Latent Heat Phenomena in Buildings and Potential Integration into Energy Balance

Wood as hygroscopic material has the capacity to absorb moisture and thus to moderate the indoor relative humidity (RH) in a building, resulting in lower ventilation demand. In addition, when moisture migrates in hygroscopic structures energy is released through latent heat phenomena. The diurnal variation of moisture content in wood hold a potential for contributing in the buildings energy balance. This study presents the theoretical energy savings in low energy buildings with interior wooden surfaces under different moisture protocols indoors. The requirements of the Norwegian Building Regulations (TEK10) are followed regarding the U-values of the envelope components. A hygrothermal simulation tool is employed to estimate the potential diurnal variations of moisture content in the wood structure. The latent heat released and absorbed is mathematically calculated for a reference building. The results show the potential of hygroscopic structures to save thermal energy by means of heat of sorption and to reduce the conductive heat losses through opaque building elements. The limitations of the phenomena are also discussed.