Thermal insulation properties of wood-based sandwich panel for use as structural insulated walls and floors

Thermal insulation and warmth-keeping properties of thick plywood-faced sandwich panels with low-density fiberboard (plywood-faced sandwich, PSW), which were developed as wood-based structural insulation materials for walls and floors, are comprehensively clarified. The properties focused on were thermal conductivity (λ), thermal resistance (R), and thermal diffusivity (D). The results for PSW panels were compared with those for commercial wood-based boards, solid wood, and commercial insulators. The λ values were measured for PSW panels and their core and face elements. As a result, the composite theory of λ was found to be appropriate for PSW composites, because the calculated/experimental λ ratios were approximately 90%. The λ values for PSW panels with densities of 340 kg/m³ (PSW350) and 410kg/m³ (PSW400) were 0.070 and 0.077W/mK, respectively. The R values for PSW350 and PSW400 were 1.4 and 1.2m²K/W, and the D values were 0.00050 and 0.00046m²/h, respectively. Consequently, the PSW provided thermal insulation properties superior to those of the boards and in terms of warmth-keeping properties were greatly advantageous over the insulators. These advantages were due to the moderate densities of PSW panels. The PSW panel with sufficient thickness showed remarkably improved thermal resistance compared with those of the boards.