EcoDesigner - Thermal Bridge Assessment

[DGSketcher]

I am still sitting on the fence whether to buy an Eco Designer licence due to the uncertainty of successful PHPP output and other aspects impacting my ROI. However, one aspect that does have my attention is the thermal bridge simulation. I am working with an off-site fabrication company and we are keen to maximise material benefits e.g. saving on ineffective insulation and reviewing elements within the structure that could be better assembled.

I am looking for any feedback on:
Whether the bridge assessment works as a real design development tool, not just an oooh that image looks pretty?
How did you assess u-values for elements/skins with bridges e.g. masonry / mortar walls & timber framing through the insulation? In a section detail I assume these need pre-calculating somewhere as EDS won't do a 3D assessment(?). Unfortunately I can't find any software for Mac that does this but on a skin by skin basis I guess I could make a spreadsheet for each building material.
There is no reference to condensation risk assessment, can EDS identify this within the software?

[furtonb]

Whether the bridge assessment works as a real design development tool, not just an oooh that image looks pretty?

Well, if you provide information how the displayed Psi-value is calculated under the hood, it could be used for a design tool, right now it's pretty images with numbers around it to look credible. /s

How did you assess u-values for elements/skins with bridges e.g. masonry / mortar walls & timber framing through the insulation?

Theoretically you could try calculating the U-value based on the composite (1D unbridged losses), then draw the unbridged construction and simulate (e.g. 1m long wall), compare and understand the results, then draw the bridged construction and adjust the U-value for the 2D effect. I'm not sure why you would need a 3D simulation for this, you can further adjust your calculations. EDS is not capable of 3D thermal bridging according to its documentation.

There is no reference to condensation risk assessment, can EDS identify this within the software?

If you have access to the temperature values, you can do an fRsi calculation based on the minimum internal surface temperature (there isn't any display for this in the UI, you can only eyeball this, I think).

For proper moisture simulation this is not the tool you are looking for.

General advice:
On the Mac side of things there isn't many programs to work with (none?).
I suggest you shortcut the struggling and install Bootcamp for energy simulation purposes.

[DGSketcher]

Thank you for the response. You have confirmed my thoughts on all fronts including the Mac availability problem. Unfortunately BigSur is coming to a Mac near me soon and Bootcamp is apparently broken. I was considering whether to invest in EDS just to see if aspects could help me in what I do, but it seems to fall over at each basic design challenge and at the local price I just can't justify it for the amount of use it would get.

To be a bit more positive, I would bite if it could provide:
1. Thermal u-Value calculations for bridged assemblies.
2. Condensation risk analysis
3. Thermal bridging assesment (possibly already working)
4. PHPP fabric data output
and the punchline...
5. it was half the price my UK dealer is asking!

Graphisoft really needs to start driving EDS to raise its appeal and knock it into a working tool. Climate change is coming, GS need to help us address it with a market leading solution!

[furtonb]

well, as of October Ladybug Tools works on macOS too - you can do a lot with them (it simulates in EnergyPlus and Radiance under the hood, both are extremely well documented and widely used), if you have a Rhino license its free to download.

it won't help you with the thermal bridge simulations, those were done based on LBNL's ecosystem, Therm and Window, which are heavily dependant on Windows, and those features are only available in a previous version ("legacy"), which is Windows-only.

so generally you can build energy modelling workflows on macOS as well, but not that detailed.
coupling it with an ARCHICAD model is a pain in the a.. right now.

4. PHPP fabric data output

what do you mean by "PHPP fabric"?

[DGSketcher]

As I understand it PHPP is a German standard for PassivHaus energy performance assessment e.g. low energy domestic buildings. It has become quite popular in the UK as a performance benchmark. From what I am reading on other threads on this forum, the available EDS PHPP export data needs a lot of work to get the correct result. I work with an associate who is a PassivHaus assessor, but at the moment it is easier for him to measure off the drawings rather than me trying to export data about the building fabric and openings etc. I know there are things that can be done with schedules, but that still requires manual transfer of the contents into the external PHPP assessment software.

Thanks for the suggestion, I will go and look up the Ladybug tools...

[furtonb]

I didn't understand "fabric" in this context, so it's a term for the "building envelope"? Sorry, non-native speaker here.

Listing U-values and related fields is also a necessity - ARCHICAD knows about those values, but it's not exposed for the interactive scheduling for some reason (all (?) the fields in the Energy Model/Structures tab). Also, the PHPP and gbXML outputs are very dependant on your model structure, if you differ from the way it expects you to model, the output quickly becomes garbage. I would love to hear about modelling best practices - is it the same model that you use for construction documentation, that is capable of an energy modelling workflow, or rather a separate, "cleaner" one?

[DGSketcher]

Yes, I am referring to the building envelope, there's a little buzz phrase in circulation in the UK of "Fabric First" with the intent of minimising reliance on mechanical services for heating etc. To confuse things further, PHPP works on the Thermal Envelope which typically excludes the external cladding to walls & roofs. The last time I tried extracting the thermal envelope data I ended up with an independent morph and assigned different surfaces to extract the wall areas and orientation. Turns out my associate could pull the data he wanted quicker manually.

I don't have an energy modelling workflow (yet) as I don't have EDS. I can see how there may some logic in modelling the thermal envelope independent of external finishes, but that brings a whole new set of problems when forming openings that could slow down the drawing process. We are being driven into a single model for construction and structural engineering, it would make sense if the same model also worked for energy assessment.

[furtonb]

We are being driven into a single model for construction and structural engineering

Feels similar. It introduces obstacles that I'm not sure how to handle: a good construction model is magnitudes more detailed than a good energy model even at the minimum necessary level of detail.

To handle the construction model, in my experience it's better to switch to an "exploded" model as soon as possible - model the load bearing, finishes, cladding, thermal envelope separately. Putting them on dedicated layers and handling "partial model views" via layer combinations is far more reliable and controllable to me than using only structural display modes. It's possible to assign properties to each layer in a controllable fashion -- not being able to label building material-level data is a big "what, why" experience to me all the time.

This approach introduces the problem of the "too detailed" model: on one hand the said energy model format (I have experience with gbXML) is not really useful anymore (way too many objects to clean up and handle). "Dumbing down" the overall model granularity for the purpose of energy modelling has less benefits than drawbacks on construction documentation - in my opinion.

Generating a simple mass model from the BIM (like you did with the morph) is a good way forward, but not losing metadata is crucial. I was playing with Grasshopper to do this in a semi-automatic way, but the integration is not there yet. Passing building material level physical properties to construction elements (thermal conductivity, etc.) is not really possible at the moment (I would love to see the way, but typing everything manually doesn't count), so calculating an aggregate thermal resistance and U-value is troublesome, the windows' glazing properties are hidden somewhere deep - you have it in the ARCHICAD model, but basically inaccessible and they won't even export to gbXML (I've done numerous tests tracking the exported file line by line). Once you start manually tracking the parameters it's faster to do it directly in your simulation engine.

Well, I went off-topic, but my issues involving thermal bridging calculations are clearly deep rooted..(: