![#](https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F2_materials-page-001-2.jpg?auto=format&crop=center&fit=crop&h=118&ixlib=php-1.2.1&w=210&s=dd82977a0838c6919ce9924d63ee38ba 210w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F2_materials-page-001-2.jpg?auto=format&crop=center&fit=crop&h=237&ixlib=php-1.2.1&w=420&s=67b25a65318e07c4f2dcbd8fb56bc5ff 420w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F2_materials-page-001-2.jpg?auto=format&crop=center&fit=crop&h=433&ixlib=php-1.2.1&w=768&s=fbd8937d3afa2d22acb42a42ec7bb8f4 768w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F2_materials-page-001-2.jpg?auto=format&crop=center&fit=crop&h=577&ixlib=php-1.2.1&w=1024&s=b14c89a7a63edff4fe8af4f0e1f35901 1024w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F2_materials-page-001-2.jpg?auto=format&crop=center&fit=crop&h=789&ixlib=php-1.2.1&w=1400&s=6853a98e932a9a2c15880126873a9e37 1400w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F2_materials-page-001-2.jpg?auto=format&crop=center&fit=crop&h=901&ixlib=php-1.2.1&w=1600&s=7e6395aa8da0593d670e8303759864fa 1600w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F2_materials-page-001-2.jpg?auto=format&crop=center&fit=crop&h=1082&ixlib=php-1.2.1&w=1920&s=f6e530bc2fec7898aa394f852f089fe0 1920w)
Systems
With help from facade consultants FMDC, we’ve calculated reference build ups to compare different facade systems. As each project is unique, we’ve found it helpful to make some simple comparison models to understand the embodied carbon weighting of different facade systems, aside from the specifics of a particular project design. We’ve just included the product manufacture stages, A1 – A3 or ‘cradle to factory gate’, to avoid the project specifics of transport, location and construction. To make fair comparisons, we’ve chosen to analyse one square metre of the solid part of the facade, including a representative amount of framing and bracketry. We chose to include a stone facing because stone is a relatively low carbon option and so the impact of the backing wall is most evident. Of course these systems are not comparable in terms of thickness, weight, fire performance, ease of achieving insulation and air-tightness, off-site manufacture, cost and programme — the balancing act needed in every design — but we wanted to isolate embodied carbon for the purpose of this research.
![#](https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F3_systems-page-001.jpg?auto=format&crop=center&fit=crop&h=118&ixlib=php-1.2.1&w=210&s=bb40ca317d530746aceaa9e70efd4d66 210w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F3_systems-page-001.jpg?auto=format&crop=center&fit=crop&h=237&ixlib=php-1.2.1&w=420&s=5a6160cc083e8ec13d1fb0aab3137335 420w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F3_systems-page-001.jpg?auto=format&crop=center&fit=crop&h=433&ixlib=php-1.2.1&w=768&s=05de40760b4407143495da77cfec9e7d 768w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F3_systems-page-001.jpg?auto=format&crop=center&fit=crop&h=577&ixlib=php-1.2.1&w=1024&s=4722e39f42b98649265e8a6230433f51 1024w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F3_systems-page-001.jpg?auto=format&crop=center&fit=crop&h=789&ixlib=php-1.2.1&w=1400&s=881c13684dc48ed31135b17e4b02fa85 1400w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F3_systems-page-001.jpg?auto=format&crop=center&fit=crop&h=901&ixlib=php-1.2.1&w=1600&s=bc97ece0591d23b5d38005b26a6c32b3 1600w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F3_systems-page-001.jpg?auto=format&crop=center&fit=crop&h=1082&ixlib=php-1.2.1&w=1920&s=ebc2e144efafcbddca7a17c79d6c8549 1920w)
This comparison clearly shows us the huge embodied carbon impact of using aluminium in facades. Being lighter weight than the other systems may have advantages for the primary structure, but the tight deflection limits imposed on the edge beams could, in fact, be detrimental for the embodied carbon of the primary structure. It’s no surprise that a facade using cross-laminated timber (CLT) as a backing wall (where fire regulations allow) has the lowest embodied carbon and could even be carbon negative over its lifespan if sequestration is taken into account. Our Teaching and Learning Building for the University of Nottingham uses CLT panels as the facade backing wall, spanning between the columns of the steel frame. It would be exciting on a future project to look at using CLT as an off-site manufactured cladding system.
![#](https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F4_IMG_7717-scaled.jpg?auto=format&crop=center&fit=crop&h=219&ixlib=php-1.2.1&w=210&s=96270a658b130525c3e1aae81449315b 210w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F4_IMG_7717-scaled.jpg?auto=format&crop=center&fit=crop&h=438&ixlib=php-1.2.1&w=420&s=5525fa968018e35a3191dc4db6267bf5 420w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F4_IMG_7717-scaled.jpg?auto=format&crop=center&fit=crop&h=802&ixlib=php-1.2.1&w=768&s=dc36947547482445df94308994139e28 768w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F4_IMG_7717-scaled.jpg?auto=format&crop=center&fit=crop&h=1069&ixlib=php-1.2.1&w=1024&s=fda64bf9774b8368194311c861d012cf 1024w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F4_IMG_7717-scaled.jpg?auto=format&crop=center&fit=crop&h=1461&ixlib=php-1.2.1&w=1400&s=e1dfa2ebfb1e651982ad1034e0238a88 1400w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F4_IMG_7717-scaled.jpg?auto=format&crop=center&fit=crop&h=1670&ixlib=php-1.2.1&w=1600&s=7fb6e3ccf9c56af443a15399268762fc 1600w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F4_IMG_7717-scaled.jpg?auto=format&crop=center&fit=crop&h=2004&ixlib=php-1.2.1&w=1920&s=4dd2ca864c65f43fad6689f17b0dcce7 1920w)
CLT panels fixed to the structural steel frame as the backing wall for the ceramic rainscreen, at our Teaching and Learning Building for the University of Nottingham
Projects
Using this calculation method for one square metre of solid facade, we can compare across Make’s projects to learn from embodied carbon opportunities and pitfalls. Looking at just the solid part of the facade removes project specifics relating to different glazing ratios and opening windows. It’s also been very interesting to compare early stage designs with as-built facades, to understand where embodied carbon can increase over the life of a project, particularly as the specialist design of the facade support structures develop.
![#](https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F5_comparison_chart-page-001.jpg?auto=format&crop=center&fit=crop&h=118&ixlib=php-1.2.1&w=210&s=3c87ed60706c990dec0cce1ce32de5b0 210w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F5_comparison_chart-page-001.jpg?auto=format&crop=center&fit=crop&h=237&ixlib=php-1.2.1&w=420&s=ca5c377a14b662b34b7ffc175d23e85f 420w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F5_comparison_chart-page-001.jpg?auto=format&crop=center&fit=crop&h=433&ixlib=php-1.2.1&w=768&s=63b6c1eb525a8a0e4c52173fad2035dd 768w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F5_comparison_chart-page-001.jpg?auto=format&crop=center&fit=crop&h=577&ixlib=php-1.2.1&w=1024&s=6e8dd6b05d911b542cf271e9d9c26262 1024w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F5_comparison_chart-page-001.jpg?auto=format&crop=center&fit=crop&h=789&ixlib=php-1.2.1&w=1400&s=7a0f0381b184939f1549d757b22caa42 1400w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F5_comparison_chart-page-001.jpg?auto=format&crop=center&fit=crop&h=901&ixlib=php-1.2.1&w=1600&s=0dc3d5ec64292f3ad587cd77b4089656 1600w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F5_comparison_chart-page-001.jpg?auto=format&crop=center&fit=crop&h=1082&ixlib=php-1.2.1&w=1920&s=83b2876abc95ceae73bba699cdd45161 1920w)
Looking at the comparison by facade type, it’s interesting to see that all the higher embodied carbon facades are curtain walls, where high embodied carbon aluminium has a huge impact. Layering up materials, as in a unitized panel with a rainscreen in front, or a ‘shadow box’ with a double-glazed unit and metal sheet behind, has a big impact on embodied carbon. Simpler facades with fewer layers are often lower carbon, and here precast concrete has a role to play. These comparisons show us where to focus our material research and design innovation in future.
The highest and the lowest
The highest embodied carbon facade that we’ve calculated so far is The Cube in Birmingham, an essay in aluminium, which we designed 16 years ago. Our design priority at the time was to reduce the amount of glazing in the facade, to reduce solar gains and save operational carbon. By creating the solidity in the facade with anodized aluminium boxes as a rainscreen in front of an aluminium unitized curtain wall, the embodied carbon is very high. There may be a time in the future, when aluminium production has decarbonised greatly, when we can see the positives of aluminium as a lightweight material that is endlessly recyclable, and unitized panels which are easily demountable and can play a part in a future circular economy. But right now, in the face of the immediate climate emergency, minimising the use of aluminium must be our priority.
![#](https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F6_00177_N926_medium-scaled.jpg?auto=format&crop=center&fit=crop&h=280&ixlib=php-1.2.1&w=210&s=eb71e623dd3d2c9668bf600e6d68097d 210w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F6_00177_N926_medium-scaled.jpg?auto=format&crop=center&fit=crop&h=560&ixlib=php-1.2.1&w=420&s=5457361871cf133cf146a6055323ebfa 420w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F6_00177_N926_medium-scaled.jpg?auto=format&crop=center&fit=crop&h=1024&ixlib=php-1.2.1&w=768&s=8e580869b3c979b644a6893fe3bc7cf5 768w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F6_00177_N926_medium-scaled.jpg?auto=format&crop=center&fit=crop&h=1365&ixlib=php-1.2.1&w=1024&s=517719fa79c0dbe8c8ab80ec82312331 1024w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F6_00177_N926_medium-scaled.jpg?auto=format&crop=center&fit=crop&h=1867&ixlib=php-1.2.1&w=1400&s=71bf683d689375232ad2dc05a3a8f160 1400w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F6_00177_N926_medium-scaled.jpg?auto=format&crop=center&fit=crop&h=2133&ixlib=php-1.2.1&w=1600&s=ce3c1ea4898a3fd3553a58a662f84054 1600w,https://make-arch.imgix.net/https%3A%2F%2Fwww.makearchitects.com%2Fwp-content%2Fuploads%2F2021%2F07%2F6_00177_N926_medium-scaled.jpg?auto=format&crop=center&fit=crop&h=2560&ixlib=php-1.2.1&w=1920&s=acdf2b6352ab18ef17ef8c8ad89aba18 1920w)
It’s no surprise that our lowest embodied carbon facade is the straw-bale building that we built for the University of Nottingham. The facade is a timber cassette, manufactured in a warehouse close to the site, insulated with straw bales that were grown on the university’s own farm. It is celebrated in this Three Little Pigs film. Once the sequestration of the timber and straw over the life of the building is considered, it’s beyond carbon negative, with the facade offsetting other elements of the build. It’s not a solution that is widely applicable to other building types, but it serves as a great reminder to use biogenic, renewable, local materials wherever possible.
Please support the movement to regulate embodied carbon within the Building Regulations, by visiting Part Z.