The Living Building Challenge is currently the most rigorous certification scheme for buildings globally, challenging designers to move from sustainability to regenerative development.
A common theme to the case studies of certified LBC buildings is the difficulty in meeting the materials imperatives.
Recognising this difficulty early in the design process allows teams to explore their options, leading to a better use of materials.
To answer how materials fit into the regenerative paradigm, I want to reflect on my experience working with the BioVale team in the recent Brickworks LBC retail centre design competition and look at how other teams met the challenge.
Construction always requires the use of resources. Replacing or retrofitting inefficient building stock can pay dividends in the near term; however, knocking down a building to rebuild an inefficient one is clearly an undesirable outcome.
The Brickworks project proposes to take the degenerated site of Austral brickworks in Burwood and create a retail centre and amenities for the neighbouring residential development and surrounding areas. The so-called brownfield site is well suited to the LBC.
When undertaking regenerative projects or sustainability assessments, the chosen emissions baseline is critical to achieving our intentions. Too often we see projects claim credits for using partially recycled steel when it is practically impossible to purchase virgin steel stock; and credits for fly ash in concrete, even though most high-performance mixes already incorporate supplementary cementitious material. To address this, the LBC sets the baseline at zero, meaning teams must account for all the embodied energy and equivalent CO2 emissions of the materials and construction works and then offset these emissions.
In order to limit the impact on the environment I follow five guiding principles for materials selection and design:
- Reduce overall materials
- Reuse existing materials
- Choose low-energy materials
- Minimise any waste generated
- Design for adaptability/end-of-life reuse
Reduction of material use
Reducing materials makes the case for stronger and tougher materials, as well as multifunctional materials. This also leads to designing smaller buildings with fewer appurtenances.
Higher performance materials such as ultra-high strength concretes, advanced structural composites and high-performance alloys are available that allow for a more efficient structure with an overall lower embodied energy; however, they are not widely used, mainly due to a lack of recognition from regulations as well as a lack of familiarity.
Advanced structural composites are sometimes incorporated into façade design and the Victorian Comprehensive Cancer Centre is a standout example, incorporating woven, composite elements fabricated by yacht builders mouldCAM.
Multi-functional materials are also a promising area of development but, again, are not widely incorporated into designs as yet.
Phase-change material facades are a good example of multi-functional material elements that are starting to receive attention.
Reducing overall materiality was not highlighted in the Brickworks submissions, although the designs did embrace large, open areas with overall less bulk.
Reuse of materials
The LBC requires that reused or salvaged materials are featured every 500 square metres. Every submission incorporated salvaged brick, a nod to the history of the site, and salvaged timber and steel elements were also featured – in a sense, the rammed-earth components could also be considered salvaged from the site.
Wherever possible, regenerative designs should take advantage of salvaged materials, although care should be taken to ensure that materials are not taken out of service ahead of time, otherwise CO2-e calculations must include a portion of their embodied energy.
Low-embodied energy materials
The most prevalent materials of modern construction have very high embodied energy: concrete, steel, aluminium and glass. The LBC requirement to source local materials places Australian projects at a disadvantage due to our high-emitting coal-fired power plants, and imported materials don’t fare much better due to the emissions involved in shipping and overland transportation to site. The key is to find locally produced materials with low embodied energy.
Timber construction has seen a resurgence lately and taller, structural timber buildings are now built every few years. The Brickworks submissions heavily featured timber, and laminated timber was the material of choice.
Properly treated and designed timber can outperform steel and concrete in terms of durability and fire performance. In some instances, the energy used to produce and transport structural timber members can be low enough that there is more carbon sequestered than emitted – a definite bonus for LBC certification. Timber also has the advantage of the established Forestry Stewardship Council certification for sustainable sourcing.
Rammed earth is another material that is increasing in popularity. Several of the Brickworks submissions featured rammed earth; however, design and loading of rammed earth is not as controlled as concrete and would require specialist input in practice.
Similar building materials such as cob, hempcrete and adobe also suffer from a lack of familiarity and knowledge regarding design and at least the perception of lower quality control. These materials are not well standardised, which poses a significant hurdle to their widespread uptake.
Geopolymer cement provides a viable alternative to Portland cement for use in concrete and studies report a reduction of CO2-e emissions of up to 80 per cent – the University of Queensland’s Global Change Institute building is Living Building Certified and makes extensive use of geopolymer concrete. When compared to Portland cement, geopolymers can have certain advantages, including strength, fire and acid resistance. Geopolymer and alkali-activated concretes also have a lengthy track record in the former Soviet Union, although the body of research is not readily available.
Locally, Wagners and Zeobond supply geopolymer concrete and its use in projects grows each year. Research into geopolymers to overcome some knowledge gaps regarding longer-term durability of embedded steel and creep behaviour is ongoing. In the meantime, conservative design and use of alternative reinforcement may be necessary. The BioVale appears to be the only submission that incorporated geopolymer concrete. Other submissions utilised high cement replacement mixes to reduce their CO2-e footprint.
Minimising waste should be considered over the whole lifecycle of any project, although it is recognised that construction waste makes up the majority of this waste and, from a design perspective, it is the most controllable. Strategies to minimise construction waste involve reducing rework through strong quality control, efficient procurement leveraged off BIM, and prefabrication.
Most Brickworks submissions highlighted prefabrication of modular elements, and the industry is increasingly taking up off-site production. Prefabrication is also perfectly suited to the use of high-performance materials and, alongside new engineered timber composites, I hope to see geopolymer precast and structural composite elements in increasing numbers.
The BioVale submission also envisioned reuse of construction waste, employing the Ecovative process to turn wood offcuts into “mushroom” composites for mall furniture.
Design for adaptability and end of life reuse
This aspect could be included under waste minimisation because it’s really about reducing waste during operations and at end of life; however, several strategies incorporated at Brickworks deserve special mention.
The winning design incorporated a simple concept that focused on adaptation for the retailers – the modular units that make up the small-box retail precinct can be rearranged as tenant needs change. The competition judges loved the idea and it was a clear winner.
Similarly, end-of-life reuse of materials was a common strategy highlighted in a handful of submissions, notably the “Difference is Living” approach of “screwed together not glued together”.
The Red List
Any article about LBC materials must make mention of the Red List, a list of banned materials that includes common materials such as PVC and neoprene as well as other less familiar materials.
Currently the LBC prohibits the inclusion of Red List materials in any final buildings but does not exclude their use during manufacture and assembly. Recognising the difficulty in sourcing the information from manufacturers, LBC’s administrator, the International Living Future Institute, has created Declare, a label that lists the ingredients of building materials. Akin to the ingredients lists that appear on packaged foods, Declare aims to promote transparency and open communication throughout the construction marketplace.
In doing so, the ILFI hopes that fewer Red List items will appear in products as increasing numbers of manufacturers adopt the Declare label. In the meantime, it is important to understand what goes into building products, a process that sometimes requires factory visits and hard conversations with producers. I understand that one of the side benefits of the Brickworks competition has been the advocacy for the Declare label.
In assessing materials for regenerative projects, there are many aspects that I haven’t covered – durability, natural finishes, thermal mass and low maintenance to name a few. I’m keen to hear your thoughts. How would you address this?
The challenge of regenerative materials can be daunting but, at the same time, it’s a challenge that is continually throwing up new opportunities and it is exciting to see how designs can come to life through the intelligent use of materials.
Will Nash is principal engineer at materials engineering and design consultancy MEnD.