Typically Flex ductwork is used in residential applications. The metal ductwork might be used if your going to have exposed ductwork in your home.
Some Duct issues could be:
*Holes and or rips in the duct
*Cracks or gaps in the plenum attaching to the unit
*Duct coming off the grill boots
and many more.
Losing air through the duct or its connections can greatly effect the quality at which your system works. Wether its a duct repair or you need to move ductwork location give us a call and we will find a solution that fits your needs.