How to adjust 100% OA for sizing systems

One of our energy modelers reviewed the idf files generated by Honeybee/OS and noticed a few issues. I’ve copied her comments into several posts, 1 per item.

#6 100% OA for sizing

Typically 100% Outdoor Air in Cooling & in heating is the default option for the percentage of outside air for sizing purposes. The designed HVAC system is a recirculated system and not a 100% outside air system. Is there a way to change the sizing option from ‘yes’ to ‘no’ for recirculating systems?

in.idf (613.1 KB)
SchoolsFirstOffice.osm (724.7 KB)

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@LelandCurtis ,

I agree that this is a weird setting for all-air systems. The reason it is that way is because this is how OpenStudio assigns it when you use the built-in methods to create the Appendix G systems. However, any engineer in their right mind would assume that these systems are recirculating in the design condition so I have gone ahead and just set this as the default:

If you sync your OpenStudio component with the gtihub, you will see that you will now get the system sizing object not using 100% outdoor air whenever the system is all-air.

I can’t imagine that this change will affect the energy use results much but it still seems like good practice and, at the least, it makes the sizing of the chillers and boilers of these systems more accurate.

Thanks Chris,

I am building a firm-wide tool and hope to keep our components to the latest stable releases rather than GitHub (makes it easier to track/deploy across multiple offices). Any idea when the next release will be?

@LelandCurtis ,

I apologize for the late response. Given the craziness of my schedule over the last few months, I didn’t know when I could get time to do the release. I can now say with certainty that it will be at the end of this month (October).

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