Adding heat sources to outdoor comfort model

New to this kind of modelling and looking for tips on approach! I’m helping with a detailed utci mapping for an outdoor space.

We want to include heat generated from several air conditioning units attached to small buildings, and maybe also some chimneys.

Looked around and haven’t really seen people exactly do this, closest is for indoor applications. Might even be interested in suggestions for how you might approach a more custom / high-effort solution, if there’s nothing turnkey.

Would be cool to be able to override MRT calculations for a surface and basically just say that it emits heat, but this does not seem to exist. Would avoid needing to do CFD for our entire model.

I’ve looked at:

  • Ladybug / Honeybee - materials for MRT assume passive radiation via sun
  • Ironbug - tough to tell without knowledge of components, most seem to assume indoor. But maybe I will ping @MingboPeng, cheers
  • Butterfly - there is a heat transfer recipe with demos for indoors, but maybe can use outdoors if we set up a wind sim?
  • Dragonfly - can set UWG building heat emmittance 0-1 but too coarse for us
  • Eddy 3d - can’t see documentation without installing and I’m currently on mac (tho open to windows solutions!)


You can create a thermal zone with certain internal setpoints that will lead to cold/hot surfaces of the thermal zone, that will be captured in the MRT calculations and hence affect the UTCI results. This should be ok for capturing the radiant effect of radiant cooling/heating systems, but it will not capture convection (will not change air temperature).

I’m also keen on learning whether it is possible to add the heating or cooling components in the outdoor analysis.

Hey @joshkpeterson

It’s clear you’ve done a bunch of research, and it seems a lot of folks are interested and puzzled by your question too.

I think @dmitry dmitry’s suggestion and conclusion is spot on. As of now, none of the components in Ladybug Tools can efficiently calculate the outdoor air temperature via convection (Butterfly can do some of this, but the complexity of outdoor thermal environments is still too much for Butterfly’s current capabilities).

However, if you’re looking to add surfaces with specific temperatures, I believe there’s a very straightforward way to do that, which will keep the model from getting overly complex.

If you keep your software updated, you’ll find a new component named “HB Other Side Temperature” in HB Energy version 1.5 and onwards. This component lets you alter surface temperature based on the input temperature (in Celsius) or the convection coefficient (in W/m2-K). You can use this to influence the mean radiant temperature around any surface. Also, in the same HB Energy version 1.5, the UTCI Comfort Map component is quite flexible.

I have created a simple surface and grid lattice to capture the computational results, as depicted in the image below.

Next, you can use the workflow illustrated in the diagram below as a control group. Please note that the HB Face defining the temperature needs to be added to the HB Rooms, even if it is ultimately an open HB Room, as this does not affect the expected results.

Finally, when previewing the results, you will clearly notice significant changes in the UTCI calculation based on different surface temperatures. In my case, the surface temperature is quite extreme at 300°C.
This is the UTCI calculated under default conditions.

This is the UTCI calculated under the conditions where the face temperature has been changed.

Clearly, modifying the surface temperature alone has an effect. But whether or not this outcome is meaningful, that’s something you’ll have to figure out on your own. if you get some results, we’d love it if you could share with us!



@ZhengrongTao @dmitry Thanks for your help, this worked brilliantly.