Beware of Flex Duct!

BEWARE of Flex Duct: This “Money Saver” could cost you thousands!

This is an example of a terrible install. It cost the homeowner less up front but the system will have multiple problems down the road including increased energy costs.

Why? Because so many contractors use it both because it’s cheaper and faster and easier to install. There are contractors that want to use nothing but flex duct for your entire system.

Not a good idea.

Flex duct was designed to only be used in short lengths

Flex Duct is ideal to use to connect the metal duct system to the register boot, Yet, in order to save a few bucks, many contractors will use flex for nearly the entire duct system.

Problems of using Flex Duct for the entirety of a system:

  • Reduces equipment efficiency and life of the equipment
  • Costing the homeowner thousands of dollars in increased utility bills
  • Earlier than  necessary replacement of equipment
For example:

Each room of your house needs a specified CFM (cubic feet per minute) of air to maintain optimum comfort. This air is naturally delivered to the room by the duct system.

A lot of contractors hold the belief that an 8″ round of flex duct will deliver 300 CFM. A few believe it will deliver 200 CFM. It won’t. Even if installed “properly” an 8″ round of flex will only deliver about 160 CFM if laid out in a straight line and not compressed or squeezed between joists etc. And that is for a run of less than 25 ft. Over 25 ft. would require a 9″ flex to deliver that same 160 CFM.A 10″ flex duct would be required to deliver the same CFM as an 8″ sheet metal duct.

To overcome this, some contractors will install equipment that is larger than necessary to try to overcome this issue.

End result: An oversized system that will cycle on and off more often than needed, reducing the life of the equipment. Improper air delivery to each room, especially rooms farthest from the air handler or blower.

This can actually reduce your SEER from 16 to 12 (or even worse) and cost you more money in energy use. You should not pay for a 16 or 18 SEER system and not have the benefits of the energy savings they were designed for.

A Proper Install

A properly designed sheet metal duct system can save the average home about 24% in energy bills (Source: The Consortium for Energy Efficiency or CEE).

Another advantage of sheet metal ducting is that zinc in the galvanized coating of sheet metal duct actually kills mold and gives great protection against organic growth of all types. Cleaning sheet metal ducts that are properly installed should almost be a non-issue if the sheet metal is sealed properly.

Flex ducting on the other hand can actually be damaged by some duct cleaning equipment.

Some states actually restrict the usage of flex duct. Unfortunately at this time New Mexico is not one of them. So what should you as the consumer do? Insist on a sheet metal duct system that only uses flex to connect the duct branch and diffuser or register. Yes, it will cost a little more initially, but it will quickly pay for itself and last much longer.

Beware the contractor that tells you that flex is as good as sheet metal. If this happens, ask them why some states have banned the use of flex for more than 5 ft. It’s just a matter of time before New Mexico insists on the same requirements.