Using US units of measure in Honeybee

I do all my engineering in US IP units. The Rhino files I would like to use will be drawn in feet however it appears that Honeybee does not recognize the units of the Rhino file and thinks the distances are meters. Without converting my drawings from units of feet to meters how can I take the volume Brep from a drawing in ft and convert it to units of meters?


Assuming you are talking about energy simulations, the answer is that the model HAS to be in meters. Energy+ works in meters. Though you can transform the results to IP units with a series of LB components (i.e.LB_uSI2uIP) that you can find in the LB tab, group 5 (Extra).

Also, @kennethwmartin ,
Rhino has really good built-in capabilities for changing units systems. You can build your model in feet and then, once your geometry is finalized, just go to Options > Units and change the units of your model to meters. When you say “yes” to the question that pops up to scale your model, it will automatically change everything that you made to have the same dimensions but in meters.
You can also use the same process in reverse to restore your model to feet (to make it easy to edit again).

Once you have geometry in meters, you can then build your Honeybee model or (if you already have a GH script up that references the geometry, just right-click on the canvass and select “recompute” to have your geometry and Honeybee update to the new units system).

I know this creates an extra 30 seconds each time you want to switch between geometry generation and energy model creation. Personally, I have done this switch enough times to annoy me such that I think I’ll add support for Rhino geometry in feet/inches in the next stable release. For now, you’ll just need to bear with the extra 30 seconds to get the workflow that you want, though, which should be small in comparison to all of the time you save through automation in a visual scripting interface.

Thank you everyone.

As I thought the process will go. I will generate my drawings in feet, convert it to meters in Rhino, run Ladybug and Honeybee and convert the results afterwards.



Hi @chris

Dusting off this old post which is somewhat applicable to my question… is there now an 100% IP unit workflow in Honeybee? I noticed in the LBT training, geometry, temperature, and internal gains all use SI units. For example, “Honeybee_Set EnergyPlus Zone Loads” inputs all appear to require SI units and the default program templates seem to assign SI units as well.

My professional experience has wired me to think in IP units. How do LBT users typically tackle this issue?

Warm Regards,

There’s now full support for creating geometry in IP. The Honeybee components in the Grasshopper definition will just read the units from the Rhino doc so you can keep you model in whatever units system that you want and you won’t have to convert it.

All of the temperature, internal gains, conductivity, etc. still need to be input in SI. The LBT 1.3 Plugin has a nifty component called the LB Unit Converter which will allow you to convert between a wide variety of units. So you can use that to convert your IP values before you plug them into the components.

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Awesome. Thanks for the response Chris!

To confirm understanding… If Rhino model is in IP units, then Honeybee components convert to sq. meters behind the scenes for area normalized energy model inputs e.g., ventilation, infiltration, internal gains, etc.

For example, assume Rhino geometry is modeled in feet, zone area = 100 sf (9.2 sq. m), desired equipment gain input = 1 W/sf. Then all user would need to do is convert 1 W/sf to W/sq. meter and Honeybee would realize that zone area = 9.2 sq. meters and not 100 sq. meters?

Yes, the geometry in the model will be converted to meters upon export to EnergyPlus/OpenStudio. And, yes, you should specify all of the loads in SI units like W/m2.

FYI, the LB Unit Converter component doesn’t currently have support for hybrid SI/IP units like W/ft2. If it ends up being a big pain point, then we can add support for them.

Thanks for the confirmation.
Lighting and equipment gains are commonly referenced in hybrid W/sf so that would benefit user. In the meantime, users can convert. The takeaway here is that geometry will be converted to meters upon export to E+/OS.