Sun PCS Air Conditioner w/Heat

[Texas Garage]

I'm ready to install my wall mounted air conditioner, but I'm not sure of how to fabricate an insulated duct capable of handling heat as well. It also requires clearance between the duct in surrounding structure. It will pass through the exterior brick, 2" x 4" wall, and drywall. I need some help! I'll post some pics of the complete garage build when I have more time.

This type of unit is normally found on portable offices and remote switching stations for telecommunications. It's rated at 1.5 tons, 4KW heat strip, 240V Single Phase. I purchased it new for $425, so I couldn't pass it up.