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constructions.xml documentation/corrections

constructions.xml documentation/corrections

Okay, I'm not sure if this is the right place to ask this but here goes:

My company is evaluating Revit's Systems Analysis tool in Revit 2022. Currently, we are using a third party program to run load calcs for buildings and are thinking about replacing it with Revit's Systems Analysis tool. We built a simple test project in Revit that consists of a one room building. In our energy settings we have the material thermal properties set to schematic types. Our intention is to run the systems analysis and then export a gbxml to our third party program to see how close the load calcs are. However, when we export the gbxml to our third party program we are noticing that some of the constructions, specifically the exterior wall constructions, are not coming in correctly. For example, when we use the schematic type 8 in lightweight concrete block, the gbxml imports a wall with TWO layers of 8 inch light weight concrete. (picture is from the third party program after the gbxml import)

mkrausMQRRX_0-1627655647378.png

 

We went into our program files and opened a document called constructions.xml. It is our understanding that this file is where all the wall constructions are defined. It appears that even in the constructions.xml document there are two layers of 8 inch concrete. 

mkrausMQRRX_1-1627655647406.png

 

 

Then we tried to change our project to a different schematic type to see if we could get the gbxml import to work with a different wall. This time we tried  4 in heavy weight concrete with air space as our schematic type for exterior walls. And again our gbxml import did not work. This time it didn't even use 4 inch walls!

mkrausMQRRX_2-1627655647277.png

 

Again, we looked in the constructions.xml file. This time we saw that there were two layers listed as "mat-AM14"

mkrausMQRRX_3-1627655647342.png

 

After digging through the constructions.xml file we confirmed that mat-AM14 was the id for a 6 inch heavy weight concrete wall - not the 4 inch heavy weight that it was supposed to be.

mkrausMQRRX_4-1627655647392.png

 

These are just the ones we found. This of course seems to be having an affect on u-values, building weight, etc. which is affecting our load calcs. We can always manually correct our third party program to have the correct wall constructions. However, as we understand it, to run a systems analysis Revit exports a gbxml to open studio which then exports data to energy plus (where the load calcs are actually performed) then energy plus sends a detailed report back to Revit that the user can see. And given that the walls also seem to be incorrectly constructed in the constructions.xml document we think that the issues we are experiencing are with Revit itself and not our third party program. Thus, our real concern is that if the gbxml is not properly exporting to our third party program then it may not be correctly exporting to open studio and would be giving us an inaccurate loads report. So, we are wondering if it would be possible for this to be corrected or for some more specific documentation/explanation to be published on this (unless it exists already). Specifically, we would like to know:

1. Why are the walls seemingly incorrectly modeled in the constructions.xml file? Was this done intentionally for some other reason?

2. If this was not done intentionally, when and will the constructions.xml file be updated?

3. Will it be possible in the future to easily modify the constructins.xml file without coding (so we can quickly make custom schematic types if we wish to)?

 

Overall I think that the Revit systems analysis has the potential to save our company a huge amount of time. But right now we need to convince our engineers that we can rely on it to produce accurate load calcs, so any information/help will be much appreciated! 

 

2 Comments
Ian_Molloy
Community Manager

Hi @mkrausMQRRX 

 

Would it be possible for you to share your model with me (ian.molloy@autodesk.com) so we can take a look?

 

Regards

Ian

 

paul_rouff
Explorer

I've experienced the same issue when exporting the gbxml file. I end up having to override the construction materials inside of the 3rd party load calc software.  I really like where the system analysis tools is headed, but until I understand how and what is exported/imported from REVIT, or find an easy way to manipulate it, I'm hesitant to fully adopted the process. 

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