Ulrich Dangel

Dispelling Misconceptions

about (Mass) Timber in the City

ulRICH

dangel

My passion for wood began when I was studying architecture in my hometown of Stuttgart in the 1990s. Through my German and Austrian heritage, it didn’t take me long to discover the westernmost Austrian province of Vorarlberg and its unique building culture — one that is heavily rooted in its timber construction tradition. After several years in practice in London, I moved to Texas to begin my academic career. Ever since arriving at UT Austin in 2005, my teaching and scholarship have revolved around designing and building with timber.

The opportunity to undertake in-depth research allowed me to explore the phenomenon of Vorarlberg, and the results were ultimately summarized in my book, Sustainable Architecture in Vorarlberg, which was published in 2010 Fig 1. While this study was specific to a particular region, the small province and its pioneering architects were instrumental in the rebirth of wood architecture in Europe, initially in the 1960s, and later in the 1980s and 1990s. Vorarlberg’s sophisticated yet sustainable building style culminated in a model for architecture worldwide, but — given the region’s unique circumstances — one that might be challenging to replicate in other parts of the world. As I concluded this work, newly developed engineered wood products — most importantly cross-laminated timber — began to enjoy increasing popularity in the construction sector Fig 2. Along with the advent of these innovative products came the promise of a host of environmental and performance benefits. These included renewability, the ability to sequester carbon, a high strength-to-weight ratio, and the potential to replace more energyintensive materials in mid-and high-rise building applications with bio-based products. The prospect of these new developments prompted me to expand my studies. As a result, I began to look at timber construction on a global scale. My objective was to investigate wood through the entire supply chain — from growth and harvest to processing, to fabrication, all the way to the installation of the finished product on-site. This involved engaging with individuals across multiple disciplines, drawing upon existing relationships, and establishing new ones. I consulted and worked with foresters, researchers, building product manufacturers, fabricators, architects, engineers, government bodies, interest groups, and non-profit organizations. Understanding the motivations and responsibilities of each individual or entity was critical to recognizing their impact on the successes and failures of building products, strategies and initiatives, and the industry at large.

My research highlighted one of the most significant dichotomies in discourse of contemporary architecture today: timber in the city, or the reintroduction of wood as the primary structural material for multistory building applications in dense urban environments. Even though wood was the most prevalent building material up to the nineteenth century, it lost its dominance in the construction sector for several reasons. Not only was it flammable (remember the Great Chicago Fire of 1871 Fig 3), but it also did not possess the structural capacities that were necessary to realize the enormous construction undertakings that came along with nineteenthcentury industrialization efforts: factories, warehouses, train stations, exhibition halls, and numerous other large-scale infrastructure projects and building types. Instead, iron, steel, and concrete, which were quickly optimized and perfected through focused scientific research, stepped into its place and became the materials of choice. Wood, with its seemingly unpredictable chemical and physical properties, became relegated to secondary construction tasks such as roof framing and non-structural applications. Then, in the 1990s and 2000s, innovations in manufacturing techniques yielded entirely new engineering solutions. The resulting mass timber products possessed unique properties and they promised the return of wood to the city as a building material. However, the introduction of

FIG 1 Sustainable Architecture in Vorarlberg: Energy Concepts and Construction Systems, Birkhäuser, 2010. Image courtesy of Birkhäuser Verlag GmbH, Basel.

FIG 2 (above) Cross-laminated Timber (CLT). Image courtesy of Stora Enso.

FIG 3 (right) The Great Chicago Fire, Chicago in Flames–The Rush for Lives Over Randolph Street Bridge, artist’s rendering by John R. Chapin, 1871. Public domain.

these novel technologies also raised many questions and concerns, leading to the emergence of numerous misunderstandings and misconceptions around increasing the use of wood in construction. My curiosity to find answers for myself and others led me to examine the circumstances more carefully. In the process, I was able to formulate explanations, clarify apparent contradictions, and debunk long-standing myths. I will elaborate on three of these misconceptions here.

THE INCREASING DEMAND FOR WOOD WILL CAUSE INCREASED DEFORESTATION

Forests are the most predominant and biologically diverse ecosystems on land, providing habitat for more than 80% of the terrestrial species of animals, plants, and insects.1 In addition, billions of people rely on forest products to satisfy their basic needs for food, energy, and shelter.2 Forests also play a critical role in the hydrological cycle by preventing soil erosion, landslides, floods, droughts, desertification, and salinization.3 Most significant is their ability to absorb and sequester carbon dioxide from the atmosphere, making them essential carbon sinks.4 There is no doubt that harvesting trees reduces the ability of forests to provide these vital services, so concerns for increased deforestation are warranted. Defined as the permanent conversion of forest land to non-forest land, deforestation causes vary widely from one region to another. While trees might be cut down to be used as timber for construction, some of the most severe deforestation occurs, in fact, when land is cleared for agricultural use, in particular for the cultivation of commodity crops and the creation of pastureland for livestock. This is of primary concern in the tropics and sub-tropics, and much work remains to be done to curb the detrimental environmental effects while simultaneously supporting sustainable economic development. In contrast, countries such as the United States and Canada are at extremely low risk of deforestation. Historical data confirms that global regions with the highest levels of industrial timber harvest and forest product output are also regions with the lowest deforestation rates. An economically vibrant forest industry is key to policies, incentives, and management practices that support sustainable timber supply and healthy demand for forest products Fig 4.

5

SOURCING OF MASS TIMBER PRODUCTS REQUIRES THE HARVESTING OF OLD-GROWTH TREES

One of the significant advantages of engineered wood production is the ability to prefabricate sizeable components used in long-span applications. Cross-laminated timber (CLT), for instance, can be manufactured in panel sizes up to ten-feet wide, sixty-feet long, and up to twenty-inches thick. Rather than relying on valued, large-diameter trees that are likely only found in old-growth forest stands, these products utilize readily available dimensional lumber. Instead, 2x4 and 2x6 boards are typically sourced from fast-growing, small-diameter trees and are laminated together to form largeformat structural components. Through these methods, modern engineering and production technologies increase the value of forests as a resource by turning low-value raw materials into high-value commodities Fig 5.

Additionally, wood is a truly renewable material as long as it is sourced sustainably. Forest certification systems, such as the Forest Stewardship Council (FSC) or the Programme for the Endorsement of Forest Certification (PEFC), support stewardship efforts and sustainable forest management objectives by ensuring that wood products come from well-managed, legally harvested forests. Wood is, in fact, the only structural building material with third-party certification programs in place to verify that products originate from a responsibly managed resource. About 19% of total US timberland is currently certified, which is well above the global average of 11%. Even though forests in federal ownership are not certified, it does not mean that they are not sustainably managed. National forests meet many of the certification requirements regarding forest planning, protection of threatened and endangered species, and others.6

MASS TIMBER BUILDINGS ARE NOT AS SAFE SINCE THEY ARE MORE SUSCEPTIBLE TO FIRE THAN STEEL OR CONCRETE BUILDINGS

Fire safety is one of the biggest concerns when building with timber. Still, there are significant differences in fire performance between conventional light-frame construction and the new mass timber systems. The structural members in light framing are relatively small in size, making them susceptible to ignition and early collapse in fires. This means they need to be protected with fire-resistant membrane barriers such as gypsum board, creating an arrangement of concealed combustible spaces. In contrast, construction with mass timber typically does not yield combustible voids, greatly reducing the risk of a concealed fire. Due to their solid nature, mass timber members also possess the inherent ability to resist fire without additional protection. Their mass allows for a char layer to form on the surface, which insulates the remaining wood from heat penetration and ignition. While the charred portion no longer fulfills any structural functions, the non-charred section retains its structural capacity over an extended period of fire exposure Fig 6. This unique characteristic makes mass timber more predictable in a fire than steel, which can deform and collapse quickly when exposed to high temperatures. Structural steel still needs to be protected with additional fireproofing, even though it is considered a non-combustible material. Besides employing the charring method as a means for fire protection, mass timber members can also be encapsulated with fire-rated boards or other non-combustible materials to satisfy building code regulations.7 Recently approved provisions allowing the construction of tall mass timber buildings up to eighteen stories — with varying degrees of fire protection of timber surfaces — will be included in the 2021 edition of the International Building Code (IBC).8

These three instances merely offer brief insight into questions that might arise when designing and building with mass timber. In my research, I gathered numerous compelling arguments for the increased use of sustainably sourced wood products as viable alternatives to non-renewable, more fossil fuel-based building materials. Efforts to share my findings culminated in the publication of Turning Point in Timber Construction in 2017 Fig 7. Envisioned as a compact reader and inspiring resource, the book’s goal was to demonstrate the potential positive effects on the global environment, local

FIG 4 Group selection harvest in British Columbia, Canada. Image by Moresby Creative, courtesy of naturallywood.com.

FIG 5 Cross-laminated timber production. Image courtesy of Stora Enso.

FIG 6 CLT panel after fire testing with clearly visible char layer. Photo courtesy of FPInnovations— web.fpinnovations.ca.

FIG 7 Turning Point in Timber Construction: A New Economy, Birkhäuser, 2017. Image courtesy of Birkhäuser Verlag GmbH, Basel. FIG 8 Time for Timber exhibit, Mebane Gallery, 2018. Image courtesy of Piston Design.

FIG 9 Centerline 14: Time for Timber, Center for American Architecture and Design, 2019. Image courtesy of the Center for American Architecture and Design.

FIG 10 “City Stoop” by Aaron McMurry and Joshua Melton, spring semester 2019. Courtesy of Aaron McMurry + Joshua Melton. FIG 11 Structural system for “City Stoop” by Aaron McMurry and Joshua Melton, spring semester 2019. Courtesy of Aaron McMurry + Joshua Melton.

FIG 12 Structural connection details for “City Stoop” by Aaron McMurry and Joshua Melton, spring semester 2019. Courtesy of Aaron McMurry + Joshua Melton.

FIG 13 “Sustainable Community of the Future” by Hailey Brown and Prarthan Shah, spring semester 2019. Courtesy of Hailey Brown + Prarthan Shah. rural economic development, and our building culture at large. The target audience was design professionals, engineers, anyone involved with forestry and timber-product manufacturing, and especially architecture students and the general public. The 2016–2018 Meadows Foundation Centennial Fellowship at the Center for American Architecture and Design allowed me to highlight my research interests at the School of Architecture. The Time for Timber exhibit in the Mebane Gallery showcased six innovative mass-timber projects from Europe and North America that represent significant contributions to sustainable building. Each case study was carefully selected based on its efforts to pioneer particular aspects of contemporary timber construction in urban contexts Fig 8. The accompanying one-day symposium brought together four invited panelists from various professional backgrounds to present their work from research or practice and engage in a dialogue about designing and building with timber. Along with a documentation of the exhibit, their thoughts, observations, and opinions were captured in the publication Centerline 14: Time for Timber Fig 9. Designing with timber continues to play an integral role in both my elective seminars and design studio courses. The Timber in the City Urban Habitat Student Design Competition, organized by the Association of Collegiate Schools of Architecture (ACSA) in collaboration with the Softwood Lumber Board, has served as an excellent vehicle to introduce students to mass timber construction in the classroom. Now in its fourth edition, the program intends to

...engage students (…) to imagine the transformation of our existing cities through sustainable buildings from renewable resources, offering expedient affordable construction, innovating with new and traditional wooden materials, and designing healthy living and working environments.9

The competition brief most recently served as the framework for my spring 2019 integrative studio. The students were challenged to reimagine a vacant waterfront site in Queens, New York through the design of a midrise, mixed-use complex that included affordable housing and several community amenities. The format of this prompt required studio projects to emphasize the tectonic expression of architecture. The challenge therefore placed a strong focus on the design implications of technical issues,

FIG 14 “Sustainable Community of the Future” by Hailey Brown and Prarthan Shah, spring semester 2019. Courtesy of Hailey Brown + Prarthan Shah.

particularly their potential for design generation and as a repository of meaning. The course’s objective was to develop a project from its initial concept to the construction detail while simultaneously ensuring that design decisions reinforce architectural ambition and intent at all scales. The resulting quality and conviction of the final projects indicated the timeliness and relevance of mass timber building systems for multi-story applications in urban areas. In addition, students were able to gain an understanding of how their use can offer viable low-energy alternatives to other, more conventional construction methods, while satisfying society’s building needs for the foreseeable future Figs 10-14. The continued advancements in engineered wood products and the emergence of new building systems highlight the need to further integrate lowcarbon mass timber construction methodologies into the architectural curriculum. As this type of construction becomes more widely established and accepted, dedicated coursework on the topic will be necessary. To this end, I have been working as the faculty lead with the ACSA and the Softwood Lumber Board to develop the call for submission for their inaugural Timber Education Prize. This award program seeks to recognize effective, innovative courses and curricula that create a stimulating and evidence-based environment for learning about timber as a material that achieves multiple design, construction, and performance objectives. Mass timber construction continues to gain momentum and offers enormous potential to address some of our society’s most pressing issues. I am hopeful that the efforts and initiatives of myself and others equally passionate about finding sustainable and resilient building solutions will set the stage for the return of wood to our cities.

(Basel: Turning Point in Timber Construction: A New Economy Ulrich Dangel, 7 Birkhäuser, 2017), 167. 8 Mass Timber Code Coalition, Understanding the Mass Timber Code Proposals: A Guide for Building Officials, https://awc.org/pdf/tmt/MTCC-Guide-Web-20180919.pdf. “2022 Timber Competition,” Association of Collegiate Schools of Architecture, 9 accessed July 2, 2021, https://www.acsa-arch.org/competitions/2022-timber- competition/.

“Forests Absorb Twice as Much Carbon as They Emit Each Year,” World Resources 4 Institute, accessed June 30, 2021, https://www.wri.org/insights/forests-absorb- twice-much-carbon-they-emit-each-year. Peter Ince, “Global Sustainable Timber Supply and Demand,” in Sustainable 5 Development in the Forest Products Industry , eds. Roger M. Rowell, Fernando Caldeira, Judith K. Rowell (Porto: Ediçoes Universidade Fernando Pessoa, 2010), 29–41. V. Alaric Sample, Will Price, Jacob S. Donnay, and Catherine M. Mater, National Forest 6 Certification Study: An Evaluation of the Applicability of Forest Stewardship Council (FSC) and Sustainable Forest Initiative (SFI) Standards on Five National Forests (Washington, DC: Pinchot Institute for Conservation, 2007), https://www.fpl.fs.fed.us/ documnts/pdf2010/fpl2010ince001.pdf.

United Nations Environment Programme (UNEP), Food and Agriculture Organization 1 of the United Nations (FAO), United Nations Forum on Forests (UNFF), Vital Forest Graphics (2009), 38. Food and Agriculture Organization of the United Nations, State of the World’s Forests 2 2014 (Rome 2014), xiii. Food and Agriculture Organization of the United Nations, Forests and Water: 3 International Momentum and Action (Rome, 2013), 1–2.