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title: Acoustic Insulation
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description: >
When to use: Sound-absorbing insulation installed within partition cavities, ceiling plenums, and floor/ceiling assemblies to attenuate airborne sound transmission between interior spaces in commercial, institutional, healthcare, hospitality, multi-family residential, and educational buildings. Covers unfaced mineral fiber (stone wool and slag wool), unfaced glass fiber batts and blankets, and mineral wool board used as cavity infill. Addresses material selection, density and thickness, integration with the host wall, ceiling, or floor assembly to achieve tested STC ratings, fire and smoke characteristics, noncombustibility, attachment in plenum and floor applications, and field verification of acoustic performance.
− Not intended for: Thermal-only insulation in building envelope assemblies (see [[syncs/building-thermal-insulation]]); duct liner and duct wrap (see [[syncs/hvac-ductwork]]); exterior acoustical wall panels, sound-absorbing ceiling tiles, or freestanding acoustic baffles; sound masking electronic systems; vibration isolation pads and seismic isolation; below-slab impact insulation for floor-floor IIC ratings as a standalone product (coordinate with floor assembly standard); firestopping at penetrations through rated assemblies (see [[syncs/firestopping]]); and acoustic seals at door and frame perimeters (see [[syncs/doors-frames-and-hardware]]).
+ Not intended for: Thermal-only insulation in building envelope assemblies (see [[sync/building-thermal-insulation]]); duct liner and duct wrap (see [[sync/hvac-ductwork]]); exterior acoustical wall panels, sound-absorbing ceiling tiles, or freestanding acoustic baffles; sound masking electronic systems; vibration isolation pads and seismic isolation; below-slab impact insulation for floor-floor IIC ratings as a standalone product (coordinate with floor assembly standard); firestopping at penetrations through rated assemblies (see [[sync/firestopping]]); and acoustic seals at door and frame perimeters (see [[sync/doors-frames-and-hardware]]).
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## The Contractor shall install the insulation type, density, and thickness specified in the referenced tested assembly without substitution.
−## The Contractor shall coordinate the cavity infill with [[syncs/gypsum-board-assemblies]] for partitions and with the applicable floor and ceiling specifications.
+## The Contractor shall coordinate the cavity infill with [[sync/gypsum-board-assemblies]] for partitions and with the applicable floor and ceiling specifications.
## Substituting a different insulation density, thickness, or material than the one in the tested assembly can change the STC by several points and may push a partition below the design intent. {note}
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## The acoustic mechanism is friction in the fiber matrix, not mass, which is why a 2.5 pcf and a 6.0 pcf stone wool batt produce nearly the same STC contribution in a typical stud-wall cavity; in most stud-wall and ceiling-plenum applications the density at which incremental improvement falls off is between 2.5 and 3.5 pcf. {note}
−## The Contractor shall coordinate with [[syncs/gypsum-board-assemblies]] for the partition design number that drives material, density, and thickness selection.
+## The Contractor shall coordinate with [[sync/gypsum-board-assemblies]] for the partition design number that drives material, density, and thickness selection.
−## The Contractor shall coordinate with [[syncs/firestopping]] for penetration-firestopping where acoustic insulation occurs in fire-resistance-rated assemblies.
+## The Contractor shall coordinate with [[sync/firestopping]] for penetration-firestopping where acoustic insulation occurs in fire-resistance-rated assemblies.
−## Where a single insulation product is intended to serve both thermal and acoustic purposes within the building envelope, the requirements of [[syncs/building-thermal-insulation]] shall govern.
+## Where a single insulation product is intended to serve both thermal and acoustic purposes within the building envelope, the requirements of [[sync/building-thermal-insulation]] shall govern.
−## The Contractor shall coordinate with [[syncs/doors-frames-and-hardware]] for acoustic seals and gasketing at door and frame perimeters in acoustically rated partitions, because door-frame leakage is the dominant flanking path in most rated rooms.
+## The Contractor shall coordinate with [[sync/doors-frames-and-hardware]] for acoustic seals and gasketing at door and frame perimeters in acoustically rated partitions, because door-frame leakage is the dominant flanking path in most rated rooms.
# Referenced Standards {toc}
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### Use of these products in cavities subject to repeated wetting, condensation, or freeze-thaw cycling is outside the scope of this standard. {note}
−### Where the building envelope assembly is also the host for acoustic insulation, vapor management shall follow [[syncs/building-thermal-insulation]] and the higher-density mineral wool products typical of envelope use shall be specified.
+### Where the building envelope assembly is also the host for acoustic insulation, vapor management shall follow [[sync/building-thermal-insulation]] and the higher-density mineral wool products typical of envelope use shall be specified.
## Fungi Resistance {toc}
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### Acoustic cavity-fill insulation in interior partitions, ceiling plenums, and floor cavities shall be unfaced.
−### Where vapor management is required by the assembly, the Contractor shall coordinate with [[syncs/building-thermal-insulation]] for the placement of a separate vapor retarder layer and shall use an unfaced acoustic product for the cavity-fill function.
+### Where vapor management is required by the assembly, the Contractor shall coordinate with [[sync/building-thermal-insulation]] for the placement of a separate vapor retarder layer and shall use an unfaced acoustic product for the cavity-fill function.
### Insulation Facing {toc}
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### Acoustic insulation is not a substitute for firestopping at penetrations through rated assemblies.
−### Penetrations — for conduit, piping, ductwork, cable trays, and other building services — shall be firestopped in accordance with [[syncs/firestopping]] and with the rated penetration designs cited on the drawings.
+### Penetrations — for conduit, piping, ductwork, cable trays, and other building services — shall be firestopped in accordance with [[sync/firestopping]] and with the rated penetration designs cited on the drawings.
−### ASTM C919 acoustic sealant shall be applied around all penetrations and at all perimeter conditions of acoustically rated partitions, coordinated with [[syncs/gypsum-board-assemblies]].
+### ASTM C919 acoustic sealant shall be applied around all penetrations and at all perimeter conditions of acoustically rated partitions, coordinated with [[sync/gypsum-board-assemblies]].
## Acoustic Sealant Coordination {toc}
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## The firestopping installer shall coordinate timing with the insulation installer; where firestop must be re-applied after cavity insulation is in place, the insulation shall be reinstated to its installed condition before the cavity is closed.
−## The gypsum-board specification (see [[syncs/gypsum-board-assemblies]]) shall be enforced to require offset of back-to-back boxes by 24 inches minimum and the use of acoustic putty pads or listed acoustic box covers in high-STC partitions.
+## The gypsum-board specification (see [[sync/gypsum-board-assemblies]]) shall be enforced to require offset of back-to-back boxes by 24 inches minimum and the use of acoustic putty pads or listed acoustic box covers in high-STC partitions.
# Mock-Ups {toc}
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### The Contractor shall document any conditions observed during installation that may affect the long-term performance of the insulation — evidence of water infiltration, inadequate climate control, or trades disturbing previously installed cavity insulation — and shall bring them to the Architect's attention before the cavity is closed.