**SPECIAL SPECIFICATION**

**SECTION 15890**

**[DUCTWORK SYSTEMS]{.underline}**

Page

PART 1 - GENERAL

1.01 Work Included 3

1.02 Related Work 3

1.03 Guarantee 3

1.04 Contractor Coordination 3

1.05 Standards And Codes 4

1.06 Definitions 4

1.07 Submittals 4

PART 2 - PRODUCTS

2.01 Sheet Metal Ductwork-Rectangular Rigid Round 5

2.02 Low Pressure Ductwork 5

2.03 Medium Pressure Round/Oval Double-Wall Ductwork 8

2.04 Seal Of Seams And Joints 13

2.05 Pvc Ductwork 13

PART 3 - EXECUTION

3.01 Installation1 4

3.02 Low Pressure Ductwork 16

3.03 Medium Pressure Ductwork 17

3.04 Opening In Ductwork 18

3.05 Flashing 18

3.06 Duct Lining 18

3.07 Installation - Pvc Ductwork 19

3.08 Tests 19

3.09 Adjusting And Cleaning 20

**SPECIAL SPECIFICATION**

**SECTION 15890**

**[DUCTWORK SYSTEMS]{.underline}**

[PART 1 - GENERAL]{.underline}

1.01 [WORK INCLUDED]{.underline}

> This section provides for furnishing and installing air ductwork for
> ventilating, exhaust, air handling unit distribution and VAV box
> distribution.
>
> Ductwork involved will be double wall round/oval, single wall rigid
> round, single wall rectangular, flexible duct and below floor PVC
> ductwork.

1.02 [RELATED WORK]{.underline}

A. [Insulation - Mechanical Systems]{.underline}: Section 15250

B. [System Component Checkout and Balance]{.underline}: Section 15901

1.03 [GUARANTEE]{.underline}

> Ductwork guarantee shall cover workmanship, noise, chatter, whistling
> or vibration. Ductwork shall be free from pulsation under all
> conditions of operation.

1.04 [CONTRACTOR COORDINATION]{.underline}

> Erect all ducts in the general locations shown on the drawing(s), but
> conform to all structural and finish conditions of the building.
> Before fabricating any ductwork, Contractor shall check the physical
> conditions at the job site and make all necessary changes in cross
> sections, offsets and similar items, whether they are specifically
> indicated on drawings or not.

1.05 [STANDARDS AND CODES]{.underline}

> A. Except as otherwise indicated, sheet metal ductwork material and
> installation shall comply with the latest edition of SMACNA Low
> Pressure Duct Construction Standards. Medium pressure round/oval
> double wall sheet metal ductwork shall comply with the latest edition
> of SMACNA High Pressure Duct Construction Standards. All air
> distribution devices (such as dampers) included in this specification
> shall comply with the latest applicable SMACNA manual.

B. Construct ductwork and all air distribution devices to NFPA 90A, NFPA
90B and NFPA 96 standards.

1.06 [DEFINITIONS]{.underline}

> A. [Duct Size]{.underline}. The duct sizes shown are inside clear
> dimension and do not include proper allowances for 1-inch acoustical
> lining, if required, and/or unless otherwise indicated.

B. [Low Pressure Systems]{.underline}. Less than 3-inches w.g. to
+3-inches w.g. positive static pressure and velocity less than 2500 fpm.

C. [Medium Pressure System]{.underline}. 3 inches through 6 inches w.g.
positive static pressure and velocities greater than 2000 fpm. (10.2
m/sec).

1.07 [SUBMITTALS]{.underline}

> A. Submit ductwork shop drawings and product data in accordance with
> Section 01300.

B. Indicate duct fittings, particulars such as gages, sizes, weld and
configuration prior to start of work for low, medium and high pressure
and exhaust systems.

[PART 2 - PRODUCTS]{.underline}

2.01 [SHEET METAL DUCTWORK - RECTANGULAR/RIGID ROUND (SINGLE-WALL)
(DOUBLE-WALL)]{.underline}

A. [Acceptable Manufacturers]{.underline}

1\. United McGill - Spiral round single and double-wall ductwork.

2\. Gowco - spiral round single and double-wall ductwork.

3\. Sheet Metal Products - spiral round sinble and double-wall ductwork.

4\. Thermaflex - insulated flexible duct.

5\. Contractor Shop Fabrication - single wall rectangular ductwork.

2.02 [LOW PRESSURE DUCTWORK]{.underline}

A. [General]{.underline}. Noncombustible or conforming to requirements
for Class I air duct materials or UL 181.

B. [Steel Ducts]{.underline}. ASTM A 525 or ASTM A 527, galvanized steel
sheet, lock-forming quality, having zinc coating of 12.25 ounces per
square foot for each side in conformance with ASTM A 90.

C. [Flexible Ducts]{.underline}. Interlocking spiral of galvanized steel
or aluminum construction, or fabric supported by helically wound spring
steel wire or flat steel bands; rated to 6 inches w.g. positive and 1
inch w.g. negative for low pressure ducts, and 15 inches w.g. positive
and 2 inches w.g. negative for medium high-pressure ducts. Insulation
shall not breed or promote fungi or bacteria, shall resist mold growth,
shall not rot or sustain vermin.

D. [Insulated Flexible Ducts]{.underline}. Flexible duct wrapped with
flexible glass fiber insulation, enclosed by seamless aluminum pigmented
plastic vapor barrier jacket; maximum 0.23 K value at 75 degrees F
\*0.034 ksi at 24 degrees C).

E. [Rectangular]{.underline}. Provide rectangular low pressure ducts
constructed of sheet metal in the following minimum gages:

[Largest Dimension U.S. Gage]{.underline}

[inches]{.underline}

12\" and less No. 26

13\" to 30\" No. 24

31\" to 54\" No. 22

55\" to 84\" No. 20

85\" and above No. 18

F. Fabricate and support in accordance with SMACNA Low Pressure Duct
Construction Standards and ASHRAE handbooks, except as indicated.
Provide duct material, gages, reinforcing and sealing for operating
pressures indicated.

G. [Rigid, Single-Wall Round]{.underline}. Furnish round, low pressure
ducts which are spiral wound, such as manufactured by United McGill
Company, or shop-fabricated round ducts with Pittsburgh lock
longitudinal seams. Use the following gages for shop-fabricated ducts:

[Diameter - Round U.S. Gage]{.underline}

[inches]{.underline}

12\" and less No. 26

13\" to 30\" No. 24

31\" to 42\" No. 22

43\" to 60\" No. 20

H. Size round ducts installed in place of rectangular ducts in
accordance with ASHRAE Table of Equivalent Rectangular and Round Ducts.
No variation of duct configuration or sizes permitted except by written
permission.

I. [Low Pressure Insulated Flexible Duct]{.underline}. Provide
factory-fabricated flexible duct for connections between low pressure
trunk ducts and supply air diffusers. Furnish flexible duct with an
airtight inner liner, insulation and outer jacket. Construct the inner
liner of coated steel helix and fabric substantially bonded together to
prevent the duct from collapsing or kinking in short radius bends.
Provide fiberglass insulation at least 1 inch thick and 3/4-pound
minimum density around the inner liner. Sheath the entire assembly with
heavy, outer vapor barrier jacket of reinforced aluminum foil kraft.
Maximum length of flexible duct is 6 feet and hold in place with strap
or clamp. Use a supply duct rated at a minimum positive working pressure
of 6 inches of water. Exhaust ducts must withstand a negative pressure
of 1 inches of water. Provide duct listed by UL at flame spread rate of
not over 25 and smoke developed rate of not over 50, and complying with
NFPA Standard 90A.

J. Construct tees, bends and elbows with radius of not less than 1-1/2
times the width of duct on centerline. Where not possible or where
rectangular elbows are shown, provide double-wall, airfoil, galvanized
sheet metal turning vanes. The turning vanes shall be fabricated in
accordance with SMACNA HVAC Duct Construction Standards.

K. For round duct, provide the elbows with a centerline radius of 1-1/2
times the duct diameter and furnish smooth elbows or 5-piece, 90-degree
elbows and 3-piece, 45-degree elbows.

L. Increase duct sizes gradually, not exceeding 15 degrees divergence
wherever possible. Divergence upstream of equipment shall not exceed 30
degrees; convergence downstream shall not exceed 45 degrees.

2.3 [MEDIUM PRESSURE ROUND/OVAL DOUBLE-WALL]{.underline}

A. [Rigid Round (Double-Wall)]{.underline}

1\. Round duct will be constructed of a perforated inner liner, a 1-inch
layer of fiberglass insulation (insulation shall not breed or promote
fungi or bacteria, shall resist mold growth, shall not rot or sustain
vermin), and an outer solid pressure shell. Duct will be of spiral
lockseam construction, provided in standard lengths of 10, 12, and 20
feet, or otherwise as specified. It will be fabricated from galvanized
steel meeting ASTM-A527 standards, and in accordance with the following
table:

**Inner Liner Outer Shell Inner Liner Inner Liner**

**Diameter Minimum Gauge Gauge Construction**

**(inches) (2-10 inches wg)**

3- 8 26 28 Standard Spiral

9-12 26 28 Ribbed Spiral

13-24 24 28 Ribbed Spiral

25-34 22 28 Ribbed Spiral

> For 1-inch insulation, the outer pressure shell will be 2 inches
> larger than the inner liner (nominal) dimension.

2\. Perforated liner perforations will be 3/32 inch in diameter with an
overall open area of 23 percent. Insulated duct will have a maximum
thermal conductivity (k) factor of 0.27 Btu per hour per square foot per
degree Fahrenheit per inch thickness at 75°F mean ambient temperature.

3\. Round fittings will be constructed of a perforated inner liner, a
1-inch (unless otherwise specified) layer of fiberglass insulation, and
an outer solid pressure shell. Fittings will be constructed of
galvanized steel meeting ASTM-A527 standards, and in accordance with the
following table:

**Inner Liner Outer Shell Inner Liner**

**Diameter Minimum Gauge Gauge**

**(inches) (2-10 inches wg)**

3-12 24 24

13-24 22 24

25-34 20 24

a\. For 1-inch insulation, the outer pressure shell will be 2 inches
larger than the inner liner (nominal) dimension.

b\. Unless otherwise specified, standing seam joints will be used
wherever possible on all fittings. All standing seam joints will be
sealed with a UL-Classified zero flame spread and zero smoke developed
cement specially formulated for bonding metal-to-metal joints.

c\. In lieu of standing seam construction, joints may be solid welded or
spot welded and bonded. All welded joints will be coated with a
protective paint, inside and out, to prevent damage to the galvanized
surface. Spot welded fittings will have all joints sealed with a
UL-Classified zero flame spread and zero smoke developed cement
specially formulated for bonding metal-to-metal joints.

d\. Elbow outer shells will be of die-stamped, gored, or mitereed
construction. Elbow liners will be gored unless two-piece mitered
construction is specified.

e\. Divided-flow fittings will be constructed with a radiused entrance
to all branch taps and with no excess material projecting from the body
into the branch tap entrance.

f\. Perforated liner perforations will be 3/32 inch in diameter with an
overall open area of 23 percent. Insulated fittings will have a maximum
thermal conductivity (k) factor of 0.27 Btu per hour per square foot per
degree Fahrenheit per inch thickness of 75°F mean ambient temperature.

4\. All double-wall duct and fittings will be furnished with both an
inner liner coupling and an outer pressure shell coupling. Outer shell
connections can be by slip joint or flanged joint; however, flanged
joints are recommended for outer shell diameters greater than 36 inches.
In either case, a slip coupling will be used to join inner liner
sections at duct-to-duct joints. Fitting liners will be extended 2
inches beyond the outer shell cutoff to provide an inner liner coupling
at duct-to-fitting joints. When flanged joints are used, angle rings
will be Van Stoned to fittings and welded to duct. Spiralmate connectors
are available.

B. [Rigid Oval (Double-Wall)]{.underline}

1\. Flat oval duct will be constructed of a perforated inner liner, a
1-inch layer of fiberglass insulation (insulation shall not breed or
promote fungi or bacteria, shall resist mold growth, shall not rot or
sustain vermin), and an outer solid pressure shell. Duct will be of
spiral lockseam construction, provided in standard lengths of 6, 10, and
12 feet, or otherwise as specified. It will be fabricated from
galvanized steel meeting ASTM-A527 standards, and with outer shell
gauges in accordance with the following table. (For 1-inch insulation,
the outer shell major and minor axes will be 2 inches larger than the
nominal inner liner dimensions).

**Inner Liner Outer Shell**

**Major Axis Dimension** **Minimum Gauge**

**(inches)**

7-22 24

23-46 22

2\. Flat oval inner liners will be fabricated in accordance with the
following table:

**Inner Liner**

**Basic Round Diameter Gauge Construction**

**(inches)**

3- 8 28 Standard Spiral

9-42 28 Ribbed Spiral

3\. Perforated liner perforations will be 3/32 inch in diameter with an
overall open area of 23 percent. Insulated duct will have a maximum
thermal conductivity (k) factor of 0.27 Btu per hour per square foot per
degree Fahrenheit per inch thickness at 75°F mean ambient temperature.

4\. Flat oval fittings will be constructed of a perforated inner liner,
a 1-inch (unless otherwise specified) layer of fiberglass insulation,
and an outer pressure solid shell. Fittings will be fabricated from
galvanized steel meeting ASTM-A527 standards, and with outer shell
gauges in accordance with the following table. (For 1-inch insulation,
the outer shell major axis will be 2 inches larger than the nominal
inner liner major axis).

**Inner Liner Outer Shell**

**Major Axis Dimension Minimum Gauge**

**(inches)**

7-34 20

Round dimensions on flat oval fittings will be constructed in accordance
with the following table:

**Inner Liner Diameter Outer Shell**

**(inches)** **Minimum Gauge**

3-34 20

Flat oval inner liners will be fabricated in accordance with the
following table:

**Inner Liner**

**Basic Round Diameter** **Gauge**

**(inches)**

3-34 24

a\. Unless otherwise specified, standing seam joints will be used
wherever possible on all fittings. All standing seam joints will be
sealed with a UL-Classified zero flame spread and zero smoke developed
cement specially formulated for bonding metal-to-metal joints.

b\. In lieu of standing seam construction, joints may be solid welded or
spot welded and bonded. All welded joints will be coated with a
protective paint, inside and out, to prevent damage to the galvanized
surface. Spot welded fittings will have all joints sealed with a
UL-Classified zero flame spread and zero smoke developed cement
specially formulated for bonding metal-to-metal joints.

c\. Elbow will be of gored or mitered construction. Flat oval mitered
elbows will be solid welded.

d\. Divided-flow fittings will be constructed with a radiused entrance
to all branch taps and with no excess material projecting from the body
into the branch tap entrance.

e\. Perforated liner perforations will be 3/32 inch in diameter with an
overall open area of 23 percent. Insulated fittings will have a maximum
thermal conductivity (k) factor of 0.27 Btu per hour per square foot per
degree Fahrenheit per inch thickness of 75°F mean ambient temperature.

5\. All duct and fittings will be provided with both an inner liner
coupling and an outer pressure shell coupling. Outer shell connections
can be by slip joint, FORC connection, or flanged joint; however,
flanged joints are recommended for sizes with major axis dimensions
greater than 42 inches. In either case, a slip coupling will be used to
join inner liner sections at duct-to-duct joints. Fitting liners will be
extended 2 inches beyond the outer shell cutoff to provide an inner
liner coupling at duct-to-fitting joints. When flanged joints are used,
angle rings will be Van Stoned to fittings and welded to duct.

2.04 [SEALS OF SEAMS AND JOINTS]{.underline}

> The entire duct system shall be sealed in accordance with Table 1-2,
> Duct Sealing Requirements, in the latest edition of SMACNA HVAC Duct
> Construction Standards.

[2.05 PVC DUCTWORK]{.underline}

A. [Acceptable Manufacturers]{.underline}

1\. PVC Plastic Company - ITS Division.

2\. Vanaire Ltd.

3\. Met-Pro Corp. - Duall Division.

B. All ductwork shall be rigid, unplasticized polyvinyl chloride (PVC)
with heat welded joints. Ducts and accessories shall conform with the
SMACNA Thermoplastic Duct Construction Manual.

C. [Materials Requirements]{.underline}

1\. Ductwork shall be extruded seamless. Compounds utilized in the
manufacture of these base components shall conform to the PVC Materials
standard ASTM D 1784-69.

D. [Duct Construction - PVC]{.underline}

1\. Extruded material where used shall be manufactured from the basis
compounds as specified above. Extruded duct shall be acceptable in sizes
6\" - 24\". The size of round duct shall be determined by the inside
diameter. The tolerance, including out of roundness should be plus or
minus 3/16 inch for diameters up to 18 inches.

2\. Extruded Round Duct. 6\" round through 18\" round to have 3/16\"
wall thickness. 24\" round to have 1/4\" wall thickness.

3\. Round extruded duct shall be available in nominal 20 ft. lengths.
Round duct fittings shall be mitered straight lengths of duct. All
fittings shall have belled ends to provide a bell and spigot joint
connection. The 90° fittings will have five (5) gore and the 45°
fittings will be three (3) gore both with 1-1/2 times center line
radius. All fittings to be designed to VA15D to assure consistent
quality and interchangeability.

E. [Duct Connections]{.underline}

1\. Round duct joints and fittings to be welded with 5/32 dia. PVC rod.

F. [Dampers (Blast Gate)]{.underline}

1\. Furnish and install dampers as indicated on the drawing and
additional dampers are to be installed at all locations where required
for balancing or adjust in the system.

[PART 3 - EXECUTION]{.underline}

3.01 [INSTALLATION - SHEET METAL DUCTWORK]{.underline}

A. [Construction Standards]{.underline}. Use construction methods which
follow the requirements outlined in paragraph 1.4, as well as SMACNA
Balancing and Adjusting publications, unless indicated otherwise in
these specifications or accompanying drawings.

B. [Reinforcement]{.underline}. Reinforce ducts having one side equal to
25 inches or more in accordance with recommended construction practice
of SMACNA.

C. [Plenum Construction]{.underline}. Construct single-wall and 2\"
(thick insulation double-wall) plenum chambers of not less than No. 20
U.S. gage meatal reinforced with galvanized structural angles.

D. [Cross Breaking or Beading]{.underline}. Cross break or bead sheet
metal for rigidity, except ducts which are 12 inches or less in the
longest dimension.

E. [Wall Penetrations]{.underline}. Where ducts pass through walls in
exposed areas, install suitable escutcheons made of sheet metal angles
as closers. At all locations where ductwork passes through floors,
provide watertight sleeves projecting 3 inches above finished floor and
flush with bottom of floor slab. Fabricate sleeves of 1/8-inch thick
steel, galvanized after fabrication. Anchor into adjacent floor slab as
required. Provide sleeves inside as well as outside chases. Support
ducts where passing through floors with steel structural angles of
adequate bearing surface, galvanized after fabrication and resting on
top of the sleeve.

F. [Interior Painting]{.underline}. Paint flat black, the interior of
metal ductwork exposed to view through grilles, registers, and other
openings. Do not install grilles, registers, or similar items until
painting is complete.

G. [Ductwork Openings]{.underline}. Provide openings in ductwork where
required to accommodate thermometers and controllers. Provide pilot tube
openings where required for testing of systems, complete with metal can
with spring device or screw to ensure against air leakage. Where
openings are provided in insulated ductwork, install insulation material
inside a metal ring.

H. [Ductwork Location]{.underline}. Locate ducts with sufficient space
around equipment to allow normal operating and maintenance activities.

I. [Sealant]{.underline}. The entire duct system shall be sealed.
Nonhardening, water resistant, fire resistive, compatible with mating
materials; liquid used along or with tape, or heavy mastic. Duct shall
be thoroughly cleaned prior to application of sealant. All transverse
joints, longitudinal seams and duct wall penetrations shall be sealed.
All ductwork shall be sealed as per seal Class A irrespective of the
duct pressure classifications.

J. [Hangar Rod]{.underline}. Galvanized steel, threaded continuously.

3.02 [LOW PRESSURE DUCTWORK]{.underline}

A. [Construction]{.underline}. Construct rectangular ducts in accordance
with the SMACNA Duct Manual. Construct round ducts in accordance with
Section III of the SMACNA HVAC Duct Construction Standards Manual.

B. [Controls]{.underline}. For control devices concealed by ceilings,
furring, or in other inaccessible locations, furnish extension rods and
appropriate recessed-type Young regulators, mounted on the surface of
the ceiling or the furring, unless specified, or shown otherwise. For
ducts which are not concealed, or ducts which are above lay-in ceiling
but accessible, provide heavy-duty, quadrant-type, adjustable regulators
having wing nuts for locking in position. Saw-mark the ends of all
operating rods for dampers and air control devices to indicate damper
position.

C. [Obstruction]{.underline}. Install streamline deflectors at any point
where dividing a sheet metal duct around piping or where other such
obstruction is permitted. Where such obstructions occur in insulated
ducts, fill space inside streamliner and around obstructions with glass
fiber insulation.

D. [Low Pressure Insulated Flexible Duct]{.underline}. Do not exceed 6
feet in length with any flexible duct. Make end connections with 3M 900
mastic and stainless steel screw band. Support duct independently of
lights, ceiling and piping.

E. [Low Pressure Duct Supports]{.underline}.

1\. Horizontal Ducts Up to 40 Inch. Support horizontal ducts up to and
including 40 inches in their greater dimension by means of No. 18 U.S.
gage band iron hangers attached to the ducts by means of screws, rivets
or clamps, and fastened to inserts with toggle bolts, beam clamps or
other approved means. Place supports on at least 8\'-0\" centers. Use
clamps to fasten hangers to reinforcing on sealed ducts.

2\. Horizontal Ducts Larger Than 40 Inch. Support horizontal ducts
larger than 40 inches in their greatest dimension by means of hanger
rods bolted to angle iron trapeze hangers. Use double nuts and lock
washers on threaded rod supports. Place supports on at least 8\'-0\"
centers according to the following:

[Angle Length Angle Rod Diameter]{.underline}

[Feet Inches]{.underline} [Inch]{.underline}

4\'-0\" 1-1/2\"x1-1/2\"x1/8\" 1/4\"

6\'-0\" 1-1/2\"x1-1/2\"x1/8\" 1/4\"

8\'-0\" 2\"x2\"x1/8\" 5/16\"

10\'-0\" 3\"x3\"x1/8\" 3/8\"

3\. Vertical Ducts. Support vertical ducts where they pass through the
floor lines with 1-1/2\" x 1-1/2\" x 1/4\" angles for ducts up to 60
inches. Above 60 inches, the angles must be increased in strength and
sized on an individual basis considering space requirements.

3.03 [MEDIUM PRESSURE DUCTWORK]{.underline}

A. [Rectangular]{.underline}. Construct rectangular ducts as noted
before. Provide reinforcing method as shown without tie rods through
60-inch size. For rods 61 inches and over, use tie rods to keep
reinforcing angles to 2-inch minimum. Use sealant (3M EC-800) or equal
and 4-inch wide Glasfab or continuous welds at all of the longitudinal
seams, and flanged (calk or gasket) transverse joints on rectangular
ducts in shop and field fabrication to provide positive seal.

B. [Round]{.underline}. Provide round, medium-pressure duct construction
as noted before. Seal joints with 3M EC-800, lapped a minimum of 3
inches, secured with sheet-metal screws and covered with sealant, over
which is applied a 4-inch wide Glasfab cloth. Apply additional sealant
until the cloth is completely embedded, or welded. Make 90-degree branch
take-offs with conical tees. Weld take-off fittings to fittings or to
the main duct. Clean and coat all welds with rust-inhibiting paint.
Stamp elbows as smooth-type, or 5- or 3-piece segmented or segmented
standing seam type,l with either type having a centerline radius of
1-1/2 times the duct diameter.

C. [Medium pressure Insulated Flexible Duct]{.underline}. Seal flexible
duct connections with 3M 900 mastic and stainless steel clamp. Support
duct independently of lights, ceiling and piping.

D. [Medium Pressure Duct Supports]{.underline}. Provide hangers and
supports in accordance Low Pressure Duct.

3.04 [OPENING IN DUCTWORK]{.underline}

> Provide opening in ductwork where required to accommodate thermometers
> and controllers. Provide pilot tube openings where required for
> testing of systems, complete with metal can with spring device or
> screw to ensure against air leakage. Where openings are provided in
> insulated ductwork, install insulation material inside a metal ring.

3.05 [FLASHING]{.underline}

> Where ducts pass through roofs or exterior walls, provide suitable
> flashing to prevent rain or air currents from entering the building.
> Provide flashing not less than No. 26 gage stainless steel or 16-ounce
> (450 g) copper.

3.06 [DUCT LINING (LOW PRESSURE - RECTANGULAR)]{.underline}

> Install glass fiber acoustical lining in all rectangular (except
> exhaust) ductwork shown on drawings. Provide 1-inch thick, 3-pound
> density, flexible lining coated on the air stream side to reduce
> attrition. Secure to duct surfaces with Foster 85-22 adhesive and
> sheet metal fasteners on 12-inch centers. Omit lining as necessary to
> permit satisfactory operation of air control devices. Coat all exposed
> edges and leading edges of cross joints with adhesive. Insulation
> shall not breed or promote fungi or bacteria, shall resist mold
> growth, shall not rot or sustain vermin.

3.07 [INSTALLATION - PVC DUCTWORK]{.underline}

> Follow manufacturer\'s written instructions and recommendations with
> the following minimum guidelines.

A. [Welding]{.underline}. All welding to be done by the hot gas fusion
welding method using PVC Filler Rod as manufactured for this purpose.
Welding shall be performed by workmen adequately trained in the art of
PVC welding. Ductwork must be air tight. Use three passes with 5/32\" (4
mm) rod. Wherever possible there shall be one interior weld in addition
to the exterior welds for added strength.

B. [Branches]{.underline}. To enter main at no more than forty-five
degrees (thirty degrees preferred) to direction of flow and wherever
practical to enter on an enlarging taper section. Branches should not
enter opposite each other. Branches to be continuously welded to main.

3.08 [TESTS]{.underline}

A. [Allowable Leakage]{.underline}. Test ductwork for leaks before
concealing. Maximum allowable leakage is 5 percent of total flow.

B. [Equipment]{.underline}. Provide equipment necessary for performing
tests, including rotary blower, orifice section and U-tube gage board
complete with cocks and rubber tubing.

C. [Risers and Branch]{.underline}. Test duct riser or branch duct
including flexible duct runouts in accordance with SMACNA manual.

D. [Mains]{.underline}. Test mains after risers and branches are tied in
and all equipment set. Close runout connections and place fan in
operation. Provide pressure in mains above design pressure. Visually
inspect joints. Repair leaks detected by sound or touch. Release mains
for completion after joints are tight.

3.09 [ADJUSTING AND CLEANING]{.underline}

> A. Clean duct system and force air at high velocity through duct to
> remove accumulated dust. To obtain sufficient air, clean half the
> system at a time. Protect equipment which may be harmed by excessive
> dirt with temporary filters, or bypass during cleaning.

END OF SECTION