A vent cover assembly is disclosed, such as for a floating or fixed floor. Example vent cover assemblies may include a support plate configured to be secured over a duct, and a flush mount vent cover. The support plate may define a plurality of first airflow apertures configured to permit airflow from the duct through the support plate. The vent cover may define a second plurality of airflow apertures that are positioned in the vent cover such that the second plurality of airflow apertures are aligned with the first airflow apertures when the vent cover is in a first installed position overlying the support plate. The vent cover may obstruct the first airflow apertures when the vent cover is in a second installed position overlying the support plate.