[2.6
FIBROUS GLASS DUCTS
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NOTE: Do not use insulation liners for ductwork at
infectious areas in hospitals, such as operational
suites, nurseries, pathological facilities,
intensive care units, and surgical wards; use
factory prefabricated sound attenuators instead.
For brig facilities, fibrous glass ductwork should
not be used in inmate housing area, areas accessible
to inmates, nor areas with concrete, gypsum board,
or plaster ceilings. Do not use fibrous glass ducts
within 300 mm 12 inches of electric or fuel fired
heaters.
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At the Contractor's option, rigid fibrous glass ductwork may be provided in
lieu of metal ductwork. Provide factory fabricated molded round sections
or flat sheets of resin bonded inert inorganic fibrous glass, faced with an
external vapor barrier, conforming to UL 181, Class 1, NFPA 90A, and SMACNA
FGDCS with the following general properties:
a.
Thickness:
Minimum 25 mm one inch;
b.
Stiffness (Product of Young' Modulus, E, and Moment of Inertia,
I), EI: 3275 kPa 475 pounds per square inch;
c.
Thermal Conductivity: Maximum 0.036 watt per meter per degree K
0.25 Btu inch per square foot per degrees F per hour; and
d.
Permeance:
0.02 maximum.
]2.7
DIFFUSERS, REGISTERS, AND GRILLES
2.7.1
Material and Finishes
Provide factory-furnished diffusers, registers, and grilles constructed of
[steel] [or] [aluminum]. Exterior and exposed edges shall be rolled, or
otherwise stiffened and rounded. [Steel parts shall be factory zinc
phosphate treated prior to priming and painting or have a baked-on enamel
finish.] Colors shall be selected or approved by Contracting Officer.
[For ductwork of pressure classes 1000 to 2500 Pa 4 to 10 inch water gage,
provide sponge-rubber gasket between flanges and wall or ceiling.]
2.7.2
Sound Pressure Level
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NOTE: The designer must observe that the standard
10 dB attenuation of sound power level takes into
consideration the various types of room effects and
ceiling transmission losses of the design place. See
details in ASHRAE "Handbook of Fundamentals."
Recommended permissible room sound pressure levels
are as follows:
NC Range, dB
Typical Application
20-25
Church Sanctuary,
Concert and Opera Halls,
SECTION 15810N
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