Here is an example of how they justify it – notice they say airflow is 3,543 CFM and then show the HVI-916 airflow as 2,730 CFM. They then qualify that by saying (for CA Title 24 New Construction). But that is not the truth. HVI-916 is required by CA for ALL whole house fans sold in the state. So each of the QC fans offered for sale misrepresent their airflow. Sad but true.