Evaluating the Humidity Responsiveness of Bacterial Cellulose for Application in Responsive, Breathable Building Skins

Pynirtzi, N; Debnath, KB; Lantzanakis, G; Bloch, K; Scott, J; Davie, C; Bridgens, B

doi:10.1007/978-3-031-33465-8_49

Evaluating the Humidity Responsiveness of Bacterial Cellulose for Application in Responsive, Breathable Building Skins

Lookup NU author(s): Natalia Pynirtzi ORCiD, Dr Kumar Biswajit Debnath ORCiD, Karolina Bloch, Dr Jane Scott, Dr Colin Davie ORCiD, Professor Ben Bridgens ORCiD

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Abstract

Breathable building skins have potential to reduce the operational energy requirements of buildings, which currently accounts for 28% of global greenhouse gas emissions. Moisture-responsive bio-based materials, such as wood and nanocellulosic fibres, can provide mechanical actuation due to their reversible shape change, through continuous wetting and drying process enabling the building envelope to passively respond to the environment while avoiding the need for mechanical ventilation. This study was conducted to evaluate the moisture responsiveness of bacterial cellulose materials that would lead to their potential use in the built environment. Thin sheets of bacterial cellulose were grown via the ‘kombucha’ process and six square samples were exposed to high and low relative humidity in a climate chamber at a constant temperature of 25∘C25∘C. . The results from eight, 4-day long, consecutive wetting-drying cycles (10% to 90% to 10% relative humidity), showed that bacterial cellulose presents significant, rapid and reversible dimensional changes. Changing from 10% to 90% relative humidity resulted in a thickness change around 15% and a weight change of 10% within one hour. The maximum changes detected were 97% in weight and 116% in thickness after 48 h at 90% relative humidity. After 24 days of cyclic testing, the cyclic dimensional changes were maintained indicating no reduction in moisture responsiveness. The outputs of this study will inform the development and integration of bacterial cellulose within breathable wall constructions, in combination with insulation, thermal mass and cladding, to provide a passive, responsive, variable porosity building skin.