Hello, I have a question for my studio. Is it possible to conduct and visualize an OTTV (Overall Thermal Transfer Value) calculation (Watt/m2) with honeybee? So, basically I need these three variables which are shown in the image below. Do I need to calculate each of them separately then do the math manually, or is there a way for me to do it automatically by inserting the parameters with honeybee?
And what will be the name of the output parameter? Seems like I cannot find any output with the name āottvā or āthermal transfer valueā. I am sorry because this is my first time learning HB. Thank you so much!
Yes, you can do this both with Honeybee-legacy and with the new LBT Honeybee plugin. To get a visualization of the overall surface energy flow with a Honeybee model, you want to use the same method that you see in this part of this sample file. However, instead of coloring the surfaces with their temperature, you want to color them with the energy flow that is output here from the āRead EP Surface Resultā component:
Note that, in order to get this data out of the simulation, you need to request surface energy flow like this:
Amazing clear answer! thank you very much, Iād give it a try as soon as I enter the schematic design phaseā¦ by the way, can you also look into my question on this thread? Since I just moved from windows to mac, and I have quite a problem with running 1.0.9 LB & HB, would be much appreciated if you can help me there since I cannot start to work, thank you so muchā¦
Hey @chris,
Iām sorry if Iām asking too much, but can you elaborate the component names and workflow from pictures youāve posted above (and this Hydra Viewer example that you gave) with the new components in 1.0.9 HB? Iām having a hard time figuring out which one is the same with the old oneā¦ thanks
All of the components that we have been pointing you to are for the legacy plugin because this topic has been categorized under honeybee-legacy. If you want to get the thermal transfer data with the new LBT 1.0.9 plugin, you want to check the single_family_energy_model.gh that is included in the .zip file that you downloaded from Food4Rhino. Specifically, the āHB Read Face Resultā component is outputting the thermal transfer data:
The calculation of heat flow is very regulated in the OTTV calculation. This is true for all OTTV regulations from various countries that use the method. As such, we CANNOT used the energy flow calculated by simulation program. It is simply not allowed.
The regulation/standard will have a method to calculate the three heat flow components (wall conducation, glass conduction and glass radiation), and we need to stick to that method. Each country has a slightly different variation of the method (different constants, etc).
If we want to calculate the OTTV of the building we simulate, simply use the envelope summary report table where all the external walls and windows are reported. Combined with the material properties, the OTTV can be calculated with spreadsheet, or R, or python, or Honeybee object for that matter. But definitely it does not involve any other output from EnergyPlus.
Calculating OTTV using āactualā heat flow from simulation result will NOT be acceptable to OTTV regulation in respective countries. It is interesting to compare the number with the OTTV calculated with respective methods, but the difference in numbers is meaningless, there is no physical meaning to it.
I have been saying this to folks in Indonesia. But apparently, there is always somebody who wants a more āaccurateā OTTV calculation using āactualā heat flow from simulation result. Hopefully this answers the original question.
Thanks for the insight, @erydjunaedy . Is the point that youāre making just that regulations donāt allow you to use a TRANSIENT calculation to compute OTTV and the calculation (for the purposes of regulation) must always be STAEADY-STATE?
If so, I can likely recommend some methods in the new Ladybug Tools SDK that can do a steady state calculation of heat flow across constructions. There will be a lot of inputs for this type of calculation since I donāt know what indoor/outdoor temperatures and incident solar should be used (at least with E+, you know that these come from a TMY EPW or DDY). But it sounds like this would be closer to what you need.
