Hello,

I'm using DIVA for GH (version 4 beta) to study the impact of road surface reflectivity on building energy consumption. I created a external surface in Rhino to represent road and plug into Shade component in GH, but encounter an error: "Solution exception:Object reference not set to an instance of an object." I've tried routing it through the brep component but it didn't work. The geometry and gh files are attached.

Also, is it appropriate to represent reflective external surfaces using Shade component? How many bounces does Viper assume in calculating solar radiations into the buildings?

Thanks,

Stella

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Hi Stella,

Technically Viper is not part of DIVA 4 (thermal modeling is now handled by the Archsim components), so I'm shifting this topic over to the "DIVA-Grasshopper (Classic)" category.

I get the same error as you with the road surface.  Must be a bug.  A quick workaround might be modeling the roads as 8 separate breps, as below.  Then things seem to work...

Best,

Jon

As for reflections, yes, you should use the Shade component to represent exterior surfaces.  Be aware, however, that Viper is purely an EnergyPlus tool, so the "ambient bounce" setting you may be familiar with in Radiance doesn't apply.  (For details, see the "Solar Radiation Reflected from Exterior Surfaces" section of the EnergyPlus engineering reference: https://energyplus.net/sites/default/files/pdfs_v8.3.0/EngineeringR...)

-Jon

Thank you so much, Jon. That solved the problem.

Another question, In Viper, the output option "Equivalent carbon emissions: electricity use", is this calculating the carbon emission from cooling, lighting and equipment? It was unclear to me whether electricity use on site includes cooling energy. What's the emission factors used for electricity and natural gas?

Best,

Xin

Jon Sargent said:

Hi Stella,

Technically Viper is not part of DIVA 4 (thermal modeling is now handled by the Archsim components), so I'm shifting this topic over to the "DIVA-Grasshopper (Classic)" category.

I get the same error as you with the road surface.  Must be a bug.  A quick workaround might be modeling the roads as 8 separate breps, as below.  Then things seem to work...

Best,

Jon

Hi Stella,

Yes, cooling is included in the on-site electricity use (it's the cooling load multiplied by the system COP).

The emissions factors are defined in the directory C:\DIVA\Thermal\Shared\EnvironmentalFactors, and are based on Deru and Torcellini 2007.  Viper looks up the factors by US State, or, for locations outside the US, uses the US national average.

Jon

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