[Greenbuilding] Ventilation for Unoccupied Tight Buildings

[conservation architect]

I have learned of some problems with college dormitories of a Passiv Haus building that was left unoccupied with not conditioned or ventilated with ERV over the summer and got some molding problems.  
I am wanting to inquire about what the best practices are for unoccupied tight buildings.  Since they are unoccupied, I would hope you could turn the energy consuming machines off.  The humidity sources within the would be reduced, (breathing, cooking, bathing, et.).  Although you would still have ambient humidity and standing water of toilets.  Perhaps it would be a good practice to drain the toilets.  This issue would be more significant in the Summer of high ambient humidity.  I live in the mixed climate of Virginia.  However, I would be interested in comments as it relates to other climates.  
My question applies to tight buildings that have active dehumidification (ac or dehumidifier) and ERV, or no active dehumidification and HRV.   
Eli 
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