HVAC modelling resources

Hi all,

Does anyone know any good resources for HVAC modelling in OpenStudio? Manuals, guides, tutorials etc.

Thanks!
Rafael

What level of expertise are you looking for with these resources? I’m hoping to pout together a tutorial series that gives high-level overview on the types of HVAC systems and how they generally work. But it’s not quite yet ready. In the meantime, I can give you some resources that are a bit beyond the beginner level.

Most of my current knowledge about HVAC systems comes from applying NREL measures to simple one or two zone models, looking at the system structure in the HVAC interface of the OpenStudio Application, and exploring the node-level temperatures after simulation to see what exactly was going on. These days, you can kinda skip the step of applying the measure by just assigning the HVAC to your Honeybee models. You can request the following output from the EnergyPlus simulation to see the node-level temperatures:

Output:Variable, *, System Node Temperature, Hourly

This one can also be pretty helpful:

Output:Variable, *, System Node Standard Density Volume Flow Rate, Hourly

NREL also has some decent tutorials to walk you through the HVAC UI, though you might have to dig through the playlists to find the ones specifically on HVAC:

And, if you really want detailed docs, almost all of the HVAC systems that you can assign with Honeybee are built using this method in the OpenStudio Standards gem. So digging through the docs there can usually help understand some of the deeper assumptions.

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thank you @chris !

I was after a medium level of expertise, mostly to learn how to translate HVAC systems from project into simulation objects with OS, E+. I’m finding my way with system layouts (plant loops, and demand side objects) but debugging simulation errors is turning out to be very hard. What works on a small sample of the model doesn’t necessarily do so for all of it.

I’m finding that simulations fail without giving a properly written error log, so any hints for debugging are super valuable - which I guess is when experience kicks in :slight_smile:

To add to your list of resources for future reference, I also found this youtube channel with some other useful tutorials for HVAC modelling in OS:

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Hey @RafaelA ,

I have no idea what types of edits you’re trying to make to HVAC or how you are making them but, if you are actually getting an IDF and starting to run the simulation, then the .err file that EnergyPlus outputs will usually tell you what’s specifically wrong. Debugging is different if the error is happening before you get to the simulation step.

Also, I would say that there are ~5 levels of HVAC workflows with Honeybee, each one requiring more expertise but allowing a finer level of control over the HVAC

HVAC Workflows with Honeybee/OpenStudio

(ordered by level of difficulty)

  1. Use the HVAC system templates that are included in Honeybee and just customize some of the high-level properties like heat recovery.
  2. Use the Honeybee HVAC templates as a starting point but manually customize some things in the OpenStudio Application before running the simulation with the HB Run OSM component.
  3. Build an entire custom HVAC system using IronBug and assign it to your Honeybee-exported OSM using the workflow described here.
  4. Use the Honeybee HVAC templates as a starting point but edit the HVAC properties using the OpenStudio SDK, either with a GHPython component like you see here or with an OpenStudio Measure.
  5. Write a GHPython component or Measure that assigns an entire HVAC system from the ground up.

Technically, there’s also manually editing the IDF but you don’t really get any more control from this than you would working with the OpenStudio SDK. Plus it’s several times more painful when you don’t have the OpenStudio SDK to manage things like the connections between HVAC equipment.

If you let me know which level you’re at, that will also help me give you advice.

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Thanks for the quick reply @chris - I’m afraid I’m somewhere in the middle there :sweat_smile:

So I’m getting the OSM file from Honeybee, with IdealAirLoads, and laying out the systems in the OpenStudio App. I found it was easier for me to understand HVAC layouts, and it seemed more accesible to replicate some tutorials that were doing something similar to what I need.

The tricky part is that we are working on an existing building with a boiler plant (two boilers on cascade) that feeds a bunch of wall radiators + a few hot water batteries on DOAS. To this plant, we are adding a new low temperature hot water circuit feeding some ceiling radiative panels.

Modelling all these in a blank grasshopper canvas seemed daunting at the beginning (specially as I had never touched Ironbug), and that’s why I went for the OpenStudio GUI. Perhaps I should reconsider.

The model is mostly set, but seems to encounter a problem with humidity on the Heating Sizing period and crashes only giving this info.

So now I’m slowly working my way through by adding the ceiling panels one at a time, from a working model.

I agree that doing this all from scratch within the OpenStudio Application is really tough and might not be possible. Specifically, the radiant metal panel ceiling is tough to set up in the OpenStudio Application from scratch. A couple of weeks ago, I just finished adding in Radiant HVAC templates into the latest development version of the LBT plugin and this includes radiant metal panel ceilings. Using that as a starting point might enable you to do it all in the OpenStudio App. Otherwise, IronBug should have everything that you need to build it from scratch.

The .err for from your simulation seems to have some good reasons for why things failed:


thanks Chris.
In the end I’ve painfully modellled an aproximation in the OpenStudio App using some fluid-to-fluid heat exchangers.

It’s great to know you’re adding Radiant HVAC templates to LBT. Replacing the constructions of a bunch of ceiling surfaces (and their adjacent floors) has been really painful in OS. I think next time I’ll jump into Ironbug, now that I have a decent understanding on how things are supposed to work.

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