Acoustical enclosures shall be of dual wall tongue and groove panel construction finished and installed aslocated and sized on the contract drawings. The use of contractor's shop constructed enclosures shall not be allowed.

Individual wall and roof panels shall be (2", 4"or 6”thick)* constructed of 18 gauge, galvanized, solid exteriorskin and a 22 gauge, galvanized, perforated interior liner with minimum 18 gauge, galvanized longitudinal stiffeners spaced a maximum of 16" apart. Floor panels shall be (2", 4" or 6” thick)* constructed of 16 gauge, galvanized, solid upper skin and 22 gauge, galvanized, solid lower skin for floor panels (intermediate floor panels shall have perforated lower skins where applicable). Spacing of internal longitudinal stiffeners shall not exceed 8". Panels shall have a maximum width of 45 1/2. Panel spans up to 16'-0" shall be furnished as one piece. Stiffeners shall have a depth equal to the panel thickness and be connected to both the inner and outer skin so as to provide an integral structural reinforcement within the panel. Panel interior shall be completely filled with a minimum three pound per cubic foot density glass fiber insulation. Insulation shall be corrosion and moisture resistant, and rated noncombustible as defined by NFPA Standard 220 when tested in accordance with ASTM E136. Surface burning characteristics per ASTM E84 shall be:

Male edge of panel shall be metal enclosed and filled with insulation. Because of the male-female joint, panels contain no insulation voids in joints between panels. Manufacturers furnishing individual panels with an open male channel shall fill the open channel with insulation as heretofore specified, which shall be attached permanently to the panel.

OPENINGS: The panel manufacturer shall provide all duct and fan openings. All piping and conduit penetrations shall be field located and cut and sealed.

Access doors shall be 24" x 66" except as noted on drawings and shall be of the prehung type constructed of 18 gauge, galvanized, all welded door frame and 18 gauge, galvanized, solid exterior and interior skins enclosing insulation as specified for panels. Doors shall be provided with a minimum of two Kason 1061 hinges and two SEMCO door latches operable from both sides of the door. Air seals suitable to provide airtight seal shall be provided between door and frame. Door swing shall be such as to open against system pressures. Each door, when required, shall have a 12" x 12" double pane safety glass viewing window.

In addition to panels, sufficient trim of a minimum of 16 gauge galvanized shall be provided in standard lengths to erect casing leaving no exposed panel edges. Base channel shall have 9/16" holes prepunched 24" on center for securing with approved fasteners to curb or pad. Sufficient panel sealant and self-tapping fasteners shall be provided to erect enclosure per manufacturer's instructions. Panel sealant shall be a gray colored, single component, non-sag, nonstaining, permanently flexible, gunnable butyl rubber of the highest quality and conforming to federal specification TT-S-001657 for "sealing compounds, single component, butyl rubber base, solvent release type." Sealant for door frame to panels applications shall be a clear colored silicone Rubber sealant conforming to the provisions of MIL-A-46106A Type 1 and certified to federal specification II-S-001543A.

Structural integrity of the completed enclosure shall provide for maximum panel deflections of 1/240 of free span when enclosure is subjected to a test pressure of 10" water column without the use of any fasteners at panel joints. Data used to determine structural performance shall have been the result of independent testing of a representative sample of the manufacturer's regular production which shall have been certified by the independent tester. Panels shall have been tested by subjecting them to an air pressure simulating the loadings imposed under normal operation. Panel tests as a result of application to artificial loads unevenly distributed over the entire panel surface will not be accepted.

Structural steel required to limit the deflection herein specified shall be designed and furnished by the enclosure manufacturer and installed by the contractor. All equipment supports shall be designed, furnished and installed by the contractor.

Acoustical performance for both airborne noise transmission and radiated noise transmission shall be as follows:

Thermal performance of panels shall provide for a U-factor of 0.10 for 2" panels and 0.06 for 4" panels or .05 for 6” panels.

Enclosure manufacturer shall have published data equal in all respects to enclosures manufactured by SEMCO Incorporated. Performance data certified by an industry recognized independent acoustical testing laboratory shall be submitted to the engineer to verify that the completed enclosure will meet or exceed the requirements in this specification. Such data shall have been the result of certified independent testing of a representative sample of the manufacturer's regular product in accordance with applicable provisions of the American Society for Testing and Materials Procedures (423-77) and (E90-70). Performance of the enclosure shall not be impaired through prolonged exposure to noise, vibration, pressure or dampness.

*Select either one or combination depending upon specific application.