Daylighting Analysis and Tools

Ramana Koti

Sustainable Building Analyst

Elements Division of BNIM Architects

Which of the following definitions for daylighting is the most relevant to you?

0

20

40

Architectural Building Energy

Consumption

Cost Lighting Energy

Savings

Load

Management

Designers (Lighting, Architects, Interior) Engineers & Energy Consultants

Source: Results of a 2006 survey on the role of daylighting in

sustainable design by Lawrence Berkeley National Laboratory and

National Research Council Canada – 120 Respondents

Role of Daylighting in Sustainable Design

Character of architecture in a region

emerges from the way designers

work with building form and the

fenestration to deal with light and

climate control. It advocates the use of

controlled daylight that, for example,

causes the exhibition volume in an art

gallery to change with time, season

and humidity, as opposed to the

exclusive use of artificial light.

Critical Regionalism

Climate Chart for Design Teams

Climate Consultant

Melaver Birmingham, Alabama

Melaver Birmingham, Alabama

A footcandle is a measure of light intensity. A footcandle is defined as the

amount of light received by 1 square foot of a surface that is 1 foot from a

point source of light equivalent to one candle of a certain type. Depending

on the sky conditions daylight can produce anywhere from 2,000 to

10,000 footcandles

Illuminance is the luminous flux per unit area on an intercepting surface at

any given point, expressed in footcandles. Commonly described as the

amount of light on a surface.

Luminance is the luminous intensity of a surface in a given direction per

unit of projected area, expressed in footcandles. Commonly described as

the amount of light leaving a surface.

Visual acuity is a measure of the ability to distinguish fine details.

Glare is the sensation produced by luminance within the visual field that is

sufficiently greater than the luminance to which the eyes have adapted to

cause annoyance, discomfort or visibility difficulty.

Common Terms

Climate

Climate consultant

Weathermaker

Weather Manager

Daylighting

Radiance

DAYSIM

IES <VE>

Ecotect

eQUEST

Energy Performance

Ecotect

IES <VE>

eQUEST

Energy 10

Glazing

LBNL Window

LBNL Optics

Modeling Tools

Project:

Four stories

120,000 square feet

$17.5 million - $145 / SF

LEED Certification:

Platinum – 53 points achieved

Team:

Architect: BNIM Architects

Owner: Missouri State Office of Administration

Tenant: Missouri Department of Natural Resources

Contractor: Professional Contractors + Engineers (PCE)

Lighting: Clanton Associates

Daylighting: Ensar Group

Lewis and Clark State Office Building, Jefferson City, Missouri

Lewis and Clark State Office Building, Jefferson City, Missouri

Lewis and Clark State Office Building, Jefferson City, Missouri

Lewis and Clark State Office Building, Jefferson City, Missouri

Lewis and Clark State Office Building, Jefferson City, Missouri

Lewis and Clark State Office Building, Jefferson City, Missouri

Lewis and Clark State Office Building, Jefferson City, Missouri

Lewis and Clark State Office Building, Jefferson City, Missouri

Lewis & Clark - Building Occupant Survey

80%

89%

43%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Overall Lighting in the building -

Comfortable or Neutral

Amount of Daylight -

Comfortable or Neutral

Perceive discomfort caused by

glare

Lewis and Clark State Office Building, Jefferson City, Missouri

Dynamic Sun/Sky conditions changing constantly

User behaviour

Differing methods/sky models used by different

tools

Raytracing tools like Radiance have a steep

learning curve

Lack of reliable metrics

Challenges to modeling Daylighting

KCPL Headquarters, Kansas City, Missouri

KCPL Headquarters, Kansas City, Missouri

KCPL Service Center, Lenexa, KS

KCPL Service Center, Lenexa, KS

Before – After, June 21 Noon Sunny, John Deere Service Shop, Greensburg, KS

LEED and Daylighting

Daylight Factor Approach

Single Point in Time

Approach (Simulated)

Single Point in Time

Approach (Measured)

Daylight Factor: The ratio of the internal illuminance at a

point in a building to the unshaded, external horizontal

illuminance under a CIE overcast sky. (CIE is the

Commission Internationale de l’Eclairage, which has

developed a series of mathematical models of ideal

luminous distributions under different sky conditions.)

Daylight Autonomy: For a sensor point, it is the

percentage of occupied times of the year when the

minimum illuminance requirement at the sensor is met by

daylight alone.

Useful Daylight Illuminances: Aims to determine when

daylight levels are useful for the occupant, in terms of being

neither too dark nor too bright (between 100 lux and 2000

lux).

Continuous Daylight Autonomy: Similar to Daylight

Autonomy except partial credit is attributed to time steps

when daylight illuminance lies below the minimum

illuminance level.

Daylight Saturation Percentage: The daylight saturation

percentage for 40 foot-candles (DSP40 ) to 400 foot-

candles (DSP400) is the percent of hours and the percent

of classroom floor area between 8 a.m. and 3 p.m., Monday

through Friday, from Aug. 15 through June 15 when daylight

provides at least 40 foot-candles or more of illumination at a

work plane located 30 inches (76 centimeters) above the

floor. Achieving

a DSP of 400 is an indicator of over-lighting and glare, and

is therefore penalized.Climate Based Next Generation Metrics

x y z DF [%] DA [%] DAcon [%] DAmax [%] UDI<100 [%] UDI100-2000 [%] UDI>2000 [%] DSP [%] annual light exposure

[luxh]

1974.000 -291.960 36.000 4.2 90 95 13 3 41 56 22 10264053

2304.000 -291.960 36.000 3.2 87 93 0 3 53 44 66 7681253

2535.960 -289.800 36.000 3.4 89 94 5 3 49 48 45 8577834

x y z DF [%] DA [%] DAcon [%] DAmax [%] UDI<100 [%] UDI100-2000 [%] UDI>2000 [%] DSP [%] annual light exposure

[luxh]

1974.000 -291.960 36.000 2.8 85 92 0 4 57 39 84 6791708

2304.000 -291.960 36.000 1.2 63 82 0 8 92 0 83 2877087

2535.960 -289.800 36.000 1.6 70 86 0 5 91 4 90 3539914

Land Institute Research Facility, Salina Kansas

100% Clerestory to the South

50% Clerestory to the South

Analysis through HDR imaging (Luminance and Illuminance)

Questions?