HTHP Home • Issue Contents • Forthcoming Papers
Thermal conductivity, resistance and specific heat capacity of chemically-treated, widely-used timber for building-envelope
Charles Antwi-Boasiako and Boakye K. Boadu
Wood has low thermal conductivity with high thermal resistance and specific heat capacity (SHC). Timber-designed building-envelopes have much resistance to solar radiation, which discomforts occupants. How chemicals alter thermal properties of preservative-treated non-durable woods for housing is inadequately studied. Two preservative-chemicals (Erythropleum suaveolens bark extract and inorganic Maneb/Lambda) influence on the SHC (determined by “method of mixtures”) and, thermal conductivity and resistance (using Lee’s Disc Apparatus) of Ceiba pentandra (a non-durable building timber) was investigated. Stakes treated with E. suaveolens and Maneb/Lambda recorded greater conductivity [(0.005 ± 0.001) × 10-3 and (0.006 ± 0.0006) × 10-3 W/m.K respectively] than C. pentandra control [(0.004 ± 0.0008) × 10-3 W/m.K]. Conductivity was greater in longitudinal surface than radial and tangential directions for all stakes. Thermal resistance of stakes rated as: control [(0.12 ± 0.0008) × 102 – (1.02 ± 0.02) × 102 m2K/W] > E. suaveolens [(0.1 ± 0.002) × 102 – (0.76 ± 0.02) × 102 m2K/W] > Maneb/Lambda [(0.1 ± 0.002) × 102 – (0.73 ± 0.02) × 102 m2K/W].
Maneb/Lambda-treated stakes obtained the greatest SHC [(6810.9 ± 12) × 106], then E. suaveolens-treated samples [(5242.1 ± 269.9) × 106] and untreated/control [(4014.2 ± 47.8) × 106]. Compared to other building materials (e.g., steel, aluminium and concrete), treated stakes have low thermal conductivity, with high thermal resistance and SHC, which is desired as an insulation material. Thus, while chemically-treated timber durability is improved, its insulating capacity to provide thermal comfort in buildings is assured.
Keywords: Heat transmission, organic preservative, specific heat capacity, steady-state, thermal insulation, wood anisotropy.