Transparent shades

Hi all and @chris @AbrahamYezioro

Does anybody know how I can create completely transparent facade shades in LBT 1.4.0?

To be sure that they are transparent, I compared the energy result of building with transparent shades with a no-shade scenario. I think they must be the same. But, the cooling and heating values differ from each other. I tried several radiance modifiers for the shades but still had different results than no-shade.

I would be grateful if you can help me with this.

Hi @berrakbalci,

Sorry I’ve been slow at replying - as you guessed work’s been busy!

I hope you don’t mind me sharing part of the pdf you sent me

I haven’t had a chance to test it myself, but I agree the results looks strange - to my eye a fully transparent shade isn’t fully transparent. This might be due to E+ or due to how HB is producing a “transparent” shade. I tried looking through the code for how this transparency schedule is being assigned to idf and comparing that to details on Big Ladder but couldn’t quite get to the bottom of it.

I found a similar question on Unmet hours

Sorry I can’t be more help - I’d recommend you open up OpenStudio and have a look at the simulation set up in there to see how the shade transparency is working. Otherwise I think this is a question @chris would probably need to input on.

Thank you so much Charlie for your reply. I think the HB Translucent Modifier component to define shade transparency is not working. Could you please have a look at it @chris ?

The component works very well for me. Do you have a specific question about it?

Hi Chris,

Thank you for your reply. How can I create completely transparent facade shades? I created the workflow below but the energy result is not the same as the no-shade scenario result.

The 100% transparent shade and no shade results seem pretty close to me: (52.2 KB)

Of course, the way that E+ models 100% transparent shades is different than the way that it models no shades but the two are close enough to be within the error any energy modeling software.

Thank you so much, Chris. Do you also get the same result for 80-degree angle shades? I think the cooling/heating/lighting result should not be angle dependant with transparent shades. But the angle affects especially cooling result considerably.

Hi @berrakbalci ,

What you are asking here is probably more for the unmethours forum than this one. Or you could probably find your answer by digging through the EnergyPlus Input/Output Reference.

If I had to guess what is going on, it looks like this section of the Input/Output reference is probably what’s causing the cooling load to go down with 100% transmittance shades:

Shading devices are assumed to be opaque to long-wave radiation no matter what the solar transmittance value is.

So, even if all of the shortwave solar energy is getting through the shade, the longwave sky heat exchange is still blocked, which is what you would expect for most transparent materials like glass. I imagine this would lower your cooling load by a bit compared to a case with no Shades at all.

Hope that helps.

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Thank you so much, Chris for your reply. Does it still apply to a shade surface with no material properties?