I've recently been investigating the different options for setting infiltration rates in Energy Plus and am hoping for some confirmation and/or correction of how I understand the different approaches available. The question is not so much about the inputs or equations for each model but rather how they can be practically used in Energy Plus.
ZoneInfiltration:DesignFlowRate
This is the model I use most often with a defined air-change rate and primarily for commercial buildings. In this case the air change rate is constant (ignoring the modifier schedule) and the infiltration rate varies with zone volume only. Is generally fine for code compliance - which is the bulk of the work I do.
ZoneInfiltration:FlowCoefficient
This model would appear to be more appropriate for residential applications but can't figure out how it can be practically applied to a multi-zone model. From blower-door tests I can get all the necessary parameters, however, this model calculates a volume flow rate that appears to be independent of any zone parameters (e.g. surface area or volume). If I create an infiltration object for each zone separately and use the experimental parameters then the same whole-building infiltration rate would be applied to each zone - which would be incorrect. (I ran a simulation today using this approach and the mass flow rate was similar but not the same for each zone - I can't explain the differences)
Given the level of uncertainty around infiltration rates it may be sensible to stick to the first option, however, it does seem valuable to be able to take into account site exposure, building height etc. which are available with the second option.
Any thoughts greatly appreciated.
