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SHEET METAL AND AIR CONDITIONING CONTRACTORS’ NATIONALASSOCIATION, INC.

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# FIBROUS GLASS DUCT CONSTRUCTION STANDARDS

RETURN TO 

# K! L!EARY FE.JfULG 

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FifthEdition

— 1979

Low Velocity Systems Two Inches W.G. Maximum Static Pressure

SHEET METALAND AIR CONDITIONING CONTRACTORS NATIONALASSOCIATION, INC. 8224 Old Courthouse Road

— Tysons Corner. Vienna. Virginia 22180

SMACNA Fibrous Glass Duct Construction Standards 

# US© SMACNA 1979

SHEET METALAND AIR CONDITIONING CONTRACTORS’ NATIONAL ASSOCIATION, INC. 8224 Old Courthouse Road Tysons Corner, Vienna, Virginia 22180



### FIRSTEDITION

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### AUGUST1968 SECONDEDITION

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### FEBRUARY 1969 SECONDPRINTING

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### JULY 1970

THIRDEDITION

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### APRIL1972 FOURTH EDITION

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### JUNE1975 SECONDPRINTING

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### SEPTEMBER1975 SUPPLEMENT

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### JUNE 1978 FIFTH EDITION

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### JUNE 1979 FIRSTPRINTING

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### MARCH 1980 SECOND PRINTING

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### JANUARY 1981

THIRDPRINTING

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### OCTOBER 1981

These Standards were developed using reliable engineering principles and research plus consultation with, and information obtained from manufacturers, users, testing laboratories and others having specialized experience. They are subjectto revision as further experience and investigation may show is necessary or desirable. Construction and products which comply with these Standards will not necessarily be acceptable if, when examined and tested, they are foundto have otherfeatures which impair the result contemplated by these requirements. The Sheet Metal ahd Air Conditioning Contractors’ National Association, and Thermal Insulation Manufacturers’ Association assume no responsibility, nor accept liability for the application ofthe principles ortechniques contained in this manual. Authoritie considering adoption ofthese standards shouldreviewall Federal, State, local and contract regulations applicable to specific installations.

SMACNA Fibrous Glass Duct Construction Standards

## PREFACE
The SheetMetal andAirConditioning Contractors’ NationalAssociation presents this standard as a recommendedmethodoffabricatingandinstalling airhandlingductsdesignedoffibrous glass mate rial as specified herein, which operates at 2” water gage static pressure or less and 2000 feet per minuteofvelocityorless. This edition reflects refinement oftechnology applicable to fibrous glass duct systems. Based on continuing improvements in fibrous glass board and additional laboratory tests ofvarious boards and reinforcements, we have expanded Section II, Fabrication of Straight Duct and Fittings, to include informationonthefabricationoften sidedduct. Also included in this edition are revised pressure sensitive tape standards. These standards were first published in September 1 973 and were included in the Fourth Edition June 1975. The re vised standards which appearin this Fifth Edition include test procedures under accelerated aging conditions. Closure systems are vital to maintaining the proper assembly of fibrous glass ducts. However, the development ofclosure system standards, ofwhich the Tape Standards are a first step, must, in the final analysis, be considered a refinement process. It is believed that the use of tapes conforming to this Performance Standard herein in accordance with the Application Stand ard herein, will resultin a quality installation where pressure sensitive tapes are used as a closure method.

V 

### Fourimprovedmethodsforfastening tie rod reinforcing wireto the supportwasherhave been de veloped andtestedbyTIMAandwehaveincludedthesealternatetie-rodterminations in Section IV, Reinforcement. A new Section VI has been added in this Fifth Edition covering the fabrication and installation of preformedroundfibrousglass duct. The Sheet Metal and Air Conditioning Contractors’ National Association gratefully acknowledges the contribution of the Thermal Insulation Manufacturers’ Association and its Fibrous Glass Air Duct Committee for their cooperation and for providing material, personnel and testing facilities. Acknowledgementandappreciation arealso duethe PressureSensitiveTape Council and members thereofwho contributed advice and the results of laboratory tests which assisted in the develop mentofthe Pressure SensitiveTapeStandards.

V 

### The Sheet Metal and Air Conditioning Contractors’ National Association extends its thanks to the followingindividualswhohavecontributedtheirtimeandtalentsinthedevelopmentofthis standard.
SMACNA TIMA Mr. Robert Segal, Chairman Mr. RobertGawne Mr. PeterHays

Farmington. Michigan Washington,D.C. Toledo. Ohio Mr. B. H.Anderson

V Mr. HaroldNepereny Mr.Win Irwin

San Leandro, California Vienna.Virginia valleyForge,Pennsylvania Mr. G. E. “Eddie” Daniel Mr. RobertE. Taylor Mr. CliffD. Smith

St. Petersburg.Florida SaltLakeCity,Utah Toledo. Ohio Mr. DanielJ. Dnscoll Mr. KeithThomas

Philadelphia. Pennsylvania Denver, Colorado Mr.WallaceE. Fizer

V Mr. HarvellSmith

Lexington.Kentucky Denver. Colorado

SMACNA Fibrous Glass Duct Construction Standards lii

# REFERENCES
The following should be used as reference material when working with the information contained in this Standard. Low Pressure DuctConstruction Standards

— 5th Edition Sheet Metal and Air Conditioning Contractors’ National Association, Inc. DuctedElectric Heat Guide forAirHandling Systems

— 1stEdition Sheet Metal and Air Conditioning Contractors’ National Association, Inc. ASHRAEHandbook andProductDirectory

— Systems andEquipment Volumes American Society of Heating, Refrigerating and Air-Conditioning Engineers. NFPA Standard90A

— 1979

— InstallationofAirConditioningandVentilating Systems National FireProtection Association. NFPA Standard 90B

— 1979

— Installation ofResidence Type Warm Air Heating and Air Conditioning Systems National Fire Protection Association. Standard for Safety

—Factory-MadeAirDuctMaterials andAirDuctConnectors UL 181

— 1974 Underwriters’ Laboratories, Inc. TestMethods forPressure Sensitive Tapes

— 6th Edition Pressure Sensitive Tape Council.

Refer to area codes and municipal ordinances for additional specific local requirements for ducted heating and air conditioning systems.

SMACNA Fibrous Glass Duct Construction Standards iv

### TABLEOFCONTENTS Page Number
PREFACE REFERENCES iv TABLEOFCONTENTS v SHORTFORM SPECIFICATIONS vii SECTION I

— PERFORMANCECRITERIAOFBOARD GeneralRequirementsforAllAirDucts 1-2 1. DuctBoard 1-2 2. Reinforcement 1-3 3. Longitudinal SeamsandTransverseJoints 1-3 4. DuctSupport 1-3 5. Vibration andNoise 1-4 6. ThermalConductivity 1-4 7. AirFriction Loss 1-4 8. FireProtection Characteristics 1-4 8. FireProtection Characteristics 1-4 Compilation ofFibrous Glass DuctCharacteristicsand Limitations 1-5 DuctDesign ReferenceData 1-6 SECTION II

— FABRICATION OFSTRAIGHTDUCTAND FITTiNGS FabricationofStraight Ducts 2-3 FabricationTools 2-3 CenterlineMethodofFabrication 2-4 Layout 2-4 Longitudinal ShiplapGrooveMethod 2-6 Add-OnAllowances 2-7 LongitudinalV-Groove Method 2-8 Add-On Allowances 2-9 Board LengthSelection Chart 2-10 FabricationofFittings 2-12 RectangularEnd Cap 2-12 Volume DamperConnection 2-14 900 Elbow Fabrication 2-16 Vaned SquareElbow 2-18 Tee Fabrication 2-20 BranchTake-Off 2-22 Transition Fabrication 2-24 One-WayTransition (Falt)

— Shiplap Construction 2-28 One-WayTransition

— “V” GrooveConstruction 2-30 Two-WayTransition (Flat)

— ShiplapConstruction 2-32 Three-WayTransition 2-34 One-WayOffset(30°1) Fabrication 2-36 Registerand GrilleConnection 2-38 DiffuserConnection (Round) 2-40 DiffuserConnection (RectangularorSquare) 2-42 Access DoorTypeA 2-44 AccessDoorTypeB 2-46 FireDamperConnection 2-48 FlangedElectricHeaterInstallation 2-50 Slip-InElectricHeaterInstallation 2-52 EquipmentConnection Details 2-54 Fabrication ofTen-SidedDuct 2-56 InstallationofTen-SidedDuct 2-61

SMACNA Fibrous Glass Duct Construction Standards VPage Number
SECTION III

— CLOSURES General 3-2 PressureSensitiveTapesforFibrousGlass Ducts 3-4 A. PerformanceStandardAFTS-100-73 3-4 1. Classification 3-4 2. MaterialsRequirements 3-4 3. RequiredPerformanceCharacteristics 3-4 4. TestProcedures 3-5 5. Compliance 3-5 Table3-1

— Specimen Selection 3-6 Table3-2

— ShearAdhesionTests 3-6 B. Application StandardAFTS-1O1-73 3-7 1. Scope 3-7 2. Procurement 3-7 3. Storage 37 4. InspectionofDelivery 3-8 5. Surface Preparation 3-9 6. Installation 3-9 SECTION IV

— REINFORCEMENT Reinforcement 4-3 ReinforcementwithChannelsandTee Bars 4-4

Table4-1

— ChannelandTeeBarSystem 4-5 ReinforcementTypes 4-6 TransverseJoints

— ShiplapType 4-8 Typical Reinforcementon48” Centerswith48”JointSpacing 4-9 TypicalReinforcementon24” Centerswith48”Joint Spacing 4-10 Typical Reinforcementon 16” Centerswith48”JointSpacing 4-11 ReinforcementwithTie-Rod System 4-12 1. Testing 4-12 2. ReinforcementMaterialsandTools Required 4-12 3. ReinforcementProcedure 4-13 4. Ductsover60” 4-13 5. LocationofReinforcements (SeeTable4-3) 4-13 Table4-3

— Tie-Rod System 4-15 Tie-RodReinforcementSystemTransverseJoints

— ShiplapType 4-16 TypicalTie-RodReinforcement 4-17 Method 1

— OriginalMethod 4-19 Method2

— Fasloop 4-20 Method3

— InternalPopRivetSleeve 4-21 Method4

— External PopRivetSleeve 4-22 Method5

— CapWasher 4-23 SECTION V

— HANGERSAND SUPPORTS Hangers

— HorizontalDuct 5-2 VerticalRiserSupports 5-4 SECTIONVI

— PREFORMED ROUND DUCT Preformed Fiberglass Duct 6-2 FabricationofStraightDuctand Fittings 6-3 InstallationofPreformedRoundDuct 6-10

SMACNA Pibrous Glass Duct Construc.tion Standards vi

### SHORT FORM SPECIFICATION
Allductworkoperatingatorbelow2”w.g. staticpressure, 2000fpmvelocityand250°Fairtempera ture shall beconstructedof 1” thickfibrousglassductboard meeting therequirements ofthelatest EditionoftheSMACNAFibrousGlassDuctConstructionStandard. Fabrication and installation ofduct and fittings shall be in accordance with the latest Edition ofthe SMACNAFibrousGlassDuctConstruction Standard. Furthermore, closuresystems forlongitudinal seamsandtransversejointsshallbeinaccordancewithproceduresnecessarytocomplywithSection Ill, CLOSURES.

SMACNA Fibrous Glass Duct Construction Standards viiSMACNA Fibrous Glass Duct Construction Standards

# SECTION I PERFORMANCE CRITERIA OF BOARD

SMACNA Fibrous Glass Duct Construction Standards

## PERFORMANCE CHARACTERISTICS General Requirements for All Air Ducts A duct system is a structural assembly whose primary function is to convey air between specific points. I fulfilling this function the duct assembly must perform satisfactorily with regard to certain fundamental performance characteristics. Elements of the assembly are sheets, reinforcement, seams andjoints. With regard to the duct assembly and its elements, theoretical and/or practical limits must be established for:

1. Dimensional stability—deformation and deflection. 2. Containment ofthe air being conveyed. 3. Vibration 4. Noise generation and transmission. 5. Exposure to damage, weather, temperature extremes, flexure cycles or other in-service conditions. 6. Support. In establishing limitations for these factors, consideration must be given to the effects of the pressure differential across the duct wall, air flow friction losses, air velocities, infiltration or exfiltration, as well as the inherent strength characteristics of the duct components. Construction methods which will permit an economical attainment of the predicted and desired performance must be determined. Analysis and Determination of Requirements for Fibrous Glass Ducts Fibrous glass ducts are fabricated from sheets of materials which have been manufactured from resin bonded inert and inorganic glass fibers. One surface of the sheet (hereinafter called duct board) has a factory applied facing (typically aluminum or reinforced aluminum) which serves as a finish and a vapor barrier. In this text only ducts fabricated from 1” thick boards are considered. Investigation and establishment of limitations for fibrous glass air ducts in the low pressure category (2” w.g. and 2000 fpm maximums) with respect to the general requirements for air ducts are as follows: 1. Duct Board 1.1 Strength and Deflection Ducts fabricated from fibrous glass board were analyzed using plate theory, beam theory and fundamental relationships of stress and strain. Board stiffness is defined by flexural rigidity. Flexural rigidity is the product of Young’s Modulus of Elasticity (E) and the moment of inertia (I). Boards are identified by ratings of 475 El, 800 El and 1400 El, respectively. Flexural rigidity rating is determined in accordance with TIMA Test Number AHS-100-74 and is an average of specimens taken from a sheet

## ofthe duct board. Duct Board Deflection—relative to a flat position of the board—is limited to one one-hun dredth (1/100) of the span. This criteria is based on stress in the material not exceeding the proportional elastic limit of the material. At atmospheric pressure, natural sag occurs in unsupported panels of duct board. Studies of natural sag and duct performance in larger duct sizes resulted in the determination that the top of a horizontal positive pressure duct over 60” in width must be fastened to the channel or tee bar as illustrated in Figures 4-3, 4-4, and 4-5, DETAIL “A.” Also, ducts reinforced with tie-rods which are over 60” in width must have conduits placed as illustrated in Figure 4-6, DETAIL “B” and Figure 4-7. In negative pressure applications, the pressure differential causes additional board deflec tion. To limit this deflection on negative pressure applications, the determination was made to attach the board to the reinforcement at spacings not exceeding 16” along the length of the reinforcing member. This applies only to the channel and tee bar as illustrated in Figure 4-2 DETAIL “B,” Table 4-2, and Figures 4-3, 4-4, and 4-5, DETAILS “B” and “C.” 1.2 Fatigue Tests In normal service conditions ducts incur pressure cycles. In investigating the potential

SMACNA Fibrous Glass Duct Construction Standards 1-2effects offatigue occurring in a duct system, sections ofeach board type (475, 800 and 1400) were cycled from atmospheric pressure to positive pressures that produced a deflection of 1/100 of the span. Each test assembly consisted of not less than three 48” long sections of duct. The tests were conducted at 5 cycles per minute for 25,000 cycles and periodic inter ruptions ofcycling were made for intermediate investigations of the duct. Following the completion of 25,000 cycles, samples were removed from the center of the board and the flexural rigidity (El) was determined in accordance with TIMA AHS-1 00-74. For comparison of board strengths and deterioration, comparable samples of new boards ofeach particular class were tested in accordance with the same TIMA test method. In each test case there was no significant reduction in the flexural rigidity of the cycled boards. 2. Reinforcement 2.1 Strength and Deflection After criteria for fibrous glass boards were established, reinforcement designs were calcu lated, fabricated, tested and modified as necessary to restrain the board within the limitation of span over 100 and to limit stress in the steel reinforcement members to 22,000 psi. 2.2 Tests Tests of reinforced ducts were made in systems incorporating straight runs, transitions and vaned elbows. Duct sizes ranging from 15” x 15” up to 96” x 42” were evaluated using either static and dynamic testing or static testing. Maximum deflections generally occurred in the center of the board between reinforcements. Using boards of 475 El, 800 El and 1400 El and selected transverse reinforcements, deflection measurements were recorded for positive or negative pressures. 2.3 Positioning Duct analysis and determination of reinforcement sizes and spacing were based on the con dition that reinforcement must be placed at transverse points for optimum joint strength, and at intermediate points as required, in both positive and negative pressure applications. See Figures 4-2 and 4-6. Moreover, on negative pressure systems using channel or tee bars, the general requirement to fasten reinforcement at distances not exceeding 16” is supplemented by a requirement to place 2” x 6” x 20 gage retaining clips on the interior of the negative pressure duct as illustrated in Figure 4-2. 3. Longitudinal Seams and Transverse Joints Recommended methods of forming and aligning duct sides are given in detail in Sections II and lii. In order to maintain alignment of the duct assembly, both longitudinal seams and transverse joints are sealed with a continuous closure system. Observation and testing in the laboratory and field installations have not disclosed evidence of objectionable leakage. See Section IV, REINFORCEMENTS, for illustrated requirements at transversejoints, and Section lii, CLOSURES, for closure of longitudinal seams. Duct closures are available with different properties and application restrictions. For Class 1 duct systems as required by NFPA 90A and 90B, a closure system approved with the rating obtained by the board manufacturer must be used. If the duct system does not require conform ance to NFPA 90A and 908 then Section III, CLOSURE, should be followed. 4. Duct Support Hanger spacings listed in Schedule 5-1 on page 5-2 are coordinated with the other performance requirements of duct elements. Hangers shall be located so that not more than one transverse joint will occur between two consecutive hangers in a support system and as noted in Sec

SMACNA Fibrous Glass Duct Construction Standards 1-3tion V, HANGERS AND SUPPORTS. In coordinating hanger requirements with joint spacing and reinforcement spacing, hangers may be attached to channel or tee bar reinforcement members. When hangers are attached to these reinforcement members, the load carried by the hanger must be transmitted to the side and bottom reinforcement members. See Figure 5-1. Hangers must be placed so as to properly support all fittings and accessories without placing the taped joints under stress. Fibrous glass duct systems outlined in this Standard are not designed to support human traffic or external loads. 5. Vibration and Noise Vibration was not formally investigated. However, observation of systems during laboratory tests and certain field installations did not disclose evidence of objectionable vibration trans mission. Acoustical absorption characteristics are given on page 1-6. This data was provided by TIMA as being representative of the minimum performance of 475, 800 or 1400 El boards. 6. Thermal Conductivity See duct design reference data on page 1-6. 7. Air Friction Loss See duct design reference data on page 1-6. 8. Fire Protection Characteristics When ducts must conform to NFPA’s Standard 90A, non-metallic ducts are required to conform to the following requirements: A. They shall be constructed of Class 1 duct materials as tested in accordance with Section 4 through 21 of Underwriters’ Laboratories Standard for Factory-Made Duct Materials and Air Duct Connectors, UL-181. B. Such ducts shall be installed in accordance with the conditions of their approval by UL. C. They shall not be used in air duct systems which operate with an air temperature higher than 250°F entering the ducts. Under UL Standard 181 Class 1 air duct materials have a flame spread rating not exceeding 25 and a smoke developed rating not exceeding 50. Furthermore, the following portions of UL-181 are applicable to fibrous glass ducts and refer to the following tests: 1) Fire hazard classification 6) Static load 2) Flame penetration 7) Impact 3) Burning 8) Erosion 4) Temperature 9) Pressure and leakage 5) Puncture 10) Collapse 11) Corrosion, mold growth and humidity

SMACNA Fibrous Glass Duct Construction Standards 1-4

## COMPILATION OF FIBROUS GLASS DUCT CHARACTERISTICS AND LIMITATIONS 1. Flexural rigidity (El)

____....._._ Average in the board not less than rating of 475, 800 or 1400 lb-in. 2 per inch of width when tested in accordance with TIMA Test Method AHS-100-74. 2. Maximum static pressure in duct __2” water gage, positive or negative. 3. Maximum air velocity in duct

___ .___.2000 fpm. 4. Maximum allowable board deflection ___Transverse span 100 5. Maximum allowable stress in steel reinforcemenL ....._22,000 psi 6. Board fatigue ___.No significant deformation ordeficiency ofduct sec tion after25,000 cycles at 5 cpm from natural sag to span/I00deflection. 7. Moisture

__ Moisture absorption of the board will not exceed 2% by weight under conditions of 120°F db at 95% R.H. for 96 hours duration. 8. Temperature

— 250°F maximum inside the duct. 1 50°Fmaximumambientoutsidetheduct. 9. Corrosion Non-corrosive in contact with steel, copper or aluminum when compared to control specimen in contact with sterile cotton. 10. Closure_

—-------------_ Closure conforming to: Class 1 duct, UL Standard 181 installed as recommended by duct board manu facturer. or SMACNAPressureSensitiveTapeStandardAFTS 100-73. (Rev. 6/77) 11. Safety standards___ NFPA 90A, as applicable. 12. RESTRICTIONS—It is recommended that Fibrous Glass Duct Systems not be used in the following applications: A. Kitchen or fume exhaust ducts, or to convey solids or corrosive gases. B. In concrete or buried below grade. C. Outdoors. D. As casings and housings. Referto the SMACNA “Low Pressure Duct Construction Stahdards.” E. Immediately adjacent to high temperature heating coils. Refer to NFPA Standard 90A, Figure Number 2-24 and 2-25 herein and the SMACNA “Ducted Electric Heat Guide” for such appli cations. F. For vertical risers in air duct systems serving more than 2 stories. 13. MOUNTING—When mounting equipment, dampers, control motors, etc., the duct system shall be adequately reinforced and supported to accommodate the additional weight ofmaterial and equip ment without damage to the duct material.

SMACNA Fibrous Glass Duct Construction Standards 1-5

### DUCT DESIGN REFERENCE DATA
The following data prepared by TIMA may be used by designers in determining thermal conductivity, acoustical absorption and friction losses in fibrous glass duct systems. The data is applicable for any of the three classes of boards. For more precise data, consult the board manufacturer’s publications.
Thermal Conductivity—BTU/in-S.F.-F°Hr. Mean Temp. Difference Conductivity F° 50 75 100 k .22 .23 .25

Acoustical Absorption Coefficients

—Minimum

—Determined with test method ASTM C423-66. Frequency, Hertz 125 250 500 .13 .44 .63

Air Friction Correction Factor 2000 4000 .83 .76

VELOCITY—FPM Roughness (e): 0.003 ft.

Air Friction Correction Factor to be applied to ASHRAE Guide friction loss for straight galvanized metal ducts. Applies to duct sizes from 8” to 40” equivalent diameter with an accuracy of ±5%.

SMACNA Fibrous GLass Duct Construction Standards on No. 6 mounting in accordance

1000 .90

1.6

1.5

1 .4

1.3

1.2

1.1

1.0

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- 300 400 500 1000 1500 2000 5000

1-6

# SECTION II FABRICATION OF STRAIGHT DUCT AND FITTINGS FABRICATION OF STRAIGHT DUCT FABRICATION OF FITTINGS

SMACNA Fibrous Glass Duct Construction StandardsSMACNA Fibrous Glass Duct Construction Standards

# FABRICATION OF STRAIGHT DUCT FABRICATION TOOLS Automatic machinery and hand tools are both available for fabrication of ducts. The tools for the centerline method are the keys to making ducts of proper size and to the assurance of tightjoints and connections. Correct settings of the blade in each tool are highly important to accurate fabri cation. It is best to check the settings before work is started, because the blades may not be in proper position when tools arrive from the factory.

15/16”

# U
FIG. No. 2.1 Orange Tool (Modified Shiplap)*

FIG. No. 2.2 Red Tool (900 V-Groove)

FIG. No. 2-4 Gray Tool (Female Shiplap)

FIG. No. 2-5 Purple Tool (Male Shiplap)

SMACNA Fibrous Glass Duct Construction Standards Thesetools removeinsulation, allowing corner folds to be made in the duct board, much like 

## a sheet metal brake bends metal. *Right hand modified corner ship/np shown; for the lefthand cut, reverse tool.

This tool makes the rabbet cut on the end of the board forthe closing cornerjoint and cuts the insulation to be stripped from the facing to form a closure flap. (Normally used with V-groove method offabrication.)

This tool is used to cut the female slip-joint (shiplap) and the rabbet for seating the edge ofthe board atthe lateral closure corner (shiplapmethod).

This tool cuts a male slip-joint (shiplap) with out requiring the board to be turned over, It also separates the insulation from the facing to form a transverse closure flap. Other Tools and Materials 1. Measuring rule. 2: Large, sturdy, broad-blade knife. 3. Outward clinch type staple gun and supply of minimum 1/2” clinch staples (See page 3-9). 4. Supply of closure materials (See Section Ill, CLOSURES). FIG. No. 2-3 Blue Tool (End Cutoff)

2-3

## CENTERLINE METHOD OF FABRICATION
As its name implies, this method involves the use ofcenterline markings on the board along which the various tools are guided for accurate cutting. While other methods of fabrication are also utilized, the centerline method of fabrication employs the same principles utilized in the fabrication of sheet metal ductwork, namely: 1. Layout is done on the board prior to forming. 2. Measurements are made in succession from centerline markings. A section of straight duct may be fabricated from one, two or four pieces of fibrous glass board using two basic methods—the V-Groove method or the Shiplap Groove method. Factors which affect the contractors’ choice are: 1. The tools and equipment owned by the contractor and whether they are automatic or hand type. 2. Whether the ducts are shop fabricated or field fabricated. Page 2-7 illustrates commonly used assembly dimensions for the Shiplap Groove method. In it, closure flaps are shown on the butt edges. In contrast, the V-Groove method illustrated on page 2-9, shows the flaps on the rabbet edges. The flap may be placed on either edge in either method depending upon the fabrication tools used or the economical use of automatic fabricating equipment.



## LAYOUT

All measurements for the centerline method are keyed to the corner breaks and closures, the same as in sheet metal practice. All measurements are marked directly on the material before any fabri cation is started. In all cases, the inside dimension (LD.) ofthe duct is the determining factor. First, determine the size of the fibrous glass board required to make the specified duct. Refer to the board length selection chart, page 2-10. Total the inside duct dimensions and the “add-on” allowances shown on the following pages for 1-piece, 2-piece and 4-piece duct assemblies.

1. Using the inside dimension of the duct and the centerline “add-on” allowance, lay out the centerline for each panel and mark.

SMACNA Fibrous Glass Duct Construction Standards 2. Cut the corner grooves.

2-ti5. Fold to form the duct section, making sure the ends are flush and that the flush edge is properly seated in the shoulder of the rabbet groove. Layout 

# OBSOLETE

SMACNA Fibrous Glass Duct construction Standards 3. Cut the male and female slip-joints (ship- 4. Prepare the flap. See that virtually all the lap). (Make sure that the horizontal blade is insulation is scraped off. On the left edge of between the insulation and facing material so the board, cut the closure joint rabbet. that the flap is retained.)

6. Flaps should be stapled with 1/2” mini mum outward clinched staples approximately 4” O.C.

2-5

# STRAIGHT DUCT LONGITUDINAL SHJPLAP GROOVE METHOD The following descriptions pertain to the illustrations shown on page 2-7. I-Piece Duct Fibrous glass duct board can be made into any size duct with a total of the inside dimensions plus allowances not exceeding 120 in. The length of the duct section will be 48 in. (minus the shiplap) which is the standard width ofthe board. It is also possible to make a 1-piece duct 10 ft. long if the sum of the inside dimensions does not exceed 40 in. After the duct is assembled, the longitudinal seam is then sealed (See Section III, CLOSURES). 2-Piece “U” Duct When the dimensions of a duct (total of the width of the four sides plus the grooving allowances) are greater than the maximum length of a single piece of fibrous glass board, 2-piece duct con struction is necessary. This design requires a “U” section and a filler cap. The “U” section is made from 2 corner grooves and 2 end cut-offs. The filler piece is fabricated with flaps. The duct sectionisthenassembledandthetwolongitudinal seamsarethen sealed(See Section Ill, CLOSURES). 2-Piece “L” Duct 2 “L” shaped parts may be formed as indicated by the diagram and the assembly completed as explained for the 1-piece and the 2-piece duct sections. 4-Piece Duct This illustration shows how a duct section may be made from 4 pieces ofboard.

CUTTING Five basic cutting operations are involved with this method: 1. Knife cut at stretchout length. 2. Shiplap for folding corners. 3. Rabbet cut for closing corner. 4. Cutting and stripping away insulation to expose longitudinal staple flap. 5a. Female rabbet cuts for a transversejoint Shiplap connection between duct section. 5b. Male rabbet cut for a transversejoint connection between duct sections.

SMACNA Fibrous Glass Duct Construction StandardsCoC)z>‘10CcnC)C0CD0C00DCo0.0.

## STRAIGHT DUCT LONGITUDINAL V-GROOVE METHOD
The following description pertains to the illustration shown on page 2-9. 1-Piece Duct Fibrous glass duct board can be made into any size duct with a total of the inside dimensions plus allowances not exceeding 120 in. The length of the duct section will be 48 in. (minus the shiplap) which is the standard width of the board. It is also possible to make a 1-piece duct 10 ft. long if the sum of the inside dimensions does not exceed 40 in. After the duct is assembled, the longitudinal seam is then sealed (See Section III, CLOSURES). 2-Piece “U” Duct When the dimensions of a duct (total of the width of the four sides plus the grooving allowances) are greater than the maximum length of a single piece of fibrous glass board, 2-piece duct con struction is necessary. This design requires a “U” section and a filler cap. The “U” section is made from 2 corner grooves and 2 end cut-offs providing the necessary flaps. The filler piece is fabricated without flaps. The duct section is then assembled and the two longitudinal seams are then sealed (See Section Ill, CLOSURES). 2-Piece “L” Duct 2 “L” shaped parts may be formed as indicated by the diagram and the assembly completed as explained for the 1-piece and the 2-piece duct sections. 4-Piece Duct This illustration shows how a duct section may be made from 4 piecs of board.

CUT11NG Five basic cutting this method:

2. V-groove for folding corners. 3. Rabbet cut for closing corner. 4. Cutting and stripping away insulation to expose longitudinal staple flap. 5a. Female rabbet cuts for a transversejoint Shiplap connection between duct sections. 5b. Male rabbet cut for a transversejoint connection between duct sections.

SMACNA Fibrous Glass Duct Construction Standards operations are involved with

1. Knife cut at stretch-out length.

2-8

## 1-PIECE DUCT

2-PIECE “U” DUCT ADD-ON ALLOWANCES Using Longitudinal V-Groove Method

D+13⁄4” 

## 4-

2-PIECE ‘1” DUCT

SMACNA Fibrous Glass Duct Construction Standards 

## 4-PIECE DUCT D

‘3’

2-9

# BOARD LENGTH SELECTION CHART One-PieceDuctforusing 1-inch-thickboard* (Alldimensionsininches)
DEPTH WIDTH OF DUCT

OF DUCT 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 6 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 7 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 8 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 9 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 10 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84
11 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 12 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 13 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 14 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 15 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94
16 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 17 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 18 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 19 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 20 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104
21 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 22 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 23 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 24 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 112 25 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 112 114 26 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 112 114 116 27 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 112 114 116 118 28 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 112 114 116 118 120 29 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 112 114 116 118 120 30 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 112 114 116 118 120
31 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 112 114 116 118 120 32 .84 86 88 90 92 94 96 98 100 102 104 106 108 110 112 114 116 118 120 33 86 88 90 92 94 96 98 100 102 104 106 108 110 112 114 116 118 120 34 88 90 92 94 96 98 100 102 104 106 108 110 112 114 116 118 120 35 90 92 94 96 98100 102 104 106 108 110 112 114 116 118 120
36 92 94 96 98100 102 104 106 108 110 112 114 116 118 120 37 94 96 98 100 102 104 106 108 110 112 114 116 118 120 38 96 98 100 102 104 106 108 110 112 114 116 118 120 39 98 100 102 104 106 108 110 112 114 116 118 120 40 100 102 104 106 108 110 112 114 116 118 120
41 102 104 106 108 110 112 114 116 118 120 42 104 106 108 110 112 114 116 118 120 43 106 108 110 112 114 116 118 120 44 108 110 112 114 116 118 120 45 110 112 114 116 118 120 46 112 114 116 118 120 47 114 116 118 120 48 116 118 120 49 118 120 50 120 *Thjs chart includes a 1-3/8” width flap. For 1-1/2” flap add 1/8”

SMACNA Fibrous Glass Duct Construction Standards 9_in

## FABRICATION OF FITTINGS RECTANGULAR END CAP
FIGURE NUMBER 2-6 Refer to Section IV, REINFORCEMENT for the reinforcing required for specific duct sizes and static pressures. When fabricating end caps, the preferred method would be to cut the end cap, with flaps on all four sides to fit snuggly within the 7/8” recess of the female slip-joint. The end cap can then be pulled tightly into the recess and fastened into position. Ifthe duct requires reinforcement, use the same size member for reinforcing the end cap as shown in DETAIL “A.” Reinforcement member will be the same length as the longest duct dimension. Sheet metal screws shall be spaced not more than 16” apart nor more than 16” from the end of the reinforcement member. Alternate screws if a tee bar is used. All seams should be closed (by positioning flaps, stapling, taping, etc.) to conform to Section III, CLOSURES). LEGEND A Rectangular duct end with female shiplap (or slip-joint) B Channel or tee bar reinforcement C Sheet metal screws D 3” diameter or 2-1/2” square washer S Flap

SMACNA Fibrous Glass Duct Construction Standards 2-12SMACNA Fibrous Glass Duct Construction Standards

### DETAILA 

# RECTANGULAR END CAP

SMACNA FIBROUS DUCT STANDARD FIGURE No.2-6

SMACNA Fibrous Glass Duct Construction Standards 2-13

## VOLUME DAMPER CONNECTION
FIGURE NUMBER 2-7 Refer to Section IV, REINFORCEMENT, for the reinforcing required for the specific duct sizes and static pressures. Volume dampers should be assembled in a sheet metal sleeve approximately 6” longer than the damper blade width. Refer to SMACNA Low Pressure Standards. Extend sleeve a minimum of 12” from the damper shaft when using a damper operator mounting bracket (only applies to the side on which the operator is mounted). This sleeve assembly should be inserted approximately halfway in each duct section and fastened with sheet metal screws and washers 6” O.C. when no mounting bracket is used. Care should be exercised in the placement of these screws to prevent interference with the damper blade opera tion. When the mounting bracket is used, place sheet metal screws and washers 2” O.C. for each bracket tab and use 6” O.C. across length as indicated. Weight of damper and/or motor must be adequately supported by hangers. Refer to Section V, for hanger details. Iftransversejoint reinforcement is required, offset sleeve assembly to facilitate damper rod opera tion. All seams should be clOsed (by positioning flaps, stapling, taping, etc.) to conform to Section Ill, CLOSURES.
LEGEND A Hanger support B Sheet metal screws and 1-1/2” metal washers C Damper blades D Sheet metal sleeve—minimum gage as per SMACNA Low Pressure Standard duct gage E Slit for damper control rod M Sheet metal screws and 1-1/2” metal washers V Damper operator mounting bracket—minimum 6” wide and 2 gages heavier than sleeve W Damper operator

Reference: Low Pressure Duct Construction Standards, published by the Sheet Metal and Air Con ditioning Contractors’ National Association, Inc.

SMACNA Fibrous Glass Duct Construction Standards 2-14O z ‘1 0 C C ‘1 C rn z 0 0 1 C rn m(b) 0 z z m r) -l zU)>C) z‘10000CDCi,CC)C-)00CC)0Cl)a,D0.a,0.0900 

## ELBOW SHIPLAP GROOVE CONSTRUCTION
FIGURE NUMBER 2-8 Refer to Section IV, REINFORCEMENT for the reinforcing required for the specific duct sizes and static pressures. The following steps demonstrate procedures for fabricating an elbow from a straight duct section, which has been fabricated using the shiplap groove method. Figure 2-8A STEP 1: Dimension “Fl” is 1/2” less than dimension “EF” (outside duct dimension). STEP 2: Dimension “GH” is the same as dimension “Fl.” STEP 3: Draw a vertical line from point “I” to point “H.” STEP 4: Make a straight knife cut through the duct board along line “HI.” STEP 5: Make cuts through the facing only along the corners defined by lines “OH” and “Fl.”

Figure 2-8B STEP 6: Remove this section of panel “B.” Figure 2-8C STEP 7: Place removed section of panel “B” at the female end of the duct section, rotating the cut section so the female shiplap end fits along line “GF.” STEP 8: Insert turning vanes (where required). Fasten with screws and washers.

DETAIL 

# frEl!

# 11111111 If]fANE

Figure 2-8D STEP 9: Tape the removed section of panel “B” in the female end of the duct section. The open ing created by the removal of this section of panel “B” will receive the male end of any duct section of corresponding size. Figure 2-8E STEP 10: Insert this duct section and staple and tape in place as per Section III, CLOSURES. The elbow is completed.

SMACNA Fibrous Glass Duct Construction Standards 2-16z.aD0z.0’0UC o0LU00o..00-cU)QVD0LUCb4LUD0aC40 zLUD0U zIIUDD0U zUcJc1DC:4LUD0•0CC’,C00CCC0C.)00CCCCCDCC0.0U.C.)Cl)

## VANED SQUARE ELBOW V 

## or SHIPLAP GROOVE CONSTRUCTION
FIGURE NUMBER 2-9 Refer to Section IV, REINFORCEMENT for the reinforcing required for specific duct sizes and static pressures. Reinforcement members, if required, may be attached to top and bottom vane runners. The vaned square elbow is fabricated from a standard straight duct section. Lay out a cutting line of 45° on both sides of the width or depth of the duct as required and cut along the line with a knife for a buttjoint. When cutting the other sides of the duct the knife must be held at the 45° angle to obtain a bevelledjoint. After separating the sections and rotating one section 1800, insert turning vanes and runners halfway into one section as illustrated and securely fasten with sheet metal screws and washers 6” O.C. at top and bottom. Attach the other section in a similar manner with the vane runners acting as a splice plate tojoin the two sections together. If vanes are not required use a top and bottom splice plate. Refer to SMACNA Low Pressure Duct Standards for turning vane details, where required. All seams should be closed (by positioning flaps, stapling, taping, etc.) to conform to Section Ill, CLOSURES. LEGEND A Plated sheet metal screws B 1-1/2” metal washers C Turning vanes (where required) S Flap

Reference: Low Pressure Duct Construction Standards, published by the Sheet Metal and Air Con ditióning Contractors’ National Association, Inc.

SMACNA Fibrous Glass Duct Construction Standards 2-18

# VANED SQUARE ELBOW V or Shiplap Groove Construction



# SMACNA FIBROUS DUCT STANDARD FIGURE No. 2-9

SMACNA Fibrous Glass Duct Construction Standards 2-19

### TEE SECTION
FIGURE NUMBER 2-10 Refer to Section IV, REINFORCEMENT for the reinforcing required for specific duct sizes and static pressures. The following steps demonstrate procedures for fabricating a tee from a straight duct section which has been fabricated using the shiplap groove method. Figure 2-bA Dimension “EF” is 1/2” less than dimension “IJ” (outside dimension). Dimension “GH” is the same as dimension “EF.” Draw a vertical line from point “F” to point “H.” Make a straight knife cut through the duct board along line “FH.” Make cuts through the facing only along the corners defined by lines “GH” and “EF.” Repeat the steps on panel “D.”

STEP 7: Remove the cut sections of panels “B” and “0.” STEP 8: Splitter dampers and turning vanes may be installed in this step. LEGEND A Turning vanes B Sheet metal screws and 1-1/2” metal washers C Channel—minimum gage sheet metal, same as item “D” below D Sheet metal sleeve—minimum gage as per SMACNA Low Pressure Standard duct gage E Splitter damper blade and control STEP 9: Cut and install a single piece end cap at the female end of the duct section.

Figure 2-bC STEP 10: Tape the section in place in the female end of duct section. STEP 11: Staple and tape the branch outlets in place as per Section Ill. Tee is completed. Figure 2-IOD A branch outlet can be added into the heel ofthis tee with the following procedure. STEP 1: Dimension “EF” is 1” shorter than dimension “HI” (outside dimension). STEP 2: Dimension “DG” is the same as dimension “EF.” STEP 3: Draw vertical lines from point “E” to point “D” and point “F” to point “0.” STEP 4: Cut through the duct board along lines ‘EFGD” and remove the cut section. STEP 5: Staple and tape the branch outlet in place as per Section Ill.

SMACNA Fibrous Glass Duct Construction Standards STEP 1: STEP 2: STEP 3: STEP 4: STEP 5: STEP 6: Figure 2-lOB

2-20>C,z>‘1a.0C0C)000CC,C)0D0CCC0CCCCC00.00C0Crb,)-0‘10CmLflz-I,w0CLi,C(b)-I-Iz-I,Cmz00-ImmLi,-l0z

### BRANCH TAKE-OFF FIGURE NUMBER 211 Refer to Section IV, REINFORCEMENT for the reinforcing required for the specific duct sizes and static pressures. Reinforcing members, if required, may be attached to the top and bottom vane runners. The methods used to fabricate and assemble the branch take-off will vary depending on the duct sizes. Installation of the sheet metal accessories will be similar to Figure 2-10 with the exception of the sheet metal corner angle. This angle should be attached to the sheet metal channel and fastened to the fibrous glass duct board with sheet metal screws and washers 6” O.C. to reinforce the cornerjoint. (See also Figure 2-12F on page 2-27 for alternate branch take-off.) All seams should be closed by positioning flaps, stapling, taping, etc.) to conform to Section III, CLOSURES. LEGEND A Turning vane (where required) B Sheet metal screws and 1-1/2” metal washers C Channel—minimum gage sheet metal, same as item “D” below D Sheet metal sleeve—minimum gage as per SMACNA Low Pressure Standard duct gage E Splitter damper blade and control F Corner angle—minimum gage sheet metal, same as item “D” above S Flap

Reference: Low Pressure Duct Construction Standards, published by the Sheet Metal and Air Con ditioning Contractors’ National Association, Inc.

SMACNA Fibrous Glass Duct Construction Standards 2-22

# BRANCH TAKE-OFF

SMACNA FIBROUS DUCT STANDARD FIGURE No. 2-11

SMACNA Fibrous Glass Duct Construction Standards 2-23

### TRANSITION FABRICATION SHIPLAP GROOVE CONSTRUCTION
FIGURE NUMBER 2-12 (Cont.) Refer to Section IV, REINFORCEMENT for the reinforcing required for specific duct sizes and static pressures. The following steps demonstrate procedures for fabricating transitions from a straight duct sec tion which has been fabricated using the shiplap groove method. When a transition is used in a “diverging” air flow and the duct size increased, the sides are to be pitched to a maximum of 200 to prevent turbulence or additional increase of static pressure. When a transition is used in a “contracting” air flow and the duct size is decreased, the sides should be pitched to a maximum of 30° to prevent turbulence or additional increase of static pressure. Figure 2-12A STEP 1: The desired location ofthe branch outlet will determine the location ofthe first transition cut, line “EF.” Make this determination and draw line “EF.” STEP 2: Make a straight knife cut through the glass and facing along line “EF.” STEP 3: Make cuts through the facing only along the corners defined by “EH” and “FG.” Figure 2-12B STEP 4: STEP 5: STEP 6: Remove this section of panel “B.” Point “I” is located 4” from point “F.” The distance from point “G” to point “J” is determined by subtracting the inside duct dimension ofthe small duct from the inside dimension of the large duct. Draw line “JI.” Figure 2-12C STEP 7: Make a straight knife cut through glass only along “JI” leaving the facing for a flap. STEP 8: Repeat steps 5 through 7 on panel “A.” Figure 2-12D STEP 9: Using a 7/8” gray tool make a female shiplap groove along line “JI” on panel “C”. Re peat on panel “A.” STEP 10: Lines “MN” and “KL” on panel “B” are the same length as line “JI.” Draw line “NL.” STEP 11: Make a straight knife cut 1/2” deep in glass only along line “NL.” This will allow panel “B” to bend along the angle created by lines “JI” and “IF.”

See page 2-26 and 2-27 for final steps and figures for shiplap groove construction of transition.

SMACNA Fibrous Glass Duct Construc.tion Standards 2-24

# TRANSITION Shiplap Groove Construction



## FIGURE 2-12B

D RGURE 2-12C

FIGURE

# 2-12D
SMACNA FIBROUS DUCT STANDARD FIGURE No. 2-12

SMACNA Fibrous Glass Duct Construction Standards 

## (Cont.) FIGURE 

## 2-12A

2-25

### TRANSITION FABRICATION SHIPLAP GROOVE CONSTRUCTION FIGURE NUMBER 2-12 Figure 2-12E STEP 12: Insert the panel “B” section and staple and tape it in place as per Section III. Figure 2-12F STEP 13: Dimensions “FO” and “EP” are one inch larger than the inside dimension of the branch outlet. STEP 14: Draw the line “OP’ and then make a straight knife cut through the glass and facing along line ‘OP.” STEP 15: Make a cut through the facing only along corner lines “EP” and “FO.” STEP 16: Remove this cut panel section. Figure 2-12G STEP 17: Insert the branch outlet and staple and tape in place as per Section III. Figure 2-12H STEP 18: Repeat all the steps above for the second taper on panel “D.” NOTE: Optional use of a take-off splitter may be inserted after step 16. Use DETAIL “A” on page 2-16 and DETAIL “1” indicated here.



### OPTIONAL

DETAIL “1”

SMACNA Fibrous Glass Duct Construction Standards 2-26

# TRANSITION Shiplcip Groove Construction



## FIGURE 2-12E



## RGURE2-12G

RGURE

# 2-12H

SMACNA FIBROUS DUCT STANDARD FIGURE No. 2-12

SMACNA Fibrous Glass Duct Construction Standards 

## P

FIGURE 

## 2-12F

2-27

### ONE-WAY TRANSITION (FLAT) SHIPLAP GROOVE CONSTRUCTION
FIGURE NUMBER 2-13 Refer to Section IV, REINFORCEMENT for the reinforcing required for specific duct sizes and static pressures. The following steps demonstrate procedures for fabrication of one-way transition (flat) using shiplap construction methods. When a transition is used in a “diverging” air flow and the duct size increased, the sides are to be pitched to a maximum of 200 to prevent turbulence or additional increase of static pressure. When a transition is used in a “contracting” air flow and the duct size is decreased, the sides should be pitched to a maximum 30° to preventturbulence or additional increase of static pressure. Figure 2-13A STEP I: Groove the same way as for a straight section of duct. Duct size is determined by the largest size duct to bejoined in the transition (for example: to transition from a 12” x 6” to an 8”x 6”, fabricatea 12” x 6” duct section). Figure 2-13B STEP 2: To create the desired transition further cuts must be made on the fabricated straight section. Lines “FG” and “HI” are the new cut lines. To locate points “F” and “H” subtract the smaller duct from the larger duct. Using the example 12”x6” to 8”x6” the subtraction is 12”—8” = 4”. Points “F” and “H” are thus 4” from points “E” and “J.” STEP 3: Draw the lines “FG” and “HI” on panels “A” and “C” ofthe straight duct section. Figure 2-13C STEP 4: Make a straight knife cut through the glass and facing along lines “FG” and “HI.” STEP 5: Point “K” is 1-1/2” from point “L.” From point “K” draw a line parallel to line “LM” and cut through the glass and facing. STEP 6: Remove the ‘KLM” strip of glass. Figure 2-13D STEP 7: Use a gray tool (female shiplap) along edges “FG” and “HI.” Figure 2-13E and F STEP 8: Form the transition duct and staple and tape panel “D” in place as per Section III.

SMACNA Fibrous Glass Duct Construction Standards 2-28C M ‘3 -TI C*)

C) z > ‘1 C 0 C C) C0 C) C C C)0 0 C C 0 U) 0 0. 0 0. 0 C b3 id ‘3 m 0 C m id ‘3

z -n 0 C C -I z -I, 0 C m z 0 ‘3 0 z m Cl) I V 0
C) C 0> fl

I —

LI 0 -TI I —I

## ONE-WAY TRANSITION V-GROOVE CONSTRUCTION
FIGURE NUMBER 2-14 Refer to Section IV, REINFORCEMENT for the reinforcing required for specific duct sizes and static pressures. The following demonstrates the fabrication of a one-way transition using the “v” groove construc tion method. When a transition is used in a “diverging” air flow and the duct size increased, the sides are to be pitched to a maximum of 20° to prevent turbulence or additional increase of static pressure. When a transition is used in a “contracting” air flow and the duct size is decreased, the sides should be pitched to a maximum of 300 to prevent turbulence or additional increase of static pressure. Refer to SMACNA Low Pressure Duct Standards for information on “Tapers-Offsets.” All seams should be closed (by positioning flaps, stapling, taping, etc.) to conform to Section Ill, CLOSURES. LEGEND

A Width of duct plus 1-3/4” allowance for V-Grooves B Height of duct (large end) plus 1-3/4” grooving and joining allowance C Height of duct (small end) plus 1-3/4” grooving and joining allowance D Cut-off(BminusC) E Width of duct plus 1”, plus 2-3/4” for flaps S Flap

Reference: Low Pressure Duct Construction Standards, published by the Sheet Metal and Air Con ditioning Contractors’ National Association, Inc.

SMACNA Fibrous Glass Duct Construction Standards 2-30C,,C,z>-U0•0C0c-C000CCC)C,00CC)0C,,0000.0zm00CDoU,-ICC,0I—I0z

### TWO-WAY TRANSITIONS (FLAT) SHIPLAP CONSTRUCTION FIGURE NUMBER 2-15 Refer to Section IV, REINFORCEMENT for the reinforcing required for specific duct sizes and static pressures. The following steps demonstrate procedures for fabrication of two-way transitions (flat) using shiplap construction methods. When a transition is used in a “diverging” air flow and the duct size increased, the sides are to be pitched to a maximum of 200 to prevent turbulence or additional increase of static pressure. When a transition is used in a “contracting” air flow and the duct size is decreased, the sides should be pitched to a maximum 3Q0 to prevent turbulence or additional increase of static pressure. Figure 2-15A STEP 1: Groove the same way as for a straight section of duct. Duct size is determined by the largest size duct to be joined in the transition (for example: to transition from a 14” x 6” to a 12” x 8” fabricate a 14” x 8” duct section). STEP 2: To create the desired transitions further cuts must be made on the fabricated straight section. Beginning at points “E” and “L” measure in on panels “A” and “C” the amount the first dimension is to be reduced. (Using the example above 14”

— 12” = 2”.) Points “F” and “K” are thus 2” from points “E” and “L.” STEP 3: Draw the lines “FG” and “KM” on panels “A” and “C.” STEP 4: Repeat step 2 above to locate the second dimension reduction (8”—6” = 2”) for points “H” and “0” on panels “B” and “D.” STEP 5: Draw lines “HJ” and “OP’ on panels “B” and “D.” Figure 2-15B STEP 6: Make a straight knife cut through the glass and facing along lines “FG” and “KM.” STEP 7: Make a straight knife cut through the glass only along lines ‘HJ” and “OP.” Do not cut through facing. Clean glass offthe triangular areas “HIJ” and “NOP.” Figure 2-15C STEP 8: With gray hand tool cut female shiplap along lines “FG” and “KM.” STEP 9: Cut through facing along line “QR.” Figure 2-1SD STEP 10: Turn panels over and re-establish correct distance (3/8”) between panels “B,” “C,” and “D.” Fold staple flaps down. Staple and tape as per Section III. Figure 2-15E STEP 11: Close into duct and staple and tape as per Section Ill. (Dotted lines show dimensions prior to reduction transitions.)

SMACNA Fibrous Glass Duct Construction Standards 2-32U, 0 z ‘1 0 C 0, C)0,0,0, C) C 0 C) 00, C 0 0 D U,0, Q. 0, 0. a,

## THREE-WAY TRANSITION
FIGURE NUMBER 2-16 Refer to Section IV, REINFORCEMENT for the reinforcing required for specific duct sizes and static pressures. When a transition is used in a “diverging” air flow and the duct size increased, the sides are to be pitched to a maximum of 200 to preventturbulence or additional increase of static pressure. When a transition is used in a “contracting” air flow and the duct size is decreased, the sides should be pitched to a maximum of 30° to prevent turbulence or additional increase of static pressure. Refer to SMACNA Low Pressure Duct Standards for information on “Tapers-Offsets.” All seams should be closed (by positioning flaps, stapling, taping, etc.) to conform to Section III. LEGEND A Width of duct (large end) pIus 1-3/4” joining allowance B Width of duct (small end) plus 1-3/4” joining allowance C Cut-off (A minus B dimension) D Height of duct (small end) pIus 1”joining allowance E Height of duct (large end) plus 1” joining allowance S Flap

Reference: Low Pressure Duct Construction Standards, published by the Sheet Metal and Air Con ditioning Contractors’ National Association, Inc.

SMACNA Fibrous Glass Duct Construction Standards 2-34U.,Az-TI0CU..CA-Iz-lmm-Izz/—Cl,>0zT10CC)DCC,C)0CC)0U,CC.mCI•)Qm-n0Cmz0t%)0-U

## ONE-WAY OFFSET (300) 

## SHIPLAP GROOVE CONSTRUCTION FIGURE NUMBER 2-17 Refer to Section IV, REINFORCEMENT for the reinforcing required for specific duct sizes and static pressures. To fabricate a one-way offset begin with a complete section of duct which has been fabricated using the shiplap groove method. Figure 2-17A STEP 1: Measure distance from end ofduct that offset must begin “AB.” STEP 2: Calculate length of offset section. EXAMPLE: for 12” offset the length will be 12”x2 = 24” STEP 3: Measure length ofoffset section “BC.” STEP 4: Strike a 15° angle from the 900 line “BD.” Mark point ‘E.” NOTE: “BH” is 90° to “AB” and = Figure 2-17B STEPS: Make a knife cut at a 15° angle through glass and facing along lines “BEH” and “CGI” on all sides of duct. Figure 2-17C STEP 6: Reverse the center section. Tape heels first as shown. Figure 2-170 STEP 7: Close duct and complete taping on all sides, as per Section III. Other angles may be used for offsets. This case was used for an illustration and any change in angle requires a different multiplier to determine the length of the offset section (Step 2 above). EXAMPLE: 45° offset requires multiplier of 1.414 in Step 2 and a 22-1/2° angIe in Step 4.

SMACNA Fibrous Glass Duct Construction Standards 2-36

## ONE-WAY OFFSET (300)



## HShiplop Groove Construction



## RGURE2-17A

# OBSOLETE

fiGURE 2-17B

FIGURE 2-17C FIGURE 

## 2-17D

SMACNA FIBROUS DUCT STANDARD FIGURE No. 2-17

SMACNA Fibrous Glass Duct Construction Standards 

## A

2-37

### REGISTER AND GRILLE CONNECTION FIGURE NUMBER 2-18 Refer to Section IV, REINFORCEMENT for the reinforcing required for the specific duct sizes and static pressures. Figure 2-ISA Grilles and registers may be installed on a sheet metal sleeve attached to the fibrous glass duct as shown in Sections A-A and alternate. When a sheet metal sleeve is used a reinforcing sheet metal plate may be installed inside the duct which should extend 3” past the opening on all sides where possible. This plate will allow the clinch lock or dove tail to rest against metal to facilitate bending or clinching. Section A-A illustrates the use of collar lock construction and Alternate Section A-A illustrates use of sheet metal angle clips in lieu ofthe collar lock. An airextractor and volume damper are installed to obtain even distribution of air on the grille or register face and air adjustment. Figure 2-18B The use of a fibrous glass duct tap may be used with an air extractor and volume damper similar to Figure 2-18A. Section B-B illustrates the use of adjustable volume dampers integral with the outlet. Ifthe volume damper is separate from the outlet, provide a sheet metal sleeve (see item C). All seams should be closed (by positioning flaps, stapling, taping, etc.) to conform to Section III, CLOSURES. Hangers and supports should follow Section V. LEGEND A Sheet metal bearing plate—minimum gage as per SMACNA Low Pressure Standard duct gage B Adjustable volume damper C Sheet metal sleeve—minimum gage, same as item A above D Supply register or grille E Air extractor F Sheet metal clip angles—minimum gage, same as item A above G Plaster frame (see register and grille manufacturer) S Flap T Tape

Reference: Low Pressure Duct Construction Standards, published by the Sheet Metal and Air Con ditioning Contractors’ National Association, Inc.

SMACNA Fibrous Glass Duct Construction Standards 2-38

# REGISTER AND GRILLE CONNECTION

• SMACNA FIBROUS DUCT STANDARD FIGURE No. 2-18

SMACNA Fibrous Glass Duct Construction Standards 

### AIR FLOW 

### FIGURE 2-18A

FIGURE 2-18B

2-39

## DIFFUSER CONNECTION (ROUND) FIGURE NUMBER 2-19 The diffuser should be connected to the fibrous glass duct using a dove-tailed stub or collar and a minimum offour sheet metal angle clips. The collar or stub is supported by a bearing plate inside the duct which should be approximately two (2) times the diameter ofthe opening. It may be necessary to install a hanger or hangers under the duct and bearing plate to support the additional weight ofthe diffuser. Refer to Figure 5-1 for hanger details. To install the diffuser in the correct position, an extension to the stub or collar may be required. LEGEND A Plated sheet metal screws B Hangers C Bearing plate—minimum 22 gage sheet metal D Sheet metal collar or stub—minimum gage as per SMACNA Low Pressure Standard duct gage E Sheet metal duct or sleeve as required to position diffuser (not required if the diffuser is supported independently from the duct system.) F Diffuser G Clips for attaching duct to collar H 1-1/2” metal washer I Fibrous glass collar S Flap

Reference; Low Pressure Duct Construction Standards, published by the Sheet Metal and Air Con ditioning Contractors’ National Association, Inc.

SMACNA Fibrous Glass Duct Construction Standards 2-40

# DIFFUSER CONNECTION ROUND



# SMACNA FIBROUS DUCT STANDARD FIGURE No. 2-19

SMACNA Fibrous Glass Duct Construction Standards 

### DETAIL A

2-41

### DIFFUSER CONNECTION (RECTANGULAR OR SQUARE) FIGURE NUMBER 2-20 The diffuser is connected to the fibrous glass duct using a collar or stub mounted in the bottom. A sheet metal duct or sleeve is connected with screws to the tabs of the collar. Tabs on the collar mounted in the bottom of the duct should be a minimum 3” long. Fasten fibrous glass duct collar to sheet metal duct or sleeve with screws and washers. Length of drop will depend on ceiling construction and diffuser location. It may be necessary to install a hanger or hangers under the duct and bearing plate to support the additional weight ofthe diffuser. Refer to Figure 5-1 for hanger details. LEGEND A Plated sheet metal screw B Hangers C Bearing plate—minimum 22 gage sheet metal D Sheet metal collaror stub—minimum gage as per SMACNA Low Pressure Standard duct gage E Sheet metal duct or sleeve as required to position diffuser (not required if the diffuser is supported independently from the duct system) F Fibrous glass duct collar G Diffuser H 1-1/2” metal washer S Flap

Reference: Low Pressure Duct Construction Standards, published by the Sheet Metal and Air Con ditioning Contractors’ National Association, Inc.

SMACNA Fibrous Glass Duct Construction Standards 2-42

# DIFFUSER CONNECTION RECTANGULAR OR SQUARE

DETAIL “A”



# SMACNA FIBROUS DUCT STANDARD

SMACNA Fibrous Glass Duct Construction Standards 

# FIGURE No. 2-20

2-43

## ACCESS DOORS TYPE-A FIGURE NUMBER 2-21
Refer to SMACNA Low Pressure Duct Standard for additional door details. The installation of access doors in fibrous glass ducts will require a sheet metal reinforcing plate for support which should extend approximately 3” past all sides of the opening. This plate should be securely fastened to the external frame of the access door with sheet metal screws 6” O.C. A door panel fabricated from a section of fibrous glass board enclosed by a metal channel frame may be used in lieu of a metal door panel.

SMACNA Fibrous Glass Duct Construction Standards 2-44

# ACCESS DOORS Type A

STEEL BUTT HINGES



# / SASHLOCKS

or hinges

SHEET METAL REINFORCING PLATE WINDOW TYPE SASHLOCK



# SMACNA FIBROUS DUCT STANDARD FIGURE No. 2-21

SMACNA Fibrous Glass Duct Construction Standards



### REINFORCING PLA SHEET METAL CHANNEL FRAME

WINDOW TYPE SASHLOCK

SECTION A-A ALTERNATE DOOR PANEL

2-45

### ACCESS DOORS TYPE-B FIGURE NUMBER 2-22 Refer to SMACNA Low Pressure Duct Standard for additional door details. The installation ofAccess Doors in Fibrous Glass Ducts will require a sheet metal reinforcing plate for support which should extend approximately 3” past all sides of the opening. This plate should be securely fastened to the sheet metal channel frame (See DETAIL “A”) with sheet metal screws 6” O.C. A door panel fabricated from a section offibrous glass board enclosed by a metal channel frame may be used in lieu of a metal door panel.

Reference: Low Pressure Duct Construction Standards, published by the Sheet Metal and Air Con ditioning Contractors’ National Association, Inc.

SMACNA Fibrous Glass Duct Construction Standards 2-46

### DETAIL ‘IA”



### METAL REINFORCING PLATE ALTERNATE DOORPANEL


# SMACNA FIBROUS DUCT STANDARD FIGURE No. 2-22

SMACNA Fibrous Glass Duct Construction Standards 

# ACCESS DOORS TYPE B;EE DETAIL “A”

SHEETMETAL BOTH SIDES INSULATED DOOR WINDOW TYPE SASH HANDLE

CHANNELFRAME

SEEDETAIL“A” SCREWS

SECTION A-A

2-47

## FIRE DAMPER CONNECTION FIGURE NUMBER 2-23 Consult the SMACNA Fire Damper Guide for details governing the construction of fire dampers and placement offire dampers in walls. LEGEND A Metal sleeve for fire dampers should extend approximately 3” past each side of the wall to facilitate attachment ofduct sections. B Angles attached to sleeve but not to wall. These are used on 4 sides of the duct and they must lap the wall 1 inch minimum. C Sheet metal screw and 1-1/2” minimum diameter washer. Use at least one per duct side, spaced at intervals not more than 16 inches. D Tape closure—to seal joint between duct and sleeve E Access door. See Figures 2-21 and 2-22 F Fire damper

SMACNA Fibrous Glass Duct Construction Standards 2-48

# FIRE DAMPERCONNECTION

CLOSURE DETAIL



# SMACNA FIBROUS DUCT STANDARD FiGURE No. 2-23

SMACNA Fibrous Glass Duct Construction Standards 

# I

Minimum Lap

2-49

### FLANGED ELECTRIC HEATER INSTALLATION
FIGURE NUMBER 2-24 Figure 2-24 illustrates the mounting of a flanged electric heater in fibrous glass duct. The proper selection and the placement of electric heaters depends upon many factors. Refer to the SMACNA Ducted Electric Heat Guide for information on the application, selection, location, installation and control of ducted electric heaters. Hangers should be installed at the sleeves to support the added weight of the heater. Refer to Figure 5-1 for hanger details. To prevent condensation, the terminal box, E, as well as the heater frame should be insulated. However, insulation must nofbe placed on the exterior ofthe terminal box. After completing assembly ofthe heater, sleeves and duct sections, closures subject to air leakage must be sealed. (See Section Ill, CLOSURES) LEGEND A Electric heater B Metal sleeve, minimum thickness 18 gage, galvanized sheet metal C 6” minimum (refer to area codes and municipal ordinances for additional specific local re quirements) D Insulation on exterior of heater frame E Terminal box factory insulated on panel with heating element penetrations. F 2” diameter (minimum) washers with sheet metal screws. Fasten board to sleeve B at inter vals not exceeding 16”. G Hanger

SMACNA Fibrous Glass Duct Construction Standards 2-50

# FLANGED ELECTRIC HEATERINSTALLATION

SMACNA FIBROUS DUCT STANDARD

SMACNA Fibrous Glass Duct Construction Standards 

# FIGURE No. 

# 2-24

2-51

### SLIP-IN ELECTRIC HEATER INSTALLATION FIGURE NUMBER 2-25 Figure 2-25 illustrates the placement of a slip-in electric heater in fibrous flass duct. The proper selection and the placement of electric heaters depends upon many factors. Refer to the SMACNA Ducted Electric Heat Guide for information on the application, selection, location, installation, and control of ducted electric heaters. Hangers should be installed at the sleeve to support the added weight of the heater. Refer to Figure 5-1 for hanger details. To prevent condensation, the terminal box, E, should be ordered with internal insulation. Insula tion must not be placed on the exterior ofthe terminal box. After completing assembly of the heater, sleeve and duct section, closures subject to air leakage must be sealed. (See Section lii, CLOSURES.) LEGEND

A Electric Heater B Metal Sleeve C 6” Minimum (Refer to area codes and municipal ordinances for additional specific local re quirements.) D Hanger E Terminal Box

SMACNA Fibrous Glass Duct Construction Standards 2-52

# SLIP-IN ELECTRIC HEATER INSTALLATION

SMACNA FIBROUS,DUCT STANDARD

SMACNA Fibrous Glass Duct Construction Standards 

# FIGURE No. 2-25

2-53

## EQUIPMENT CONNECTION DETAILS FIGURE NUMBER 2-26 Figure 2-26 illustrates the different equipment connection details for fibrous glass duct. Each detail is a combination of fibrous glass duct with sheet metal clips, screws, washers and tape. Equipment determines which detail or details are to be applied for the fabrication of connec tions. Flanges or collars on equipment vary; therefore, select the detail which best meets the requirements. All seams should be closed as per Section Ill, CLOSURES. Refer to Section V, HANGERS AND SUPPORTS, for specific details. LEGEND A Plated sheet metal screw B 1-1/2” metal washer C Formed pocket clip with button punch snap lock—minimum 22 gage D 3”xl” formed sheet metal angle—minimum 22 gage E Formed sheet metal “5” slip—minimum 22 gage F 3” long sheet metal clip—minimum 22 gage T Tape

SMACNA Fibrous Glass Duct Construction Standardsci’ >C,•1ci.0C0 C.’000,CC) C-)00CC)0CC)0, a0’0.0,

### TEN-SIDED DUCT

FIGURE 2-27


### Approximately round in shape, this configuration is a suitable substitute for round duct.

SMACNA Fibrous Glass Duct Construction Standards 2-56Ten-sidedductcan befabricatedfrom ductboard using a grooving machine with adjustable gang tooling. Grooving knives are adjusted using a gauge for propersetting.

SMACNA Fibrous G)ass Duct Construction Standards FABRICATION OFTEN-SIDED DUCT

.5, ‘S

S.

- FIGURE2-28

2-57Ten-sided ducts can be fabricated in sections up to 1O’-O” long.

Where material require ments exceed board width, a staple flap joint with staple fasteners is used.

.SMACNA Fibrous Glass Duct Construction Standards FIGURE 2-29

FIGURE 2-30

2-5R

### Board Utilization The following table showstheoptions available fabricator should always check material made in converting standard duct board sizes into on hisparticularmachinefordimensionalaccu duct. The table is based on ideal tool settings. racy before producing large quantities ofduct. Because ofvariation in blade settings, tool bar Thefabricatorshouldalsoselectthebestcombi height and in the size of sheet metal fittings nation of duct board length versus drop-off which might be used with tensided-duct, the factors which fit his particular application.

Duct Board Utilization Chart Using 4’O” Wide Board
Nom. Stretchout, In. 10Ft. Long Ducts 4 Ft. Long Ducts 4Ft. Long Ducts Full Half(1) l.D. Made From 10 Ft. Board Made From8 Ft. Board Section Section No. of Material Dropoff No. of Material Drop off, No. of Material Drop off, Inches 10 Sides 5 Sides Sect. Left, In. S.F. Sect. Left, In. S.F. Sect. Left, In. S.F.

5 23-1/2 12-1/4 2 1 0.8 5 2-1/2 0.8 4 2 0.7 6 26-5/8 13-7/8 1-1/2 7-1/2 6.3 4 13-1/2 4.5 31/2 2-1/4 0.8 7 29-3/4 15-3/8 1-1/2 2-7/8 2.4 4 1 0.3 3 6-3/4 2.3 8 32-7/8 17 1 15-1/8 12.6 3-1/2 4-3/8 1.5 2-1/2 13-1/4 4.4 9 36 18-1/2 1 12 10.0 3 12 4.0 2-1/2 5-1/2 1.8 10 39-1/8 20-1/8 1 8-7/8 7.4 3 2-5/8 0.9 2 17-3/4 5.9 11 42-1/4 21-5/8 1 5-3/4 4.8 2-1/2 13-7/8 4.6 2 11-1/2 3.8 12 45-3/8 23-1/4 1 2-5/8 2.2 2-1/2 6 2.0 2 5-1/4 1.8 13 48-1/2 24-3/4 1/2 23-1/4 19.4 2 23 7.7 1-1/2 22-3/4 7.6 14 51-5/8 26-3/8 1/2 21-5/8 18.0 2 16-3/4 5.6 1-1/2 18 6.0 15 54-3/4 27-7/8 1/2 201/8* 16.8 2 10-1/2 3.5 1-1/2 13-3/8 4.5 16 57-7/8 29-1/2 1/2 18-1/2 15.4 2 4-1/4 1.4 1-1/2 8-5/8 2.9

* Denotes Useable Material Note: (1) Half Section—5 sides with stapling flap. When Class 1, UL 181 requirements are con Joining 2 halfsections requires 2 longitudi- sidered, the Manufacturers UL Listing and In naljoints struction Sheetmustbe consultedforlimitations.



### Examples: 1. 5” nominal l.D. Ten-sided Duct can be made from 10’ long duct board in 2 ways, both with minimum drop off, 20 LF of Duct in 10 ft. lengthsrequiresonlyonecircumferentialjoint. 2. In making 4 ft. long 7” nom. l.D. Ten-sided Duct, 10ft. ductboardwillyield4sectionswith essentially no drop off; 8 ft. duct board yield 3 sectionswith2.3 S.F. ofscrap.

SMACNA Fibrous Glass Duct Construction Standards 2-59

### 2-60 SMACNA Fibrous Glass Duct Construction Standards 

# : 

# : :

—•

FIGURE 2-31 FIGURE 2-33

FIGURE 2-34 Circumferentialjoints are formed using appro priatetools. Male andfemaleendscanbefabri cated while the material is in the flat or after the ten-sided duct has been formed. These joints are made with shiplap and stapleflaps or with internal metal sleeves. Return air duct must bejoined using internal metal sleeve. Referto Section VI

— Premolded Round Ductfor procedures for fabricating fittings from ten-sided duct. FIGURE 2-32INSTALLATION OF TEN-SIDED DUCT
HANGING Ten-sided fibrous glass duct should be hung so that the hanger will not damage the duct facing. Straps or saddles 

### in contact with the duct should be a minimum of2” wide. Sharp edges and burrs should be avoided. Hangers should be spaced on maximum 6’-O” centers. Where practical hanger should be located at a ductjoint.

SMACNA Fibrous Glass Duct Construction Standards 

# —H -4——2” minimum —). [4 2” minimum FIGURE 2-35 FIGURE 2-36



### ROD OR WIRE 12 gage minimum



# —H [4—2” minimum FIGURE 2-37

2-61SMACNA Fibrous Glass Duct Construction Standards

# SECTION III CLOSURES

SMACNA Fibrous Glass Duct Construction Standards

## CLOSURES GENERAL Closure systems are a vital element in the proper assembly offibrous glass duct systems. Avarietyof closure systems has been offered within the industry. Included are: 1. Pressure sensitive tapes 2. Heat activated tapes 3. Mastic and glass fabric tape 4. Contact adhesive (under flaps on duct) 5. Formed and extruded mechanical closures 6. Combinations ofthe above With the publication ofthe third edition ofthe SMACNAFibrous Glass Duct Standards in April 1 972, SMACNA resolved to expedite development of general standards for closures. However, present knowledge and technology does not permit the writing ofa single standard which would adequately govern all types of closure systems. Since pressure sensitive tape is the most widely used closure system, the standardization effort was begun with this method. Performance Standard AFTS-100-73 (Rev. 6/77) and Application Standard AFTS-1O1-73 (Rev. 6/77), for pressure sensitive tape in conjunction with fibrous glass duct board, are incorporated in this manual of standards. Compliance with these is considered mandatory when pressure sen sitivetapes are used as a closure method. Most codes andprojectspecificationsrequirethatnonmetallicductconstructionconformto NFPA-90A or NFPA-90B or UL 181, Class 1 requirements. Under present UL-iBi listing procedures, the composite duct assembly is rated. Thus, closure techniques are not transferable from one board manufacturerto another. When C/ass 1, UL-181 construction isrequired, the closure systemhaving an approvedlisting with theparticularfibrousglass ductproductmustbe usedin accordance withthe listing andthe recommendations ofthe boardmanufacturer. Closure systems other than pressure sensitive tapes have achieved Class 1, UL-181 listing. Further more, although tapes compliant with the SMACNA Pressure Sensitive Tape Standards will have a fire hazard rating (Flame spread and smoke development) that coincides with that in the current UL-181 (and in ASTM E-84), compliance with AFTS-100-73 (Rev. 6/77 does not signify compliance with UL-181. However, tapes compliant with SMACNA standards have also been included in systems which obtained Class 1 listing, but SMACNA does notguarantee thattheywill do so. In acknowledging the variables discussed herein itisthe intentofthesefibrous glass duct standardsto require that closures comply with the following stipulations: 1. When Class 1, UL-1 81 construction is required (by specification external tothese standards) any closure system compliant therewith may be used unless a pressure sensitive tape closure is selected, in which case the tape closure shall fulfillthe additional requirementofcomplyingwith the SMACNA Pressure Sensitive Tape Standards AFTS-100-73 (Rev. 6/77) and AFTS-1O1- 73 (Rev. 6/77). 2. When Class 1, UL-1 81 construction is not required, careful consideration shouldbe givento any deviation from the listed closures. Such deviation should consider: (a) compliance with paragraph 1 above, or (b) a pressure sensitive tape closure compliant with SMACNA AFTS-1 00-73 (Rev. 6/77) and AFTS-101-73 (Rev. 6/77). (c) a closure system which will be capable of demonstrating compliance with the general performance criteria outlined in Section I, PERFORMANCE CRITERIA OF BOARD, of the Fibrous Glass Duct Construction Standards

. . . to an extent equivalent to that afforded by compliance with the SMACNA Pressure Sensitive Tape Standards. The burden ofproofshall rest with the sponsor of such alternative method.

SMACNA Fibrous Glass Duct Construction StandardsAlthough SMACNA will continue to develop and improve requirements for closure systems, and it desires to receive knowledge of new products and methods, SMACNA does not approve proprietary products and cannot attempt to investigate every closure system appearing in the market place. Until such time as complete and all-encompassing performance standards are developed for closure systems, contracting parties will have to judge proposed methods in consideration of existing standards and supplemental requirements in project specifications. The development of closure standards must, 

### in the final analysis, be considered a refinement process.

SMACNA Fibrous Glass Duct Construction Standards 3-3

## PRESSURE SENSITIVE TAPES FOR FIBROUS GLASS DUCTS A. PERFORMANCE STANDARD AFTS-100-73 (REV. 6/77)
1.0 CLASSIFICATION 1 .1 The material and performance requirements in this Specification are applicable for pressure sensitive tape closures for fibrous glass air ducts asdescribed in SMACNA’sFibrous Glass Duct Construction Standards, 5th Edition, 1 979 

### 2.0 MATERIAL REQUIREMENTS 2.1 Material: Thetape shall consistofan aluminum foil coated on one sidewith apressure sensitive adhesivewith orwithouta liner. The minimum nominal widthofthetape shall be 21/2”; 

### minimum width shall be 1/32’? less than nominal. 

### 2.2 Facing: Facing shall be mill finish, dead soft aluminum foil. This facing shall be imprinted in repeated intervals not exceeding 36”, to permit

### permanentidentificationof(afterinstallation): (a) the name of the manufacturer and SMACNA, (b) date of manufacture in month and year, 

### and (c) manufacturers product number. Any imprinting which fades, rubs off, or for any 

### reason is rendered unreadable, by normal application procedures and conditions, thereby destroying the permanent identification ofthe tape will be deemed 

### in non-conformance with 

### this specification. 2.3 Adhesive: The surface on one side ofthe aluminum foil shall be completely coveredwith a non

### toxic adhesive. There shall be no separation ofthe adhesivefromthebacking upon unwinding of the roll, nor shall the adhesive transferto the liner when a liner is involved. 2.4 Rolls: Tape shall be evenly and uniformlywound on 3” l.D. cores. Cores shall be sufficiently rigid to preventdistortion oftherollundernormal conditions oftransportation and use. Tapebacking shall be freefromwrinkles andfromgaps between linerandadhesive. Thelengthoftheroll shallbe60yardsor multiplesthereof,withatoleranceof—2’ 0”,unlessotherwisespecified. 3.0 REQUIRED PERFORMANCE CHARACTERISTICS 3.1 Tapes shall have minimum performancecharacteristics stated herein. The determination ofsuch characteristics and properties shall be made in accordance with procedures described in this Standard. 3.2 TensIle Strength: The cross directiontensilestrengthofthetapeshall average25 lbs. orgreater per inch ofwidth when tested in accordance with PSTC-31, Tensile Strength and Elongation. 3.3 Fire Hazard Classification: When tested in accordance with ASTM Standard E84, the tape in conjunction withfibrousglassductboardshallhaveaflamespreadrating notexceeding 25 and
a smoke developed rating not exceeding 50. 3.4 ShearAdhesion: The tape shall sustainthe loads indicated in Table 3-2 herein fora period of6 

### hours, withoutfailure, when tested in accordance with PSTC-7, ShearAdhesion. 3.5 Peel Adhesion at 180°: Thetape shall have a minimum average of60 ounces peel adhesion per inch widthwhentestedin accordance with PSTC-1 with a 15 minutedwell time. Dwelltime shall 

### be defined in Table 3-2. PSTC Appendages A, B, C and D apply in PSTC-1. 3.6 Results: To be deemed to be compliant with this Standard, all tests in Table 3-1 must be conducted using material from the samethree roll lot. Testsfortensile strength, shear adhesion, peel adhesion andfire hazard musthavethe required ratings onthree rollsfromthetapelot,with the number of specimens per roll selected in accordance with Table 3-1. Furthermore, the following conditions shall govern: 36.1 Alltest methods are intendedto producetestvaluesfor a single roll. Referencesto average values in Table 3-1 refer to averaging of measurements on a single roll and not to an average ofall sample rolls.

SMACNA Fibrous Giass Duct Construction Standards3.6.2 To rule out the possibility of error in test procedures, ifthe testresults ofany roll do not conform to the requirements prescribed in the Standard, the original three rolls shall be discarded and three additional rolls shall be selected and tested. Iftest results of any one additional sample roll does notconformtorequirements, thetape maybedeemedtobe noncompliant. 4.0 TEST PROCEDURES 4.1 A complete series oftests mustbe conducted from rolls in the “as received” condition. A second series oftests must be conducted for all properties exceptfire hazard in accordance with section 4.2.1. Testperformed inordertodeterminecompliancewiththeperformance requirements ofthis standard must be certified by an approved independent laboratory. 4.2 Testprocedures are outlined in Part3 andTables 3-1 and 3-2. Referenceto PSTCtests shall mean tests listed in “TestMethodsforPressure SensitiveTapes,” 6th Edition, publishedbythe Pressure Sensitive Tape Council, 1201 Waukegan Road, Glenview, Illinois 60025. References to ASTM Tests shall mean designated standardprocedurespublishedbytheAmerican SocietyforTestingof Materials, 1916 Race Street, Philadelphia, Pa. 19103. 4.2.1. Thetape in standard roll form is to be placed inan atmosphereof66° C and 80% R.H. fora seven dayperiod. Then allowedtoconditiontwentyfourhours at23° C and50% R.H. Using a 4.5 pound roller, perform all tests in Tables 3-1 and 3-2 with the exception ofthe fire hazard test. Tapemustcontinuetopass SMACNA Performance StandardAFTS-100-73 asrevised.
4.3 Laboratory reports must contain but not be limited to: (A) Accurate identification ofthe tape product. (B) Listing ofthe test methods. (C) Quantitative test results as indicated in Table 3-1. (D) Test dates. 5.0 COMPLIANCE 5.1 Information on independent test laboratories and on detailed procedures for ascertaining com pliance is available from SMACNA, 8224 Old Courthouse Road, Vienna, Va. 22180. 5.2 Routine quality control procedures shall include selection, testing and retention of an adequate number of sample rolls from production runs. Retained samples and test data shall be made available for confirmation of compliance if compliance is challenged by a party having a vested concern. Additional tests may be conducted as arranged by the parties concerned. 5.3 Quality Control records must be retained for an indefinite period and sample tape rolls must be kept for a period ofthree years.

SMACNA Fibrous Glass Duct Construction Standards 3-5

### TABLE 3-1—-SPECIMEN SELECTION (See 4.2-1)

Measured 1 PSTC-31 3 ASTM-E84 1 Shear Adhesion See Table 3-2 Low Temperature Short Term Long Term High Temperature Peel Adhesion Results Reported Roll Minimum

1” Average value for each roll Roll Actual

1” Testduration per specimen 1” Testduration perspecimen 1” Testduration perspecimen 1” Test duration per specimen 1” Average for each roll and value for each specimen

1. All tests listed in Table 3-1 shall be conducted on material taken from the same 3 roll lot. 2. Ifcompliance ratings arechallenged, fortestsperformedtoconfirm compliance, anaverageof5 specimens perroll shall be used wherever one or three are specified. See Parts 3, 4 and 5. 3. Roll down must be performed using a 4.5 pound roller.


### TABLE 3-2—SHEAR ADHESION TESTS (See 4.2-1)

PSTC Application Tests Conditions Dwell Test Time Conditions Test Test Load Duration

1. All specimens are selected perTable 3-1. 2. Exceptas modified herein, all specimens shall bepreparedinaccordancewith PSTCTestMethodsforPressureSensitive Tapes, 6th Edition. AppendageA (Standard Conditions). Appendage B (TestEquipment). AppendageC (CleaningTest Surfaces) and Test Methods 7, 9 and 11 as referenced. 3. Conditions listedat7340F, 50% Ri-I. shallbecontrolledwithintolerancelimits listedinAppendageA,i.e. ±3.6° Fand ±2% R.H. 4. Dwell time is the time thatthe test specimen is in contactwith thetestpanel, afterrolling, priorto application ofthetest load. 5. Tapeandtestpanelsshallbemaintainedatapplicationconditionsaminimumofonehourpriortoapplyingtapetothetest panel. 6. Referto Parts 3.0 and 4.0 for evaluation oftest results. 7. RoIl down must be performed using a 4.5 pound roller.

SMACNA Fibrous Glass Duct Construction Standards Test Width Tensile Strength Fire Hazard Class Basic Test Compliance Tests Specimen Method Specimen/Roll Width

3 3 3 3 3 PSTC-1

NOTES

Specific Test Low Temperature 11,7 40°F, Dry Panel 15 Mm. 40°F 5 lbs. 6 hrs. Short Term 7 73.4°F, 50%RH 15 Mm. 73.4°F, 50%RH 5 lbs. 6 hrs Long Term 7 73.4°F, 50%RH 24 Hrs. 73.4°F, 

### 50% RH 10 lbs. 6 hrs. High Temperature 9,7 73.4°F, 50% RH 15 Mm. 150°F 1 lb. 6 hrs.
NOTES

3-6

### B. APPLICATION STANDARD AFTS-1O1-73 (REV. 6/77) 1.0 SCOPE 1 .1 Requirements herein are applicable forpressure sensitive aluminum (dead soft) foil backed tapes used in closure systems outlined in Section II, FABRICATION OF STRAIGHTDUCTAND FITTINGS. Section II is applicable for fabrication and assembly of air duct systems in which the air velocity does not exceed 2000 feet per minute and the static pressure does not exceed 2” water gage, positive or negative. See Part 6.4.3 for service temperature limitations. 1.2 Closure systems utilizing pressure sensitivetapes shall conform to SMACNATAPE STANDARDS. Compliance with SMACNA Tape Standards does not constitute compliance with UL 181, C/ass 1 construction. Several types ofclosure systems can comply with UL 181, Class 1 requirements. When the duct system mustcomply withNFPA 90A and/orUL 181, the closuresystemidentified by the boardmanufacturer for thatpurpose mustbe used. 2.0 PROCUREMENT 2.1 Provisions for procurement of tapes complying with the SMACNA Pressure Sensitive Tape Standards for Fibrous Glass Duct should include the following stipulations: 2.1 .1 Tape shall complywith SMACNA Performance StandardAFTS-100-73. (Rev. 6/77) 2.1 .2 Tape shall be pressure sensitive type with mill finish, dead soft aluminum foil backing. 2.1 .3 Tape backing shall be imprinted in repeat intervals not exceeding 36’ to permitidentifica tion of (after installation): a) Thename ofthemanufacturerandSMACNA b) The date ofmanufactureinmonth andyear cLManufacturers ProductNumber 2.1 .4 Ifcontract documents require compliance with UL 181. Class 1 ductconstruction, purchase conditions should so state. See Part 1.2. 2.1 .5 Shipping cartons shall give manufacturer’s name, tape width, roll length, number of rolls per carton and date of manufacture by month and year. In addition, recommended storage conditions and maximum service conditions (1 50°F) shall appear on tape cartons. 2.1 .6 A specification data sheet completely describing the product and confirming compliance with Standard AFTS-100-73 (Rev. 6/77), as determined by independent laboratory tests, should be required. The data sheet should also contain information on service limitations, shelflife and recommendedstorage conditions. 2.1 .7 Tapes shall be packed in a mannerthat prevents adhesion between adjacent rolls. (Specify other packaging requirements desired.) 2.1 .8 If you have not previously used the particular tape on the particular board contemplated, consult a representative of the board manufacturer regarding compatibility of tape and board. 3.0 STORAGE 3.1 Shelf life of pressure sensitive tape is limited and is influenced by storage conditions. The tape should be stored in original cartons under moderate and dry warehouse conditions in which the atmospherictemperature is not less than 50° nor more than 85°F. Forbestresultstapeshouldbe used within 1 year from date of manufacture. If the tape is stored under controlled conditions above, the tape may be expected to remain functional for two years. 3.2 Store tape in original cartons and out ofdirect sunlight. 3.3 Observe recommended storage conditions published by the manufacturer and printed on tape containers. 3.4 If tape is stored at temperatures above 85°F for a period exceeding 30 days, unsatisfactory adhesive performance may result. 3.5 Iftape is stored attemperaturesbelow50°F, itmustbereconditioned priorto use byplacement in awarm environment (approximately 70°F) for a period not less than 12 hours.

SMACNA Fibrous Glass Duct Construction 5tandards 3-7

### 4.0 INSPECTION OF DELIVERY 4.1 Confirm that the tape complies with the requirements of the purchase order and SMACNA Performance Standard. See ProcurementConditions. Inquire astodateoflastcompliancetestifin doubt. 

### 4.2 Check quantity, roll size, and packaging. 4.3 Examine a sample roll. 4.3.1 Tapes shall be evenly and uniformly wound on 3” l.D. core. 4.3.2 The roll should not have gaps between the adhesive and the foil or between the adhesive and the inner liner. 4.3.3 For unlined tapes the roll should not be distorted; however, lined rolls may show some distortion due to line slippage and shipping. 4.3.4 Tape ends shall be securely tabbed. 4.3.5 Wrinkles should not be present in the backing. 4.3.6 Tapes should be completely and uniformly covered with adhesive. 4.3.7 Unrolling should not result intransferofadhesive. On linedrolls removal ofthe line should not result in transfer of adhesive. 4.4 A specification data sheet signifying compliance with applicable standards should be available upon request.

SMACNA Fibrous Glass Duct Construction Standards 3-85.0 SURFACE PREPARATION 5.1 In order to obtain satisfactory adhesion and bonding, the surface on which tape will be applied must be clean and dry. Dust, dirt, oil, grease, fingerprints, moisture and similar substances may result in adhesion and bonding failure when present. For best results, prior to applying thetape, the application surface should be wiped clean and dry with safe solvent and oil free, lint free rags or paper towels. Iftape is stored attemperatures below 50°, itmustbereconditioned priorto useorplacementin a warm environment (approximately 70°F) for a period not less than 12 hours. 5.2 To prevent entrapment of ice crystals which adversely influence bonding, duct surfaces mustbe 50°F or highertemperature when tape is to be applied to them. 5.3 Condensation on duct surfaces may occurwhen ductsections orductboardmaterials arebrought from a cold environment into a warmer environment. When such conditions exist, special provisions mustbe madeto insurethatrroistureis notpresentontheductsurfacewhentapes are applied. 5.4 Surfaces should be as free from wrinkles or other projections as practicable. 6.0 INSTALLATION 6.1 Preparejoint, seam or other closure arrangements for ducts to conform to Section II, FABRICA TION OF STRAIGHT DUCT AND FITTINGS.

Flaps should be stapled with 1/2”minimum outward clinched staples approximately 4” O.C. FIGURE NUMBER 3-1

6.2 Prepare duct surfaces as required by Part 5.0 6.3 Removetapefrom roll, discard linerifpresent, aligntapecarefullywith seams andjoints, pulltaut and press in place, taking careto avoidwrinkles andfolds. Use asoftmaterialtoapplypressureto the backingto smooththetape surface and makeitconformtovalleys andindentationsintheduct surface. 6.4 Precautions: 6.4.1 Prevent adhesive surface of tape from coming in contact with foreign matter prior to installing the tape.

SMACNA Fibrous Glass Duct Construction Standards 3-96.4.2 Avoid exposing adhesive surface to dust laden atmospheric conditions before applying. 6.4.3 Tapes in conformancewiththis documentare notratedforapplicationonducts inwhichthe internal air temperature exceeds 250°F and the external environmental temperature exceeds 150°F. 6.4.4 To avoid accidents and falls, due to its slippery nature, tape liner should be discarded immediately into a proper container. 6.4.5 Tapes appliedbelow 50°F shall be installed incompliancewith Parts 5.1, 5.2 and7.0 ofthis Standard, and also comply with tape manufacturers installation requirements. 6.5 Tape must lap 1” minimum on adjacent surfaces to be sealed. Referto Section Il, FABRICATION OF STRAIGHT DUCT AND FITTINGS for arrangement of flaps. At ajoining of a metal duct to a fibrous glass duct the tape must lap the metal duct at least 3/4” and the fibrous glass duct 1 Ends of tape onjoints and seams should lap one tape width, minimum. The minimum width to accommodate these requirements is 2-1/2”.

Tape with SMACNA Pressure Sensitive Tape complying to AFTS-100-73 (Rev. 6/77) or the appropriate UL-181 Class 1 air duct closure system recommended by the board manufacturer. FIGURE NUMBER 3-2

6.6 Tapes of greater width can be selected. However, the user may at his option use two or more wraps of 2-1/2” tape with at least 3/4” lap oftape layers, to satisfy closure requirements. 6.7 Pressuretests ofassembled ducts should not be conducted within 24 hours ofinstallation oftape closures. (Field test pressures of 150% of rated negative or positive pressure may be requiredby certain contracts.) 7.0 LOW TEMPERATURE INSTALLATION PROCEDURE (RECOMMENDED FOR TEMPERATURES BELOW 50°F) 7.1 Equipment 7.1 .1 Heat Source: standard household iron or any commercial sealing iron able to hold a sole plate temperature of400°F. 7.1 .2 “Squeegee” type straight edge application tool.

SMACNA Fibrous G’ass Duct Construction Standards 

# b

3-10

### 7.3 Procedure 7.3.1 Observe all requirements and precautions indicated in SMACNA AFTS-1O1-73 (Rev. 6/77) Section 5.0 and 6.0. 7.3.2 Set the sealing i’ron for a temperature of 400°F. ±25°F. and allow to preheat for five minutes. (Note: A household iron set on “linen” or “high” will achieve the desired temperature.) 7.2.3 Pass the iron once over the bond area to achieve initial working tack. 7.2.4 Quickly position the tape on the pre-heated area. 7.2.5 Pass the iron two orthree times over the taped area using a rapid “ironing” motion. 7.2.6 Complete the bond by rubbing the tape vigorously with the “squeegee” applicator. 

### 7.3 Precautions 7.3.1 Do not use a sealing iron with a plate temperature above 500°F. or below 300°F. 7.3.2 Apply sufficient heatto leavethebondarea warmtothetouchforapproximately one minute after the heat source is removed. 7.3.3 Do notoverheatthe taped area! Excessive heat appliedto the foil face stock may result in a rupture ofthe adhesive anchorage tothefoil. Thiswill resultin a lessening ofultimatebond strength. 7.3.4 Accurate control of the temperature of the heat source is absolutely critical. Use no heat source which cannot be temperature controlled (i.e., torch or heat gun.)

SMAcNA Fibrous Glass Duct Construction Standards

11SMACNA Fibrous Glass Duct Construction Standards

# SECTION IV REINFORCEMENT

SMACNA Fibrous Glass Duct Construction StandardsSMACNA Fibrous Glass Duct Construction Standards

## REINFORCEMENT This section deals with the reinforcement ofthe duct to maintain conformance to deflection limits. A limitation of one one-hundredth (1/100) of the span is used as the criteria for duct board de flection. The proportional elastic limit stress of the material is the basis for this criteria. Using this criteria, reinforcement designs were calculated, fabricated, tested and modified as necessary to restrain the duct within the limits of span divided by 100. Reinforcements are based on these investigations and schedules are provided for determining size and placement of reinforcement members. This section is divided into two parts, one using formed channel or tee bars and the other a new method using tie-rods. The first part is provided with a reinforcement schedule using formed channels or tee bars. Based on duct size, static pressure and board type, reinforcement members are spaced and given sizes and gages. Three types of reinforcement are described; the channel, tee made from angles and the formed tee. Each is identi fied in the schedule. Also included are procedures and devices to prevent the board from sagging due to its own weight; however, this would apply only to ducts over 60” wide. Positive and nega give pressure duct requires retaining clips as shown in Figure 4-2. Drawings show typical rein forcement members on 16, 24 and 48 inches on center. The second part of this reinforcement section illustrates a new method of reinforcement using a tie-rod system. This is an alternate method to sheet metal channels or tee bars for positive pre sure fibrous glass duct systems. The tie-rod reinforcement system described is another method of limiting the deflection of duct systems and thereby eliminating excessive stress on both the duct board and closures. For purposes of clarification, tie-rod systems are defined as a galvanized wire 12 gage or heavier with washers. All the performance characteristics and limitations found in the previous section are found in this alternate for positive pressure systems. A schedule ofreinforcement was developed similar to the channel or tee bar based on testing and field evaluation. This schedule gives spacing of wires depending on static pressure in the duct, duct size, and board type. Examples of typical selections are given to aid in the use of the sched ule. Ducts over 60” require a special center anti-sag device which consists of a 1/2” diameter sup port conduit with washers on the inside and outside of the duct. Figures 4-6 and 4-7 illustrate the basic tie-rod system and anti-sag details and placement of wires. Each duct dimension should be treated individually using the reinforcement schedule. It is important to remember that the tie-rod system is an alternate reinforcementforpositive pressure systems only.

SMACNA Fibrous Glass Duct Construction Standards

## REINFORCEMENTWITH CHANNEL AND TEE BARS REINFORCEMENTS IN TABLE 4-1 1. Reinforcement in Table 4-1 is designed for installation on the side of a duct of the dimension listed. Although the reinforcement size in Table 4-1 is designed for the particular side of the duct on which it is applied, due to installation economics, a single size of reinforcement, based on the maximum duct dimension, can be used around the entire perimeter of the duct. Further more, the contractor may establish a shop standard as a condensed version of Table 4-i which results in the use offewer sizes ofgages of reinforcement members AS LONG AS EACH MIN IMUM SPECIFICATION OF SIZE, GAGE AND SPACING LISTED IN TABLE 4-1 IS SATISFIED. See Examples 1, 2 and 3. EXAMPLE NO. 1: Duct Size 40” x 30” @ 1/2” Static Pressure

EXAMPLE NO. 2: I 475EI 800E1 1400EI 24” sp., 22 gage-i” 48” sp., 22 gage-i” None None None None



## 475 El 30

Duct Size 48” x 26” @ 1” sp. 475 El 1400 El

EXAMPLE NO. 3: Duct Size 72” x 48” @ 2” sp. 475 El 800 El 1400 El 16” sp., 18 gage-i” 16” sp., 18 gage-i” 24” sp., 18 gage-i-1/4” 16”sp., 22 gage-i” 24”sp., 22gage-1-i/4” 24”sp., 22 gage-i” 16” sp., 18 gage-i” 16” sp., 18 gage-i” 24” sp., 18 gage-i-i/4”
2. Size and spacing of tee and channel shaped reinforcement are identical for positive and nega tive pressure application. 3. See Figure 4-i on page 4-7 for illustrations ofreinforcing members. 4. See Figure 4-2 on page 4-8 for supplementary fasteners required on all negative pressure applications. 5. See Note A on page 4-8 for supplementary fasteners required on positive pressure duct greater than 60” in width. 6. Transverse and longitudinal joints shall be sealed with a continuous closure system (See Sec tion Ill, CLOSURES) and reinforcement shall be positioned at joints as shown in Figure 4-2 on Page 4-8. 800 El 48” side 24” sp., 22 gage-i” 24” sp., 22 gage-i” 48” sp., 22 gage-i-i/4” 26” side 24” sp., 22 gage-i” 48” sp., 22 gage-I” None Use wrap of 24” sp., 22 gage-i” 24” sp., 22 gage-i” 48” sp., 22 gage-i-i/4”

SMACNA Fibrous Glass Duct Construction StandardsTABLE 4-1

— CHANNEL AND TEE BAR SYSTEM SCHEDULE OF REINFORCEMENT FOR 1” THICK BOARD RECTANGULAR FIBROUS GLASS AIR DUCTS 2000 F.P.M. MAXIMUM VELOCITY

1. Size of reinforcement is listed by height dimension. All widths are 3” 2. Gage listed is Manufacturers Standard Gage. 3. Tees made from angles may be used in lieu offormed tees. 4. See additional notes on page 4-4.

SMACNA Fibrous Glass Duct Construction Standards 475 El BOARD REINFORCEMENT 800 El BOARD REINFORCEMENT 1400 El BOARD REINFORCEMENT

NOTREQUIRED NOTREQUIRED

NOTES:

4-5

## REINFORCEMENTTYPES FIGURE NUMBER 4-1 1. Any one of the three types of reinforcements may be used. The corners of the wrap must be formed from continuous members or securely fastened by bolts, rivets, screws, staples or welds. 2. Spot welds must be good quality, of arrangement shown here, and must be Continuous across the member. Staples, rivets, bolts or self-tapping screws may be used as fasteners.

SMACNA Fibrous Glass Duct Construction Standards 4-6

### CHANNEL

TEE From Angles

TEE Formed 

# REINFORCEMENT TYPES

NOTE 1

NOTE



# SMACNA FIBROUS DUCT STANDARD FIGURE No. 4-1

SMACNA Fibrous Glass Duct Construction Standards 

### OR Typical See Note 2

‘/4” 

### SEE NOTE 2 OR

‘/“

### Typical See Note 2
NOTE 1



### SECTION A-A

4-7

## TRANSVERSE JOINTS—SHIPLAP TYPE FIGURE NUMBER 4-2

DETAILA POSITIVE PRESSURE APPLICATION Reinforcement over loint preferred or not more than 2” off loint over the female cut. DETAIL B NEGATIVE PRESSUREAPPLICATION Reinforcement at folnt.

CAUTION: The shiplap arrangement shown in the details above must be observed. Failure to do so will result in system failures. 1. Reinforcement when required by Table 4-1. Tees and channel are interchangeable for use with either positive or negative pressure systems. 2. Facing—on board with female lap. 3. Tape—See Section III, CLOSURES. The closure material should be centered overthe edge offlap. 4. Facing—on board with male connection. This must be lapped over the facing on the female lap and stapled. 5. Staple—with outward clinch type stapler, placed along the joint as required. (See Section Ill, CLOSURES.) 6. 2”x6”x20 gage galvanized sheet metal clip—(see detail page 4-9)—REQUIRED ON NEGATIVE PRESSURE DUCTS which require reinforcement. They are spaced not more than 16” apart nor more than 16” from the longitudinal edge of a duct side. See Table 4-2, below for minimum quantity for duct size range. Spacing should always be from longitudinal center line ofduct.
TABLE 4-2
Transverse Dimension Minimum Number ofclips or washers Per Reinforcing Member 16”-32” 1 33”-48” 2 49”-64” 3 65”-80” 4 61”-96” 5 7. Plated sheet metal screws—#lOxl-1/2”. Two are required for this type of clip. Screw heads may be inside the duct. NOTES: A. In order to control natural sag, supply ducts over 60” in width must have the board fastened to the top member of the transverse reinforcement at mid span. The attachment may be a sheet metal screw which penetrates the reinforcement, the board and a retaining washer (see Figure 4-3 through 4-5, DETAIL “A”) on the inside,face ofthe board or other suitable method. B. Ducts with negative pressures shall have retaining clips atjoints as shown in Figure above. C. All clips or washers must have turned edges to prevent cutting into duct surface.

SMACNA Fibrous Glass Duct Construc.tion Standards 4-Fl

# TYPICAL REINFORCEMENTON48”CENTERS WITH48”JOINTSPACING

Fastening required attop center of ducts over 60” wide only. 48” along longitudinal center line ofdud.

SUPPLY DUCT Positive Pressure

CLIP DETAIL

RETURN DUCT Negative Pressure

correct 

### posilion

Diameter or 2W’ Square Washer (Alternateplacementof

### dip saews acrossthewidthofdud) 

### Section atDuctJoints (RETURN DUCT) At negative pressure joints only per spacing schedule in Table4-2. See Figure 4-2. up



### es 2-Holes for No. 10 S.M. Screws 2”x6x20 

### ga.clip

wrong position wrong position



# SMACNA FIBROUS DUCT STANDARD FIGURE No.4-3

SMACNA Fibrous Glass Duct Construction Standards 4-9

# TYPICAL REINFORCEMENTON24”CENTERS WITH48”JOINTSPACING

correct posihon



### 3” Diameter or 2Y ” Square Washer (Alternateplacemento clip saews acrossthewidthofdud) 

### At negative pressure joints only per spacing schedule in Table4-2. See Figure

### 4.2. — I



### ofdud. Fastening required at top center of ducts over 

### 60” wide oniy. 48” along longitudinal center line

SUPPLY DUCT Positive Pressure 

# © 

# LZ
Diameter or

—

### 2W’ Square Washer

See spacing schedule in Table 4.2 

### zz HANNEL 

### OR TEE

RETURN DUCT Negative Pressure

wrgrig 

### position

Section 

### atDuctJoints (RETURN DUCT)


# SMACNA FIBROUS DUCT STANDARD FIGURE No.4-4

SMACNA Fibrous Glass Duct Construction Standards 

### 4-10

### Diameter or 2Y ” Square Washer See spacing schedule in Table 4-2



### wr91g position 

# TYPICALREINFORCEMENTON 16”CENTERS WITH48”JOINTSPACING

/3” Diameter or 21/2 

### Square Washer (Alternateplacementofdip sa’ews acrossthewidth ofduct) At negative pressure loints only per spacing schedule in Table4-2. See Figure 4-2. 

# SMACNA FIBROUS DUCT STANDARD

SMACNA Fibrous Glass Duct Construction Standards 

# FIGURE No.4-5 Fastening required attop center of ducts over 60” wide only. 48” along longitudinal center line ofduct.
SUPPLY DUCT Positive Pressure

RETURN DUCT Negative Pressure

correct position 

# 0 

# 1

Section atDuctJoints(RETURN DUCT)

4-1 14-12 SMACNA Fibrous Glass Duct Construction Standards

# OBSOLETE

REINFORCEMENT WITH TIE-ROD SYSTEM (ONLY FOR USE WITH POSITIVE PRESSURE) 1. TESTING This system of reinforcement was tested for deflection, fatigue and leakage and the methods used and described in Section I, PERFORMANCE CRITERIA OF BOARD were followed. All the requirements for air ducts established for the previous positive pressure systems were met by the alternate tie-rod system. Deflection—Maximum deflections of ducts under positive pressure with this reinforcing sys tem are less than 1/100 of the span, thus keeping stress in the duct board below the propor tional elastic limit as required by the performance characteristics. Fatigue—Ducts were constructed utilizing the tie-rod reinforcement system as described here in. Observations before and after 25,000 pressure cycles showed no significant structural changes to either the duct material or the reinforcing assembly. Leakage—Different combinations of tie-rod reinforcement were tested for static pressure of 2” w.g. Each section consisted of a 59”x6-1/2”x12 foot long fibrous glass duct with sealed ends and with wires spaced on 16”, 24”, or 48” centers. Leakage was determined for each spacing arrangement and the measured leakage was within accepted limits. 2. DUCTS OVER 60” Large duct spans experience natural sag due to the weight of the duct board when not pres surized. To prevent this, anti-sag assemblies should be installed on duct spans over 60”. The anti-sag assembly consists of 4 washers, wire and a piece of support conduit, and should be located in relation to the shiplap joint, as shown in Figure 4-6. These do not replace reinforce ments required at that point but are additional. Note that these supports must be installed before duct sections arejoined. 

### 3. LOCATIONS OFREINFORCEMENTS (SeeTable4-3) The following schedule and Figure 4-6 show the proper location and frequency of reinforce ment in relation to duct span, system static pressure, and board type.

SMACNA Fibrous Glass Duct Construction Standards

## REINFORCEMENT IN TABLE 4-3 1. Reinforcement in Table 4-3 is designed for installation on any side of a duct of the dimension listed. Each side will be reinforced as per Table 4-3 and spacing shown will be for 16”, 24”, or 48” in the longitudinal direction with a maximum 16” spacing across the duct span. The fol lowing examples will illustrate Table 4-3.

EXAMPLE NO. 1: Duct 37” x 24” @ 1/2” static pressure 475 El 800 El 1400 El

EXAMPLE NO. 3; Duct 75” x 50” @ 2” static pressure 475 El 800 El

2. See Figure 4-6 on page 4-16 for details oftransversejoint. 3. See Figure 4-7 on page 4-17 for typical layout ofreinforcements. 4. Referto item 2on page4-13, forductswith span over60’ ac. Across 1g. = Longitudinal 1400 El 37” side 2 ac. & 24” 1g. 2 ac. & 48” 1g. None 24” side None None None EXAMPLE NO. 2: Duct 50” x 27” @ 1” static pressure 475 El 800 El 1400 El 50” side 3 ac. & 24” 1g. 3 ac. & 24” 1g. 3 ac. & 24” 1g. 27” side 1 ac. & 24” 1g. 1 ac. & 48” 1g. None

75” side 4 ac. & 16” 1g. 4 ac. & 16” 1g. 4 ac. & 24” 1g. 50” side 3 ac. & 16” Pg. 3 ac. & 24” 1g. 3 ac. & 24” 1g.

SMACNA Fibrous Glass Duct Construction Standards

### Economic Comparison ofthe 1992 and 1995 Model Energy Codes 5/16/96

Introduction Section 109 ofthe NationalAffordable Housing Act, as amended by theEnergy Policy Act of 1992, requires HUD to set energy efficiency standards forpublic and assistedhousing. These standards are requiredto “...meetthe requirements ofCABO ModelEnergy Code, 1992, or, in the case of multifamily highrises, the requirements ofASHRAE Standard 90.1-1989.” Furthermore, HTJD is requiredmeettherequirements ofrevisions ofthe Model Energy Code (MEC) and Standard 90.1-1989 “...unless the secretaries determine that compliance with such revised code or standard wouldnotresult in a significantincreasein energy efficiency orwould notbe technologically feasible oreconomically justified.” This proposal is to determine whetherthe 1995 MEC5, and, formultifamily high rises, the recent Addendato 90.1-1989, will increase energy efficiency and aretechnologically feasible oreconomically justified. An economic analysis comparingthe requirements ofthe Council ofAmerican Building Official’s (CABO) 1992 and 1995 Editions ofthe ModelEnergy Code (MEC) and ofrecentAddenda to Standard 90.1-1989 will be conducted and areportwill beproduced. The main emphasis will be on theMEC, Standard 90.1-1989 willbe briefly addressed. Two additional, relatedproposals are included: A proposal for ataskto update HUD training 

### materials forthe 1992 MEC andproduce a video foruse on 1{UD’s satellite network, and Aproposal for ataskto customize MECcheck

### compliance materials forthe 1995 Edition of the MEC foruse in HUD’s loan guaranteeprogram. Background TheMEC is revised on an annual basis. Code changeproposals ofany kind can be submitted by anyone. A committee formedby CABO meets each springto considerand vote uponproposedcode changes to theMEC. TheMEC is normallyrepublished every 3 years, withthe firstedition issued in 1983, andupdated editions publishedin 1986, 1989, 1992, and 1995. A special 1993 edition was published because anumberofsignificantcode changes were approvedby the CABO committee in the previous year. The significantdifferences betweenthe 1992 and 1995 MEC are: The 1995 MEC has more stringent wall insulation (U 0 -value) requirements formultifamily buildings in all locations. The 1995 MEC has more stringentceiling and single-family wall insulation (U 0 -value) requirements in single-family homes inmilder, southern locations. The 1995 MEC references the 1993 ASHRAE

### Handbook--Fundamentals, while the 1992 MEC 1

### references the 1985ASHRAEHandbook--Fundamentals. Relative to the 1985 Handbook, the 1993 Handbookdirects the userto assume ahigherfraction ofthe exteriorwall areais occupied by framing and notinsulation. This effectively results in afurtherincrease in stringency in wall insulation requirements in the 1995 MEC. The 1995 MEC has new ductinsulationR-valuerequirements. The 1995 MEC strengthens the duct-sealingprovisions and applies themto all supply andreturn ducts. The 1995 MEC has highermaximum airleakage rates forwood and vinyl windows and lower maximum airleakagerates for sliding doors.

• The 1995 MEC adds provisions to limitheatloss and airinfiltrationthrough recessed lighting fixtures locatedin the building envelope.

• The 1995 MEC adds specifications forinput values foruse in Chapter4 Systems Analysis compliance approach. The 1995 MEC adds areference to the National Fenestration Rating Council (NFRC) standard forthermal properties ofglazing assemblies andprovides default values forproducts not evaluatedto the NFRC standard. The 1995 MEC adds criteriato specifically correctformetal stud framing in wall thermal calculations. The 1995 MEC eliminates thepotentialforinsulating the walls ofaventilated crawl space ratherthan the floorabove. There are various other, less significant, “administrativ&’ code changes between the 1992 and 1995 MEC. Many ofthese changes consistofclarification ofrequirements and deletion ofrepetitive or unnecessary text. Mostofthese othercode changes will have no impacton the energy efficiency levels ofthe code. ASHRAE Standard 90.1-1989 has undergone some minorchanges since the enactment oftheEPAct legislation. Thetechnicalcommittee supporting ASHRAE Standard 90.1-1989 has approvedfour Addenda (? C,F,G,I?) since the EPActlegislation was enacted. Additionally, acodified version ofthe Standard has been created. TaskDescription Comparison ofthe 1992 and 1995 Editions ofthe ModelEnergy Codes Each ofthe code changes fromthe 1992 andthe 1995 MEC listedin the background willbe individually examined. Constructioncostchanges and energy consumption costchanges willbe estimated fortypical HUD-supportedhousing. Overall changes in energy efficiency fromthe 1992 to the 1995 MEC will be estimatedbased on the aggregateresults ofthe individual code changes. All administrative code changes which do not affectenergy efficiencyrequirements will notbe examined oraddressed.

2

### often tied to the consumption rateperhousehold; higherconsumption rates can resultin lower (or higher) average unitcosts forenergy. Energyprices will be convertedto the estimated average marginal energy costs.
To determine the economicjustification ofthe 1995 MEC relative to the 1992MEC requires information on costs ofspecific energy-efficiency measures. Costdatawill be obtainedfrom documented sources andrecentdatawill be used wheneverpossible. Ifmore than one construction practice is common (forexample, the use ofbatt andblowninsulation in ceilings), we will analyze the mostcost-effective practice from an energy-efficiency standpoint. We will consideronly measures which are commonly used (i.e., technologically feasible), butwifi notnecessarily consideronly the mostcommon practice.
The change in the MEC ceiling and wall U 0 -valuerequirements for 881 cities across the U.S. Eight common heating fuellequipmenttypes wifibe examined. The economic and energy usage results of this analysis willbe aggreagated to aweighted national average using recenthousing startdata and heating fuellequipmentmarket share data. Comparison ofthe Current Codified Version ofASIIRAE Standard 90.1-1989 to the Version 

### ThatExisted as ofthe EPActLegislationEnactment Only a small minority ofthe housing builtorfinancedunderthe auspices ofHUD are required to comply withASHRAE Standard 90.1-1989 (multifamily highrisebuildings offourormore stories). Because ofthis, the main focus ofprojectwillbe on the comparison ofthe 1992 and 1995 Editions of the MEC (single-family houses and lowrise multifamily buildings). The impact ofthe changes to ASHRAE Standard 90.1-1989 fromthe versionthatexistedin October 1992 to the current version will be examine, butin limited detail. This detail willbe sufficientto make adetermination on whether the changes will increase energy efficiency and are technologically feasible and economicallyjustified.
Deliverable
The deliverable will be areportcomparingthe 1995 MEC to the 1992MEC. The reportwill documentthe methodology and economic and other assumptions used in the analyses. Eachindividual change containedinthe 1995 MEC relative to the 1992MEC that affects the energy efficiency requirements willbe addressedindividually withthe economic and energy impactofeach change documented. The impacts on cost-effectiveness and energy efficieticy ofall changes to theMEC in aggregate willbe reported. A short section ontherecentchanges to ASHRAE Standard 90.1-1989 willbe included. Thereportwill includerecommendations on whetherHUD should adoptthe 1995 

### MEC andthe currentcodified version ofASHRAE Standard 90.1-1989 as requirements forHUD assistedhousing. Budget $35,000

4