Daylighting Analysis and Tools

Daylighting Analysis and Tools
Ramana Koti
Sustainable Building Analyst
Elements Division of BNIM Architects

Which of the follow ing definitions for daylighting is the m ost relevant to you?

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

40

20

0
Architectural Building Energy Cost Lighting Energy Load
Consumption Savings Management

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

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

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

Project:

Four stories

120,000 square feet

$17.5 million - $145 / SF

LEED Certification:
Platinum – 53 points achieved

Lewis and Clark State Office Building, Jefferson City, Missouri

Lewis & Clark - Building Occupant Survey

100%
89%
90%
80%
80%

70%

60%

50% 43%
40%

30%

20%

10%

0%
Overall Lighting in the building - Amount of Daylight - Perceive discomfort caused by
Comfortable or Neutral Comfortable or Neutral glare


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 Service Center, Lenexa, KS

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

Daylight Factor Approach

Single Point in Time
Approach (Simulated)

Single Point in Time
Approach (Measured)

LEED and Daylighting

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

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

50% Clerestory to the South
annual light exposure
x y z DF [%] DA [%] DAcon [%] DAmax [%] UDI<100 [%] UDI100-2000 [%] UDI>2000 [%] DSP [%]
[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

Analysis through HDR imaging (Luminance and Illuminance)

Daylighting Analysis and Tools

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