Thermal Characterization of Sustainable Materials of Marine Origin

The search for environmentally friendly insulation materials is a paramount issue in green buildings. This work examined organic materials of marine origin (algae and plants), including Sargassum and Posidonia oceanica, for their high acoustic performance and low environment impact, being natural-ly abundant organic raw materials and, in most cases, a waste product. Storms hit the beaches, dropping these seaweeds creating accumulations, which are regularly removed and thrown into dumpsters. The reason for the interest in these materials is their fibrous and highly porous nature, through which sound can be effectively lowered in intensity. In previous studies, the sound absorption coefficients were measured in lab tests and vary with density: for Posidonia oceanica (with an average density of 120 kg/m³), the sound absorption coefficients vary between 0.7 and 0.9, and for Sargassum (with an average density of 150 kg/m³), between 0.6 and 0.8, depending on the frequency and sample thickness, respectively. In addition to the acoustic performance, these materials show a rather good thermal insulation. Thermal conductivity values of Posidonia oceanica were relatively lower (0.048–0.061 W/mK), particularly at low densities, and therefore it is likely to see use in light insulation. Sargassum, with thermal conductivity in the range 0.060 to 0.069 W/mK, was discovered to be acous-tically better at higher densities, as expected after its structure, and therefore it is likely to see use in stationary applications where weight is secondary in importance. The observations verify that Sargassum and Posidonia oceanica can be a viable alternative to conventional insulation materials, both for high thermal-acoustic performance and ecological sustainability. The optimal density of the samples plays a key role in balancing thermal insulation and sound absorption, opening new pathways to the use of zero-impact raw ma-terials in buildings.