Using Honeybee THERM to Calculate Psi-Values

Hello Ed. I attended your workshop at RPI last November and it was great! Thank you for sharing your knowledge and tools! I’m trying to learn Ladybug and Honeybee as well as Grasshopper in general this summer.
I have a question. I built a parapet detail and placed it in your file (Psi_Calc_Example_190917 [Internalized].gh). The Python Script (Heat Loss) component shows a warning saying: “1. Pipe: Vicarious argument deduced from defaults at position 2. Add value for ‘caps’: ‘0’.”
I have no idea how to solve it with my level of skills. Is it serious? Does it affect actual calculations? Everything else seems to be working well.
I also ran a simulation on your paraper geometry stored in file and it has the same issue. It may be happening because of newer HB version, but I can’t be sure.
I hope it is not stupid question. Let me know if you have any ideas.
Thank you in forward.

Hi @sholoa

Good to hear from you! Glad to hear you are jumping into the GH/HB/LB world. And yes, happy to advise:

I am sorry about that error, thats entirely my fault - I was sloppy in my code there and left out an input that I should have included. To help visualize, it’s attempting to make a ‘pipe’ (extrude) along a line segment in the scene and the ‘pipe’ command actually requires two input parameters, but I only gave it one. So it’s saying it’ll be using a default for the missing argument.

But no: it’s not serious at all and won’t affect the calculations - its just a warning about the visualization of the geometry in the scene and telling you (me) that I wasn’t as explicit as I should have been in the code. Luckily it’s smart enough to handle that mistake though. So don’t worry about it - it’s just related to the way those ‘thick lines’ show up in the viewport to help you see whats going on there. I’ll definitely fix it up though and will post a revised definition when I have a chance to take a closer look.

For sure let me know if you run into any other questions of hiccups though! Happy to take a look.

Thank you for answering!

Thanks for sharing Ed!

Hello Ed!
I was wondering if you might have an updated link for the two files that you linked to in July 2018:

  • Part 1: THERM for Beginners
  • Part 2: THERM for Intermediate Users
    It seems the files are no longer there but I expect they’d be able to help out a few folks. Is it more that they have been replaced with newer files or have they been renamed.

Thank you so much, it is incredibly appreciated!

Woops! Sorry @JDev

I had updated some website stuff and relocated those files. You can find them now at:

Note that is a bit updated from the original ones I posted back in 2018 and bit more comprehensive.

Note also that if you are interested, we’ll have a brand new video-course/series on the detailed use of THERM for Psi-Value calculation coming out soon through NAPHN. Keep your eyes out for that coming in the next few months.

best of luck with it.

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Hi @edpmay , I’d like to ask how to implement the Psi Values into HB model using LBT?

Hi @fn

Unfortunately EnergyPlus does not have a built in method for handling thermal bridges that I know of. There are some methods I have seen used in the past as ‘work arounds’ but I think the best method for accounting for those construction thermal bridges at this point is to build in their effects into the U-Values of the building.

This method is not great, and is a lot more complicated than just having the ability to input Psi-Values and lengths, but we don’t have any option in E+ currently, so its probably the best we can do. (In WUFI-Passive or PHPP, by contrast, we can input Psi-Values quite easily).

For a detailed explanation, I would recommend checking out the ASHRAE Handbook of Fundamentals, Chaper 27 (27.6: 2016) for an explanation of how they recommend incorporating things like slab-edge thermal bridges into your U-Factors.

You can also see some other examples of a different way ASHRAE recommends doing this type of thing in their 90.1 Appendix G, Users Manual, ‘Building Envelope’ section. They recommend (require?) that certain thermal bridges are included in this manner, primarily the ones related to the floor-slabs and concrete beams.

Again, neither of those processes is not ideal, and are overly complicated and lead to needlessly complicated models. But its the way(s) they recommend right now, so far as I know.

Until the E+ software is capable of handling Psi-Values, this would be the only option I’m afraid.

All the best,