Learning from Kigali: Lessons for climate-positive design

Terraced crops climb the slopes of every mountain in northern Rwanda, continental Africa’s most densely populated nation. Nearly every speck of arable land is taken so people push into protected forests — and each other. Land scarcity contributed to Rwanda’s genocide in 1994.

When presenting our work on reducing embodied carbon in our projects in Kigali, we’re often asked some version of the question: “You can do that in Rwanda, but how can this translate to a developed context?”

The simple answer is that at this point in time, all places around the globe have much in common. COVID-19 has revealed just how much our industry—from developed markets in North America to land-locked emerging markets in Africa—depends on a global network of material and labour exchanges. Our projects in Rwanda have faced the same delays and material shortages as those in Boston, most notably with specialty items related to electrical and water infrastructure, manufactured in Southeast Asia.

Fortunately, construction on our Kigali-based projects resumed largely unimpeded after an initial eight-week shutdown. This was a direct result of actions taken by the Government of Rwanda to manage the pandemic, along with early design decisions to source the vast majority of materials and labour for our projects in-country. After a decade of working in this manner, our Kigali office has become deeply familiar with the materials, processes, and people that it engages. As a result, our projects have become more resilient and impactful—and our practice more sustainable.

The more nuanced answer to this question is contingent upon one’s willingness to challenge the status quo. Our initial unfamiliarity with Rwanda was somewhat of a blessing, as we had no preconceived notions of what was normative construction practice. The opportunity to work in Rwanda has fundamentally changed our understanding of how to practice architecture and engineering.

Conversations like those held over the window schedule for Munini Hospital with Bruce Nizeye, our long-time mentor and quantity surveyor, have lifted our eyes past the pages of the catalogue to see the actual materials, labour, and supply chains that are activated by specifications. In responding to a sketched window, Nizeye asked us: What glass do you want?  If you want this kind, it comes from this supplier in Tanzania, along this road, and can’t exceed this size, because of the type of trucks that make that journey.

Similarly, the dimensions specified for the window’s frame would dictate whether it could be manufactured on site in rural Rwanda, or would come from a metal shop in Kigali, or Nairobi, or India. The specifics of how our team drew that opening quickly began to have significant, direct impacts on the project’s supply chain. By drawing with certain dimensions—ones that were not necessarily the “norm”—we could direct the enormous capital associated with the project towards Rwandan labour, specifically in the underserved rural area immediately around the project.

Towards Half

A year ago, we wrote a letter to the editor of this magazine outlining the urgent need for Canadian architects to undertake a “radical refocusing towards embodied energy.” MASS has been working hard to ensure this conversation is front and centre for all of our projects—whether in Santa Fe, Boston, or Mombassa—at all stages. We’re doing Life Cycle Assessments and material research early on to ensure projects track towards the 2030 emissions targets.

From the outset of designing the Rwanda Institute for Conservation Agriculture (RICA), we’ve been focused on finding ways to halve the project’s embodied footprint. We’ve dug test-pits, conducted structural analysis of soils and timber, visited timber mills in Rwanda, Uganda, and Tanzania, inspected steel sections in Nairobi, and worked with a ceramic tile manufacturer to establish the country’s first Environmental Product Declaration (EPD). These efforts have allowed us to confidently specify low-carbon materials and assemblies that are certainly not the regional norm. The structure is largely made of earth blocks harvested from the project’s site, while the overall design minimizes the use of cement and steel, optimizes passive systems, and embodies only 58 percent of the emissions of “business as usual.”

We’re actively exploring the advantages and limitations of existing Life Cycle Assessment tools in the various contexts we operate, and have developed our own accounting systems to fill the gaps. We’re collaborating with industry leaders like Arup, Transsolar, Atelier 10, Bionova, and Priopta to improve and expand how we’re accounting for emissions across the life of a project—including strategies for on-site sequestration through landscape. Through engaging and acting to address this challenge, we have learned some basic lessons that we’re now bringing to all our projects, in North America and Africa alike.

Lean

The big ticket in emissions reductions is a project’s structure. We are achieving lighter, less carbon-intensive structures by working with structural engineers early to reduce spans, introduce columns, and reduce reliance on steel and concrete to transfer loads.

At RICA, we established structural grids and constrained window and door dimensions to allow compressed earth blocks and rammed earth walling to take the majority of the loading. This led to a dramatic reduction of reinforced concrete across the project, resulting in a 48 percent embodied carbon reduction in that aspect of the assembly.

Clean

Simple changes to the materials being specified in a project’s assembly can result in big Global Warming Potential reductions. Spending time to become familiar with EPDs and the databases and tools used to compare them (EC3, One Click, and Athena) often reveals significant differences between material choices.

At JJ Carroll, a seniors’ housing project in Boston, we switched our under-slab insulation from XPS—a material that uses harmful HFC blowing agents—to EPS. We also changed our above-grade insulation from glass-wool to cellulose. We see these as low-hanging-fruit from an emissions standpoint.

Old School

Looking at how buildings in a certain region were constructed a century ago can bring up options for emission reductions. What systems were employed? Where were the materials sourced and manufactured? How have they performed? What locally abundant materials have fallen out of fashion, and might we look to engage them in new ways?

At RICA, we discovered that a huge proportion of the project’s carbon footprint was hidden in the reinforced concrete foundations we had initially designed. We had worked with stone foundations on other smaller-scale projects to save costs, so we began evaluating the feasibility of using stone foundations at RICA. Rolling back the clock to employ stone reduced the emissions of the foundations by 250 percent.

Question the Status Quo

We often come across statements like “We don’t have access to these products,” or “That isn’t how things are done here.” We see these as opportunities to help make the dramatic changes required of our system. We can encourage new materials and suppliers into the market by specifying them now. We’ll spend the additional time needed to advocate for why importing something or supporting an upstart is the right move from a climate perspective. We often question standard practices, and work with engineers and contractors to find lower-emitting solutions.

At JJ Carroll, we are working with the project’s structural engineer to fine-tune the use of concrete and achieve reductions. We’re asking basic questions: How are we specifying concrete mix proportions? Have strengths been specified based on what is needed in different parts of the building, and at different times in the construction process? What prescriptive requirements are placed on the concrete? How many mixes are being used? Do we require EPDs? How do mixes compare to NRMCA benchmarks?

Over the past year, Canada has taken globally recognized actions to address the embodied emissions of construction. The leadership displayed by Vancouver’s City Council, the National Research Council, Builders for Climate Action, and local chapters of the Carbon Leadership Forum illustrates what is possible if we place emphasis on this issue. I’m hopeful that Canadian architects and engineers can learn from the experiences of colleagues—including our work in Kigali—to inform projects across the country, taking full advantage of each region’s constraints and opportunities.

Canadian ex-pat architect Kelly Alvarez Doran is a Senior Principal at MASS Design Group. He leads the practice’s office in London, UK, and oversees its work in Europe and East Africa.

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