Working on an in-law suite addition - unconditioned crawlspace placement of HVAC unit.
A few code questions/concerns:
What is the minimum R value insulation that can be used on ducts in crawlspace? Especially the return duct?
Code for R value, duct material and wrap/sealant?
What is the feedback for using building cavities as supply and return duct lines?
We are finding panned bays in this space similar to the image below and planned use of wall cavities in the main living space with NO plans for low returns…

Finally if someone can answer Y/N if the following is required in PA?
Float pan under suspended unit?
Vibration Hangers?
Air duct blast testing after completed install?

I appreciate all help - We are concerned that we need to go into a stop work order tomorrow if corrections are not made. Any assistance is greatly appreciated.

I am not in PA but I can answer most of your questions that are common sense in the HVAC world.

As a installer we always used 2 inch foil or plastic backed insulation on both supply and return air round ducts and one inch glued on fiberglass on rectangular duct. Wood chases are generally allowed on return air only. Wood is not allowed on supply air duct due to the moisture content and mold issues if an A/C unit A-coil is in use.

Yes on a safety pan if A-coil is in use
yes on vibration hangars
Air duct blaster is not normally required but is a good idea if its in your installation contract. Your local Authority having jurisdiction in PA may require it but not where I am located

Here is an example of what not do with wood;-)