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DUCT CONSTRUCTION STANDARDS

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SHEET METAL AND AIR CONDITIONING CONTRACTORS’

NATIONAL ASSOCIATION, INC.
OBSOLErE

FIBROUS GLASS

DUCT CONSTRUCTION STANDARDS

RETURN TO

K! L!EARY

FE.Jf ULG ROOM

Fifth Edition — 1979

Low Velocity Systems

Two Inches W.G. Maximum Static Pressure

SHEET METAL AND AIR CONDITIONING CONTRACTORS NATIONAL ASSOCIATION, INC.

8224 Old Courthouse Road —

Tysons Corner. Vienna. Virginia 22180

SMACNA Fibrous Glass Duct Construction Standards

U S
© SMACNA 1979

SHEET METAL AND AIR CONDITIONING CONTRACTORS’

NATIONAL ASSOCIATION, INC.

8224 Old Courthouse Road

Tysons Corner, Vienna, Virginia 22180

FIRST EDITION — AUGUST 1968

SECOND EDITION — FEBRUARY 1969

SECOND PRINTING — JULY 1970

THIRD EDITION — APRIL 1972

FOURTH EDITION — JUNE 1975

SECOND PRINTING — SEPTEMBER 1975

SUPPLEMENT — JUNE 1978

FIFTH EDITION — JUNE 1979

FIRST PRINTING — MARCH 1980

SECOND PRINTING — JANUARY 1981

THIRD PRINTING — 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 subject to 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 found to have other features 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 of the principles or techniques contained in this

manual. Authoritie considering adoption of these standards should review all Federal, State, local and

contract regulations applicable to specific installations.

SMACNA Fibrous Glass Duct Construction Standards
PREFACE

The Sheet Metal and Air Conditioning Contractors’ National Association presents this standard as a

recommended method of fabricating and installing air handling ducts designed of fibrous glass mate

minute

rial as specified herein, which operates at 2” water gage static pressure or less and 2000 feet per

of velocity or less.

This edition reflects refinement of technology applicable to fibrous glass duct systems. Based on

continuing improvements in fibrous glass board and additional laboratory tests of various boards

and reinforcements, we have expanded Section II, Fabrication of Straight Duct and Fittings, to

include information on the fabrication of ten sided duct.

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 1 975. The re

vised standards which appear in this Fifth Edition include test procedures under accelerated aging

conditions.

However,

Closure systems are vital to maintaining the proper assembly of fibrous glass ducts.

the development of closure system standards, of which 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

method.

ard herein, will result in a quality installation where pressure sensitive tapes are used as a closure

V

Four improved methods for fastening tie rod reinforcing wire to the support washer have been de

veloped

Reinforcement.

and tested by TIMA and we have included these alternate tie-rod terminations in Section IV,

A new Section VI has been added in this Fifth Edition covering the fabrication and installation of

preformed round fibrous glass duct.

The Sheet Metal and Air Conditioning Contractors’ National Association gratefully acknowledges

the

Duct

contribution of the Thermal Insulation Manufacturers’ Association and its Fibrous Glass Air

Committee for their cooperation and for providing material, personnel and testing facilities.

Acknowledgement and appreciation are also due the Pressure Sensitive Tape Council and members

thereof

ment

who contributed advice and the results of laboratory tests which assisted in the develop

of the Pressure Sensitive Tape Standards. V

The Sheet Metal and Air Conditioning Contractors’ National Association extends its thanks to the

following individuals who have contributed their time and talents in the development of this standard.

SMACNA

TIMA

Mr. Robert Segal, Chairman Mr. Robert Gawne Farmington. Michigan Washington, Mr. Peter Hays D.C. Toledo. Ohio

Mr. B. H. Anderson V Mr. Harold Nepereny San Leandro, California Mr. Win Irwin Vienna. Virginia valley Forge, Pennsylvania

Mr. G. E. “Eddie” Daniel Mr. Robert E. Taylor St. Petersburg. Florida Mr. Cliff D. Smith Salt Lake City, Utah Toledo. Ohio

Mr. Daniel J. Dnscoll

Philadelphia. Pennsylvania Mr. Keith Thomas

Denver, Colorado

Mr. Wallace E. Fizer V

Lexington. Kentucky Mr. Harvell Smith

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 Duct Construction Standards — 5th Edition

Sheet Metal and Air Conditioning Contractors’ National Association, Inc.

Ducted Electric Heat Guide for Air Handling Systems — 1st Edition

Sheet Metal and Air Conditioning Contractors’ National Association, Inc.

ASHRAE Handbook and Product Directory — Systems and Equipment Volumes

American Society of Heating, Refrigerating and Air-Conditioning Engineers.

NFPA Standard 90A — 1979 — Installation ofAir Conditioning and Ventilating Systems

National Fire Protection Association.

NFPA Standard 90B — 1979 — Installation of Residence Type Warm Air Heating and Air Conditioning

Systems

National Fire Protection Association.

Standard for Safety — Factory-Made Air Duct Materials and Air Duct Connectors UL 181 — 1974

Underwriters’ Laboratories, Inc.

Test Methods for Pressure 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
TABLE OF CONTENTS

Page

Number

PREFACE

REFERENCES iv

TABLE OF CONTENTS v

SHORT FORM SPECIFICATIONS vii

SECTION I — PERFORMANCE CRITERIA OF BOARD

General Requirements for All Air Ducts 1-2

1. Duct Board 1-2

2. Reinforcement 1-3

3. Longitudinal Seams and Transverse Joints 1-3

4. Duct Support 1-3

5. Vibration and Noise 1-4

6. Thermal Conductivity 1-4

7. Air Friction Loss 1-4

8. Fire Protection Characteristics 1-4

8. Fire Protection Characteristics 1-4

Compilation of Fibrous Glass Duct Characteristics and Limitations 1-5

Duct Design Reference Data 1-6

SECTION II — FABRICATION OF STRAIGHT DUCT AND FITTiNGS

Fabrication of Straight Ducts 2-3

Fabrication Tools 2-3

Centerline Method of Fabrication 2-4

Layout 2-4

Longitudinal Shiplap Groove Method 2-6

Add-On Allowances 2-7

Longitudinal V-Groove Method 2-8

Add-On Allowances 2-9

Board Length Selection Chart 2-10

Fabrication of Fittings 2-12

Rectangular End Cap 2-12

Volume Damper Connection 2-14

900 Elbow Fabrication 2-16

Vaned Square Elbow 2-18

Tee Fabrication 2-20

Branch Take-Off 2-22

Transition Fabrication 2-24

One-Way Transition (Falt) — Shiplap Construction 2-28

One-Way Transition — “V” Groove Construction 2-30

Two-Way Transition (Flat) — Shiplap Construction 2-32

Three-Way Transition 2-34

One-Way Offset (30°1) Fabrication 2-36

Register and Grille Connection 2-38

Diffuser Connection (Round) 2-40

Diffuser Connection (Rectangular or Square) 2-42

Access Door Type A 2-44

Access Door Type B 2-46

Fire Damper Connection 2-48

Flanged Electric Heater Installation 2-50

Slip-In Electric Heater Installation 2-52

Equipment Connection Details 2-54

Fabrication of Ten-Sided Duct 2-56

Installation of Ten-Sided Duct 2-61

SMACNA Fibrous Glass Duct Construction Standards

V
Page

Number

SECTION III — CLOSURES

General

3-2

Pressure Sensitive Tapes for Fibrous Glass Ducts 3-4

A. Performance Standard AFTS-100-73 3-4

1. Classification

3-4

2. Materials Requirements 3-4

3. Required Performance Characteristics 3-4

4. Test Procedures

3-5

5. Compliance

3-5

Table 3-1 — Specimen Selection 3-6

Table 3-2 — Shear Adhesion Tests 3-6

B. Application Standard AFTS-1O1-73 3-7

1. Scope

3-7

2. Procurement

3-7

3. Storage

37

4. Inspection of Delivery 3-8

5. Surface Preparation 3-9

6. Installation

3-9

SECTION IV — REINFORCEMENT

Reinforcement

4-3

Reinforcement with Channels and Tee Bars 4-4

Table 4-1 — Channel and Tee Bar System 4-5

Reinforcement Types

4-6

Transverse Joints — Shiplap Type 4-8

Typical Reinforcement on 48” Centers with 48” Joint Spacing 4-9

Typical Reinforcement on 24” Centers with 48” Joint Spacing 4-10

Typical Reinforcement on 16” Centers with 48” Joint Spacing 4-11

Reinforcement with Tie-Rod System 4-12

1. Testing

4-12

2. Reinforcement Materials and Tools Required 4-12

3. Reinforcement Procedure 4-13

4. Ductsover60”

4-13

5. Location of Reinforcements (See Table 4-3) 4-13

Table 4-3 — Tie-Rod System 4-15

Tie-Rod Reinforcement System Transverse Joints — Shiplap Type 4-16

Typical Tie-Rod Reinforcement 4-17

Method 1 — Original Method 4-19

Method 2 — Fasloop 4-20

Method 3 — Internal Pop Rivet Sleeve 4-21

Method 4 — External Pop Rivet Sleeve 4-22

Method 5 — Cap Washer 4-23

SECTION V — HANGERS AND SUPPORTS

Hangers — Horizontal Duct 5-2

Vertical Riser Supports 5-4

SECTION VI — PREFORMED ROUND DUCT

Preformed Fiberglass Duct 6-2

Fabrication of Straight Duct and Fittings 6-3

Installation of Preformed Round Duct 6-10

SMACNA Pibrous Glass Duct Construc.tion Standards

vi
SHORT FORM SPECIFICATION

All ductwork operating ator below 2” w.g. static pressure, 2000 fpm velocity and 250° F air tempera

ture shall be constructed of 1” thick fibrous glass duct board meeting the requirements of the latest

Edition of the SMACNA Fibrous Glass Duct Construction Standard.

Fabrication and installation of duct and fittings shall be in accordance with the latest Edition of the

SMACNA Fibrous Glass Duct Construction Standard. Furthermore, closure systems for longitudinal

seams and transverse joints shall be in accordance with procedures necessary to comply with Section

Ill, CLOSURES.

SMACNA Fibrous Glass Duct Construction Standards

vii
SMACNA 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

and joints. 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 of the 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 of the 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

1-2
effects of fatigue occurring in a duct system, sections of each 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 of cycling 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

of each 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 transverse joints, 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

1-3
tion 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. 2per 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 or deficiency of duct sec

tion after 25,000 cycles at 5 cpm from natural sag to

span/I 00 deflection.

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°F maximum ambient outside the duct.

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

fa ctu re r.

or

SMACNA Pressure Sensitive Tape Standard AFTS

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. Refer to 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 of material 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

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1-6
SECTION II

FABRICATION OF STRAIGHT

DUCT AND FITTINGS

FABRICATION OF STRAIGHT DUCT

FABRICATION OF FITTINGS

SMACNA Fibrous Glass Duct Construction Standards
SMACNA 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 tight joints

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”

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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

These tools remove insulation, 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 left hand cut, reverse tool.

This tool makes the rabbet cut on the end of

the board for the closing corner joint and cuts

the insulation to be stripped from the facing

to form a closure flap. (Normally used with

V-groove method of fabrication.)

This tool is used to cut the female slip-joint

(shiplap) and the rabbet for seating the edge

of the board at the lateral closure corner (shiplap method).

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 of centerline 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.) of the 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-ti
5. 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 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. The filler piece is fabricated with 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 pieces of board.

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 transverse joint Shiplap connection between duct section.

5b. Male rabbet cut for a transverse joint connection between duct sections.

SMACNA Fibrous Glass Duct Construction Standards
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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 transverse joint Shiplap connection between duct sections.

5b. Male rabbet cut for a transverse joint 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-Piece Duct for using 1-inch-thick board* (All dimensions in inches)

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.

If the 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

2-12
SMACNA Fibrous Glass Duct Construction Standards
DETAIL A

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 half way 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.

If transverse joint 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

2-14
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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

2-16
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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 butt joint. When cutting the other sides of the duct the knife must be held at the 45°

angle to obtain a bevelled joint.

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 to join 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 of this 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
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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 corner joint. (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 of the branch outlet will determine the location of the 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 of the small duct from the inside dimension of the large duct. Draw line “JI.”

Figure 2-1 2C

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 2-1 2G

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

RGURE 2-12G

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 prevent turbulence or additional increase of static pressure.

Figure 2-1 3A

STEP I: 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 12” x 6”

to an 8” x 6”, fabricate a 12” x 6” duct section).

Figure 2-1 3B

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 1 2”—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” of the 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 2-1 3E 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

2-28
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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

2-30
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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 2-1 5A

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 off the 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 2-1 5E

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

2-32
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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 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.

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

2-34
U.,

A

z

-TI

0

CU..C

A

-I

z

-l

m

m

-I

z

z

/—

Cl,

>

0

z

T10C

C)

DCC,C)0

CC)0

U,CC.

m

CI•)

Q

m

-n

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mz

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t%)

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 of duct 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 of offset 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)

H

Shiplop Groove Construction

RGURE 2-17A

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 of the collar lock.

An air extractor 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. If the 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 of four 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 of the opening.

It may be necessary to install a hanger or hangers under the duct and bearing plate to support the

additional weight of the 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 S MACNA 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 of the 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 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 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

DETAI L “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

/

SASHLOCK S

or hinges

SHEET METAL

REINFORCING PLATE

WINDOW TYPE

SASH LOCK

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 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 sheet metal channel frame (See DETAIL “A”) 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.

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

DOOR PANEL

SMACNA FIBROUS DUCT STANDARD FIGURE No. 2-22

SMACNA Fibrous Glass Duct Construction Standards

ACCESS DOORS

TYPE B

;EE DETAIL “A”

SHEET METAL

BOTH SIDES

INSULATED DOOR

WINDOW TYPE

SASH HANDLE

CHANNEL FRAME

SEE DETAIL “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 of fire dampers in walls.

LEGEND

A Metal sleeve for fire dampers should extend approximately 3” past each side of the wall to

facilitate attachment of duct 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 DAMPER CONNECTION

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 nof be placed on the exterior of the terminal box.

After completing assembly of the 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 HEATER INSTALLATION

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 of the 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 Standards
ci’

>C,•1

ci.

0C0

C.’

0

0

0,

C

C)

C-)

0

0

C

C)

0

CC)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

2-56
Ten-sided duct can be fabricated from duct board

using a grooving machine with adjustable gang

tooling.

Grooving knives are adjusted using a gauge for

proper setting.

SMACNA Fibrous G)ass Duct Construction Standards

FABRICATION OF TEN-SIDED DUCT

.5, ‘S

S. -

FIGURE 2-28

2-57
Ten-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 showsthe options available fabricator should always check material made

in converting standard duct board sizes into on his particular machine for dimensional accu

duct. The table is based on ideal tool settings. racy before producing large quantities of duct.

Because of variation in blade settings, tool bar The fabricator should also selectthe best combi 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. 10 Ft. Long Ducts 4 Ft. Long Ducts 4 Ft. Long Ducts

Full Half (1)

l.D. Made From 10 Ft. Board Made From 8 Ft. Board

Section Section No. of Material Drop off 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 half sections requires 2 longitudi- sidered, the Manufacturers UL Listing and In

nal joints struction Sheet must be consulted for limitations.

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.

lengths requires only one circumferential joint.

2. In making 4 ft. long 7” nom. l.D. Ten-sided

Duct, 10 ft. duct board will yield 4 sections with

essentially no drop off; 8 ft. duct board yield 3

sections with 2.3 S. F. of scrap.

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

Circumferential joints are formed using appro

priate tools. Male and female ends can be fabri

cated while the material is in the flat or after

the ten-sided duct has been formed. These

joints are made with shiplap and staple flaps or

with internal metal sleeves. Return air duct

must be joined using internal metal sleeve.

Refer to Section VI — Premolded Round Duct for

procedures for fabricating fittings from ten-sided

duct.

FIGURE 2-32
INSTALLATION OF TEN-SIDED DUCT

HANG ING

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 of 2” 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 duct joint.

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

2-61
SMACNA 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 of fibrous glass duct systems. A variety of

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 of the above

With the publication of the third edition of the SMACNA Fibrous 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 of a 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

sitive tapes are used as a closure method.

Most codes and project specifications require that nonmetallic duct construction conform to 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

manufacturer to another. When C/ass 1, UL-181 construction is required, the closure system having

an approved listing with the particular fibrous glass duct product must be used in accordance with the

listing and the recommendations of the board manufacturer.

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 not guarantee that they will do so.

In acknowledging the variables discussed herein it is the intent of these fibrous glass duct standardsto

require that closures comply with the following stipulations:

1. When Class 1, UL-1 81 construction is required (by specification external to these standards) any

closure system compliant therewith may be used unless a pressure sensitive tape closure is

selected, in which case the tape closure shall fulfill the additional requirement of complying with

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 should be given to 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 of proof shall

rest with the sponsor of such alternative method.

SMACNA Fibrous Glass Duct Construction Standards
Although 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’s Fibrous Glass Duct

Construction Standards, 5th Edition, 1 979

2.0 MATERIAL REQUIREMENTS

2.1 Material: The tape shall consist of an aluminum foil coated on one side with a pressure sensitive

adhesive with or without a liner. The minimum nominal width of the tape 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 permanent identification of (after installation): (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 of the tape will be deemed in non-conformance with

this specification.

2.3 Adhesive: The surface on one side of the aluminum foil shall be completely covered with a nontoxic adhesive. There shall be no separation of the adhesive from the backing upon unwinding of

the roll, nor shall the adhesive transfer to the liner when a liner is involved.

2.4 Rolls: Tape shall be evenly and uniformly wound on 3” l.D. cores. Cores shall be sufficiently rigid to

prevent distortion of the roll under normal conditions of transportation and use. Tape backing shall be

free from wrinkles and from gaps between liner and adhesive. The length of the roll shall be 60 yards or

multiples thereof, with a tolerance of —2’ 0”, unless otherwise specified.

3.0 REQUIRED PERFORMANCE CHARACTERISTICS

3.1 Tapes shall have minimum performance characteristics stated herein. The determination of such

characteristics and properties shall be made in accordance with procedures described in this

Standard.

3.2 TensIle Strength: The cross direction tensile strength of the tape shall average 25 lbs. or greater

per inch of width 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 with fibrous glass duct board shall have a flame spread rating not exceeding 25 and

a smoke developed rating not exceeding 50.

3.4 Shear Adhesion: The tape shall sustain the loads indicated in Table 3-2 herein for a period of 6

hours, without failure, when tested in accordance with PSTC-7, Shear Adhesion.

3.5 Peel Adhesion at 180°: The tape shall have a minimum average of 60 ounces peel adhesion per

inch width when tested in accordance with PSTC-1 with a 15 minute dwell time. Dwell time 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 same three roll lot. Tests for tensile strength, shear adhesion,

peel adhesion and fire hazard must have the required ratings on three rolls from the tape lot, with

the number of specimens per roll selected in accordance with Table 3-1. Furthermore, the

following conditions shall govern:

36.1 All test methods are intended to produce test values for a single roll. References to average

values in Table 3-1 refer to averaging of measurements on a single roll and not to an

average of all sample rolls.

SMACNA Fibrous Giass Duct Construction Standards
3.6.2 To rule out the possibility of error in test procedures, if the test results of any 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. If test results of any one

additional sample roll does not conform to requirements, the tape may be deemed to be noncompliant.

4.0 TEST PROCEDURES

4.1 A complete series of tests must be conducted from rolls in the “as received” condition. A second

series of tests must be conducted for all properties except fire hazard in accordance with section

4.2.1. Test performed in order to determine compliance with the performance requirements of this

standard must be certified by an approved independent laboratory.

4.2 Test procedures are outlined in Part 3 and Tables 3-1 and 3-2. Reference to PSTC tests shall mean

tests listed in “Test Methods for Pressure Sensitive Tapes,” 6th Edition, published by the Pressure

Sensitive Tape Council, 1201 Waukegan Road, Glenview, Illinois 60025. References to ASTM

Tests shall mean designated standard procedures published by the American Society for Testing of

Materials, 1916 Race Street, Philadelphia, Pa. 19103.

4.2.1. The tape in standard roll form is to be placed in an atmosphere of 66° C and 80% R.H. for a

seven day period. Then allowed to condition twenty four hours at 23° C and 50% R.H. Using

a 4.5 pound roller, perform all tests in Tables 3-1 and 3-2 with the exception of the fire hazard

test. Tape must continue to pass SMACNA Performance Standard AFTS-100-73 as revised.

4.3 Laboratory reports must contain but not be limited to:

(A) Accurate identification of the tape product.

(B) Listing of the 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 of three 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” Test duration per specimen

1” Test duration per specimen

1” Test duration per specimen

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. If compliance ratings are challenged, for tests performed to confirm compliance, an average of 5 specimens per roll 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 per Table 3-1.

2. Except as modified herein, all specimens shall be prepared in accordance with PSTC Test Methods for Pressure Sensitive

Tapes, 6th Edition. Appendage A (Standard Conditions). Appendage B (Test Equipment). Appendage C (Cleaning Test

Surfaces) and Test Methods 7, 9 and 11 as referenced.

3. Conditions listed at 7340 F, 50% Ri-I. shall be controlled within tolerance limits listed in Appendage A, i.e. ± 3.6° F and ± 2%

R.H.

4. Dwell time is the time that the test specimen is in contact with the test panel, after rolling, prior to application of the test

load.

5. Tape and test panels shall be maintained at application conditions a minimum of one hour prior to applying tape to the test

panel.

6. Refer to Parts 3.0 and 4.0 for evaluation of test 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

PSTC-1 3

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 for pressure sensitive aluminum (dead soft) foil backed tapes

used in closure systems outlined in Section II, FABRICATION OF STRAIGHT DUCTAND 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 sensitive tapes shall conform to SMACNA TAPE STANDARDS.

Compliance with SMA CNA Tape Standards does not constitute compliance with UL 181, C/ass 1

construction. Several types of closure systems can comply with UL 181, Class 1 requirements.

When the duct system must comply with NFPA 90A and/or UL 181, the closure system identified

by the board manufacturer for that purpose must be 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 comply with SMACNA Performance Standard AFTS-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 permit identifica

tion of (after installation):

a) The name of the manufacturer and SMA CNA

b) The date of manufacture in month and year

cLManufacturers Product Number

2.1 .4 If contract documents require compliance with UL 181. Class 1 duct construction, 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, shelf life and recommended storage conditions.

2.1 .7 Tapes shall be packed in a manner that 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

atmospheric temperature is not less than 50° nor more than 85°F. For best results tape should be

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 of direct 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 If tape is stored at temperatures below 50°F, it must be reconditioned prior to use by placement in

a warm 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 Procurement Conditions. Inquire as to date of last compliance test if in

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 in transfer of adhesive. On lined rolls removal of the 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

3-8
5.0 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 the tape, the application surface should be wiped clean and dry

with safe solvent and oil free, lint free rags or paper towels.

If tape is stored at temperatures below 50°, it must be reconditioned prior to use or placement in 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 must be

50°F or higher temperature when tape is to be applied to them.

5.3 Condensation on duct surfaces may occur when duct sections or duct board materials are brought

from a cold environment into a warmer environment. When such conditions exist, special

provisions must be made to insure that rroisture is not present on the duct surface when tapes are

applied.

5.4 Surfaces should be as free from wrinkles or other projections as practicable.

6.0 INSTALLATION

6.1 Prepare joint, 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 Remove tape from roll, discard liner if present, align tape carefully with seams and joints, pull taut

and press in place, taking care to avoid wrinkles and folds. Use a soft material to apply pressure to

the backing to smooth the tape surface and make it conform to valleys and indentations in the duct

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

3-9
6.4.2 Avoid exposing adhesive surface to dust laden atmospheric conditions before applying.

6.4.3 Tapes in conformance with this document are not rated for application on ducts in which the

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 applied below 50°F shall be installed in compliance with Parts 5.1, 5.2 and 7.0 of this

Standard, and also comply with tape manufacturers installation requirements.

6.5 Tape must lap 1” minimum on adjacent surfaces to be sealed. Refer to Section Il, FABRICATION

OF STRAIGHT DUCT AND FITTINGS for arrangement of flaps. At a joining 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 on joints 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 of tape layers, to satisfy closure requirements.

6.7 Pressure tests of assembled ducts should not be conducted within 24 hours of installation of tape

closures. (Field test pressures of 150% of rated negative or positive pressure may be required by

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 of 400°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 or three 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 heat to leave the bond area warm to the touch for approximately one minute

after the heat source is removed.

7.3.3 Do not overheat the taped area! Excessive heat applied to the foil face stock may result in a

rupture of the adhesive anchorage to the foil. This will result in a lessening of ultimate bond

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

11
SMACNA Fibrous Glass Duct Construction Standards
SECTION IV

REINFORCEMENT

SMACNA Fibrous Glass Duct Construction Standards
SMACNA Fibrous Glass Duct Construction Standards
REINFORCEMENT

This section deals with the reinforcement of the 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 of reinforcement 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 reinforcement for positive pressure systems only.

SMACNA Fibrous Glass Duct Construction Standards
REINFORCEMENT WITH 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 of fewer sizes of gages 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 of reinforcing 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 Standards
TABLE 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 of formed 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

NOT REQUIRED NOT REQUIRED

NOTES:

4-5
REINFORCEMENT TYPES

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

DETAIL A

POSITIVE PRESSURE APPLICATION

Reinforcement over loint preferred

or not more than 2” off loint over

the female cut.

DETAIL B

NEGATIVE PRESSURE APPLICATION

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 over the edge of flap.

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 of duct.

TABLE 4-2

Transverse Dimension Minimum Number of clips 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 of the board or other suitable method.

B. Ducts with negative pressures shall have retaining clips at joints 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 REINFORCEMENT ON 48” CENTERS

WITH 48” JOINT SPACING

Fastening required at top

center of ducts over

60” wide only. 48” along

longitudinal center line

of dud.

SUPPLY DUCT

Positive Pressure

CLIP DETAIL

RETURN DUCT

Negative Pressure

correct

posilion

Diameter or

2W’ Square Washer

(Alternate placement of dip saews across the width of dud)

Section at Duct Joints (RETURN DUCT)

At negative pressure joints only per

spacing schedule in Table 4-2. 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 REINFORCEMENT ON 24” CENTERS

WITH 48” JOINT SPACING

correct

posihon

3” Diameter or

2Y” Square Washer

(Alternate placement o clip saews

across the width of dud)

At negative pressure joints only per spacing schedule in Table4-2. See Figure 4.2.

— I

of dud.

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 at Duct Joints (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

TYPICAL REINFORCEMENT ON 16” CENTERS

WITH 48”JOINT SPACING

/3” Diameter or

21/2 Square Washer

(Alternate placement of dip sa’ews

across the width of duct)

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 at top

center of ducts over

60” wide only. 48” along

longitudinal center line

of duct.

SUPPLY DUCT

Positive Pressure

RETURN DUCT

Negative Pressure

correct

position

0

1

Section at Duct Joints (RETURN DUCT)

4-1 1
4-12

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 are joined.

3. LOCATIONS OF REINFORCEMENTS (See Table 4-3)

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 of transverse joint.

3. See Figure 4-7 on page 4-17 for typical layout of reinforcements.

4. Refer to item 2 on page 4-13, for ducts with span over 60’

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 of the 1992 and 1995 Model Energy Codes

5/16/96

Introduction

Section 109 of the National Affordable Housing Act, as amended by the Energy Policy Act of 1992,

requires HUD to set energy efficiency standards for public and assisted housing. These standards are

required to “...meet the requirements of CABO Model Energy Code, 1992, or, in the case of

multifamily high rises, the requirements of ASHRAE Standard 90.1-1989.” Furthermore, HTJD is

required meet the requirements of revisions of the Model Energy Code (MEC) and Standard 90.1-1989

“...unless the secretaries determine that compliance with such revised code or standard would not result

in a significant increase in energy efficiency or would not be technologically feasible or economically

justified.”

This proposal is to determine whether the 1995 MEC5, and, for multifamily high rises, the recent

Addenda to 90.1-1989, will increase energy efficiency and are technologically feasible or economically

justified. An economic analysis comparing the requirements of the Council of American Building

Official’s (CABO) 1992 and 1995 Editions of the Model Energy Code (MEC) and of recent Addenda

to Standard 90.1-1989 will be conducted and a report will be produced. The main emphasis will be

on the MEC, Standard 90.1-1989 will be briefly addressed.

Two additional, related proposals are included:

A proposal for a task to update HUD training materials for the 1992 MEC and produce a

video for use on 1{UD’s satellite network, and

A proposal for a task to customize MECcheck compliance materials for the 1995 Edition of

the MEC for use in HUD’s loan guarantee program.

Background

The MEC is revised on an annual basis. Code change proposals of any kind can be submitted by

anyone. A committee formed by CABO meets each spring to consider and vote upon proposed code

changes to the MEC. The MEC is normally republished every 3 years, with the first edition issued in

1983, and updated editions published in 1986, 1989, 1992, and 1995. A special 1993 edition was

published because a number of significant code changes were approved by the CABO committee in

the previous year.

The significant differences between the 1992 and 1995 MEC are:

The 1995 MEC has more stringent wall insulation (U0-value) requirements for multifamily

buildings in all locations.

The 1995 MEC has more stringent ceiling and single-family wall insulation (U0-value)

requirements in single-family homes inmilder, southern locations.

The 1995 MEC references the 1993 ASHRAE Handbook--Fundamentals, while the 1992 MEC

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references the 1985 ASHRAE Handbook--Fundamentals. Relative to the 1985 Handbook, the

1993 Handbook directs the user to assume a higher fraction of the exterior wall area is

occupied by framing and not insulation. This effectively results in a further increase in

stringency in wall insulation requirements in the 1995 MEC.

The 1995 MEC has new duct insulation R-value requirements. The 1995 MEC strengthens the

duct-sealing provisions and applies them to all supply and return ducts.

The 1995 MEC has higher maximum air leakage rates for wood and vinyl windows and lower

maximum air leakage rates for sliding doors.

• The 1995 MEC adds provisions to limit heat loss and air infiltration through recessed lighting

fixtures located in the building envelope.

• The 1995 MEC adds specifications for input values for use in Chapter 4 Systems Analysis

compliance approach.

The 1995 MEC adds a reference to the National Fenestration Rating Council (NFRC) standard

for thermal properties of glazing assemblies and provides default values for products not

evaluated to the NFRC standard.

The 1995 MEC adds criteria to specifically correct for metal stud framing in wall thermal

calculations.

The 1995 MEC eliminates the potential for insulating the walls of a ventilated crawl space

rather than the floor above.

There are various other, less significant, “administrativ&’ code changes between the 1992 and 1995

MEC. Many of these changes consist of clarification of requirements and deletion of repetitive or

unnecessary text. Most of these other code changes will have no impact on the energy efficiency

levels of the code.

ASHRAE Standard 90.1-1989 has undergone some minor changes since the enactment of the EPAct

legislation. The technical committee supporting ASHRAE Standard 90.1-1989 has approved four

Addenda (? C,F,G,I?) since the EPAct legislation was enacted. Additionally, a codified version of the

Standard has been created.

Task Description

Comparison of the 1992 and 1995 Editions of the Model Energy Codes

Each of the code changes from the 1992 and the 1995 MEC listed in the background will be

individually examined. Construction cost changes and energy consumption cost changes will be

estimated for typical HUD-supported housing. Overall changes in energy efficiency from the 1992 to

the 1995 MEC will be estimated based on the aggregate results of the individual code changes. All

administrative code changes which do not affect energy efficiency requirements will not be examined

or addressed.

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often tied to the consumption rate per household; higher consumption rates can result in lower (or

higher) average unit costs for energy. Energy prices will be converted to the estimated average

marginal energy costs.

To determine the economic justification of the 1995 MEC relative to the 1992 MEC requires

information on costs of specific energy-efficiency measures. Cost data will be obtained from

documented sources and recent data will be used whenever possible. If more than one construction

practice is common (for example, the use of batt and blown insulation in ceilings), we will analyze the

most cost-effective practice from an energy-efficiency standpoint. We will consider only measures

which are commonly used (i.e., technologically feasible), but wifi not necessarily consider only the

most common practice.

The change in the MEC ceiling and wallU0-value requirements for 881 cities across the U.S. Eight

common heating fuellequipment types wifi be examined. The economic and energy usage results of

this analysis will be aggreagated to a weighted national average using recent housing start data and

heating fuellequipment market share data.

Comparison of the Current Codified Version of ASIIRAE Standard 90.1-1989 to the Version

That Existed as of the EPAct Legislation Enactment

Only a small minority of the housing built or financed under the auspices of HUD are required to

comply with ASHRAE Standard 90.1-1989 (multifamily high rise buildings of four or more stories).

Because of this, the main focus of project will be on the comparison of the 1992 and 1995 Editions of

the MEC (single-family houses and low rise multifamily buildings). The impact of the changes to

ASHRAE Standard 90.1-1989 from the version that existed in October 1992 to the current version will

be examine, but in limited detail. This detail will be sufficient to make a determination on whether

the changes will increase energy efficiency and are technologically feasible and economically justified.

Deliverable

The deliverable will be a report comparing the 1995 MEC to the 1992 MEC. The report will

document the methodology and economic and other assumptions used in the analyses. Each individual

change contained in the 1995 MEC relative to the 1992 MEC that affects the energy efficiency

requirements will be addressed individually with the economic and energy impact of each change

documented. The impacts on cost-effectiveness and energy efficieticy of all changes to the MEC in

aggregate will be reported. A short section on the recent changes to ASHRAE Standard 90.1-1989

will be included. The report will include recommendations on whether HUD should adopt the 1995

MEC and the current codified version of ASHRAE Standard 90.1-1989 as requirements for HUD

assisted housing.

Budget

$35,000

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