• Energy Research

Bio-based and natural building materials can support the building sector to reduce its environmental impact. In this study, experimental research was developed to evaluate the performance of giant reed when used as a building thermal insulation. Reed was chosen due to its high availability and close relationship to Portuguese vernacular architecture. The role of the reed’s origin in this context, its physical characteristics and its durability aspects were evaluated. The results showed that the performance of the reed boards was compatible with their use as a thermal insulation material, regardless of the reed’s origin. Denser boards showed better results. Under the favourable conditions related to the reed’s water content, mould growth could occur.

Knowing the properties of vernacular materials is crucial to heritage conservation and to develop innovative solutions. Reed, considered to be a carbon-neutral and a carbon dioxide sink material, has been used for centuries for diverse uses. Its high availability and properties made it a popular building material, including in Portuguese vernacular architecture. An experimental investigation was conducted to evaluate the physical performance, thermal performance, and durability of the reed found in Portugal since the characterisation of this material was not found in previous studies. The influence of geometric characteristics and the presence of nodes on these properties were also analysed, and the results showed that they are irrelevant. The studied reeds were found to have an adequate thermal performance to be used as thermal insulation. Their thermal resistance (1.8 m2·°C/W) and thermal conductivity (0.06 W/m·°C) are under the requirements defined by Portuguese regulations on thermal insulation materials. Overall, the physical characteristics (moisture content, density, and retraction) are compatible to its use in the construction. Concerning durability, there was only a trend for mould growth in particular environments. The results provide valuable data to be considered in the development of new construction products based on this natural and renewable material. Additionally, considering the studied samples, the reed found in Portugal has characteristics suitable for use as a building material, especially as a thermal insulation material.

The construction sector plays an important role in climate change. Thus, there is a pressing need to construct buildings that reduce heat losses, use natural and local materials, exploit renewable sources and ensure high comfort levels with a minimum environmental impact. Reed, considered carbon-neutral and a carbon dioxide sink material, has been used for centuries for diverse uses. Its properties and high availability made it a popular building material, as seen in Portuguese vernacular architecture. Knowing the properties of the reed is a crucial step to ensure successful heritage conservation, optimising these materials, and developing innovative solutions. This paper studies the potential of using giant reed from different Portuguese regions as a thermal insulation material. Giant reed board prototypes (15 x 15 x 5 cm, about 235 kg/m3) were built. Their thermal performance was tested in a hotbox, according to ASTM C1363‑19. The results show that the giant reed harvested on the northern coast of Portugal has better thermal performance than reeds from other regions. However, regardless of the region of the country where the giant reed was harvested, it has a satisfactory thermal resistance (Re ≥ 0.30 (m2.ºC)/W), allowing its use as a thermal insulation material in the buildings.