def calc_qv_delta_p_ref(n_delta_p_ref, vol_building):
    """
    Calculate airflow at reference pressure according to 6.3.2 in [2]

    :param n_delta_p_ref: air changes at reference pressure [1/h]
    :param vol_building: building_volume [m3]

    :returns: qv_delta_p_ref : air volume flow rate at reference pressure (m3/h)
    """

    # Eq. (9) in [2]
    return n_delta_p_ref * vol_building