UTILIZATION OF CORK RESIDUES FOR HIGH PERFORMANCE WALLS IN GREEN BUILDINGS

摘要

Large amounts of waste material of forestry and agricultural processes are still underutilized. An interesting eco-friendly alternative utilization of the organic residues of agricultural and forestry processes is to be found in the thermal insulation of buildings. Such natural materials are produced through energy-efficient processes; restrict the emissions of volatile compounds, which are harmful in indoor environments; are easily recycled; and are obtained from local natural resources or from the waste materials of the agricultural and forestry industry (Baccilieri et al., 2016). Cork is one of the most popular natural materials used as insulators. It is obtained from the bark of the Quercus suber and only 25% of it, the high quality cork, is used to produce bottle stoppers, while the remaining 75% becomes waste material of the process. The building sector accounts for 40% of consumed primary energy, 20% of which is used to heat and cool indoor environments through HVAC systems. Though several intervention strategies are possible, latest studies have highlighted that a conscious design of the building envelope is the most suitable solution to reduce environmental burdens. Actually, its components considerably affect the energy performances of buildings mitigating the effects caused by variable external environmental conditions and reducing expenditure by 50-70%. Only in the last few years, research has been targeted to the development of innovative solutions to improve the energy performances of the building envelope by studying and using biocompatible natural insulating materials. This paper proposes a multilayer agglomerated cork wall with two air cavities and a central OSB (Oriented Strand Board) load-bearing structure that can be used as an external vertical partition in buildings located in Mediterranean climate areas. Specific graphs were developed to rapidly establish thermal insulation characteristics also taking into account ISO standard 13786 and the performances required from the building. The wall, which was composed of 6.5 cm-thick external layers of agglomerated cork, for a total thickness of 20 cm, had a periodic thermal transmittance value below 0.12 W m-2 K-1. The same performances can be obtained using perforated brick walls, of at least 50 cm of length, insulated with no less than 5 cm of rock wool, for an overall weight per unit area over 20 times higher.