Using OtherEquipment to Approximate Thermal Bridges?

Hi all,

I wonder if anyone has any experience using the OtherEquipment object to approximate the impact of linear construction thermal bridges on Zone energy consumption?

As has been discussed elsewhere, there is no direct E+ input for Psi-Values related to linear construction thermal bridges. Incorporating these construction thermal bridges into the clear-field U-Values (as @SaeranVasanthakumar illustrates here) can work and is the workaround recommended by the ASHRAE 90.1 Appendix G User Manual, but is not ideal for my use-case.

In the new Phius Revive program rules, they indicate that:

To account for linear thermal bridges in EnergyPlus, an object could be created for psi-value-based linear thermal bridging. This can be accounted for by using an EnergyManagementSystem:Program to calculate a conduction heat transfer based on the temperature delta, and applying that gain or loss to an OtherEquiptment object.

which sounds like an interesting approach that may work much better?

Adding an OtherEquipment object is fairly straightforward, but I don’t think I understand the part about the EnergyManagementSystem:Program ? I get that the OtherEquipment wants watts as the input unit, and Psi-Values are always in W/mk, so you’d need to account for the dT somehow, but I don’t follow how the EMS:Program object would do that? Does anyone have any experience using these components in this manner?

I’m very curious and would like to try it out.



May it is not a good method. As showed Class other equipment is similar to Class electric equipment .

Hi @minggangyin ,

thanks for the input! I’m curious why you think it is not a good method though? Are you thinking it would not work for some technical reason, or are you suggesting you think it is cumbersome and confusing to do it this way?


Hey @edpmay ,

I can understand the general concept of what they are suggesting and I could imagine pretty clearly how you could use the Other equipment object with an EMS program to account for additional heat gain of a thermal bridge. I didn’t realize that OtherEquipment could be used to model a heat loss but, if E+ allows you to specify a negative value for the Watts of the equipment, then it should work.

In general, EMS programs are just conditional statements that set certain variables with expressions. Once you get the basic concept, they’re pretty straightforward to apply. So, for your case here, you could make a conditional statement based on EMS temperature sensors that you place in the zone and Outdoors. This gives you a Delta T that you can use to adjust the OtherEquipment power.

For best integration with Honeybee, you could do this either with additional IDF strings or by postprocessing the OSM with the OpenStudio SDK. I’m not very picky between the two but I have a slight preference for the latter and you can see some cases where I have post processed the EMS controls that we use in Honeybee to control the AirflowNetwork here:

Hope that helps

@edpmay - Have you tried Thermal Bridging & Derating (or TBD), an OpenStudio Measure? It’s been used recently by other LBT users. It works off of an OpenStudio model (.osm), but will work with an .idf (although additional steps are required). It offers what you’ve expressed (“approximate the impact of linear construction thermal bridges on Zone energy consumption”), but it is limited to what @MichaelDonn identifies as the smearing approach (simply because that’s what most energy codes/standards require). We hope to extend TBD towards automating the generation of surface “slivers” (an alternative approach, described more clearly in ASHRAE 90.1 2022 - look up Table 11.5.1, under “5. Building Envelope”). This alternative is preferable with contrasting transient effects (between e.g. mass wall and linear thermal bridge), or for localized surface temperature assessments (e.g. condensation). But other than that, TBD should handle what you’re after. Do let us know if you’ve come across any issues with TBD; we’re keen on improving it (when we have time).

EDIT: Re-reading, noticed I wasn’t really answering your question. We had initially considered OtherEquipment + EMS (instead of the surface “sliver” approach). The former fell out of favour as it would be of little help to assess localized surface temperatures and condensation, for instance.