ADC GreenBook 6th Edition - JPL

Air Duct Council Greenbook 6th Edition JP Lamborn co.

Sixth Edition

Flexible Duct Performance and Installation Standards

AIR DUCT COUNCIL 1300 Sumner Ave. Cleveland, OH 44115 - 2851

Telephone: (216) 241 - 7333 Fax: (216)241 - 0105 Email: info@flexibleduct.org Web: www.flexibleduct.org

Mission Statement of The Air Duct Council

The purpose for which the Air Duct Council is formed as stated in its Certification of Incorpora- tion, are in general to promote and further the interests of manufacturers of air distribution equipment, more specifically flexible air ducts and related products, and the interests of the general public in the areas of safety, quality, efficiency energy conservation, and to this end develop programs approved and supported by the membership that legally promote and further these interests such as: • To encourage, assist and support the maintenance and development of credible and effective industry standards for installation, use and performance of flexible duct products, to promote the use of those standards by various code bodies, government agencies, architects, engineers, heating and air conditioning contractors, etc. so that the best interests of the public may be served. • To collect and disseminate lawful information of value to members of the Council, the general public and others and to act as a clearing house for all such information, as well as providing a means by which the interests of the individual members of the Council can be protected, defended and supported more vigorously and effectively in legal association with others who share those interests .

ADC Bylaws, Article 1, Section 2 (2013 )

Table of Contents

Introduction

Scope

Common Terms

Design 3.1 Installation Restrictions and Use Limitations 3.2 Benefits 3.3 Common System Layouts 3.4 Sizing 3.5 Thermal Resistance 3.6 Thermal Performance Certification 3.7 UV Light 3.8 Fire Safety 3.9 Fire - Resistance Rated Assemblies 3.10 Bathroom Exhaust and Vents 3.11 Deeply Buried Duct

5 5 5 6 7 9 9

10 10 10 11 11 12 12 12 13 14 15 17 17 21 21 22 23 23 24 24 25 25 25 25 26 26 27 29 29 29 30 30

Inspection & Installation

4.1 Installation Key Points 4.2 Air Duct or Air Connector 4.3 Bends 4.4 Routing, Sagging & Snaking 4.5 Supporting Flexible Ducts 4.6 Compression 4.7 Installation Instructions

4.8 Fittings, Fasteners & Sealing 4.9 Typical Installation Locations 4.10 Contact with Fixtures 4.11 Leakage 4.12 Condensation 4.13 Field Alterations 4.14 Personal Protective Equipment (PPE)

Care

5.1 Cleaning 5.2 Replacement 5.3 Repair

ADC Test Standards

6.1 Performance Values 6.2 Performance Requirements 6.3 Material Characteristics

6.4 Methods of Test 6.5 Product Marking 6.6 Product Certification 6.7 Product Packaging

Reference Standards

APPENDIX APPENDIX A Reference Pressure Drop Chart APPENDIX B UL181 Tests APPENDIX C Typical Duct Types APPENDIX D Duct Accessories APPENDIX E Flexile Duct Installation Checklist

32 32 33 34 35 37

INTRODUCTION

Introduction

The Air Duct Council Flexible Duct Performance & Installation Standards (Greenbook) was first introduced to the HVAC industry in 1980. This standard has been the installation and performance guideline for the flexible duct industry for many years. This edition seeks to make it easier to locate topics of interest for installers, inspectors, designers and homeowners. Each chapter addresses a specific interest, but it was written in a way that is easy for anyone to follow and understand regardless of background or expertise in HVAC.

Disclaimers

As with all the previous editions the information contained within this document is a recommendation of best practices based on the available knowledge of the members of the ADC. Authorities considering adoption and/or reference of this standard should review all federal, state, local and other applicable regulations. The Air Duct Council assumes no responsibility nor accepts any liability for the application or techniques contained in the standard.

CHAPTER SUMMARY

Chapter 1 Scope

Establishes the breadth of this document.

Chapter 2 Common Terms

Establishes some commonality of terms. Some terms in this document may be unfamiliar or uncommon to the readers. To help reduce confusion some of the more important terms have been defined in this section.

Chapter 3 Design

The Design information in this manual is for informational purposes, and to answer many typical design questions. The best sources for designing a duct system can be found in ACCA Manual D for Residential Buildings and ACCA Manual Q for Commercial Buildings.

Chapter 4 Inspection & Installation

Emphasis for inspectors and installers. Examples of the proper way to install flexible ducting. A checklist found in Appendix D is a handy tool for anyone interested in the proper installation of flexible ducting.

Chapter 5 Care

Common questions regarding duct replacement and/or duct cleaning.

Chapter 6 Performance

Performance standards that the ADC has determined are important to ensure that customers receive the best possible product.

Chapter 7 Reference Standards

The list of standards referenced in this document.

CHAPTER 1: SCOPE

This standard sets forth instructions for properly installing flexible ducts in air distribution systems. This standard includes requirements for both insulated and non - insulated flexible ducts. No attempt is made in this standard to designate a specific material or construction.

Flexible ducts shall be categorized as either Air Ducts or Air Connectors in accordance with testing and listing requirements in Appendix B.

Special considerations not covered by this standard may be required when installing flexible ducts are used in:

• Industrial applications; i.e. particulate conveying, corrosive atmospheres, excessive temperatures, etc.

• Outdoor applications; i.e. continuous exposure to direct sunlight, weather elements etc.

Ducts shall be listed in conformance to NFPA Standard 90A & 90B.

• They shall be tested in accordance with Underwriters Laboratories Standard for Factory - Made Air Ducts and Air Connectors, UL 181.

• Such ducts shall be installed in accordance with the conditions of their listing.

CHAPTER 2: COMMON TERMS

Air Barrier The membrane of the flexible duct which actually contains the air volume.

Air Connector A category of flexible duct not meeting the requirements of an Air Duct per UL 181 Standard (not tested for flame penetration, puncture and impact) and having limitations on use, length and location as defined by NFPA 90A and 90B. Air Connectors are identified by a “ round shape ” listing label of the listing agency. Air Duct A category of flexible duct tested and classified as to the Surface Burning Characteristics in accordance with the UL 181 Standard and identified by a “ rectangular shape ” listing label of the listing agency. Authority Having Jurisdiction The organization, office or individual responsible for and having final approval concerning use of flexible duct and its installation. Classification For purposes of this standard, a method of identifying, marking and specifying flexible duct as related to listing category, physical style, positive pressure class and velocity type. Equivalent Length Additional length added to the actual duct length in duct sizing calculations to account for the frictional resistance of fittings, bends, etc. (see Total Equivalent Length).

Excess Length The difference between the fully stretched cut length and the measured, straight - line, entrance - to - exit span length.

Flexible Duct A preformed, flexible, tubular passage for supply, return and exhaust air in HVAC systems. For purposes of this document, the terms designated Air Duct and Air Connector are used interchangeably, however not in their intended use and application. Friction Loss (Bends) The static pressure loss in bends of flexible duct, expressed as a dimensionless coefficient (Co) at a specified bend radius ratio. Co is a dimensionless coefficient which represents the ratio of the total pressure loss to the dynamic pressure in terms of velocity pressure. Friction Loss (Straight) The static pressure loss in a straight run of flexible duct, expressed in inches of water gauge (IWC) per 100 feet [Pa/m].

Inner Core/Liner That portion of insulated flexible duct which determines the internal dimensions and inner physical form.

Installation Instructions A manufacturer ’ s printed instructions in accordance with the terms of their listing which advises the method and materials to install the flexible duct.

Leakage The time rate of air volume loss expressed in cubic feet per minute (cfm) [L/s].

Listed A published list by a recognized approving agency acceptable to the authority having jurisdiction stating that the flexible duct, tape, mastic, and clamp have been tested to and comply with the applicable Standard UL 181/UL 181B and maintains periodic inspection to assure production of the listed products are in accordance with the listing. Listing Mark/Label A printing, tag or other marking device of the listing agency permanently and prominently affixed to the listed product that certifies compliance to the applicable Standard UL 181/UL 181B and contains recommendations relating to installation and maximum physical conditions of use.

COMMON TERMS

Lot A collection of units of a product of a single category, style, class and type manufactured under essentially the same conditions and from which a sample is to be drawn and inspected for conformance to specification.

Permeance The time rate of water vapor transmission through the vapor barrier expressed in U.S. perms [ng/(s·m 2 ·Pa)].

Pressure The positive or negative static pressure expressed in inches of water gauge (IWC) [Pa].

Radiated Noise The sound power level transmitted through the duct wall, expressed in decibels (dB).

Sag The distance deviation, expressed in inches per lineal foot [mm/m] of flexible duct, from a horizontal or inclined plane between suspension points on installed flexible duct.

Snaking Unnecessary directional change in any plane (horizontal, vertical, inclined) that produces excess pressure drop.

Sound Attenuation (Insertion Loss) The extent to which sound power level is reduced (attenuated) as it travels through a flexible duct, expressed in decibels (dB). Sound Generation The sound power level which is generated by the movement of air through a flexible duct, expressed in decibels (dB). Thermal Conductivity (k) The time rate of heat flow through unit thickness of an infinite slab of homogeneous material in a direction perpendicular to the surface, induced by unit temperature difference. Expressed in BTU - in./hr. - ft. 2 - °F [W/(m - °C)]. Thermal Resistance (R) The mean temperature difference, at equilibrium, between two defined surfaces of material or a construction that induces a unit heat flow rate through unit area. Expressed in hr. - ft. 2 - °F/BTU [(m 2 - °C)/W].

Total Equivalent Length The sum of actual duct length and the equivalent length of fittings, bends, etc (see Equivalent Length).

Ultraviolet (UV) Light Invisible radiation in the electro - magnetic spectrum lying between visable light (380nm) and x - rays (100nm).

Vapor Barrier/Retarder The outer membrane of an insulated flexible duct.

Velocity The average time rate of air flow expressed in feet per minute (fpm) [m/s].

CHAPTER 3: DUCT DESIGN

3.1 Installation Restrictions and Use Limitations

3.1.1 Flexible Duct Installation

Flexible ducts shall be installed in accordance with the conditions of their listing and manufacturers installation instructions.

3.1.1.1 Shall not be installed in concrete, buried below grade or in contact with the ground.

3.1.1.2 Shall be interrupted at the immediate area of operation of electric, fossil fuel or solar energy collection heat sources to meet listed equipment clearances specified.

3.1.2 Flexible Air Connectors Installation

3.1.2.1 Shall not be installed in lengths greater than 14 ft. [4.3 m] for any given run.

3.1.2.2 Shall not be spliced together with short collars to circumnavigate the 14 ft. [4.3 m] limitation.

3.1.2.3 Shall not pass through any wall, partition or enclosure of a vertical shaft with a 1 hour or more fire resistive rating and shall not pass through floors.

3.1.3 Vertical Risers

Shall not be used for vertical risers serving more than two stories in height.

3.1.4 Temperature Limitations

Shall not be used in systems with enter air temperature higher than 250°F [121°C].

3.1.5 Duct Penetrations

Shall not penetrate a wall where fire dampers are required.

3.1.6 Additional Uses

Shall not be used to vent appliances for cooking, heating, fireplaces, and clothes drying unless approved and recommended by the appliance manufacturer.

3.2 Benefits

Flexible air ducts provide multiple benefits and advantages.

Foremost, except for those intentionally perforated for acoustical purposes, flexible air ducts have impervious inner liners—meaning they have zero leakage when properly connected and sealed. This attribute is instrumental in helping systems achieve the extremely low leakage levels desired today by most building owners.

In addition flexible air ducts come pre - insulated with multiple R - value offerings. This allows for lower duct installation costs as the ducts do not have to be wrapped and sealed after - the - fact.

Flexible air ducts also have inherently better sound attenuation performance due to the non - rigid inner liner. Net insertion loss values are higher as compared to standard sheet metal pipe.

Flexible duct are densely packaged allowing for easier transport to the job site and can be more easily routed around building obstructions.

When properly sized and installed per the procedures in this standard, flexible air ducts are a cost effective and efficient option for HVAC duct systems.

DUCT DESIGN

3.3 Common System Layouts

Most HVAC systems are designed as Radial, Trunk & Branch, or a mixture of the two systems. Some examples of these systems are shown below.

3.3.1 Radial System

Radial Duct Systems also commonly referred to as spider configurations; generally consist of a supply plenum that is centrally located to the conditioned space. Duct runs branch off the plenum typically in a radial pattern to supply individual spaces with specific heating/cooling requirements.

Figure 1

3.3.2 Trunk & Branch Systems

Trunk and Branch Systems consist of a main supply plenum with large diameter takeoffs to support the main supply of air flow. As the main supply ducts/extended plenums progress smaller diameter take off branches supply individual spaces with specific heating/cooling requirements. Sometimes longer trunks will need to be reduced in order to maintain proper flow rates.

Figure 2

DUCT DESIGN

3.4 Sizing

An efficient HVAC system must include properly sized ducts, regardless of duct type, shape, or configuration. Ducts should be sized according to the predetermined energy loads in order to provide necessary heating or cooling throughout the space. Oversizing or under sizing ductwork can lead to unbalanced air distribution and added strain for the HVAC unit resulting in energy loss. The fan in an HVAC system generates positive pressure in the system which results in the flow of air through the ductwork as it seeks equilibrium. As the air flows through the ducts the positive pressure decreases due to friction from the duct surface characteristics, changes in direction from bends, wyes, etc. This decrease is referred to as pressure drop, or friction loss, and it can be measured in inches water column (IWC). Each system component, direction change, etc. produce a resistance to airflow. This resistance creates a pressure drop measured in inches water column (IWC) which is physically equivalent to the pressure drop produced by a straight section of duct. For example—a 90 degree bend in flexible duct is considered to be 20 equivalent feet of duct because it exhibits the same pressure drop as 20 feet of straight duct (see Figures 4, 5, & 6). In determining the correct size, sum the total equivalent length of the duct run, including straight duct, bends, fittings, mixing boxes, and entrance and exit losses (See Figure 3 and example below). Size the duct using this total pressure drop value.

Figure 3

The worksheet for determining the total pressure drop of the duct run depicted in Figure 3 will look like this:

Entrance fitting = Total duct length =

35 ft. 12 ft. 20 ft. 20 ft. 35 ft.

2 x 45° bends (2 x 10’) = 1 x 90° bend (1 x 20’) =

Exit fitting =

Total Equivalent Length =

122 ft.

Although the distance from plenum to terminal end in this example is approximately 12 feet, the total equivalent length used to determine the correct duct diameter would be 122 feet.

The equivalent length values for bends & fittings represented above are default values from ACCA Manual D and based on 900 fpm at 0.08 IWC/100 ’ for supply ducts and 700 fpm at 0.08 IWC/100 ’ for return ducts. The flexible duct system should be designed per the requirements of ACCA Manual D Residential Duct Design and Manual Q Commercial Duct Design.

DUCT DESIGN

When determining the proper duct size the equivalent length for bends must be used.

90 - degree Bend (Figure 4) A 90 - degree bend has pressure drop equal to approximately twenty (20) lineal feet of flexible duct.

45 - degree Bend (Figure 5) A gradual 45 - degree bend has pressure drop equal to about ten (10) lineal feet of flexible duct.

180 - degree Offset (Figure 6) A 180 - degree offset has pressure drop equal to about forty (40) lineal feet of flexible duct.

Figure 4

Figure 5

Figure 6

DUCT DESIGN

3.5 Thermal Performance

Flexible Duct Media (FDM) is used to resist the flow of energy in insulated flexible air duct. Heat flows into the duct during cooling or out of the duct during heating. The quantity of heat flowing into or out of the duct is controlled by the FDM ’ s thermal resistance — commonly called R - value. Requirements for air distributing duct R - values vary depending on the energy code being enforced. The minimum R - value in conformance with this standard is R - 4.2 [0.74]. To accommodate these requirements, ADC manufacturers insulated flexible duct with R - value ratings of R4.2 [0.74], 6.0 [1.06], and 8.0 [1.41]. Special applications may call for R - values beyond 8.0. Uninsulated ducts are considered to have no R - value rating. Flexible duct R - values shall be based on insulation only and not include air barriers, air films, vapor barrier, or other ducting components.

Some helpful equations and terms related to Thermal Resistance, Thermal Conductance, and Thermal Conductivity are listed below. Heat Transfer is always from the hot side to the cold side of the insulation.

3.5.1 Thermal Conductivity (k and λ )

Thermal conductivity is a material property of FDM and the measure of its ability to conduct heat flowing through unit thickness per unit area per degree of temperature. It is often abbreviated as k in IPS units or λ n SI units.

3.5.2 Thermal Conductance (C - value)

Thermal Conductance is the measure of the ability of the FDM to conduct heat flowing through an actual FDM thickness per unit area per degree of temperature.

Equation 1: C - value = (k or λ ) / (thickness of FDM when laid flat at room temperature conditions)

3.5.3 Thermal Resistance (R - value)

Thermal Resistance is the measure of the ability of the FDM to resist heat flowing through an actual FDM thickness.

Equation 2: R - value = 1 / C - value

Equation 3: R - value = (thickness of FDM when laid flat at room temperature conditions) / (k or λ )

3.6 Thermal Performance Certification

ADC maintains a third - party verification and certification protocol for flexible duct R - value ratings in accordance with Sections 6.2.1 and 6.6.1 of this standard.

A testing and follow - up program was established with UL and ETL in 1993 for flexible ducts listed and labeled to the UL181 Standard. This program includes testing at the flexible duct and the insulation manufacturer ’ s locations to classify component materials and flexible ducts. Continued follow - up testing at the factories insures continued R - Value classification. The program test method measures the thermal conductivity (k) value for the insulation at the intended duct wall thickness and verify the flexible duct components are manufactured to provide the required wall thickness to achieve the R - Value. Thermal performance ratings are based on the conductivity value for the insulation when tested in a flat configuration and do not include air barriers, air films, vapor barrier, or other ducting components. Most building codes emphasize the above requirements for determining duct R - Values and include language indicating duct insulation R - Values shall be based on the insulation and the installed wall thickness only. Look for the ADC Seal of Certification for Thermal Performance.

DUCT DESIGN

3.7 UV light

Some polymeric materials used to manufacture nonmetallic flexible ducts may degrade with prolonged exposure to ultraviolet (UV) light radiation. UV radiation occurs naturally in sunlight or can be artificially generated by specialized lamps. The outer barrier (jacket) may degrade if ducts are installed outside in direct sunlight or within attics, crawl spaces, etc. where direct sunlight enters, e.g. turbine vents, sky lights, canopy windows, etc. The inner core (liner) may degrade if ducts are positioned near a bio - treatment lamp (UV emitter) installed within the HVAC system. Unless the product is specifically designed to withstand exposure to UV radiation from sunlight or from specialized lamps, special care shall be taken to ensure the outer vapor barrier and inner core material are shielded from the direct path of such radiation. Reference the manufacturer ’ s recommendations for specific product information related to UV exposure.

3.8 Fire Safety

Flexible ducts cannot be considered “ noncombustible ”, except metallic non - insulated ducts, but they are generally regarded as “ limited - combustible ”. The UL 181 Safety Standard for “ Factory - Made Air Ducts and Air Connectors ” is used to investigate safety performance as referenced in the applicable International Codes (ICC), Uniform Mechanical Code (IAPMO), the applicable National Fire Protection Code/Standard (NFPA), and various other state and local codes. The UL 181 Standard has been used for more than 40 years for evaluating duct safety. The testing procedures were developed by taking a wide range of safety related installation situations into consideration, including structural integrity and flammability characteristics. Four (4) fire tests are used to investigate the flammability and burning characteristics of flexible duct as follows:

3.8.1 Surface Burning per UL 181 Section 7

The Surface Burning Characteristics (Flame Spread and Smoke Development) for both interior and exterior duct using the 25 ft. [7.6m] tunnel test method that is published in UL 723, the American Society of Testing and Materials (ASTM E84), the National Fire Protection Association (NFPA 255) and the American National Standards Institute (ANSI)

3.8.2 Burning Test per UL 181 Section 11

Ease of ignition/burning test using a Bunsen burner on both the inner core and outer jacket of the duct.

3.8.3 Flame Penetration Test per UL 181 Section 10

Flame penetration test using a specifically designed test apparatus to evaluate the retardation of flame passage from exterior to interior of the duct.

3.8.4 Flame Resistance Test per UL 181 Section 8

Component flame resistance test conducted on tapes, fabrics, adhesive, and related components that are exposed direction to the air system.

3.9 Fire Resistance - Rated Assemblies

A fire - resistance rating refers to the period of time an assembly is able to contain a fire and perform its intended structural function. UL ’ s product category for Fire - resistance Ratings (BXUV) covers fire - rated assemblies for floor - ceilings, roof - ceilings, beams, columns, walls and partitions based upon the test method and acceptance criteria in UL 263 (ASTM E119), "Fire Tests of Building Construction and Materials." The ratings are expressed in hours (i.e. - 1 hour fire rating). When an assembly complies with the test criteria, a detailed description of the assembly, its performance in the fire test, and other pertinent specifications for materials, certification coverage and alternate assembly details are included in the fire resistive assembly report. These assemblies are published on UL ’ s Online Certifications Directory Product iQ, www.ul.com/PiQ. Many designs allow the use of Class 0 or Class 1 flexible air ducts and air connectors. This directory of fire - resistance designs should be consulted to determine the requirements for air ducts within a particular assembly design.

DUCT DESIGN

3.10 Bathroom Exhausts and Vents

Flexible air ducts and air connectors listed and labeled in accordance to UL 181 are required to pass UL 181 Section 13 Mold Growth and Humidity Test. This test ensures that materials in air ducts are resistant to high humidity conditions and that mold introduced to the duct surface will not grow or spread. This testing requirement along with proper installation will allow flexible air ducts and connectors to be used in bathrooms as well as other high humidity applications or applications with the potential for mold growth.

Ducts used for exhausting bathrooms and vents in cold weather climate zones shall be insulated in order to avoid issues with condensation collecting on the inside surface of the ducts.

3.11 Deeply Buried Duct

The Air Duct Council is aware that certain local, state, and national building codes allow for the practice of encapsulating ducts within additional insulation materials. Additionally the codes allow for partially or deeply burying ducts under blown - in insulation when installed in attics. Although this can be considered an energy efficient method for improving the overall thermal performance of the system, encapsulating or burying ducts that already contain an outer vapor barrier can potentially lead to moisture problems when the ducts are installed in areas of the country conducive to condensation such as ASHRAE Climate Zones 1A, 2A, and 3A. In addition, encapsulating flexible ducts may invalidate the manufacturers listing to the UL181 Standard and/or the warranty. Care should be taken when considering the practice of encapsulating or burying a flexible duct system in this manner.

Figure 7

CHAPTER 4: INSPECTION & INSTALLATION

4.1 Installation Key Points

SIZED - Flexible duct shall be properly sized per the requirements of ACCA Manual D or Manual Q as applicable .

Time should be taken to complete sizing calculations for air distribution systems. This is not specific to flexible duct systems, any ducting system should be properly sized per the requirements of ACCA Manual D (Residential) or Manual Q (Commercial).

ROUTED - Flexible duct runs shall be properly routed to minimize sagging and “ snaking ”

Ducting systems should ALWAYS run in the most direct path from starting point to termination point. Every unnecessary turn or sag in the duct increases friction and reduces air flow.

EXTENDED - Flexible duct shall be installed fully extended using the minimum length needed to make connections.

Along with being installed in the most direct path the ducting should be fully extended. Ducting that is not extended can increase pressure drop and reduce air flow.

BENDED - Flexible duct bends shall be greater than or equal to 1 duct diameter.

Sharp bends in ducting significantly increase pressure drop. Keep bends to great than or equal to one (1) duct diameter and properly supported.

SUPPORTED - Flexible ducts shall be properly supported.

Duct supports shall be a minimum of 1.5” in width with wider supports recommended in installation areas conducive to condensation. Horizontal duct runs shall be supported at maximum 4’ intervals and vertical risers at maximum 6’ intervals.

SEPARATED - Flexible ducts should be separated in areas conducive to condensation.

To prevent condensation forming on the outer surface of the duct, a gap should be present to allow free air flow over the outer duct surface. Locations where two duct surfaces are in contact can lead to condensation.

SEALED - Flexible duct connections shall be properly sealed using listed and labeled sealing materials and methods.

Care shall be taken to properly seal the ducting using materials listed and labeled to the UL standard. Improper sealing and installation methods can lead to leakage which can reduce system efficiency.

Note: An Installation Checklist can be found in Appendix E of this manual. This checklist can be used by installers or inspectors to ensure that the ducting is installed properly.

4.2 Air Duct or Air Connector

Flexible ducts are classified by their performance when tested to UL 181 Standard for Safety, Factory - Made Air Ducts and Air Connectors. The standard includes seventeen (17) tests covering fire testing, tests for physical characteristics, and product performance testing. Sixteen (16) test are applicable to Air Ducts and thirteen (13) tests are applicable to Air Connectors. One (1) is reserved for testing Joining Materials. (Refer to Appendix B for testing detail.)

In many cases, Air Ducts and Air Connectors look similar in appearance. The only way to be sure whether a flexible duct is an Air Duct or Air Connector is to examine the listing label on the product.

• Flexible Air Ducts will have a rectangular or square listing label and include the words “ Air Duct ”.

• Air Connectors will have a circular listing label which identifies it as an “ Air Connector ”. In addition, Air Connectors will include the words “ For installation in lengths not over 14 ft. ”

INSPECTION & INSTALLATION

4.3 Bends

When making bends to flexible air ducts or air connectors, the diameter of the bend shall be greater than or equal to one (1) duct diameter (see Figures 8 & 9). If the bends are less than one (1) duct diameter this can significantly increase pressure drop throughout the system resulting in a reduction in the overall system efficiency and performance. For bends made prior to or after a metal connection, extend the duct straight for at least one duct diameter length before and after the connection points. This avoids potential damage to the duct from the fitting edges while also improving the airflow.

For proper support, place strapping both before and after a 90 degree bend that is made in the middle of a duct run.

CORRECT BENDS

Figure 9

Figure 8

Figure 10

INSPECTION & INSTALLATION

INCORRECT BENDS

Ducts shall not be crimped tightly against joist or truss members, or against pipes, wires, and other building materials.

Duct runs shall be made with the minimum practical length needed to make the connection from one fitting to the next. Excessive duct length and bends increase pressure drop and reduce overall system efficiency and performance. Ducts shall not be installed with excess length intended for future building changes.

Figure 11

4.4 Routing, Sagging, & Snaking

Flexible air ducts and connectors should always be installed in the most direct route possible. Changing directions multiple times will increase the friction rate of the duct thus decreasing the air flow in the HVAC system. Flexible air ducts and connectors must be installed in the straight condition without sag. Extra supports should be used to prevent sag where 90° bends are made by placing straps both before and after the bend. Excessive sag creates more friction reducing air flow in the air distribution system.

INCORRECT ROUTING

Figure 12

Figure 13

INSPECTION & INSTALLATION

4.5 Supporting Flexible Ducts

4.5.1 Hanger Straps Material & Width.

Various materials are used regionally to hang and support flexible air duct. The ADC does not specify a particular material in our installation instructions. However, ADC does make the following statement:

Hanger or saddle material in contact with Flexible Air Ducts and/or Flexible Air Connectors shall be of sufficient width and rigidity to prevent any restriction of the internal diameter of the duct when the weight of supported sections rests on the hanger or saddle material. In no case will the material contacting the duct or connector be less than 1 - 1/2” wide. For flexible duct installed in Climate Zones 1A, 2A, and 3A (refer to the IECC US Climate Zone Map) where higher levels of heat and humidity are likely it is recommended that a hanger or saddle material be not less than 3” wide to support the flexible duct. This recommendation is to reduce the likelihood of condensation at the point of contact with the hanging material and flexible duct due to compression of the fiberglass insulation potentially caused by the supporting material and the weight of the duct.

Figure 14

Figure 15

INSPECTION & INSTALLATION

4.5.2 Support Spacing

Flexible duct shall be supported at maximum 4’ intervals horizontally and 6’ intervals for vertical risers.

Figure 16

Figure 17

4.5.3 Ceiling or Truss Supports

Ceiling beams or truss members may be used to support flexible duct provided they do not exceed 4’ intervals, and are at least 1 ½ ” wide.

Figure 18

INSPECTION & INSTALLATION

4.6 Compression

Unnecessary longitudinal and circumferential compression of flexible duct significantly increases pressure drop resulting in reduced air flow and loss of system efficiency. Care should be taken to insure flexible ducts are installed fully extended and not compressed. A simplified, yet easily understood, comparison can be made by looking at the common garden water hose. Kinking a garden hose reduces or chokes off the water flow. Also, a long garden hose will have lower water pressure than a much shorter one. Movement of air through ducts is effected in the same manner.

4.6.1 Longitudinal Compression.

Flexible air ducts and air connectors should always be installed to their fullest length without longitudinal compression. Due to the helical configuration of flex duct inner cores, excess longitudinal compression significantly increases pressure drop and reduces performance. (See Figure 19)

4.6.2 Circumferential Compression.

Flexible air ducts and air connectors are intended to be installed in their original round configuration. For optimal air flow, care should be taken to avoid compressing the duct circumferentially along its length. Ducts should not be forced into small building cavity areas that result in compression of the duct wall and/ or the duct inner liner diameter. Incidental compression when connecting to oval pipe or fittings is acceptable. Compressing the duct vapor barrier and insulation can reduce the duct thermal performance characteristics and could also result in localized condensation. (See Figure 20)

Figure 19

Figure 20

4.7 Installation Instructions

All connections, joints and splices shall be made in accordance with the manufacturer ’ s installation instructions. Always reference the manufacturer ’ s installation instructions for more detailed requirements.

Due to the wide variety of ducts and duct assemblies with special end treatments (factory installed fittings, taped ends, crimped metal ends, etc.), only the standardized installation instructions were shown.

INSPECTION & INSTALLATION

4.7.1 Installation Instructions for Air Ducts and Air Connectors - Nonmetallic with Plain Ends

Connections - Using Tape and Fasteners

Splices - Using Tape and Fasteners

1. After desired length is determined, cut completely around and through duct with knife or scissors. Cut wire with wire cutters. Fold back jacket and insulation.

1. Fold back jacket and insulation from core. Butt two cores together on a 4" [100 mm] min. length metal sleeve.

2. Slide at least 1" [25 mm] of core over fitting and past the bead. Seal core to collar with at least 2 wraps of duct tape. Secure connection with clamp placed over the core and tape and past the bead.

2. Tape cores together with at least 2 wraps of duct tape. Secure connection with 2 clamps placed over the taped core ends and past the beads.

3. Pull jacket and insulation back over cores. Tape jackets together with at least 2 wraps of duct tape.

3. Pull jacket and insulation back over core. Tape jacket with at least 2 wraps of duct tape. A clamp may be used in place of or in combination with the duct tape.

NOTES: 1. For uninsulated air ducts and air connectors, disregard references to insulation and jacket. 2. Use beaded sheet metal fittings and sleeves when using nonmetallic clamps. 3. Use tapes listed and labeled in accordance with Standard UL 181B and marked “181 B - FX ”. 4. Nonmetallic clamps shall be listed and labeled in accordance with Standard UL 181B and marked “181 B - C ”. Use of nonmetallic clamps shall be limited to 6 in. w.g. [1500 Pa] positive pressure.

INSPECTION & INSTALLATION

4.7.2 Alternate Installation Instructions for Air Ducts and Air Connectors - Nonmetallic with Plain Ends

Connections and Splices - Using Mastic and Fasteners

Step 1 After desired length is determined, cut completely around and through duct with knife or scissors. Cut wire with wire cutters. Pull back jacket and insulation from core.

Step 2 Apply mastic approximately 2" [50 mm] wide uniformly around the collar of the metal fitting or over the ends of a 4" [100 mm] min. length metal sleeve. Reference data on mastic container for application rate, application thickness, cure times and handling information.

Step 3 Slide at least 2" [50 mm] of core over the fitting or sleeve ends and past the bead.

Step 4 Secure core to collar with a clamp applied past the bead. Secure cores to sleeve ends with 2 clamps applied past the beads.

Step 5 Pull jacket and insulation back over core ends. Tape jacket(s) with at least 2 wraps of duct tape. A clamp may be used in place of or in combination with the duct tape.

NOTES: 1. For uninsulated air ducts and air connectors, disregard references to insulation and jacket. 2. Use beaded sheet metal fittings and sleeves when using nonmetallic clamps. 3. Use mastics listed and labeled in accordance with Standard UL 181B and marked “181 B - M ” on container. 4. Use tapes listed and labeled in accordance with Standard UL 181B and marked “181 B - FX ”. 5. Nonmetallic clamps shall be listed and labeled in accordance with standard UL 181B and marked “181 B - C ”. Use of nonmetallic clamps shall be limited to 6 in. w.g. [1500 Pa] positive pressure.

INSPECTION & INSTALLATION

4.7.3 Installation Instruction for Air Ducts and Air Connectors - Metallic with Plain Ends

Connections and Splices - Using Tape or Mastic and Sheet Metal Screws

1. After cutting duct to desired length, fold back jacket and insulation exposing core. Trim core ends squarely using suitable metal shears. Determine optional sealing method (Steps 2 or 5) before proceeding.

4. Secure to collar/sleeve using #8 sheet metal screws spaced equally around circumference. Use 3 screws for diameters under 12" [300 mm] and 5 screws for diameters 12" [300 mm] and over.

2. When mastics are required and for pressures 4" w.g. [1000 Pa] and over, seal joint with mastic applied uniformly to the outside surface of collar/sleeve. (Disregard this step when not using mastics and pro- ceed to Step 3).

5. For pressures under 4" w.g. [1000 Pa] seal joint using 2 wraps of duct tape applied over screw heads and spirally lapping tape to collar/sleeve. (Disregard this step when using mastics per Step 2).

3. Slide at least 1" [25 mm] of core over metal collar for attaching duct to take off or over ends of a 4" [100 mm] metal sleeve for splicing 2 lengths of duct.

6. Pull jacket and insulation back over core. Tape jacket with 2 wraps of duct tape. A clamp may be used in place of or in combination with the duct tape.

NOTES: 1. For uninsulated air ducts and air connectors, disregard references to insulation and jacket. 2. Use mastics listed and labeled to Standard UL 181B and marked ”181 B - M ” on container. 3. Use tapes listed and labeled to Standard UL 181B and marked “181 B - FX ”. 4. Nonmetallic clamps shall be listed and labeled in accordance with Standard UL 181B and marked “181 B - C ”.

INSPECTION & INSTALLATION

4.8 Fittings, Fasteners & Sealants

4.8.1 Fittings

Sheet metal fittings to which flexible ducts with plain ends are attached shall be beaded and have a minimum of 2 inches [50 mm] collar length. Beads are optional for fitting when using metal worm - gear clamps or when attaching metallic flexible ducts using sheet metal screws. Sheet metal sleeves used for joining two sections of flexible duct with plain ends shall be a minimum of 4 inches [100 mm] in length and beaded on each end. Beads are optional for sleeves when using metal worm gear clamps or when joining metallic flexible ducts using sheet metal screws.

4.8.2 Mastic

Mastic shall be listed and marked “ UL181B - M ”.

4.8.3 Tapes

Tape shall be listed and marked “ UL181B - FX ”.

4.8.4 Nonmetallic Fastener (Plastic ties)

Plastic ties often called zip ties shall be listed and marked “ UL 181 B - C ”.

Flexible duct secured with nonmetallic fasteners shall be limited to 6 inches W.G. [1500 Pa] positive pressure.

4.8.5 Metallic Fasteners

Metallic fasteners are not required to be listed.

4.8.6 Screws

ADC does not recommend the use of metal screws for making connections and splices with non - metallic flexible air ducts. Procedures and materials (tapes, mastic, fasteners) for connecting and splicing non - metallic flexible ducts are evaluated using UL181B Standard which does not address the use of metal screws. Potentially, metal screws can damage the components in some non - metallic flexible ducts.

ADC allows the use of sheet metal screws for making connections and splices with metallic flexible air ducts.

4.9 Typical Installation Locations

4.9.1 Ducts in Attics

When installing flexible ducting in attics, the ducts can be suspended from the rafters using an appropriate strap material and proper spacing. Flexible ducts can also rest on ceiling joists or truss supports provided the support centerline spacing does not exceed four (4) feet and the support surface is at least 1 - 1/2” in width. (Refer to Section 4.5 Supporting Flexible Ducts) Avoid installing ducts in areas where exposure to direct sunlight will occur (e.g. turbine vents, sky lights canopy windows, etc.). As most flexible ducts are intended for Indoor Use Only, this exposure to UV radiation can lead to eventual deterioration of the outer vapor barrier. (Refer to 3.7 UV Light) Avoid running ducts unnecessarily high up against the roof line. Attic spaces are generally significantly hotter closer to the roof line and this elevated temperature can significantly affect the energy efficiency of the duct system and potentially increase the occurrence of condensation.

INSPECTION & INSTALLATION INSPECTION & INSTALLATION

4.9.2 Ducts in Crawl Spaces

In accordance with the building codes, ducts installed under a building structure shall not be in contact with the ground. All duct surfaces shall be at least 4” above the earth (i.e. not sitting directly on dirt, rocks etc.). In addition, the crawl space shall shield the ducting from environment exposure. For installations where the duct may be exposed, such as a mobile home crossover duct, only ducts designed and intended for use under exposed conditions shall be used. Care must also be taken to ensure that the area under the structure is free from potential flooding. Flexible duct vapor barriers offer protection to the insulation from normal moisture vapor transfer; however, ducts sitting in standing water from flooding will deteriorate and not perform as designed.

4.9.3 Ducts in Walls and Between Floors

Flexible air ducts can be installed in walls and between floors. When installed vertically in walls the ducts shall be supported by straps at six (6) feet maximum intervals (Refer to Section 4.5 Supporting Flexible Ducts). For exterior walls refer to the appropriate energy code for the minimum insulation required between the ducts and the exterior space.

4.9.4 Ducts in Plenums

The building codes require that materials installed in plenums have a Flame Spread Index of 25 or less and a Smoke Developed Index of 50 or less when tested in accordance with ASTM E84. All listed and labeled Class 1 or Class 0 Flexible Air Ducts and Air Connectors meet this requirement and therefore may be installed within a plenum.

4.9.5 Ducts in Fire Resistant Rated Assemblies

Refer to Section 3.7 for materials allowed in Fire Resistant Rated Assemblies.

4.9.6 Ducts Exposed to the Elements

Unless specifically designed and labeled for outdoor use, flexible air ducts and air connectors shall not be used outdoors. Refer to the appropriate energy code for specific duct insulation requirements when ducts are installed outdoors.

4.10 Contact with Fixtures

4.10.1 Hot Equipment

Flexible air ducts shall be installed with a minimum clearance to an appliance as specified in the appliance manufacturer ’ s installation instructions. They shall not be installed in contact with boilers, steam pipes, or other equipment that exceeds the duct manufacturer ’ s maximum recommended use temperature.

4.10.2 Pipes

Contact with pipes, both metal and plastic, should be avoided when possible, but incidental contact with pipes should not cause damage to the flexible duct. Pipe manufactures instructions must be used to determine if contact with the flexible ducting will lead to degradation in the piping material.

INSPECTION & INSTALLATION INSPECTION & INSTALLATION

4.11 Leakage

Flexible duct has inherently low leakage properties due to the impervious nature of the materials used as the air barrier. These give the flexible duct itself leakage rates less than 0.5% of air volume when proper connections are made to the other systems.

A higher than expected leakage rate can occur at connections if improper materials or careless work practices are used. To assure a low leakage rate for flexible duct systems, the following is required:

• Reference applicable industry manuals (SMACNA, NAIMA) for making round tap - ins into and sealing fitting joints to rigid ducts, plenums, etc. • Make flexible duct connections/splices in accordance with the manufacture ’ s recommended installation instructions for this Standard. • Seal flexible duct connections with sealing materials listed and labeled to Standard UL 181B. Mechanically secure connections with approved clamping material. • Repair any rip, tear or hole in the air barrier using materials listed and labeled to Standard UL 181B and methods recommended by the manufacturer.

4.12 Condensation

In areas with high humidity, it is possible for condensation to form on flexible duct surfaces. Condensation will form when the temperature of any surface is lower than the dew point temperature of the surrounding air. This phenomenon is commonly observed on a glass of ice water placed in a warm, humid environment. It is important to note that ducts with high R - value insulation can decrease the likelihood of condensation. For correct thermal performance, the duct needs to be exposed to ambient air on all sides without insulation compression.

To reduce condensation there are several installation practices to avoid when working in areas prone to condensation.

4.12.1 Practices to Avoid

4.12.1.1 Duct Contact

When ducts make contact, the temperature between the ducts could easily drop below the dew point temperature. (Figure 21)

Figure 21

4.12.1.2 Insulation Compression

Compressing the thickness of duct insulation significantly impacts duct thermal performance resulting in surface condensation. Avoid compressing the duct insulation.

INSPECTION & INSTALLATION INSPECTION & INSTALLATION

4.12.1.3 Insulation Contact

Avoid laying duct directly on attic insulation in areas conducive to condensation.. Ducts should be properly suspended to allow free circulation of ambient air around all surfaces of the duct. See section 4.5 for proper duct support.

Figure 22

4.12.1.4 Adding External Insulation

Avoid adding extra insulation to the outside of the duct. Encapsulating or burying ducts that already contain an outer vapor barrier can potentially lead to moisture problems when the ducts are installed in areas of the country conducive to condensation. In addition, encapsulating flexible ducts may invalidate the manufacturers listing to the UL181 Standard and/or the warranty. Care should be taken when considering the practice of encapsulating or burying a flexible duct system in this manner.

4.12.1.5 Tight Strapping

Avoid installing duct supports too tightly this can lead to surface condensation.

4.12.1.6 Exposed Metal Fittings

Exposed metal fittings lead to condensation. All metal fittings should be insulated per the requirements in the building code.

4.12.1.7 Improper Sealed Inner Core

Avoid air leakage from flexible duct inner cores. Unconditioned air permeating the surround insulation leads to surface condensation.

4.12.1.8 Porous Inner Core

The use of porous inner liners should be avoided in areas conducive to condensation. (i.e. Perforated Acoustical Products)

4.12.1.9 Torn or Unsealed Vapor Barriers

Air infiltration through the exterior vapor barrier can result in condensation formation on the exterior of the inner liner.

4.13 Field Alterations

Alterations made in the field, such as applying additional overwraps of insulation or barriers, adding spray - foam insulation, surface painting, applying internal sanitizers or spray sealants, etc. may compromise the fire safety performance of the duct and void the manufacturer ’ s listing and/or product warranty.

4.14 Personal Protective Equipment

Insulated flexible air ducts generally contain fiberglass insulation and steel wire. Where necessary, wear eye protection, use a properly fitted approved respirator, and wear long - sleeve loose fitting clothing and gloves during installation.

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