BUILDING PHYSICS 14 Explanation regarding the joint insulation value Kij Numerous Kij values were measured in the research project “Vibro-acoustics in the planning process for timber structures”. In addition, measured data of comparable assemblies from different European institutes have been compiled and assessed. The analysis in the table below shows the median values of the joint insulation values for various joint situations. Case Joint type Transmission direction Joint insulation value 1 “Vertical transmission” Path Ff KFf = 20 dB 2 “Horizontal transmission” Path Ff Ceiling, continuous KFf = 3 dB 3 “Horizontal transmission” Path Ff Ceiling, separated KFf = 12+10lg(m2' / m1') 4 “Mixed transmission” Path Df and Fd KFd = 14 dB KDf = 14 dB 5 “Horizontal transmission” Paths Ff, Df, Fd Walls of BBS 125 KFf = 12 dB KDf = KFd = 16 dB Figure 11 – Flank sound transmission with CLT BBS 125 elements In the structure consisting of CLT BBS 125, always 1.25-mm wide wall elements are lined up side-by-side and joined with a wooden riser, which has an acoustic effect like a separating cut (see Figure 11). Consequently, not case 1 must be expected for KFf with a continuous flanking wall, but the more favourable case 3. This was proven by means of the measurements in the course of the aforementioned research project. Likewise based on the acoustically favourable construction design using CLT BBS 125 elements, the RFf measuring results show that with the execution of a separating cut in the flanking wall on the partition wall axis, the KFf value from case 1 must be used in the calculation for this case. NOTE These projections with favourable effects on sound insulation can be chosen only when the exterior wall does not consist of large-format elements. Furthermore, any potentially existing direct planking on the interior side of the flanking wall must not extend beyond the partition wall.
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