A vent cap assembly for use with a drain waste vent pipe under roof-mounted photovoltaic (PV) panels is provided. Such vent cap assemblies are adapted to fit over a cut-down roof vent pipe to maintain airflow from the vent pipe and prevent debris from entering the pipe. Vent cap assemblies can include a cap portion and a mounting bracket, the cap portion having an inner cavity accessed through an opening in an underside of the cap and the mounting bracket having one or more inwardly extending elongate members for engaging an outer surface of the vent pipe to secure the cap assembly to the pipe. The mounting bracket can include multiple inwardly extending tabs distributed about the bracket that laterally deflect and securely engage the vent pipe when the cap assembly is pressed onto the pipe.