Section 15291, Commercial/Residential Duct Systems

PART 1.00 - GENERAL

1.01 Scope

A. Work covered by this specification consists of furnishing all labor, equipment, materials and accessories, and performing all operations required, for correct fabrication and installation of fibrous glass duct liner in sheet metal commercial or residential air duct systems, in accordance with applicable project drawings and specifications, subject to terms and conditions of the contract:

1. Installation of all air duct systems operating at internal air velocities not exceeding rated duct liner limitations and internal air temperature not exceeding 250˚F (121˚C).
   
2. Duct liner products shall conform to the requirements of ASTM C 1071 and ASTM C 665.
3. Duct liner products shall perform in accordance with the requirements of ASHRAE 62-2001.
4. The manufacturer's product identification, R-value, NFPA 90A/90B, and other required labeling information shall appear on the air stream surface.
5. Duct liner adhesive shall conform to the requirements of ASTM C 916.
6. The finished duct system shall meet the requirements of NFPA 90A and 90B, including
7. Duct liner products shall conform to the requirements of ASTM E 84 with a flame spread index not greater than 25 and a smoke developed index not greater than 50 per NFPA 255, UL 723, and CAN4/ULC-S102.
8. The air stream surface shall have no evidence of flaming, glowing, smoldering, visible smoke, or delamination, cracking, or reduction in thickness when tested in accordance with ASTM C411 at a temperature not less than 250oF (121oC).
9. When tested in accordance with NFPA 259, the insulation shall, have a potential heat value not exceeding 3500 Btu/lb (8141 Kj/kg).
10. Duct liner products shall exhibit no microbiological amplification per ASTM C 1338 when tested per ASTM G 21-96 (fungi test) and ASTM G 22-96 (bacteria test)

B. Dimensions shown on the plans are finished inside dimensions.

C. Fabrication and installation shall conform to manufacturer's recommendations and to the requirements of the latest edition of North American Insulation Manufacturers Association Fibrous Glass Duct Liner Standard (hereinafter referred to as NAIMA FGDLS) or of Sheet Metal and Air Conditioning Contractors National Association HVAC Duct Construction Standards - Metal and Flexible (hereinafter referred to as SMACNA HVAC DCS).

1.02 Delivery and storage of materials

A. All materials and/or fabricated, insulated duct sections and fittings shall be delivered to the job site in good condition and stored in a safe, dry place.

B. All materials shall be protected from dust, dirt, moisture, and physical abuse before, during, and after installation. Wet or contaminated duct liner shall be replaced.

PART 2.00 - PRODUCTS

2.01 Insulated duct system

A. All supply ducts, return ducts, and related fittings shall be insulated with duct liner meeting the requirements of ASTM C 1071 as follows:

1. Type I - Flat, in roll form, in thicknesses of 1/2 to 2 in. (13 to 51mm) in 1/2 in. (13mm) increments. Maximum thermal conductivity at 75˚F (24˚C) mean temperature: 0.31 Btu•in/hr•ft2•˚F ( = 0.045 W/m•˚C).
2. Type II - Flat, in sheet form, in thicknesses of 1 to 2 in. (25 to 51mm) in 1/2 in. (13mm) increments. Maximum thermal conductivity at 75˚F (24˚C) mean temperature: 0.27 Btu•in/hr•ft2•˚F ( = 0.039 W/m•˚C).

PART 3.00 - EXECUTION

3.01 Receiving Inspection

A. All materials shall be inspected to verify that the duct liner product may be installed in accordance with project drawings, operating performance parameters and limitations, and provisions of NAIMA FGDLS or SMACNA HVAC DCS.

3.02 Insulation of straight ducts and fittings

A. All portions of duct designated to receive duct liner shall be fully insulated, with all joints neatly butted and no interruptions or gaps. Duct liner shall be installed with the surface printing exposed to the air stream.

B. Duct liner shall be adhered to the sheet metal with 90% (minimum) coverage of adhesive complying with requirements of ASTM C 916.

C. If not already coated by the duct liner manufacturer, all transverse edges not receiving sheet metal nosing shall be coated. Longitudinal joints in duct liner should occur at the corners of ducts. If duct size and standard duct liner product dimensions may make exposed longitudinal joints necessary, exposed joints shall be coated with adhesive designed for duct liner application meeting requirements of ASTM C 916. Such joints shall be secured with mechanical fasteners in accordance with NAIMA FGDLS, treated as transverse joints.

D. Duct liner shall be mechanically fastened with weld-secured or impact-driven fasteners so as to compress the insulation no more than 1/8 in. (3 mm) based on nominal insulation thickness, installed perpendicular to the duct surface. Spacing of mechanical fasteners with respect to interior duct dimensions shall be in accordance with NAIMA FGDLS or SMACNA HVAC DCS. Fastener heads or washers shall have a minimum area of 0.75 in.2 (5cm2) with beveled or cupped edges.

E. Metal nosings (channel or zee) shall be securely installed over transverse liner edges facing the airstream at fan discharge and at any point where lined duct is preceded by unlined duct. Also, where air velocities exceed 4,000 fpm (20.3 m/sec), metal nosing shall be installed on upstream edges of all lined duct sections.

F. Flexible duct liner shall be folded and compressed at corners of rectangular duct sections, or shall be cut and fit to assure a lapped, compressed corner joint.

G. Rigid duct liner shall be cut and fit to assure tight, overlapped corner joints. Top pieces of rigid duct liner shall be supported at the edges by side pieces.

H. Installation of two layers of duct liner is not recommended. If the specification forces the use of multiple layers, the following steps shall be taken:

1. First layer of duct liner shall be adhered to the sheet metal in the usual manner.
2. Top layer of duct liner shall be adhered to bottom layer using a minimum of 90% adhesive coverage.
3. Mechanical fasteners shall be of the proper length for the double layer of duct liner.
4. Leading edges of double layer duct linings shall be treated to prevent separation of the two layers in accordance with requirements for single layer applications as determined by air velocity.

I. All ductwork joints and seams shall be sealed in accordance with specification seal class rating.

3.03 Final Inspection

A. Upon completing installation of lined duct and before HVAC system start-up, ductwork shall be visually inspected to verify that duct liner has been correctly installed and to confirm that the duct system is free from construction debris.

3.04 Commissioning

After the lined duct system is completely installed and ready for service, a final inspection of the entire system shall be conducted. This inspection should include, at minimum, the following steps:

1. All registers, grilles, and diffusers shall be checked to ensure that they are clean and free from construction debris.
2. All filters shall be checked in accordance with their manufacturers' instructions. Specified grade of filters shall be used at all times system is operating.
3. Supply openings shall be covered with filter media prior to system start-up to catch any loose material that may remain inside the ductwork.
4. The HVAC system shall be turned on and allowed to run until steady state operation is reached.
5. Temporary filter media shall be removed from supply openings and, along with it, any loose material blown downstream and caught by the filter media.
6. Air delivery performance shall be checked to ensure that it meets all requirements and complies with SMACNA leakage specifications.

3.05 Safety precautions

A. All job site operations shall be conducted in compliance with applicable provisions of the Occupational Safety and Health Act, NAIMA's Health and Safety Partnership Program (HSPP) and all state and/or local safety and health codes and regulations that may apply to the work. Consult manufacturer's Material Safety Data Sheet (MSDS) when appropriate.