Research conducted by ROCKFON and NGC Testing Services1 shows that a lightweight plenum barrier positioned vertically above the wall, blocking the plenum, can provide a STC/CAC 50 level of blocking when combined with a stone wool ceiling system. This option can decrease the cost of the ceiling, allow for greater aesthetic flexibility and prevent the need to control noise leaks through the ceiling system. The plenum barrier should be installed with care ensuring no large openings while taping or caulking small openings, gaps and cracks.
- 5/8" gypsum board (type X) – 1 layer
- Sealed install2 (caulk & tape)
- 3-1/2" thick ROXUL AFB® Semi-Rigid Batt Insulation
- Alternative STC 50 plenum barrier options
- Chicago Metallic Tee-Bar suspension grid
- ROCKFON stone wool ceiling panels – optimized for sound absorption
- Noise control measures for noise flanking paths through lights, grilles, diffusers – not required
- CAC 50 (with plenum barrier)
- Lab test #NGC6015023_R1
- 5/8" gypsum board (type X) – 1 layer one side, 2 layers other side
- 3-5/8" steel studs (25 gauge) spaced 16" on center
- 3" thick ROXUL AFB® Semi-Rigid Batt Insulation
- STC 50 (lab test3 #TL-93-333)
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 ROXUL are subsidiaries of the ROCKWOOL Group.