l3_lightingii

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ARCH 676 Building SimulationARCH 676 Building Simulation

Instructor: Christoph Reinhart, Ph.D.Instructor: Christoph Reinhart, Ph.D.

March 21: Lighting II (Radiance)March 21: Lighting II (Radiance)

Ecotect DF calculation Radiance DF calculation


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Mar 7 14.30 17.00 Building Simulation & Climatic Considerations

Mar 14 12.30 13.30 Drop in Lab (voluntary, Room 206)

14.30 17.00 Lighting Simulation I (Ecotect)

Mar 21 12.30 13.30 Drop in Lab (voluntary, Room 206)

14.30 17.00 Lighting Simulation II (Radiance)

Apr 04 12.30 13.30 Drop in Lab (voluntary, Room 206)

14.30 17.00 Thermal Simulation I (Ecotect)

Apr 11 14.30 17.00Student Presentations

Course Outline


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Skylight DesignSkylight Design

Scenario: You are helping the Real Canadian Superstore with thedaylighting concept for their new Montreal store. Internal storedimensions are 40m x 40m x 7m. Their standard display shelvesare 2.5 m high, 1m deep, and 10m long. The shelves can beinstalled back to back or against a wall. The target illuminance forthe vertical displays under design sky conditions is 800 lux. Youare allowed to cover up to 10% of the roof with Double Glazed

Aluminum Frame skylights.

Question: How many daylit display shelves can you fit into thestore, leaving a minimum aisle width of 2m?


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difference between horizontal and vertical illuminance

Some values for museum lighting:


CIEDivision 3 TC3-22 Museum

lighting and protection against radiation damage


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difference between horizontal and vertical illuminance

Some values for museum lighting:



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ReferencesRadiance tutorials: /arch676/winter2005/Radiance/Radiance.html

Course Project

Any questions? Did you find the project guidelines?

Software issues

Ecotect a very good tool.

Desktop Radiance Installation (problem with WinImange under XP)

set default location in Ecotect Model>> Model Settings >> Location>> set asdefault

Announcements:

Workshop on Daysim on Mar 23rd in the afternoon at cole Polytechnique.

Misc


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Review Lighting Design IElements needed

Target Values (min. illuminance level, luminance distribution,

Daylight Factor, Daylight Autonomy)

Sky Model (overcast, clear sky, isotropic)

Area of Interest (analysis grid)

Analysis Tool (simulation, spreadsheet)

Material Properties


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Photometric QuantitiesCharacterize how a space is perceived.

LuminousFlux

LuminanceLuminousIntensity

Illuminance

Computer simulation: luminances and illuminances


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Sky Conditions Design Sky Values

Square One web site

Design Sky values are derived from a statistical analysis of outdoorilluminance levels. They represent a horizontal illuminance level that isexceeded 85% of the time between the hours of 9am and 5pm throughoutthe working year. Thus they also represent a worst-case scenario that you

can design to and be sure your building will meet the desired light levels atleast 85% of the time.

Limitation in Ecotect. Climate files are not used by lighting simulation.


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Split Flux Method

SC = direct component

ERC = externally reflected component

IRC = internally reflected component

DF= SC + ERC + IRC

UK Building Research Establishment (BRE)


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Split Flux Method in Ecotect

Square One web site

A geometric version of the Split Flux Method (BRE)

Raytracing: each ray represents an approximately equal solid angle of sky


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Square One web site

A Sky Component (SC) is modified by:

relative sky illuminance of that particular sky patchrelative angle of sky patch makes with a horizontal surface

visible transmittance of each glazing material through which it travels


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Square One web site

An Externally Reflected Component (ERC) is modified by:

luminance of the sky it would have hit reflectance of the material assigned to the external object

relative surface angle and glazing transmittances


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Square One web site

An Internally Reflected Component (IRC) is modified by:

store internal surface reflectance of the object altitude angle of the ray is used to determine which parts of the IRCformula the ray contributes to.


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Limitations of the Ecotect Approach

BRE Daylight Factor method

Ecotect cannot consider multiple reflections.

Therefore, Ecotect underestimates indirect daylight solutions that rely on the

reflection of light off multiple surfaces.


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Physically based backward raytracer no fudge factors.

A wide variety of material properties and sky models.

Longish learning curve.

Magic lies in simulation parameters.

Radiance Lighting II


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Backward vs. forward raytracerBackward vs. forward raytracer

forward raytracer backward raytracer (Radiance)


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Exporting from EcotectExporting from Ecotect

(1) define a camera view

(2) Ecotect lighting simulation

(3) Export to Radiance


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Export to RadianceExport to Radiance

1 Wm-2 = 179 Lux


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Sky RadSky Rad

1 Wm-2 = 179 Lux

# Sky definition.

!gensky 4 1 12.76 -c -a 45.500 -o -73.700 -m -75.000 -B 40.307263

skyfunc glow sky_mat

0 0 4 1 1 1 0

sky_mat source sky

0 0 4 0 0 1 180

skyfunc glow ground_glow

0 0 4 1 .8 .5 0

ground_glow source ground

0 0 4 0 0 -1 180


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Gensky (sky description in Radiance)Gensky (sky description in Radiance)

Under Google type: Radiance gensky

-s Sunny sky without sun. The sky distribution willcorrespond to a standard CIE clear day.

+s Sunny sky with sun. In addition to the sky distributionfunction, a source description of the sun is generated.

-c Cloudy sky. The sky distribution will correspond to astandard CIE overcast day.

-i Intermediate sky without sun. The sky will correspondto a standard CIE intermediate day.

+i Intermediate sky with sun. In addition to the skydistribution, a (somewhat subdued) sun is generated.

-u Uniform cloudy sky. The sky distribution will becompletely uniform


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Material Properties Opaque Surfaces

specular

reflectance

diffuse

reflectance

mixed

reflectance

For a perfectly diffuse

surface (Lambert surface)

holds:

E.g. paper, drywall

EL =


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PlasticPlastic

Only internal properties used for Radiance.

Red/Green/Blue: (246/255)=0.965

SpecularityRadiance= 0.2 *SpecularityEcotect

void plastic PlasterCeiling

0

0

5 0.965 0.965 0.965 0.02 0


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MirrorMirror

If SpecularityEcotect>0.75 => mirror material

Red/Green/Blue: (246/255)=0.965

void mirror PlasterCeiling

0

0

3 0.965 0.965 0.965


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Lighting Analysis Ecotect -Lighting Analysis Ecotect -

Montreal, design sky 7215 lux, full precision


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Ecotect -ab 0


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R Compagnon


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-ab 1Ecotect


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-ab 2Ecotect


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-ab 4Ecotect


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ambientbounces

ambientdivision

ambientsampling

ambientaccuracy

ambientresolution

directthreshold

directsampling

5 1000 20 0.1 300 0 0

resolutionambient

accuracambientxensionsceneimum dimmaxaa and ar: 100m x 0.1 /300~3cm(window moullion)


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-ab 8Ecotect


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Shading Devices/ Indirect IlluminationShading Devices/ Indirect Illumination

Higher raytraing parameters for blinds raytracing detail

ambientbounces

ambientdivision

ambientsampling

ambientaccuracy

ambientresolution

directthreshold

directsampling

7 1500 100 0.1 300 0 0

resolutionambient

accuracyambientxensionsceneimum dimmaxaa and ar: 10m x 0.1 /300~0.3cm

(blind slat)


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Mirror MaterialMirror Material

Virtual light sources


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GlassGlass

Red: (227/255)*TN(0.88)

void glass ClearFloat_6mm_MF

0

0

3 0.661 0.742 0.742

Li it f R diLi it f R di


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Limits of RadianceLimits of Radiance

Radiance will not necessarily find the sun.


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indirect 0

detail medium

variability medium

quality medium

interior view exterior view

VisualizationVisualization


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indirect 1

detail medium

variability medium

quality medium

interior view exterior view

VisualizationVisualization


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indirect 2

detail medium

variability heigh

quality medium

default exposure adjusted

Light ExposureLight Exposure


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indirect 2

detail medium

variability medium

quality medium

Ecotect materials Radiance materials

MaterialsMaterials


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(1) Submit your project ideas by Thursday.

Assignment for next week


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QuestionsQuestions

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