EP construction - definition and calculation


Any answer or reference to information is highly appreciated

I am running an analytical validation of a workflow I created in EnergyPlus-Honeybee, by comparing it to a simulation in IDA ICE.
When defining the wall construction in IDA ICE (or any construction) it automatically assigns the Resistivity to account for radiation and convection on the inner and outer surfaces of the wall. The Resistivity to account for radiation and convection is calculated as an average over the year and is used as a default value for U-value calculations in many nordic countries.

Do you need to add the radiation and convection Resistivity as a layer in the EP construction or does EP take the radiation and convection on the surfaces into account when running the simulation?

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See this for the material definition. The inputs with the “_” at the beginning are required (thickness, conductivity and density). The R value is then calculated by E+. Also the simulation process accounts for radiation and convection, though, this is a one node calculation per surface.


I’m not sure Honeybee-EnergyPlus is the right tool to validate your IDA ICE workflow. Caveat: I have never used or heard of IDA ICE before, this is based on your description of the U-value calculation. My thinking is, if IDA ICE is using an average radiation and convection for it’s heat balance, and E+ is calculating it per timestep, then discrepancies will arise due to any thermal mass absorbing and releasing heat per timestep at different rates in E+. Does IDA ICE take a specific heat capacity input, or is it just the U-value?

@AbrahamYezioro, what are your thoughts on this?


From their website seems to be that IDA ICE is also a hourly based (or timestep) simulation software.
Saying so it could be interesting to compare results. I don’t know what you need to define the materials/constructions there and i believe the ball is now on @tobiaspedersentsp to explain better and/or report back his findings.

Makes sense. And I should add if there is very low specific heat capacity of materials in the building being tested, then it shouldn’t make a difference.

Thanks for the responses and thank you @AbrahamYezioro, this was what I was looking for:

@SaeranVasanthakumar it is the other way around - I am using IDA ICE to validate my E+_Honeybee workflow. And hence I need to make sure that I input all parameteres in the same way.

More information about capabilities of IDA ICE compared to E+ and others (dated 2005):
bs05_0231_238.pdf (104.9 KB)

Best Tobias

Hi @tobiaspedersentsp,
if I have not misunderstood the request, EnergyPlus offers a wide selection of different methods to determine the values ​​of “hc, ext” described in the Engineering Reference page 91 (SimpleCombined, TARP, MoWiTT, DOE-2, AdaptiveConvectionAlgorithm). By default it should be DOE-2, which is a combination of the detailed MoWiTT and BLAST convection model, different from glass to wall, but it is also possible to associate different algorithms with different surfaces. The same to determine the values ​​of “hc, int” described on page 105 of the same guide. By default it should be TARP which is related to the convective heat transfer coefficient with respect to the surface orientation and to the difference between the surface air temperature and the area temperature. There are more than 34 different algorithms for calculating the internal convective coefficient.
I am very interested to compare results. You can public it?

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@MassimilianoBusnelli - thank you very much for the elaboration ! I will post the results here, when I have them

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I need to define the “heat transfer coefficient” for all of the components, is there any way that I can define it in honeybee?