The Carbon Footprint of Buildings:
A look into Sustainable Materials and Design Processes
Introduction
In the past decade, there has been an increasing awareness of the building and construction sector’s environmental impacts. Now, in 2020, we’re starting to see climate policy come into focus:
This year California required nearly all new single-family homes to include solar photovoltaic cells. In New York City, any building undergoing major construction must include the addition of solar panels. Solar panels mandates are a strong first step, and a great example of a top-down approach to sustainability, but they only account for one part of the larger picture of sustainability.
In this paper, we will look into the specifics of the carbon associated with the building and housing sector and discuss two different businesses and how they are approaching sustainability in the housing sector.
Buildings and the Environment
All humans require shelter from the elements. As the population expands, there will always be a demand for new homes and buildings. In the United States alone, over 240 single family homes are completed every day. (1)
Globally, buildings emit nearly one-third of all the planet’s resources, contribute up to 25% of all solid waste, and one-third of all greenhouse gas emissions(GHGs). Additionally, construction, renovation, and maintenance of buildings contribute 10–40% of countries’ Gross Domestic Product(GDP). (2)
Operational and Embodied Emissions
There are two main categories of carbon emissions that make up the vast majority of carbon emissions in the building and construction industry. These include embodied emissions, which is the emission required to produce new materials and transport them to the construction site. Operational carbon is the energy demand that a building needs to keep the facility functional. Looking at the building in this way relies heavily on a life cycle analysis perspective of both the construction materials and the building itself. Figure 1 shows the life cycle of a building, and figure 2 illustrates the difference between embodied carbon and operational carbon.
When we analyze the relationship between operational and embodied carbon, there are several factors to consider. When we analyze buildings, we need to understand that embodied carbon emissions only occur from the building’s construction stage. Operational carbon begins as soon as the structure is finished, and the lights are on. A building’s operational energy is fixed to the number of years of service. As the lifespan of the building increases, the percent contribution of embodied carbon decreases. For example, a building with a service life of 50 years has an embodied carbon contribution 22% higher than the same building with a service life of 150 years. (4)The lifespan of a building has a direct correlation with the proportion of operational to embodied carbon emissions.
The second factor influencing the relationship of operational carbon to embodied carbon is the energy demand of the building. Many construction companies design with energy efficiency in mind; therefore, decreasing the energy demand necessary to run the facility every year; thus, it’s operational carbon is significantly lower than a traditional building. The embodied energy in low-energy buildings was between 9% and 46%, while in conventional buildings, it was between 2% and 38%. (6)
Lastly, the third factor that influences the relationship between embodied and operational carbon is the building location. “In examining the relationship between the building location in terms of country and climate and overall life cycle carbon footprint calculations, the study matched life cycle carbon footprint calculations with climate types. This relationship can potentially be attributed to the different fuels and heating technologies used across countries, rather than to climate variation.”(7)
What are the ways the building construction sector can reduce its carbon footprint?
Operational Carbon
From an operational reduction strategy, the concept is straightforward. Build in a way that reduces the energy consumption by first designing the building to utilize passive solar and trees to deciduous trees to shade the building in the summer and allow sunshine in the winter months. Next, incorporate energy-efficient technologies such as LED lights, low energy certified appliances, and optimizing the building’s HVAC system temperature for peak and non-peak hours.
Using a low carbon electricity source has a dramatic effect, as mentioned earlier. If the construction site is not on a relatively clean grid, it’s encouraged to include solar power generation installation.
The aforementioned solutions are brief as the conversation and research of reducing operational carbon are very popular and easy to find. These solutions and technology exist, but that would not solve the challenge of embodied carbon.
Embodied Carbon
Embodied carbon reduction strategies are more difficult due to the lack of materials that contain the strength needed to achieve a robust and resilient building structural frame with a low carbon footprint. We often use wood, concrete, and steel because they are cheap and strong, and many people worldwide know how to build with them in a structurally sound way.
Construction Climate Challenge summarizes the pressing issue with their statement below.
“The manufacture of building materials makes up 11% of total global greenhouse gas emissions, according to the latest data from the United Nations Environment Programme. That 11% might sound small compared with the impact of operational energy (28%), but for new construction, embodied carbon matters just as much as energy efficiency and renewables. That’s because the emissions we produce between now and 2050 will determine whether we meet the goals of the 2015 Paris climate accord and prevent the worst effects of climate change.” (8)
Given that our society prefers replacing old buildings with new buildings, this trend will continue. However, if we look at the carbon cost of producing such new materials and the burden construction and demolition landfills have, it is easy to see that this is problematic. If we were building with carbon reductions as the priority, there would be a higher interest in refurbishing existing buildings and reclaiming materials no longer in use.
The private sector has been proactive in creating solutions by using onsite resources and using reclaimed materials. As we know from the three R’s, reducing is the most significant impact, and these materials reduce the need for brand new construction materials. Regenerative Systems, a company measuring their carbon footprint on map-collective.com, is implementing these strategies as a part of their core construction principles.
Regenerative Systems
Regenerative Systems designs aim to connect and complement the immediate environment and focus on natural aspects that have contributed to human health and well-being. They achieve this by using both onsite earthen materials and reclaimed materials, such as reusing concrete, metal, and wood from previous projects, therefore reducing their embodied carbon. Many of the reclaimed materials are found in the neighborhood, avoiding the mistake of transporting materials from hours away, thus outweighing the carbon benefits from using reclaimed materials. Addressing their operational carbon impact, Regenerative Systems’ uses solar power in harmony with old technology such as thermal mass and aspect ratios to bring the most significant gains in heating and cooling buildings, thus making their solar system more efficient.
RGS’s past projects have been implemented worldwide, including Cameroon, Chile, and Tanzania, where concrete-block houses are common. While these particular designs haven’t been academically studied, we can compare their practices with similar peer-reviewed projects to get a sense of the carbon they have avoided. A study done in Nicaragua compared an earthen residential home to the concrete block housing that is standard practice. In this study, the residential house built with earthen materials reduced the embodied carbon by 65%. (9) Considering that Regenerative systems utilizes reclaimed materials and their avoidance of using fuel to heat earthen materials into bricks or “cooked earth,” regenerative systems embodied footprint could have embodied reductions as high as 78% compared to a concrete block house. That’s a considerable improvement, not to mention the gains from waste reduction.
Regenerative Systems should be celebrated for their reduction in embodied carbon; as this company goes far beyond embodied carbon. In addition, their designs utilize rainwater, wastewater, and even greywater to grow plants and food crops, thus improving the land around them, addressing aspects of the environment that are forgotten in many building construction plans. Lastly, their designs analyze the needs of the people, often solving problems for communities that have been disrupted and/or have limited resources.
Beyond Carbon:
After analyzing the building sector’s landscape, there’s an underlying philosophical question that needs to be addressed. Are we designing to the best of our abilities while being transparent of our limitations to create modern solutions to modern problems? This question is posed as we have discovered that not all “green” design is the end-all-be-all alternative to sustaining the building sector.
There is a disconnect between public perception and actual green buildings. If you’re not a sustainability analyst, it is difficult to tell genuine effort and where the discrepancies lie. The marketable one-size-fits all green housing approach. Are often formulaic approaches falling short by not improving the land around it, not taking full advantage of the natural materials onsite, or considering the region’s climate.
For example, a company may celebrate that they’re using materials such as reclaimed shipping containers, used tires but fail to mention the amount of steel or concrete they’re using. At times it appears as smoke and mirrors. Look at our pretty recycled bottles and not at the concrete. Or look at the industrial sheik of corrugated steel of shipping containers but not at the structural steel needed to stack two containers.
Moving forward, when thinking about sustainable design, we need to be critical. Is this design taking into account the land, it’s climate, operational, and embodied carbon? Is it possible that or are we being misled by a marketable design that exploits humanity’s desire to do the right thing in a time where our future seems grim? To avoid this, we need to think about each company’s motives and look for transparency and genuine concerns. We want to elevate companies, such as Regenerative Systems, who are taking these complexities into account, putting in hard work to be transparent, knowing that there is always room for improvement. Our realities are complex and require diligent solutions, and there is still much work to be done.
Conclusion
There are many moving parts to sustainable solutions. Reducing a building’s operational and embodied carbon footprint are two significant parts of sustainable design; building designers need to consider material usage, water, and wastewater impacts that buildings have on the environment. This article highlighted the carbon aspect to facilities but recognizes that there are many sustainable dimensions to building design that we need to address beyond the scope of carbon. In harmony with the current solutions, we must do our due diligence to see the underlying motives of sustainable building design by being analytical, not cynical. After all, we’re all in the business of making the world a better place, even if it’s one building at a time.
References:
- US Census Bureau, Characteristics of New Housing Highlights https://www.census.gov/construction/chars/highlights.html
- Northeast Sustainable Energy Association, Beyond Energy Efficiency: Why Embodied Carbon in Matterials Matters (2018) https://www.buildingenergymagazine-digital.com/eneb/0218_fall_2018/MobilePagedArticle.action?articleId=1422002#articleId1422002
- Skanska Conceives Solutions to Embodied Carbon in Construction Materials (2019) https://www.usa.skanska.com/who-we-are/media/press-releases/238250/Skanska-Conceives-Solution-for-Calculating-Embodied-Carbon-in-Construction-Materials%2C-Announces-Transition-to-OpenSource-Tool
- Rauf and Crawford (2015). http://dx.doi.org/10.1016/j.energy.2014.10.093
- Schwartz, Y., Raslan, R., and Mumovic, D (2018) https://doi.org/10.1016/j.rser.2017.07.061
- Satori and Hestnes (2006). 249–257. DOI: 10.1016/j.enbuild.2006.07
- Schwartz, Y., Raslan, R., & Mumovic, D., (2017) https://doi.org/10.1016/j.rser.2017.07.061
- Construction Climate Challenge, How to reduce ’embodied carbon’ in the construction process (2018) https://constructionclimatechallenge.com/2018/10/10/reduce-embodied-carbon-construction-process/
- Estrada, Mariana, A case study of cob earth based building technique in Matagalpa, Nicaragua–LCA perspective and rate of adoption. (2014).https://www.diva-portal.org/smash/get/diva2:695576/FULLTEXT01.pdf
