Research conducted by Rockfon® and NGC Testing Services1 shows that a lightweight plenum barrier made of stone wool insulation or gypsum board positioned vertically above the wall, blocking the plenum, can provide an STC/CAC 45 level of blocking when combined with a stone wool ceiling system. This design approach can decrease the cost of the ceiling, allow for greater aesthetic flexibility and prevent the need to control noise leaks through the ceiling system.
Running the ceiling grid continuously over the tops of interior partitions is sometimes utilized so that future reconfiguration of the walls does not require replacement of the ceiling grid. In other cases, pre-manufactured demountable walls typically stop at the underside of the suspended ceiling. When the ceiling grid passes over the walls, install the double layer plenum barrier as shown in the detail below.
Sources
1 Madaras, G. and Heuer, A. (2016). “Optimizing Ceiling Systems and Lightweight Plenum Barriers to Achieve Ceiling Attenuation Class (CAC) Ratings of 40, 45 and 50”. Proceedings of the New England NoiseCon-16: Revolution in Noise Control conference, Providence, RI, 13-14 June, 2016. Electronic publication by the Institute for Noise Control Engineering.
2 The ‘sealed install’ method for the gypsum board plenum barriers is similar to fire-rated wall construction in that it includes cutting the gypsum board to within 1/4” of elements penetrating the plenum barriers. The gaps around penetrating elements, as well as small holes, joints, screw heads, perimeter edges, etc., are all taped or caulked/sealed.
3 The referenced laboratory test(s) are part of an extensive, multi-year testing program conducted by the National Research Council Canada (NRCC) and published by the Institute for Research in Construction (IRC). For more details, including 1/3 octave band transmission loss data, refer to internal reports IRC-IR-693, October 1995 and IRC-IR-761, March 1998. The research program was partially funded by ROXUL, Inc. ROCKFON and ROCKWOOL are subsidiaries of the ROCKWOOL Group.
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