Ductwork comes in all shapes and sizes, galvanized metal ductwork allows the most air capacity to be delivered to your rooms per foot because it has the least friction resistance.
Flex ductwork is easy to install but it's a treacherous road should your contractor have taken it. There are many pitfalls were simply unbeknown to many HVAC contractors on the implications of their work. Here is a short list of pitfalls Green ID's energy auditors typically find in an attic.
1. Improper size
"I'm supposed to put a 18" duct but I only have a 14", I'll just make it fit!" I feel that's a common thought HVAC contractors have when doing these horrible installs. Not only does undersized ductwork chock off your airflow, robbing your home of its full air capacity, but it makes your unit work harder and drives up your energy bills.
2. Too many wye splits.
Every wye split adds 10 feet in length to your duct runs, so after the 4th wye split don't be surprised that the airflow is weak when your heating and cooling system needs to add an extra 40 feet of run to its load.
3. Leaks.
Arizona home performance standards require that every flex connection be sealed with mastic for a 50 year plus lifespan. If your ductwork is not properly sealed, every time the HVAC unit kicks on you are throwing money out the window by heating and cooling the attic. In homes older than 20 years duct tape may have been used as a "sealer." Duct tape may be a universal fixer of all things except when it comes to your ductwork. It doesn't take long for duct tape in the attic to become loose and its adhesive deteriorated.
4. Evap cooler (swamp cooler).
If your home ever had a swamp cooler, the swamp cooler ductwork may still be connected to the main ductwork of the house.
