Sustainable Building Design

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Construction detail of ETFE envelope, Kengo Kuma Architects (Image © Rosa Urbano Gutiérrez & Laura de la Plaza Hidalgo, Elements of Sustainable Architecture, 2020)

Many of us are familiar with the Paris Agreement and the various competing, sometimes audacious proposals by big tech leaders (Bill Gates, Jeff Bezos, Elon Musk, etc.)  tabling  solutions to meet the goals set by UN to reduce CO₂ emission 45% by 2030 and reach net-zero by 2050, Where are we today and what are the next steps? We will investigate this in the context of Sustainable Building Design and Embodied Carbon.

The global average temperature in 2019 was 1.1℃ higher than it was prior to the industrial period1, with 1.5℃ considered a major tipping point. This change is only likely to accelerate given the context that carbon dioxide emissions have increased by about 90% since 1970² and carbon dioxide equivalents (non-CO₂ greenhouse gases) have also increased significantly. Without dramatic change and a shift towards Sustainable Building Design we will exceed the 1.5°C mark by mid century. 

Research points to the fact that the concentration of greenhouses over the past century are unprecedented over thousands of years. We can see the many effects of this in the rise of global temperatures, more severe tropical storms, increased droughts, rising sea levels and glacial ice melts³. Society has come to realize the importance of taking immediate actions collectively and vigorously. As attitudes change and society realizes the importance of sustainable goals, Industries and business within them investing in sustainability will outperform other traditional profit-oriented peers. Lets discuss the importance of Sustainable Building Design in this context.

The importance of the Building Industry

Construction is a big player in the human contribution to greenhouse gases . Within the industry the importance of Sustainable Building Design and Embodied Carbon is being realized. As an industry the building and construction sector is responsible for approximately 40% of all greenhouse gas emissions annually. This includes two major sources – 28% in Operational Carbon (such as electricity, water, and gas to keep the building functioning) and 11% Embodied Carbon – the carbon footprint associated with a material or the sum of all energy required to produce these materials and is embodied in the material itself.

Whole Building Design -3
CO2 Emissions by sector (Statistics Courtesy of the Global Alliance for building Construction)

While it may not be easy to reduce the former, considering the demands the increasingly growing human population place on buildings, there are ways to provide for Sustainable Building Design and enhance performance such as rainwater attenuation systems, renewable energy sources and high efficiency lighting amongst other examples. Read more about this in our Green Building Design article.

The latter is concerned with the efficient use of material  and lowering of embodied carbon which becomes even more important as building operations are decarbonised. This is where structural engineers and architects in a particular can make a difference. We need to focus our designs on sustainability and seek out ways to reduce the embodied carbon. To accommodate growth in the human population the global building stock will have to double by 2060 by adding 2.48 trillion sq. ft. to put this into context. This is equivalent to adding an entire city of New York every month for 40 years 40 years⁴. To minimize the impact of this we need to look at increasing building reuse and refurbishment and change the way we use materials in design. We also need to employ a different design philosophy, now governed largely by cost and aesthetics, to a philosophy and initiative focused more on sustainability. 

Taking action

Engineers Declare is a good example of designers taking action. This is a public declaration of the need to change and commit to positive action⁵. Designers are looking outside the confines of project constraints and are gradually seeing the bigger impact that they are having on the world and a sustainable infrastructure. This is engineers and architects opportunity to lead a change that will have a profound impact on the future of the planet. Read more on our Whole Building Design article. What does this actually involve? Firms need to track and log embodied carbon associated with their designs. They need to assess the use of one material type versus another in terms of financial parameters, or architectural constraints but also its environmental impact. When choosing between concrete, steel, or timber think outside the realms of cost and constructability but also embodied carbon. 

As contributors to the built environment we are obliged to inform and educate our clients around the environmental impacts of their design related preferences, which should take cognizance of the long term environmental effect. The assessment of cost should no longer only include the project itself but its cost implications to the planet – eventually to our offspring. This will, increasingly in time, impact the success of their development in financial terms as building occupants are increasingly valuing and paying more for sustainability focused designs. We cannot cover all the aspects of decarbonising building design in this article but, below we have outlined a few pertinent examples. 

Planning/Design

The earlier designers start to incorporate sustainable concepts, the more impactful their interventions will be. Below is a conceptual graphic comparing conventional design processes and integrated design processes. Design software companies developed products that simulate the energy efficiency of a building design alongside the environmental conditions using programmatic parameters and incorporating design decisions. Ladybug and Honeybee plug-ins in Grasshopper (Rhino 3D) are good examples which provide feedback on energy use, daylight, lighting, and the connection to weather data for analytical purposes. Customizing the design of HVAC systems according to site characteristics can bring many benefits. The coordinated combination of passive and active controls can maximize mechanical efficiency for ventilation and maintain thermal balance during various weather conditions and thus minimize Operational Carbon.

A comparison of effort, effect, and cost over time in conventional design processes and integrated design processes (David Bergman, Sustainable Design - A Critical Guide, p.24)
A comparison of effort, effect, and cost over time in conventional design processes and integrated design processes (David Bergman, Sustainable Design - A Critical Guide, p.24)

In spite of the advancement in these softwares, they can also incur significant cost and training, and are therefore inaccessible for many small to medium sized companies. There is also guiding principles in passive design that work well and there is strong historical data providing  evidence of the importance of such principles – eg. the massing of buildings considering the relative location of user space and service core, the lower surface-to-volume ratio if possible, and the concept of chimneys/double skins for the optimized conservation of thermal conditions and human comfort.

At a higher level, the selection of a site, the adoption of urban farming to reorganize community living and limit the transportation of resources, also offer potential benefits  for designers, planners and environmental researchers.

Materials/Logistics 

The Institute of structural engineers has set up a climate emergency task group,  provides guidance on how to calculate embodied carbon in your design and ways to set carbon targets⁷The website gives an outline of ways we can reduce the embodied carbon of structural concrete, most of which is associated with the cement (or more specifically with cement production due to decomposition of limestone into lime), followed by steel and then aggregates.

Aggregates account for approx. 80% of the mass but only 5% of the embodied carbon. Therefore, our focus should be on the reduction of cement and steel, not the aggregates. The supplementary cementitious materials (SCM’s) such as granulated blast slag and fly ash (byproducts of steel blast furnaces) can help bring cement and thereby embodied carbon down. These do impact the development of strength gain and strike time for contractors. Suppliers also often ask for more cement content, as requested by contractors to ultimately facilitate placing. We need to stop these practices and think sustainable. The advancement of new materials, which you can learn more about in our Innovations and Trends article will also help.

Low carbon concrete illustration retrieved from The Concrete Center - Concrete Compass: Low carbon concrete
Low carbon concrete illustration retrieved from The Concrete Center - Concrete Compass: Low carbon concrete

As a structural engineer some other interesting facts is that generally floors contribute the most in terms of structural elements impact on the building overall embodied carbon. Lower grade concrete with higher comparatively higher amounts of SCM’s perform better that higher-grade concrete with lower SCM. The SE 2050 commitment is focused on transforming the structural engineering practice in a holistic way focusing on embodied carbon reduction and getting to net zero carbon structural systems by 2050⁹.

It is also important for designers to prioritize local  and if possible recycled materials instead of the alternatives requiring extensive transportation and added environmental impact. The selection of materials will be more based on the available supply chain data and additionally EPD (Environmental Product Declarations) provided by contractors and manufacturers. This will allow designers and their clients to select the ones with the lowest embodied carbon impacts.

Collective effort 

There are many more aspects other than materials that designers can address when considering the cradle-to-grave lifecycle of projects. In the case of Reuse, close to 2/3 of the current building area that exists today will remain till 2050⁴. We should look to improve the efficiencies of these existing buildings that were designed and built with outdated codes, criteria and environmentally ignorant practices. Reusing existing buildings can cut embodied carbon by about 70% compared with demolishing and rebuilding⁸. Designers can look to many options to reduce embodied carbon even in new builds. One of the key elements is actively looking into design alternatives with a lower carbon footprint, agreeing on carbon tracking targets and making these targets relevant project key milestones. A mindset to constantly learn and share data on the results of industry-wide implementations is essential to this effort, which after all is aimed at enhancing the quality of our lives and those of future generations..

Together engineer, architect and client can make a sizable impact on the embodied carbon of new builds. If you have any thoughts, please comment below. Thanks for reading!

Resources:

  1. https://www.unep.org/explore-topics/climate-change/facts-about-climate-emergency

  2. https://www.epa.gov/ghgemissions/global-greenhouse-gas-emissions-data

  3. https://www.usgs.gov/faqs/what-are-some-signs-climate-change-1?qt-news_science_products=0#qt-news_science_products

  4. https://architecture2030.org/buildings_problem_why/#:~:text=Buildings%20generate%20nearly%2040%25%20of%20annual%20global%20GHG%20emissions.

  5. https://www.engineersdeclare.com/

  6. https://www.ipcc.ch/sr15/chapter/chapter-3/

  7. https://www.istructe.org/resources/climate-emergency/#2.%20Low%20carbon

  8. https://www.istructe.org/journal/volumes/volume-98-(2020)/issue-11/introduction-to-refurbishment-feasibility-stage/

  9. https://se2050.org/

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