Zone Multipliers with DesignSpecification:OutdoorAir

Hi Unmet Hours community,

This question pertains to EnergyPlus, version 9.6, but likely other versions.

I have noticed that in the DoE Commercial Reference Building Models, that DesignSpecification:OutdoorAir (DSOA) objects which are referenced by zones with multipliers usually use the "Outdoor Air per Zone", while most others use "Outdoor air per Zone Floor Area". This value is also seen to be much larger (ref: Large Hotel guestroom zones with multipliers vs. zones without).

After a deep look into the IOR, I have not found the answer: Does the zone sizing algorithm take zone multipliers into account when calculating outdoor air required by DSOAs? And how does this answer change depending on the method of DSOA input?

Thanks in advance! David

You can easliy check by yourself.

Let's say you have a 10-story building. All floors have the same layout. Each floor has one zone wih 100m2. The total floor area of the building is 100 * 10 = 1000m2.

Multiplier: 10

DesignSpecification:OutdoorAir: Flow/Zone, 0.1m3/s

Then, the total outdoor air flow rate for the zone with multiplier (i.e. the whole building) is 0.1m3/s * Multiplier 10 = 1m3/s

If you set DesignSpecification:OutdoorAir: Flow/Area, 0.001m3/s-m2, the total outdoor air flow rate for the zone with multiplier (i.e. the whole building) is 0.001m3/s-m2 * 100m2/Zone(without multiplier) * Multiplier 10 = 1m3/s

Multiplier is multiplied by DesignSpecification:OutdoorAir you input. Please input the outdoor air flow rate before multiplied in DesignSpecification:OutdoorAir.