HVAC engineer here - this looks great Chris. How are you doing the humidity control out of interest? I've done a few datacentres that won't touch ultrasonic humidifiers because they generate dust in areas with hard water. Less of an issue in resi but perhaps something to consider. Also, are you doing energy recovery for your fresh air intake? If you're ducting both intake and exhaust/spill, is there any opportunity to direct the exhaust/spill air back through the external condenser on the way out to get some extra efficiency?