Abstract:

Objective: Modern timber structure walls, such as wood frame walls and cross-laminated timber (CLT) walls, face significant limitations in airborne sound insulation and thermal performance. Sound insulation is constrained by low-frequency resonance effects and sound bridge transmission, while thermal performance is compromised by thermal bridging through wood frames. These limitations hinder their ability to meet the functional requirements of prefabricated building envelopes. To overcome the limitations of single-material walls in terms of sound insulation and thermal performance, this study proposes an innovative wood frame-autoclaved aerated concrete (ALC) composite wall system based on the complementary advantages of ALC and wood frame structures, aiming to provide a high-performance envelope solution for prefabricated construction. Method: Five full-scale wall specimens were designed and constructed, with a 180 mm thick single-layer ALC solid plate wall serving as the control group. The composite walls incorporated key technical measures, such as conventional or staggered wood frames (SPF dimension lumber), ALC solid or hollow-core plates (with glass wool filling in the cavities), and gypsum board sheathing. Airborne sound insulation was measured over the 100–5 000 Hz frequency range (18 one-third-octave bands) in a standardized laboratory according to GB/T 19889.3. The weighted sound reduction index (R_w) and spectrum adaptation terms (C;C_tr) were calculated. The wall thermal transmittance (K-value) was calculated based on GB 50176. Thermal bridging effects were analyzed, and the mechanisms for thermal performance optimization were elucidated. Result: The sound insulation and thermal performance of the wood frame-ALC composite walls significantly surpassed those of the single-layer ALC wall, conventional wood frames and single-layer CLT walls. Notably, the composite wall with staggered wood frames and an ALC hollow-core plate achieved R_w > 51 dB, representing improvement of 8, 13 and 17 dB, respectively, compared to the single-layer ALC wall [R_w(C;C_tr)=43(0;?3) dB], the conventional wood frame wall [R_w(C;C_tr)=38(?3;?10) dB], and the single-layer CLT wall [R_w(C;C_tr)=34(0;?3) dB]. This enhanced insulation stems from multiple mechanisms: the staggered wood frames interrupt vibration transmission paths; the ALC hollow-core plates filled with glass wool increase sound wave reflection; and the deep cavity formed an efficient acoustic spring that significantly suppresses low-frequency resonance. Performance gains were particularly pronounced within the key frequency range of daily living noise (160–630 Hz). Simultaneously, the K value of the staggered wood frame-ALC hollow-core plate composite wall was reduced to 0.396 W·m^?2K^?1, which was 54.8%, 16.5%, and 35.5% lower than that of the single-layer ALC wall (K=0.877 W·m^?2K^?1), the conventional wood frame wall (K=0.474 W·m^?2K^?1), and the single-layer CLT wall (K=0.614 W·m^?2K^?1), respectively. This thermal optimization mechanism lies in the staggered wood frame design, which effectively interrupts continuous thermal bridge pathways, and the ALC hollow-core plates filled with glass wool, which forms a gradient thermal barrier that reduces the equivalent thermal conductivity. The proposed composite wall system achieved a surface density of 87.6 kg·m^?2, which is 41.0% lower than that of the single-layer ALC wall (148.5 kg·m^?2). Moreover, The composite wall system outperformed both conventional wood frame walls and single-layer CLT walls in terms of sound insulation, thermal performance, fire resistance, and durability. Conclusion: The staggered wood frame-ALC hollow-core plate composite wall achieves a synergistic breakthrough in sound insulation and thermal performance with a total wall thickness of less than 210 mm, meeting the acoustic requirement for external walls in residential buildings (R_w+C_tr≥45 dB) and the energy efficiency limit for cold regions (K≤0.45 W·m^?2K^?1). Through integrated physical mechanisms, including sound bridge interruption, thermal bridge optimization, and dual sound-thermal energy dissipation, this study fundamentally addresses the inherent trade-off between sound insulation and thermal performance in lightweight wall systems, providing theoretical support and a product foundation for the design of high-performance prefabricated building walls.

Key words: wood frame-ALC composite wall, thermal performance, frame optimization, thermal bridging, synergistic improvement