I’m a new user of TALLY and am currently looking into curtain wall systems.
Is there a way to change the curtain wall system type here? On my end, the drop down bar doesn’t show me any other options as opposed to the written options on the right (Kawneer 1620,1630,2250,7500). Is this because all of them have identical properties?
Adding a screenshot below. If anyone has an idea please shed some light!
Welcome to the Tally world! Material definitions are locked in in Tally. You can’t change or add anything into the system, outside of custom IGUs and custom concrete mixes. If you’re working in the US, Tally’s default curtain wall options are “good enough,” ie in most cases, they’ll work and are better than no information. To make them “better,” you have to start playing with how Revit reports data and how Tally works with this reported data. For curtain wall mullions, Revit reports a length of the mullions, and uses a cross section to determine the volume. This cross section is based off of the mullion family, which can be great, but often we don’t model the family exactly as it is in real life. if the family is pretty simply (just exterior lines) you could end up with a solid block of aluminum if you choose aluminum for your definition. The folks who developed Tally developed a faster work around with the mullion definitions, which are based off of Kawneer profiles. These are roughly correct for the different kawneer systems included in the Tally definitions. How you work with that gets into the trade offs of LCA. For our projects (mostly in the US) we typically use Kawneer curtain wall systems, so I suggest that the folks doing the LCA choose a similar profile to the one in our design. If there isn’t a an exact profile, I suggest going with a similar, larger profile, just to assume a conservative impact. If there’s more information on something like a custom mullion that’s very different, we’ll do a cross section of the mullion and then try to back it into tally, either through a manual entry for volume in the mullion definition (using manual takeoffs), or we’ll try to apply another material definition using the same manual take off volumes.
Hope that helps.
Justin, thank you for your thorough explanation - this helped me understand the process better. Happy Holidays!
@jaein, another option here is to define the mullions and curtain panels themselves.
The “curtain wall system” options (or any option that says “system” in tally) include preset assumptions about components. This is great for acoustic ceilings (usually modeled as a flat pane, but tally assumes metal framework too), or early design / shoebox modeling. The curtain wall system assumes a set amount of material over the surface area of the whole curtain wall.
Since curtain walls have varying mullion and panel dimensions. I typically recommend defining the mullions as mullions by length and picking the closest profile, and modeling the panels to reflect the panel type (spandrel, glazing, etc.). This does omit some sealant and other assumptions that are captured in the system definition, but at least I can state that omission and know that my quantities are accurate, which is important because accurate quantity takeoffs are an important basis of an LCA.
After getting takeoffs, you could look for EPD data on a specific product. This is challenging because the categories for this data (glazing, openings, CW), are currently evolving, so I’d almost recommend looking for low-impact CW components as a separate, second step that happens after the LCA.
This is accurate based on my understanding and testing; would love to know if I’m misunderstanding anything or if others have thoughts.
Hi Jesse, thank you for sharing your detailed suggestions. I will try them out. I’m finding it interesting how there are multiple ways to model and log different materials!