Written? ?by? ?Michael? ?Salka? ?
January? ?4,? ?2021?

Can modest actions such as turning off the lights when leaving a room, reprogramming thermostats and investing in high quality doors and windows, insulation, renewable energy systems and energy-efficient appliances really make a meaningful difference in terms of alleviating global climate change?

The answer is, of course, a resounding yes – but only if combined with other, more systemic, greenhouse gas (GHG) emission reduction strategies. This is because all the decisions we make when inhabiting or renovating our buildings address what are known as ‘operational’ emissions, but cannot alter the already determined ‘embodied’ emissions generated during the extraction, processing, transportation and installation of our building products and materials.

According to a report by the Global Alliance for Buildings and Construction [1], buildings account for nearly 40% of global GHG emissions. That’s more than either the entire industrial (32%) or transportation (23%) sectors. Therefore, reducing the adverse environmental impact of buildings is of the utmost priority. The 11% of global GHG emissions from building materials and construction (embodied) might seem negligible against the 28% from building operations (operational), except for three, critical, factors:

First, when considering only new construction between today and 2050, instead of 70% of building sector emissions being operational and 30% embodied, the proportion embodied carbon is responsible for jumps dramatically to almost half [2];

Second, it is only the emissions we produce between now and 2050 which will determine whether or not we meet the goals of the 2015 Paris climate accord and thus prevent the most destructive effects of climate change [3]; 

Third, though constructing new buildings should always be viewed as a last resort in favor of remodeling and renovation because avoiding the use of new materials eliminates their impacts altogether, the reality is we will inevitably be compelled to build many new buildings by 2050 to meet the rapidly rising demand. The United Nations (UN) predicts the human population to increase by 2 billion in the next 30 years, from 7.7 currently to 9.7 billion by 2050 [4]. To better understand the scale of this growth in terms of the imminent need for new buildings, contemplate the equivalent of a new city of 5.5 million inhabitants being constructed each month.

While strategies for optimizing operational emissions have become general knowledge codified by widespread certification programs like LEED (Leadership in Energy and Environmental Design), effective practices for optimizing embodied emissions are still much less frequently implemented or commonly known. This is a major problem, given that unlike operational emissions which can be reduced over time with energy efficiency updates and the use of renewable energy, embodied emissions can never be diminished after a building is completed. In the same way that operational emissions can reach or even exceed net-zero, imagine if the other half of new construction emissions coming from embodied sources could also reach or exceed net-zero. To achieve the vision of the Paris Agreement, we must not merely imagine this possibility, but make it a reality.

Timber is uniquely positioned to address this challenge as the sole renewable primary building material. Recent technological developments, notably cross-laminated timber (CLT), enable unprecedentedly tall building structures made with prefabricated and highly industrialized mass timber elements. Moreover, with intelligent design, these timber elements can be made to be reusable or recyclable, their ‘waste’ can be repurposed as particle board or other composite products, and they can store more carbon through the photosynthetic removal of carbon dioxide (C02) from the atmosphere during the formation of their base wood than is emitted throughout the whole extraction, manufacturing and installation process, thereby contributing to what is referred to as ‘carbon sequestration’. In other words, building with timber empowers architects and designers to create contemporary buildings which lock up more atmospheric carbon than is released for their production.

An academic study published in the Journal of Sustainable Forestry [5] concluded that replacing other energy and carbon-intensive construction materials like steel, concrete, and brick with wood could reduce 14% to 31% of global CO2 emissions and 12% – 19% of global fossil fuel consumption. However, the solution is clearly not as straightforward as directly substituting one material for another. Successfully transitioning to a paradigm of mass timber construction raises many crucial, systemic issues and opportunities.

Foremost, we’re obliged to tackle the intuitively pressing question of whether the environmental gains of building with substantially more wood truly outweigh the apparent environmental harm of cutting down trees. This is a profoundly complex, interdisciplinary inquiry with aspects far beyond the scope of this article. Here, it will suffice to summarize a couple of key points:

One, although the rate of global deforestation has decreased over the past three decades, an estimated 420 million hectares of forest (approaching 10% of the world’s total forested area) have been lost since 1990 through conversion to other uses, primarily agriculture [6];

Two, the usual argument that young trees absorb carbon at a faster rate than old trees implies it’s beneficial to cut broad areas of old growth and replant has been largely superseded by novel understandings of the value of the biodiversity, ecosystem services and mycorrhizal fungal networks mature forests offer but simplistic ‘tree plantations’ cannot [7].

Nonetheless, researchers conclude we currently harvest approximately 20% of forests’ potential growth, and an additional 38% would have to be harvested to accomplish energy and carbon reduction goals while meeting the need for new buildings relying on mass timber technologies like CLT [8]. Therefore, the collective forest stock can significantly surpass our demand if managed with ‘moderate intensity’ by integrating sustainable policies like selective harvesting, strategic replanting, species diversification and the protection of indigenous communities. Certification schemes, for instance as promoted by the Forest Stewardship Council (FSC), currently cover about 30% of global forest production and are essential to ensure the aforementioned requirements for long term sustainability are respected. The Think Wood campaign further identifies extensive parallel advantages to such management, including mitigation of fires, the replenishment of waterways, habitat expansion, rural job creation and an overall reduction in carbon emissions [9].

Apart from the topics of ecology and forestry, vast adoption of mass timber architecture complements a shift in the construction sector toward prefabrication, industrialization, rapid deployment, off-site manufacturing and design for disassembly due to the inherent nature of wood as a lightweight yet strong and easily machined material. On top of the comparatively lower energy and carbon required to fabricate timber building elements, these strategies generate extra rewards by shortening construction time, reducing waste, reducing errors, improving working conditions, maximizing precision and minimizing on-site disturbance. This shift requires greater design control and increased manufacturing accuracy, thus positioning architects, engineers, and designers as vital actors. These actors will also prove indispensable in leveraging the many thermal, acoustic, visual, hygienic, and other potentials of wood to support inhabitant’s wellbeing as evidenced by Dr. Graham Lowe [10].

To educate the new generation of professionals in the nuanced ecological, technological, and technical aspects of mass timber design, the Institute for Advanced Architecture of Catalonia (IAAC) is launching the groundbreaking, 100% online, Master in Mass Timber Design (MMTD) at the end of January, 2021, with applications opening again in June and October [11].


[1] Global Alliance for Buildings and Construction. 2018 Global Status Report. 2018. Available in this link.
[2] Architecture 2030. New Buildings: Embodied Carbon. 2020. Available in this link.
[3] United Nations Framework Convention on Climate Change. Paris Agreement. 2015. Available in this link.
[4] United Nations. Population. 2019. Available in this link.
[5] Chadwick D. Oliver, Nedal T. Nassar, Bruce R. Lippke & James B. McCarter. Carbon, Fossil Fuel, and Biodiversity Mitigation With Wood and Forests. Journal of Sustainable Forestry. March 2014, Vol. 33, Pg. 248 – 275. Available in this link.
[6] Food and Agriculture Organization of the United Nations. The State of the World’s Forests. 2020. Available in this link.
[7] Suzanne W. Simard, Kevin J. Beiler, Marcus A. Bingham, Julie R. Deslippe, Leanne J. Philip & François P. Teste. Mycorrhizal networks: Mechanisms, ecology and modeling. Fungal Biology Reviews. April 2012, Vol. 26, Issue 1, Pg. 39 – 60. Available in this link.
[8] Chadwick D. Oliver, Nedal T. Nassar, Bruce R. Lippke & James B. McCarter. Carbon, Fossil Fuel, and Biodiversity Mitigation With Wood and Forests. Journal of Sustainable Forestry. March 2014, Vol. 33, Pg. 248 – 275. Available in this link.
[9] Think Wood. 2020. Available in this link.
[10] Graham Lowe. Wood, Well-being and Performance: The Human and Organizational Benefits of Wood Buildings. Forestry Innovation Investment. April, 2020. Available in this link.
[11] Institute for Advanced Architecture of Catalonia. Master in Mass Timber Design. 2019. Available in this link.