Solar and visual absorptance for EP simulation

Hello guys,

I run a simulation with rammed earth, so I define my own materials with EPOpaqueMat component and when I change the solar absorptance and visual absorptance coefficients because I’d like to see the impact of reflectance I don’t see any change in the operative Temperature. Is that right or I have to change also the thermal absorptance? I am looking forward to hearing from you.

Thank you in advance!


Hi Yorgos,

I’m a beginner at this but have run some simulations with just changes in the visual absorption of materials and have gotten slightly different results for heating, cooling, and lighting loads. Mainly I have found that when I change my visual absorption to a lower value my heating load goes down by a bit, cooling goes up, and lighting goes up by a bit. These were just one time tweaks so I don’t know if they would represent any sort of trend.

I’ve also encountered a weird problem where changing the visual absorption with the EPOpaqueMat component hasn’t actually changed the value once it gets into the IDF file, instead it goes to a default value of 0.7. and I have had to change those values manually in the IDF to get the right results.

I was looking through the forum to see if anyone else was encountering the same problem of the visual absorption for opaque materials resetting to default (0.7) but have yet to find any similar reports. Could it be because I am using version 0.065? I’ve tried on two different computers and have had the same problem reoccur.

in.idf (89.2 KB)
shoebox massing template.3dm (99.0 KB)
shoebox massing template (804.6 KB)

@kimtse1 ,

I’m sorry that this is too large of a file for me to figure out where the material reflectance is differing between the Grasshopper definition and the IDF. Can you send me as small of a Grasshopper definition as is needed to recreate the error? Devang makes note of this in the forum guidelines that he wrote and it really helps us figure out what the issues are.

Hi Chris,

Sorry for uploading such a large file.
I have been able to replicate the error with this simplified script: (595.2 KB)

When I enter Visible Absorptance values for these materials they get over-written to the default 0.7 in the IDF file:

in.idf (138.6 KB)

Thank you so much for taking a look!