Marina -

I have not followed this thread very closely, so I don't know exactly what

you are trying to model in Radiance, but thought I would make one comment,

which may or may not be useful.

You say that the constructions you are trying to model are not in the IGDB,

and then you say that you want to model a laminate.

I just want to make sure that you know you can make a laminate in Optics,

depending on what you are using for the glass and interlayer values.

There is a detailed write-up of how to make laminates in Optics on our

Optics Knowledge Base website:

http://windows.lbl.gov/materials/optics5/CurrentVersion/Optics_Knowledge_Bas

e.htm

Click on the link for "NFRC Procedure for Creating Laminates" and you will

get to another page, and there you can click on "Laminate Procedures" for

the detailed description of the process. Here is a direct link to that PDF:

http://windows.lbl.gov/software/NFRC/Training/LaminateProcedure-Final.pdf

Robin Mitchell

Windows & Daylighting Group

Lawrence Berkeley National Laboratory

[mailto:[email protected]] On Behalf Of marina

aviles olmos

## ···

-----Original Message-----

From: [email protected]

Sent: Monday, May 04, 2009 8:24 AM

To: Radiance general discussion

Subject: Re: [Radiance-general] Description of complex glass systems

(geometry+ material)

Hi Marija, hi Jack

Thanks for your mails.

Some glass types I want to simulate are not in the IGDB, so I will

describe the glasses with the measurements-method,

but I am not really sure I have understood this method properly. There

are those precisions that make radiance so great, but sometimes also

difficult to learn. Could you tell me if this would be then right as

follows?

This is the hole double glazing geometry description:

#window geometry:

double_glazing_a polygon window

0

0

12 0 -0.18 0

0 -0.18 3.34

4.13 -0.18 3.34

4.13 -0.18 0

Then I should measure the interior pane (a laminated float glass with an

interlayer) and separately the exterior pane (a 4 mm float glass). The

hole input data are then:

Red: 700nm -- rf1_r rb1_r rf2_r rb2_r t1_r t2_r

Green: 546nm -- rf1_g rb1_g rf2_g rb2_g t1_g t2_g

Blue: 436 -- rf1_b rb1_b rf2_b rb2_b t1_b t2_b

Then substitute these in the formel you said and this would be the

complete description of the double glazing material:

#window material:

void BRTDfunc double_glazing_a

10

if(Rdot,cr(fr(rf1_r),ft(t1_r),fr(rf2_r)),cr(fr(rb2_r),ft(t2_r),fr(rb1_r)))

if(Rdot,cr(fr(rf1_g),ft(t1_g),fr(rf2_g)),cr(fr(rb2_g),ft(t2_g),fr(rb1_g)))

if(Rdot,cr(fr(rf1_b),ft(t1_b),fr(rf2_b)),cr(fr(rb2_b),ft(t2_b),fr(rb1_b)))

ft(t1_r)*ft(t2_r)

ft(t1_g)*ft(t2_g)

ft(t1_b)*ft(t2_b)

0 0 0

glaze2.cal

0

9

0 0 0

0 0 0

0 0 0

I also try to understand how this calculation system is related to the

physical process. So I have another question.

If I measure with a spectrometer the complete normal reflectance and

transmittance of a double glazing, the interior reflectances are already

in the total measurement. So I understand that, also when in the

physical reality the total reflectance of a double glazing could be the

input data for the simulation, the calculation system of radiance

calculates only right if you specify the interior reflectances and the

calculation take place within the BRTD function. Am I right on that?

Thanks again,

Marina

Hi Marina,

Yes you want to describe the glass geometry, that is one polygon

representing the multiple layers of the physical makeup. The material is

what should represent the behavior. If you take the output from Optics

and run it through optics2rad you will get a single BRTDfunc material

description. One thing to be careful of is that this is dependent on the

correct orientation (normal) of the glass geometry. I believe that the

normal is supposed to be pointing "into" the interior of the building.

One way to check normal orientation in radiance is to assign

(temporaryily) a "glow" material to the glass geometry and view it. The

sides that are "black" are the back sides of the geometry, the sides

that are not black are the positive normal side.

Regards,

-Jack de Valpine

Marija Velickovic wrote:

Hi Marina,

1.glazing geometry

Always define glazing object as a polygon, no matter how many layers

of glass it contains in real world.

Double clear, laminated and other glazings differ only in BRTDfunc

(light transmittance and reflectance distribution function), while

real glazing width is not important here.Note that polygon face should be oriented towards building interior.

##########

2.glazing material

Since BRTD function for double glazing is different then for single

glazing, I don't suggest using of simple glass material.

Procedure we use is next:

*Measure each glass layer transmittance and reflectance data. If you

can measure their r,g,b components it is good, if not use the same

value for all 3 components.

or

*Export from IGDB (using Optics5 I suppose), each layer separately.

And write down transmittances/reflectances you have in BRTD functions.

Note that in Optics5 front side of the glazing is towards outside, so

their front and Radiance "front" are different.So you should have next parameters for double glazing parameters after

measures or after export:

rf1 - interior pane front reflectance (towards the room)

rb1 - interior pane back reflectance (towards the exterior pane)

rf2 - exterior pane front reflectance (towards the interior pane)

rb2 - exterior pane back reflectance (towards the exterior)

t1 - interior pane transmittance

t2- exterior pane transmittance

r,g,b - red, green and blue color components

*For clear glass layers front and back reflectance are always the same

/

void BRTDfunc double_glazing

10

if(Rdot,cr(fr(rf1_r),ft(t1_r),fr(rf2_r)),cr(fr(rb2_r),ft(t2_r),fr(rb1_r)))

if(Rdot,cr(fr(rf1_g),ft(t1_g),fr(rf2_g)),cr(fr(rb2_g),ft(t2_g),fr(rb1_g)))

if(Rdot,cr(fr(rf1_b),ft(t1_b),fr(rf2_b)),cr(fr(rb2_b),ft(t2_b),fr(rb1_b)))

ft(t1_r)*ft(t2_r)

ft(t1_g)*ft(t2_g)

ft(t1_b)*ft(t2_b)

0 0 0

glaze2.cal0

9

0 0 0

0 0 0

0 0 0

/In glazing definition function

if(Rdot,cr(fr(rf1_r),ft(t1_r),fr(rf2_r)),cr(fr(rb2_r),ft(t2_r),fr(rb1_r)))

means:

-if light is incident to the front side of the glazing then

reflectance is cr(fr(rf1_r),ft(t1_r),fr(rf2_r))

-else (light is incident to the back side) reflectance is

cr(fr(rb2_r),ft(t2_r),fr(rb1_r))Functions for double glazing reflectance and transmittance are defined

in *glaze2.cal *script which is provided with Radiance:

-cr(refl1, trans,refl2) - is reflectance distribution for double

glazing as function of light incident angle. refl1 is reflectance of

first glazing pane, refl2 of the second one, and tran1 is

transmittance of the first glazing pane

-ft(t) - transmittance distribution for single glazing as function of

light incident angle. For double glazing total transmittance is

ft(t1)*ft(t2)Hope this helps,

Marija

De Luminae <http://www.deluminaelab.com>------------------------------------------------------------------------

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