Revit to Trace700 energy modeling workflow DISCUSSION

[Wynged1]

hey there

This post will hopefully generate some discussion about what workflows people are using to do load calculations for their buildings which are modeled in Revit.

My goal is to leverage the computer's ability to automate tasks as much as possible while doing our load calculations in Trace700. The .gbxml export process is on it's own way too cumbersome to be worth doing 10+ times for a project.
After trying many different ways of getting information about spaces into Trace this is what I've come up with:
1) add spaces to the model according the thermal zone layout guidelines.
2) Use the automatic space namer to transfer the room names from the architectural model to your spaces. (Check in a schedule that the names make sense)
3) Export the .gbxml file, ignoring the exterior walls and volume aspects
4) Using a basic .xml file editor, delete all of the extra information in the file that does not immediately pertain to spaces, ie anything not in the </Building> or the </Campus> sections
5) Use Trace700 to run the calcs, then export that information back to the .gbxml and into Revit where it is available to be put in a space tag etc.


That is the best process I've come up with so far. It obviously requires a few different tools, but it speeds up getting the basic room area geometry into Trace, and still allows you to export the results back into the Revit model.
Does anyone have a different process they prefer? Can anyone see (or make) a way to add basic exterior wall geometry as well, besides keeping the .gbxml data, which I think we can all agree, is too detailed/cumbersome for repeated quick modeling.

[dennis howell]

I agree, as will most everyone on this blog will, the current method of building a Space model (fill all volumes of the building: occupied, plenum, chases, columns, etc) is too time consuming and cumbersome. One alternative method I endorse, I learned at the ASHRAE conference in Atlanta last year. That method had you go into the architect's file and make ceilings a non-Space-boundary. Consequently, the Spaces in the occupied area would fill up to the next floor above. I asked alot of questions about this method and they explained that in these external analysis programs, such as Trane Trace, it was much easier to setup the specifics of the plenumb/occupied areas. THey then could use the gmxml export/import to get the basics within their analysis program and then repopulate that data into the occupied spaces so that the hvac modelers would have feedback on how much airflow was needed. I asked how accurate it was and they admitted they would get a 10%-25% difference from when they did it the combursome way. But, as they said, it was perfectly fine for those 'early on in the project' estimates of the needed hvac system.

Have you found that you "have to" clean out the extra info (#4) to get the info needed or do you do that just to make the file smaller and easier to work with?

[Wynged1]

--On modeling plenums--
Making ceilings non bounding is definitely an important step to speeding up modeling. Once I accidentally modeled every space in a building as having a roof because I did not account for that.

--With regards to that extra information--
Yes, I do have to, because I basically don't want Revit to export any of the wall and wall opening information. The "extra info" is the information on Analytic surfaces.

When importing a .gbxml file which is straight out of revit into trace the rooms have a lot of walls, some of which are 6" or less, and arrise simply because the exterior wall meets a beam, or some other such small feature. These extra walls make it difficult to easily check and work with the model in trace, and I find it very hard to catch mistakes. In addition, it does not always correctly interpret windows, especially if the architect has made a custom window.

So, knowing that I will have to go through room by room to check the walls anyways, I get rid of them and enter that information manually. I decided to find a way to get as much information as I could out of Revit, and clear out the rest. I would love for there to be a popup menu during the .gbxml export that would give you options for what sort of information you would like to export.

[tys90]

I let Revit populate my roofs, walls and windows. It's pretty easy to catch mistakes once you calculate your loads. I don't usually have problems with windows or walls, roofs seem to cause a lot of issues though. Large skylights or weird tilts on roof areas are the common problems. I don't know if it's faster to import the walls/windows and then check them or just to input them yourself. Depends on the complexity of the building really. We did an oval shaped building and being able to export geometry was huge for us in that project.

I always do a check on the 3D analytic model in Revit before I export. It's easy to spot missing roofs, walls that are too tall, missing windows, etc if you are visually checking it.

I may use your method on the more simple rectangular buildings with standard windows and wall angles. I think it can be just as fast to input them manually versus having to review all the exports.

[neightyeight]

At our office we link the architectural model into an energy model Revit file that we maintain. Within that I do a simple traceover of all the walls, floors, windows, doors, roofs. There are some tricks that I've gotten used to in order to get the gbxml export very clean. I then place all the spaces and name them. From there I can export to gbxml and review for proper surface translation in the dialogue box, after which we import that into HAP. We can also run this gbxml file through Green Building Studios and get a .inp file for eQuest. The benefit here is that when the architect updates the model I can just go back into our simplified model and adjust walls to match. It seems to work well enough so far except that HAP occasionally reads the gbxml file geometry incorrectly.

[rrubert]

So, do you guys feel that the ways you've been doing this Revit-Load calc software export/import saves time?

Once you import the data back into Revit, and it goes back into the space, how has that been helpful to you?

[Wynged1]

I definitely feel that I save time compared to entering all of this information into Trace manually. Even just importing the room labels and Square footage of each space saves time, and I feel reduces the number of errors.

My goal of importing the information back into Revit is to get all of the information at the designers finger tips as easily as possible. Once the information is imported into Revit a Space tag can be made that puts the necessary information about the space right in the model or on a printout for quick easy reference, rather than shifting through the hundreds of pages of room checksums.

The next step I see in making use of these tools is adding a simple duct fitting that can have an airflow associated with it early in the project so that duct airflows will be calculated by Revit. Then a schedule could be used to check the over all design, and compare the needed load with the designed cooling/heating provided.

[Wynged1]

neightyeight

I wonder if you could elaborate a little more on the procedure you use. So you link in the architectural model, and then trace all of the geometry? Do you copy monitor so that changes to the Arch model are reflected in your energy model revit file? do you use any complex features or do you find that the most basic walls floors windows and doors do the trick. This approach interests me because I have had to use a detached architectural model, which means with any update I essentially have to do it again. I would love a way for a linked model to allow changed to propogate through to my energy model. Besides adding and removing spaces I believe that the .gbxml import/export can actually make changes to a Trace file automatically.

I love the interest in the thread. Keep on automating.

Do you have experience with ArchRevit?

[tys90]

The .gbxml can update the TRACE file when you re-import it IF all the room names AND numbers are identical.

[Wynged1]

yea, totally. Fortunately, if I use the architectural room names and use the space re-numberer add-on I can be confident that most of the rooms will be updated, and the others should throw warnings that I can then investigate manually.