In buildings, structural systems have dominated the conversation about carbon thus far, with more scrutiny on the high embodied energy of concrete and steel. However, the facade also contributes to a building’s overall carbon footprint and is increasingly receiving attention for this aspect of environmental performance.
In addition to wood-based envelope components, designers and manufacturers have been developing bio-based alternatives to the other common facade materials of metal, cementitious, and polymer composites.
Just as mass timber becomes more widely adopted for structure, bio-based materials are likely to become more common in envelope systems as a carbon-conscious construction method.
The BioBuild project sponsored by the European Commission is the “world’s first self-supporting facade panel made of biocomposites,” according to Arup.
Developed in partnership with GXN Innovation, whose prototype biocomposite panel first appeared in its 2009 Louisiana Pavilion, the BioBuild facade consists almost exclusively of natural fibers and resins. In the primary system, two external shells made of flax fibers solidified with bio-polyester are backed with insulation.
The 13’ x 7’-6” (4 m x 2.3 m) modules, each incorporating a window, utilize half the embodied energy of conventional construction materials. Three other building systems include a rain screen system made of jute fibers and furan (sugar cane-based) resin, internal partitions composed of flax and furan, and suspended ceilings made of jute and bio-polyester. All BioBuild system components may be easily disassembled and recycled.
The Osirys Project, also funded by the European Union, gathered 18 organizations including UNStudio to research and develop new biocomposite building products. Like BioBuild, the effort resulted in multiple systems: a multi-layered facade, a curtain wall, and an interior partition system. The team sought to replace most traditional components with bio-based materials in each design.
For example, the curtain wall system consists of biocomposite profiles, glass panels, a biobased surround, and biocomposite shading panels. In addition to reducing carbon emissions, the components of the Osirys systems emit less volatile organic compounds (VOCs) than many standard building products, thus delivering better air quality.
A more specialized technology is a bio-based facade trellis. This envelope product is the result of a collaboration between Bcomp, a fiber producer, and Temca, a composite manufacturer. Installed on the new Cité Scolaire Internationale Jacques Chirac school in Marseille, France, the trellis provides shade and imparts a distinctive visual pattern for the facade.
Each lightweight panel consists of flax fibers molded in one of five different patterns and reinforced with glass fibers and polyester resin. The modules are coated with a UV-protective surface that extends their longevity. The French Scientific and Technical Center for Building (CSTB) confirmed the product’s technical performance as a cladding application.
Biocomposite facade systems like these are still in the early stages of development and are a long way from widespread commercialization. Although renewable fibers like flax or jute may be available in large quantities, the industrial processes necessary to transform these raw materials with compatible resins into reliable facade components are novel.
Bioresins are still relatively uncommon, therefore motivating manufacturers to employ standard petroleum-based resins—which significantly limits the ability for future recycling and diminishes the original purpose of using bio-materials.
Nevertheless, technological advances generally face early challenges in their development and require additional investments to overcome the hurdles associated with rigorous testing and production scaling.
Meeting future climate and resource targets will necessitate the development of carbon-friendly facade alternatives, and it is unreasonable to expect wood to fulfill this function exclusively as a material. Thus, biocomposite facade systems are a welcome contribution that indicates an exciting future in building envelope technology and design.
