What is Flexible Insulated Duct?

A flexible, tubular passage for supply, return and exhaust air used in heating, ventilation and air conditioning systems. It can replace galvanized pipe and helps reduce heating and cooling loss as well as condensation build-up.

How are the types of Flexible Insulated Duct classified?

Flexible insulated duct can be classified into 2 categories: Air Duct or Air Connector.

What is an Air Duct?

An air duct is a category of flexible duct that has been tested and classified by the surface burning characteristics in accordance with the UL 181 standard. An Air Duct can be identified by the rectangular shape label that the manufacturer applies to the duct.

Why are there two types of jacket – Black and Silver?

The jackets are vapor barriers. The vapor barrier is the outer membrane of the flexible insulated duct. For a stronger more durable vapor barrier your choice should be silver jacket as it is heavy duty, tear resistant and has a reinforced scrim.

How do you install Flexible Insulated Duct?

See attached installation instruction sheet per the Air Diffusion Council. Website www.flexibleduct.org


  • Avoid installations where exposure to direct sunlight can occur i.e. turbine vents, skylights etc. Prolonged exposure to sunlight will cause degradation of the vapor barrier
  • Repair torn or damaged vapor barrier jacket with duct tape listed and labeled to UL 181 standard
  • Install duct fully extended. Do not install in compressed state or use excess lengths
  • Approved joining materials include: ½” wide aluminum, galvanized or stainless steel clamps, nylon ties for low pressure systems (2” W.G.) or tapes listed and labeled in accordance with UL181B standard and marked 181B-FX

How do you connect pieces of duct together?

All connections, joints and splices shall be made in accordance with the manufacturer’s installation instructions. General guidelines include:

  • Peel back jacket and insulation from core. Butt two cores together on a standard 4” metal sleeve
  • Tape cores together with at least 2 wraps of duct tape. Secure with 2 clamps.
  • Pull jacket and insulation back over cores. Tape jackets together with at least 2 wraps of duct tape.

What is an R-Factor?

R-Factor is the thermal resistance. A higher R Value represents a better insulating material. The minimum value is R4.2. The R Value requirements for air distribution ducts can vary depending on the energy code being enforced.

What are the available R-Factors?

Dundas Jafine offers Flexible Insulated Duct with R Value ratings of 4.2, 6.0 and 8.0.

Where would I find the R-Factor?

Dundas Jafine prints the R-Factor on the end flaps of the carton packaging, on the vapor barrier (jacket) of the duct as well as on the Air Duct identifying UL label that is applied to the duct.

What is UL 181?

UL 181 is the standard that has been used for over 30 years for evaluating safety. The testing procedures were developed by taking a wide range of safety-related installation situations into consideration. These include structural integrity and flammability characteristics. Four (4) fore tests are used to investigate the flammability and burning characteristics of flexible ducts.

What is Class 1?

Class 1 represents a material which shall have a flame spread rating of not over 25 without evidence of continued progressive combustion and a smoke-developed rating of not over 50.

What does “Listed” mean?

A published list by a recognized approving agency acceptable to the authority having jurisdiction stating the flexible duct, tape and mastic has been tested to and complies with the applicable standards of UL 181 / UL181B and maintains periodic inspection to assure production of the listed products are in accordance with the listing. Factory made air ducts must be tested and listed in accordance with (UL) Underwriters Laboratories Standard for factory-made air ducts UL 181.

What is an Air Connector?

An Air Connector is a series of flexible ducts that do not meet the requirements of an Air Duct as per the UL 181 standard. An Air Connector is not tested for flame penetration, puncture and or impact and has limitations on use, length and location. Air Connectors are required by UL to be identified by a round shape listing label that is applied by the manufacturer.

Why is the installation length restricted to 14’ for an Air Connector?

The installation of air connector products, in lengths greater then 14’, are not recommended by Underwriters Laboratories. UL restricts labeling of an air connector to a maximum of 14’.

What appliances are not recommended for Flexible Insulated Duct?

Air ducts and air connectors should not be used to vent any appliance for cooking, heating or clothes dryer venting unless approved and recommended by the appliance manufacturer.

Who is UL?

UL (Underwriters Laboratories) is an independent, not for profit product safety testing and certification organization. It was founded in 1894.

What is Class 0?

Class 0 refers to a material that shall have surface burning characteristics of zero (flame spread / smoke development).

What is the R-Value of Aluminum Duct?

Uninsulated duct does not have an R-Value rating.

What is permeability?

The time rate of water vapor transmission through the vapor barrier.

What is leakage?

The time rate of air volume loss, expressed in cubic feet per minute (CFM)

Does it matter which way the draft blocker is installed?

The draft blocker has been designed to work in one direction only. Please ensure you read the directions on the packaging carefully and follow the direction of the arrows indicated on the product.

Where can I source an oval duct for use with the Recessed Dryer Box?

An oval duct is not required for this product. Our standard round duct will squeeze into the oval shape of the dimension required.

Can the Recessed Dryer Box be installed upside down?

If used in this position, the draft blocker will not function properly. We suggest removing the draft blocker if using in this type of installation.

How can I extend the semi-rigid aluminum duct to its maximum length?

The best way to extend the duct is to have a person pull from each end of the duct while slightly twisting counter clockwise. Ensure you are holding onto the duct itself and not any collars that may be attached.

Can the aluminum elbow or aluminum pipe be used for in-wall applications?

It is recommended to check with your local building code for gauge and aluminum thickness requirements, before installing any aluminum products inside your wall.

Can additional pieces of the aluminum pipe be added together to form a longer duct?

Additional pieces can be added to form a longer length. However, if being used for dryer venting purposes, the ducts should be taped together as screws can cause a lint trap.