Bio-based insulation materials and their hygrothermal performance in a building envelope system (ETICS)

Abstract

Bio-based insulation materials (such as wood or hemp) are emerging as a promising alternative in building envelope applications, aiming at improving in-use energy efficiency. When compared to common insulation materials (rock and glass wool or petrol-based foams) biobased materials present the advantage of being renewable, with a low embodied energy and CO 2 neutral or negative. Moreover, these materials have a distinct hygrothermal performance, as the sorption/desorption of water vapour in their porous structure, in dynamic equilibrium with their surrounding environment, constantly modifies their hygric and thermal properties while causing energy transfers itself. In this paper, the hygrothermal performance of two different bio-based materials in outdoor conditions is evaluated. The first is an innovative light-weight composite made from corn pith and alginate. The second a commercially available wood insulator. The materials are tested alone and as components of external thermal insulation systems (ETICS) and compared to a conventional polystyrene foam. The results show how the sorption process influence the hygrothermal performance of the materials when the surrounding conditions modified. When subjected to cyclic changes in temperature and relative humidity, the bio-based materials tested show a lower temperature variation than polystyrene. This is in part due to their lower thermal diffusivity, but also to the water absorption and desorption mechanisms occurring within the materials, which were measured by the change in mass of the materials during the tests. The differences in the thermal performance were more noticeable when the insulation materials were tested alone than when these were tested as a part of an ETIC System.

Gypsum and lime stablised earth-rice husk composite

“…Bio-based materials are showing promise in the race for sustainably focused alternative building refurbishment solutions, aiming to improve in-use energy efficiency and often contributing to an improvement in internal air quality (Palumbo et al 2018). EN 16575 (2014) states that the "term bio-based product refers to products wholly or partly derived from biomass, such as plants, trees or animals.…”

“…It was found that plant-based insulation materials sequester atmospheric carbon dioxide through photosynthesis. Further stating that "typically the sequestered carbon dioxide is greater than the embodied carbon dioxide involved in their manufacture"; pointing to the notion that by using these plant-based bio-insulation materials in practice, could lead to the net embodied carbon dioxide of the building being heavily reduced and potentially resulting in a negative carbon footprint for the building (Lawrence et al 2013) (Cetiner & Shea, 2018) (Palumbo et al 2018).…”

Recycling of organic residues to produce insulation composites: A review

“…Insulation boards are produced either by using adhesives or by hot-pressing. In addition to conventional synthetic adhesives, natural binder, e.g., starch, casein, sodium alginate (Palumbo et al, 2015(Palumbo et al, , 2018, gelatine (Ismail et al, 2021) and natural rubber latex (Tangjuank, 2011), as well as inorganic binders, e.g., gypsum (da Rosa et al, 2015), lime (Ismail et al, 2020(Ismail et al, , 2021 and sodium silicate (Bakatovich et al, 2018;Bakatovich and Gaspar, 2019), were studied to produce insulation boards. Since the binding capacity of mineral materials like gypsum and lime is low, high proportions of these binders are necessary to ensure sufficient stability (Ismail et al, 2020).…”

Sustainable bio-based earth mortar with self-healing capacity

“…By understanding the way in which a material adsorbs/desorbs water molecules in a dynamic hygrothermal environment gives an indication of a materials ability to be used as a passive thermal management panel. In addition to be developed as a 'self-healing' building material, a further benefit earth construction and the combination of bio-based materials are notable for their ability to improve indoor air quality (Darling et al, 2012;Palumbo et al, 2018). As all samples had the same exposed surface area they can compared via the change in mass of each sample per m 2 , the first cycle within the climatic chamber is exhibited in Figure 2.…”