Guideline to daylight simulations in DAYSIM · 1 Guideline to daylight simulations in DAYSIM This is a guideline to daylight simulations with MicroShade® in DAYSIM. DAYSIM is a daylighting

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Guideline to daylight simulations in DAYSIM

This is a guideline to daylight simulations with MicroShade® in DAYSIM. DAYSIM is a

daylighting analysis software that calculates the annual daylight availability in buildings

based on the Radiance backway raytracer. DAYSIM has been developed at Harvard

University, the National Research Council Canada and Fraunhofer Institute for Solar

Energy Systems.

Daylight metrics

DAYSIM calculates a series of climate-based

daylight metrics including daylight autonomy

(DA) and useful daylight illuminance (UDI).

Furthermore DAYSIM can calculate the

daylight glare probability (DGP) for glare

assessments. DAYSIM can also calculate

the simpler daylight factor (DF).

MicroShade® model

Together with Fraunhofer Institute for Solar

Energy System a Radiance model of

MicroShade® MS-A has been developed. The

model has been validated against angle

dependent transmittance measurements.

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Usage

The MicroShade® model is a description of

the MicroShade® layer only. In order to

model MicroShade® in a window two

polygons are needed; the outer polygon is

the MicroShade® layer and the inner polygon

is the glazing. The two polygons together

model the MicroShade® window. The surface

normal of the polygon representing

MicroShade® should face the exterior, see

figure.

The material description for MicroShade®

MS-A is enclosed in the following files:

MicroShadeMS-Amat.rad, which should

be stored in the folder

C:\Daysim\materials

Microshade_a.cal, which should be

stored in C:\Daysim\lib

Please contact MicroShade A/S at

[email protected] in order to get the

two files.

The material description for the glazing is the

same as without MicroShade®.

Simulation parameters should minimum be

set to “Scene Complexity 2”, as MicroShade®

can be compared to venetian blinds in

complexity.

Simulations with DAYSIM

DAYSIM offers three kinds of daylight

simulations; Useful Daylight Index (UDI),

Daylight Autonomy (DA) and Daylight Factor

(DF).

The useful daylight illuminance (UDI) and

daylight autonomy (DA) are calculated with

the chosen weather data file, while the

daylight factor (DF) is calculated with a CIE

standard overcast sky as default.

Definition of angles in relation to MicroShade®. N is the

normal vector, α is the solar height, β is the rotation around the normal and γ is the azimuth.

x

The daylight factor is a very simple daylight

assessment method and it is therefore

recommended also to use the daylight autonomy

and/or the useful daylight illuminance as a

supplement to the daylight factor assessment.

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Get started with DAYSIM

This part is for first time users of DAYSIM.

In order to make daylight simulations with MicroShade® in DAYSIM you need to install the following

programs:

DAYSIM – http://www.daysim.com/download.html - to make the daylight simulation

Google SketchUp - http://sketchup.google.com/ - to prepare the 3D model

Su2ds - http://code.google.com/p/su2ds/downloads/list - a plugin for SketchUp to export the

3D model from SketchUp to DAYSIM and to import the results from DAYSIM to SketchUp in

order to visualize the results.

Instead of SketchUp also Ecotect or Rhino can be used to create the model geometry. However, it is

not described in this guideline.

The following tutorials will be good to read:

Tutorial on the Use of Daysim Simulations for Sustainable Design by Dr. Christoph F.

Reinhart, Harvard University, Graduate School of design, Cambridge, MA 02138, USA, 2010

www.daysim.com/pub/Daysim3.0.Tutorial.pdf

Su2ds by Josh Kjenner, Manach Isaac Architects, 2010

http://code.google.com/p/su2ds/downloads/detail?name=su2ds.manual.pdf&can=2&q=

Radiance Tutorial by Axel Jacobs, 2010.

http://www.jaloxa.eu/resources/radiance/documentation/docs/radiance_tutorial.pdf

Preparation of the 3D model in SketchUp

Create your model geometry The 3D model is drawn in SketchUp going

through the following steps:

Create two polygons where the outer layer is

corresponding to the MicroShade® and the

inner layer is corresponding to the glazing.

The surface normal of the MicroShade®

polygon should face the exterior.

The walls should have a thickness.

Draw a ground around your building.

The name of your model should not contain

spaces, as DAYSIM do not allow spaces in

paths and names.

Assign materials Place the

“C:\DAYSIM\materials\DaysimMaterialsForSketchUp”-

zipfolder in “C:\Program Files\Google\Google

SketchUp 8\Materials” and unpack the folder.

Apply the “DaysimMaterialsForSketchUp” materials to

the inner surfaces. Do not assign materials to the

outside surfaces, as DAYSIM/Radiance can only cope

with one material for each surface.

Use the su2ds plugin “Materials → count conflicts” to

make sure that each face has one material only. If any

conflicts are counted use “Material → resolve

conflicts”.

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Set location Use su2ds plugin to set location.

Plugin → su2ds →Set location

Create a sensor point mesh Create a sensor point mesh in a separate layer using

the su2ds plugin.

Plugin → su2ds →Create sensor point mesh

Export you model to DAYSIM Use su2ds plugin to create a header file for

DAYSIM.

Remember that all visible layers will be

exported and hence your mesh layer should

not be visible.

Choose the weather data file to be used in the

simulations.

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Daylight simulations in DAYSIM The 3D model is now ready for daylight simulations. To conduct the daylight analyses in DAYSIM go through

the following steps:

Open project Open your project in DAYSIM by opening the

header file you exported from SketchUp

The file is called “name.hea”.

Weather data If you did not choose a weather data file when

you exported your model. Go to “Site” and

“Load Climate File” and choose your weather

data file.

Weather data files can be downloaded from

http://apps1.eere.energy.gov/buildings/energy

plus/weatherdata_about.cfm in epw format or

Meteonorm data can be used – see the

DAYSIM Tutorial.

Edit materials Go to “Building” and check if your model looks

as the one you exported.

Edit the material file by clicking the bottom

”Edit Material”. The material you chose for the

MicroShade® layer should be replaced with the

MicroShade® MS-A. See the following

example.

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Example The material “GenericSingleGlazing90” is

replaced with MicroShade® MS-A.

The blue text is taken from the file

“MicroShadeMS-Amat.rad”, while the black

text is the modified text.

# void glass GenericSingleGlazing90 # 0 # 0 # 3 0.980123 0.980123 0.980123 void glass microshade_air 0 0 4 1 1 1 1 void plastic microshade_metal 0 0 5 0.1 0.1 0.1 0.017 0.005 void mixfunc GenericSingleGlazing90 4 microshade_air microshade_metal trans microshade_a.cal 0 1 0

A rotation of MicroShade

® is normally done to optimize

the g-value. For vertical facades MicroShade® are

never rotated, while MicroShade® in roof windows can

be rotated depending on the orientation and tilt of roof.

Rotation should be considered for orientations

between northeast (45˚) and northwest (315˚) for all

roof windows. Please contact MicroShade A/S in these

cases to get the right rotation angle.

For a façade window with MicroShade® the structure is

“open” downward and “closed” upward (z-direction),

due to the tilt of the micro-lamellas in MicroShade®. In

case of a horizontal window with MicroShade® it is

important to notice that the structure is “open” towards

west and “closed” towards east (x-direction) as default.

Set Radiance Simulation

Parameters Scene Complexity 2 should be used when

calculating with MicroShade® MS-A.

MicroShade® is comparable to venetian blinds.

Rotation angle β, 0= no rotation, 90=90˚ rotation anticlockwise, 180 (upside down)= 180˚, 270= 270˚ rotation anticlockwise seen from the exterior

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Run Simulations Mark “Calculate daylight coefficients”.

Mark “Combine daylight coefficients with

climate file”.

The easiest is to create a batch-file which can

be run anytime from windows.

Analysis The parameters for daylight analysis for

daylight autonomy (DA) and useful daylight

index (UDI) should be set.

Specify work plane sensors if only some of the

sensors are in the working plane.

Start Daylighting Analysis.

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Results The results can be treated in any data analysis

tool, e.g. excel, MatLab or for visualization the

results can be imported into SketchUp via

su2ds plugin.

The results are found in the folder:

C:\DAYSIM\”project_folder”\”name_of_project”

\res

If you have any questions regarding daylight simulation with MicroShade® MS-A you are welcome to contact

MicroShade A/S.

All information is intended as guidance. MicroShade A/S reserves the right to make amendments and changes

to product specifications. MicroShade A/S cannot be held responsible for the correctness of the information,

nor responsible for the content of the links to third parts provided in this document.

MicroShade A/S

Gregersensvej 1F

2630 Taastrup

Denmark

Tel: +45 7214 4848

[email protected]

www.microshade.dk