HVAC and indoor climate

grasshopper honeybee-legacy
1

Hi all,

I’m using LB/HB as a first choice in design analysis of daylight and energy, and really appreciate how far the development has progressed. I find that recent additions of more hvac system components, among other functionalities, is significantly widening the relevance of the toolset.

Meanwhile having used the tools for some time now and have gone through the forum, in my opinion a few critical system controls is still missing - unless I’m missing some understanding.

In order to really make the hourly energy analysis valuable in early massing studies etc. the consideration of indoor climate can be more detailed. The HVAC capacities, max. airrate and min. inlet temperature should be within comfortable ranges and hardsized by user input to reduce internal draft problems. If not considered I find that the analysis could possibly demonstrate good energy behavior and reasonable operative temperature but in reality could cause a bad indoor environment - and when “rectified” at a later stage the energy consumption will increase.

I would like to know how it is possible in HB to set-up a HVAC system with these ventilation controls and a “unlimited” convective/radiant heating system, and how to deal with the issues mentioned below. The inputs parameters exists in the components, but I can’t seem to get the right system behaviour.

In the attached file I have gone through 4 scenaries, each with seperate issues in setting up the system (As no template appearantly supports the combined setup the heating system is simulated using an inlet temperature of 99 degrees).

Thanks a lot!

Jon

hvac_control.gh (916 KB)

2

I since learned that using the OpenStudio system, “Packaged VAV w/ Reheat”, is seems to be possible to successfully hardsize the airrate and cooling supply air temperature to control the resulting draftrate.

However it would be very usefull, for engineering purposes, to have more knowledge available on the OS systems including what is hardcoded in the HB components in relation to BigLadder’s EnergyPlus documentation, and on adding systems using additionalStrings.

I have very limited experience with E+ and really hope you can make sense of this post?

Also I ask the developers if you know of any validation work, BESTTEST etc., regarding the whole workflow of writing the input file from HB, to running E+ and reading the results in GH?

Thanks again

3

Hi John,

Sorry for the late reply. I will ask OpenStudio development team about this. They may/should have documentation somewhere about all the default values in systems. To my knowledge (and it should be confirmed by Chris) we don’t overwrite the default values that are coming from the template.

For now you can use OpenStudio app to open the osm files and access all the input values.

Back to validation, Honeybee uses EnergyPlus, and OpenStudio which also uses EnergyPlus for running the simulations. We have done several checks to make sure the generated idf file matches the inputs from Grasshopper but haven’t tried BESTTEST or similar test procedures.

Mostapha