Adding duct leakage losses on predicted zone heating load

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Hello all

I am developing some EMS overrides to control a dual fuel hybrid HVAC system to switch between gas or electric mode. The decision is taken prior to HVAC manager call, as a result I am unable to predict the duct leakage induced increased zone heating load. Assuming that the ducts are passing through plenums-what are my options to predict duct leakage induced increased heating demand during zone load prediction calls?

-Abir