OTTV (Overall Thermal Transfer Value) calculation method with Honeybee?

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?
OTTV-calculation-formula

And what will be the name of the output parameter? Seems like I cannot find any output with the name ‘ottv’ or ‘thermal transfer value’. I am sorry because this is my first time learning HB. Thank you so much!

Hey @kocat ,

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 “Read EP Surface Result” component:

image

Note that, in order to get this data out of the simulation, you need to request surface energy flow like this:

You will see that the resulting data includes both the net conduction through surfaces as well as the solar gain in the case of windows.

3 Likes

Hello @chris,

Amazing clear answer! thank you very much, I’d give it a try as soon as I enter the schematic design phase… 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 much…

Hey @chris,
can you tell me the component names on the pictures that you have posted above? thank you

Hi @kocat. The component is “Honeybee_Generate_EP_Output” Component under honeybee legacy.

1 Like

Hi, @Asisnath, thanks for the reply.
What about the second picture? What are the two components?

@kocat

Hey @chris,
I’m sorry if I’m asking too much, but can you elaborate the component names and workflow from pictures you’ve posted above (and this http://hydrashare.github.io/hydra/viewer?owner=chriswmackey&fork=hydra_2&id=Custom_Radiant_Heating_Cooling_System&slide=0&scale=2.6945686462030816&offset=-1344.5907420378494,-259.84456630719353 example that you gave) with the new components in 1.0.9 HB? I’m having a hard time figuring out which one is the same with the old one… thanks

Hey @kocat ,

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 “HB Read Face Result” component is outputting the thermal transfer data:

Hi @chris and @kocat

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 “actual” 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 “accurate” OTTV calculation using “actual” heat flow from simulation result. Hopefully this answers the original question.

Thanks for the insight, @erydjunaedy . Is the point that you’re making just that regulations don’t 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 don’t 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.

OTTV.gh (451.0 KB)
@kocat ou can try this for basic calculation

Hi, I just created an OTTV script using E+
You can test it and use it for free if you want :slight_smile:

1 Like

Automatic OTTV Reporting Tool

Dear Ladybug users,

We’ve created a Free OTTV Tool to calculate Overall Thermal Transfer Value automatically according to your local code.

1- Upload your IDF or GBXML file via this form: https://forms.gle/VGX51h5vgA8EFyZQ8

2- Download your OTTV Report according to your local code.

3- Improve your OTTV Output by modifying your Inputs via Table.

For more info, Feel free to email me

archimick@gmail.com

Michael

1 Like