guideline to daylight simulations in daysim · 1 guideline to daylight simulations in daysim this...
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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
www.microshade.dk