance

Examples of spaces with variety of daylight ratings per the new metrics

At the end of this course, participants will

learn:

Daylight

Is An Existing Resource In All Buildings!

Daylighting

An important strategy to

Achieve deep energy savings

Achieve deep energy savings

Daily Patterns of Lighting Circuit Current and Daylight

Illuminance in a Space with Aggressive Dimming Controls

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Lighting Circuit Current (A) on/off state

Daylight Illuminance on Window (fc)

Monitored energy savings from Sidelighting Photocontrols Field Study, Heschong Mahone Group, 2005. http://h-m-g.com

California Commercial End-Use Survey (CEUS) 2006 http://capabilities.itron.com/CeusWeb/Default.aspx

Daylighting

An important strategy to

Maintain a healthy and productive indoor environment

Improved school test scores

Improved retail sales

Improved office productivity

Better sleep, physical activity and quality of life

Daylighting And Productivity CEC PIER Studies. http://www.h-m-g.com/Projects/daylighting/projects-PIER.htm

Impact of Workplace Daylight Exposure on Sleep, Physical Activity and Quality of Life. http://www.journalsleep.org/resources/documents/2013AbstractSupplement.pdf

Can we mandate daylit buildings?

How do we optimize benefits ?

while minimizing energy use?

How do we describe good/better/best for daylight designs

How much daylight is needed for comfort?

What provides the productivity benefits?

What is needed for circadian health?

How is visual comfort under daylight conditions different than electric lighting?

Can we evaluate success? and failure?

Good daylight design

Climate Sunny / Cloudy Sun angle

Faade design Window layout Orientation Glazing area VLT

Space Geometry Small private office Large open office

Ceiling Height Window on one or more

facades Interior surface colors

Furniture layout High partition Low partition

Blinds/Shades Usage Type

Depends on many factors

Need for a daylight evaluation Metric

In order to establish requirements for daylit buildings, there needs to be a performance standard

that ensures that occupants needs for visual comfort will be met

that allows designs to be optimized for the most energy efficient means to deliver that comfort

We want metrics that are sensitive indicators of good daylighting

CEC PIER Daylight Metrics Research Project

GOALS

Establish new daylight metrics based on annual simulation output tied to qualitative evaluations

Build a consensus on these metrics for use in standards, codes and programs

TEAM

Lead by Heschong Mahone Group (Now a TRC Company) Supported by an international team of daylighting experts

Guided by IES Daylight Metrics Committee (formed 2006)

What is a Metric?

Measurement Metric Criteria

Individual bits of information

Measurements assembled into a meaningful

scale

The goal of the metric

Example (Body Mass Index): Weight Height

Research Methodology

Assess study sites (61)

Across US (7 cities)

Collect expert (5) and occupant (10) assessments of daylight quality

3 types of spaces considered

Classrooms

Offices

Libraries

Survey Form

Research Methodology

Create detailed annual simulation models

Standardized methodology for all study spaces

Simulation tool that models annual hourly climate of site, evaluates interior daylight illuminance

Simulation Results

Hourly Illuminance Results Per sensor (1ft x 1ft)

Processed into Annual Daylight Autonomy per sensor

More hours with daylight Less hours with

daylight

Research Methodology

Compare quality assessments to simulation metrics

Metrics Investigated: DA, sDA, UDI, DSP, DAMax, cDA ...

To determine best predictors of daylight quality

Use nested linear regression to find metrics which best predict occupant and expert assessments

Results - New Daylight Metrics

Two new climate based daylight metrics identified

Best correlation with occupant and expert assessment

When the occupants and experts told us

Daylight is sufficient

I enjoy being in this room

I can work with electric lights off

These metrics also predicted better values

Adopted by the IES officially in 2012 (LM-83-12)

Spatial Daylight Autonomy (sDA300/50%)

A measure of daylight illuminance sufficiency for a given area

Reports a percentage of floor area that exceeds a specified illuminance level, e.g., 300 lux, for a specified amount of annual hours, e.g., 50 percent of the hours from 8:00 am to 6:00 pm

Preferred threshold: sDA300/50% 75% of analysis area.

Nominally acceptable threshold: sDA300/50% 55% of analysis area.

Annual Sunlight Exposure (ASE1000,250h)

Evaluates the potential source of visual discomfort from direct sunlight.

It is defined as the percent of an analysis area that exceeds a specified direct sunlight illuminance level, e.g., 1000 lux, more than a specified number of hours, e.g., 250 hours per year.

Preferred threshold: ASE1000,250h < 3% of analysis area

Nominally acceptable threshold: ASE1000,250h < 7% of analysis area

Example 1: Daylight Autonomy Plot

More hours with daylight

Less hours with daylight

Total space area = 500 sf

Example 1: sDA300/50% Calculation

340 sf or

68%

sDA300/50% = 68% for this space

Total space area = 500 sf 75%

55%

Preferred

Nominally Acceptable

sDA300/50%

Example 2: sDA300/50% Calculation

Total space area = 1200 sf

More hours with daylight

Less hours with daylight

Example 2: sDA300/50% Calculation

216 sf or

18%

sDA300/50% = 18% for this space

Total space area = 1200 sf 75%

55%

Preferred

Nominally Acceptable

sDA300/50%

What are the new metrics sensitive to?

Climate Sunny / Cloudy Sun angle

Faade design Window layout Orientation Glazing area VLT

Space Geometry Small private office Large open office

Ceiling Height Window on one or more

facades Interior surface colors

Furniture layout High partition Low partition

Blinds/Shades Usage Type

sDA and ASE rating of a space depends on

Orientation

South North North w skylights

Blinds Operation

Blinds open Blinds operated

(using 2% sun penetration trigger, blinds closure by blind group)

Blinds closed

Metrics sensitivity

Rewards spaces with little sun penetration Spaces with well designed overhangs Spaces with North orientation.

Rewards spaces with deep daylight penetration Higher window head height Light redirecting technologies

Rewards spaces with multi-directional daylight Spaces with windows on more than one wall Spaces with windows and skylights

Metrics sensitivity

Penalizes spaces with no blinds/shades (and no overhangs) Spaces that admit too much direct sun

Penalizes deep spaces Spaces with large floor plans where a large portion of the

occupied space is away from a daylight source

Penalizes spaces with low daylight levels Spaces with dark windows Spaces with small windows

Metrics limitations

Quantifying visual discomfort Annual Sunlight Exposure is a proxy for visual discomfort

Not a luminance based metric

A luminance based glare metric likely to provide better correlation to visual discomfort

No luminance based glare metric (yet )

A space-level metric Needs to be calculated for each space in a building

Cannot be very easily translated to the whole building

Simulation tools for daylight metrics

To calculate the new metric, the simulation tool needs some minimal capabilities

Annual hourly simulation - using a weather file

Report results for a sensor grid

Assign blinds/shades to window groups in a space

Model blinds operation based on sun penetration

Minimum sky patch resolution

Minimum solar disc resolution

Simulation tools for daylight metrics

Radiance 3-Phase method (aka. Dynamic Radiance)

Open Studio

DaySim

Autodesk 360 Rendering

IES-VE

And others

Radiance

Radiance is a set of lighting simulation and rendering tools made freely available by LBNL since about 1990

Considered the gold standard for simulation accuracy

Uses ray-tracing (slow, but powerful)

Point calculations are pretty fast

Nice images take longer

Annual simulation even longer

Radiance 3-Phase Method

Also known as Dynamic Radiance Approach

Is a new method to use Radiance for fast, matrix-based annual daylighting calculations

Developed along with the PIER Daylight Metrics Research Project with funding from Southern California Edison

Addresses the needs for

Annual analysis using weather files

Parametric simulation runs capabilities

Realistic blinds and shade modeling assumptions

Radiance v4.1

A suite of programs for the analysis and visualization of lighting and daylighting based on reverse ray-tracing http://radsite.lbl.gov/radiance/

Daylight Metrics: Calculated using Radiance 3-Phase Method

SimBuild 2010 Paper: http://www.ibpsa.us/pub/simbuild2010/papers/SB10-DOC-TS08A-01-Saxena.pdf

Tutorial: http://www.radiance-online.org/learning/tutorials/Tutorial-ThreePhaseMethod.pdf

DaySim

Radiance-based annual daylighting analysis software with an easy to use user-interface

http://daysim.ning.com/

Daylight Metrics:

Outputs sensor grid illuminance, sun penetration hourly results

Capable of outputs range from climate-based daylighting metrics

DAYSIMps developed by Penn State can calculate and output sDA and ASE

Open Studio (NREL)

A collection of software tools to support whole building energy modeling using EnergyPlus and advanced daylight analysis using Radiance https://openstudio.nrel.gov/downloads

Daylight Metrics: Capable of performing an annual climate-based daylight

simulation, using the 3-phase method with BSDFs https://openstudio.nrel.gov/getting-started-developer/getting-

started-radiance/openstudios-radiance-functionality-documentation

Autodesk 360 Rendering Illuminance

A cloud-based rendering service that can generate illuminance images for Revit models to quantify the effects of natural and artificial lighting on rendered surfaces or sensor points http://rendering.360.autodesk.com/index.aspx

Daylight Metrics Capabilities limited to generating rendered scenes and sensor outputs

for now

sDA and ASE calculation from within UI coming soon

http://autodesk.typepad.com/bpa/2013/04/illuminance-learning-about-lightingdaylighting-analysis-1.html

IES-VE

A whole building energy performance modeling software, with a Radiance module (RadianceIES) that allows detailed daylight calculation and rendering http://www.iesve.com/software/download-centre

Daylight Metrics Capabilities limited to generating rendered scenes and sensor outputs

for now

sDA and ASE calculation from within UI coming soon

Which simulation tools will NOT work

DOE 2 based simulation programs eQUEST

Visual DOE

EnergyPRO, etc.

EnergyPlus (Split flux)

These programs use the split flux method which has many approximations of daylighting calculations

Also in-built restrictions on number of sensors (limited to 2 per space) means a sensor grid cannot be developed

Implications for Codes and Standards

Voluntary codes LEED LEED version 4 (launching November 2013) has adopted the

new metric

Up to 3 points for showing that the building is well daylit using the new sDA and ASE metrics 2 points for showing 55% sDA300/50%

3 points for showing 75% sDA300/50%

Alternatively, using old method found in LEED 2009 2 points for showing 75% of reg. occupied space that at 9am and

3pm on the equinox, will be between 300 lux and 3000 lux

Note additional point awarded for using the new metrics!

Implications for Codes and Standards

Energy codes Title-24

Title-24 2013 version does not include a performance path with the new metrics

Current compliance calculation tool is DOE 2 moving to EnergyPlus in the next round (?)

Both tools in current versions cannot calculate the new metrics

However, development of Open Studios Radiance module opens the possibility of EnergyPlus simulation with Radiance

Implications for Codes and Standards

Energy codes Title-24 Current daylighting requirements

Require photocontrols in most spaces with windows and skylights

Requires large open buildings to have skylights

A future version of the code can potentially require a minimally daylit building By referencing a minimum threshold on the new metrics

This would ensure that building is designed to optimize occupant comfort - while providing energy savings

This concludes The American Institute of Architects

Continuing Education Systems Course

Mudit Saxena Associate Director

Tel: (916) 962-7001

MSaxena@trcsolutions.com