Thermal Bridging Accuracy

[Alex C]

I am looking at the viability of the EcoDesigner energy analysis tools for use within our office. I have a small model and I did a thermal bridge calculation of the perimeter slab edge condition and loaded that into overall energy analysis, however I noticed that there is a discrepancy with the Psi values. What's shown int he thermal bridge simulation window is totally different from the value that shows up on the structures page. Is this an error is there something I am missing?

Operating system used: Mac Apple Silicon 12 Monterey

 

[Miha Nahtigal · Accepted solution]

I would guess the bug is in unit conversion or it might be "just" a unit display bug.

1,07 W/mK = 0,62 Btu/Ft hr F

[Miha Nahtigal]

Besides that I don't think your detail has correct soil dimensions (that would also depend on standards used).

According to ISO 10211:2008 you should model soil cutting it at least min(20 meters ; 2,5 B'), where B' = A / 0,5P, on the outer side of the detail and downwards in the soil and at least min(4 meters ; 0,5 B').

[Alex C]

Ahhh that makes sense. I have never actually used any thermal bridging software so thank you for the tip about the standards.

[jrmrt]

@Miha Nahtigal - I didn't realize that you could change the analysis window to run the TB model correctly.  Can you also indicate where the psi value should be analyzed from in the view?

I'm used to working in Flixo.  In that program, when you do a 2D thermal bridge analysis, you have to set the u-value of the two assemblies that are meeting, and then indicate where along the detail the analysis is being taken from.  I'm attaching an example.

If Archicad can actually do this analysis per ISO 10211, it would save us a huge amount of time!

Thank you!

 

[Miha Nahtigal]

In AC you control the dimensions with the size of detail (thermal bridges are simulated from details).

I do not know how AC simulates/calculates thermal bridges. The way you described in your attached image is certainly the right one too.