Critical mass
10 TRENDS FOR 2023
What if the future for commercial construction lies within a return to the world’s first great construction material – wood? From modular low-rise housing to taller commercial structures, structural timber products offer a range of environmental and other health and wellbeing benefits that will increasingly appeal to real estate developers, investors and occupiers in a world where decarbonization remains one of the biggest challenges facing the built environment.
While timber has long been the predominant medium for single-family homes and small-scale construction in North America, modern composite wood materials are becoming more widely used in larger commercial buildings around the world. Cross-laminated timber (CLT) and related products are contributing to the growing number of “mass timber” buildings, where the primary load-bearing structure is made of these wood materials.1 Even though steel and concrete remain the most popular building material for commercial construction, the growth of environmental consciousness allied to a range of other potential advantages of timber products is driving investors and contractors to seriously consider them as alternatives.
What is it?
Timber cut directly from trees is one of mankind’s longest-serving construction materials, but it suffers from a number of disadvantages. In particular, it is limited in size, has low cross-grain load-bearing capability and is combustible in its natural state. Hardwoods offer superior performance to more plentiful softwoods but are slower growing. However, cross-laminated timber (CLT) and related products such as glulam and nail-laminated timber have been developed in recent decades that don’t suffer from these limitations.
CLT can be stronger and more structurally flexible than steel or concrete.
First introduced in the early 1990s in continental Europe, CLT is a fabricated wood product that combines prepared sections of timber using glue or other fixings. The wood planks are laid perpendicular to each other taking advantage of the longitudinal strength of the natural wood fibers, resulting in a construction material that can be stronger and more structurally flexible than steel or concrete. It can be used to create panels for walls and floors as well as beams and other load bearing components, used independently or in combination with other construction materials.
Multiple advantages
As a manufactured product, CLT and related products can be produced in many forms, shapes and sizes. CLT panels are prefabricated off site, which can reduce construction times, cost and waste before they are transported to site. They can be less noisy and disruptive to assemble than conventional materials which is an advantage in dense urban areas. CLT is also lighter than steel or concrete, reducing the load on foundations (which therefore require less cost and fewer materials) and making them easier to lift, meaning they need smaller machines to put together. Timber structures can therefore be used on sites where access or ground conditions are unsuitable for heavier construction.
Not only are they strong but their natural flexibility also means timber structures have excellent seismic-resistant properties, making them suitable for taller structures in areas prone to earthquakes.2 However, the primary attraction of structural timber products is their sustainability credentials.
Timber structures have excellent seismic-resistant properties.
Reducing environmental impact
Decarbonizing construction is one of the built environment’s critical challenges, given the sector accounts for 37% of worldwide energy-related CO2 emissions.3 The rise of whole life carbon assessments (WLC) as a method of assessing emissions is increasing the scrutinization of carbon intensive new builds. Conventional materials can be a large part of the problem as – in the whole life cycle of a building – the embodied carbon in them typically account for 10 to 20% of the whole carbon footprint. In a typical new office building, the structure represents over 50% of the initial embodied carbon.4 Globally, concrete alone is estimated to account for 8% of total CO2 emissions5 whilst the most popular steel production method – Basic Oxygen Furnace production – emits up to 2 tons of carbon dioxide for each ton of crude steel. In 2022, the steel industry was responsible for 7% of global carbon emissions.6 Using mass timber could reduce environmental impact given that the timber is sourced from producers that use sustainable forestry management.7
The production of CLT and other mass timber materials requires significantly less energy than that of steel or concrete. The embodied carbon of a structure is measured by the greenhouse gas emissions produced during the production, procurement, and installation of the components and materials in a building’s structure.8 Research estimates that potential carbon savings for the housing industry alone could reach 100 billion tonnes by 2100 if housing construction transitioned to timber from steel and concrete.9 The global alternative construction material market is already big business, estimated to be worth $190 billion in 2020 and forecast to grow by around 75% to reach $330 billion by 2030.10
Besides the decreased environmental impact of mass timber production, there are advantages to mass timber that reduce a building’s carbon footprint across its lifecycle. Throughout a building’s period of operation, well designed mass timber construction decreases energy use. Timber boasts natural insulating qualities that can be 10 times more effective than that of concrete and 400 times that of steel.11 Combined with energy efficient design standards - such as the Passivhaus Principles12 – timber construction can provide insulation and airtightness benefits, lowering the requirement for additional insulation and energy dedicated to heating and cooling. It can also reduce the need for plastics or other artificial insulating materials.
Well-designed mass timber construction decreases energy use.
In addition to reducing embodied carbon and annual energy usage, mass timber also has carbon absorptive capabilities that allow it to act as a carbon sink through a process of sequestration.13 Throughout their lifecycle, trees absorb carbon which they continue to store until the wood is burned or decomposes. It is estimated that, for each cubic meter of CLT, nearly one ton of COs is sequestered.14 To ensure that this biogenic carbon is not released following the end of the building life, this panelized mass timber can be introduced to the circular economy as the modular nature of timber construction lends the material to adaptable reuse and repurposing.15
Reaching new heights
Mass timber markets are growing rapidly. In 2021, the global CLT market was valued at $806 million and is expected to see annual growth of 15% through 2028, expanding the market to $2.07 billion.16 The majority of the demand is still in Europe, mass timber’s birthplace, but construction usage is expanding in North America and has increased exponentially since its introduction in 2012.17 Funding is increasingly available for research and the development of the sector, from philanthropic organizations such as Built by Nature18 and government entities such as the U.S. Department of Agriculture.19
Each year, developers are pushing the boundaries of mass timber construction. Once relegated to low-rise construction, mass timber and CLT constructions are increasing in height and square footage. The international standards for mass timber buildings changed in 2021 when the International Building Council expanded their maximum height allowance for Business and Residential Occupancies to 270 feet, or 18 stories.20
Today, there are around 139 mass timber buildings around the world with 60 located in Europe alone. The tallest mass timber construction in the world – the Ascent in Milwaukee, Wisconsin at 285 feet (87m) – was developed by Thornton Tomasetti in August 2022, providing 259 residential units, ground floor retail, and a rooftop terrace. The IBC allows height restrictions to be flexed for concepts that demonstrate proper safety testing.21 Over the next few years, mass timber structures will continue to rise in height with four projects taller than Ascent being proposed in the three months following the building's completion. The introduction of a new French sustainability law, which will require all new public buildings to be constructed with at least 50% timber or other natural materials, will further drive the growth of hybrid timber structures.22
Over the next few years, mass timber structures will continue to rise in height.
Challenges do remain, and not every country is fully embracing timber construction. Fire safety is a commonly raised concern, which is superficially understandable given that wood is inherently combustible. However, mass timber components meet fire resistance rating requirements (FRR) set by national building codes across North America and the United Kingdom. Even when timber does burn, a char layer forms on the outside which protects the interior allowing panels and beams to maintain their structural integrity. In fact, if protected with non-combustible materials in the same way steel structures require, timber construction can actually outperform competing construction materials.23
However, following the Grenfell disaster in 2017 in which a fire in a 24-storey residential block in west London claimed the lives of 74 people, the U.K. government introduced restrictions that impacted the use of CLT.
These restrictions made it difficult to obtain affordable property and construction insurance for mass timber buildings as insurance assessments overvalued potential fire risk.24 To address the lack of obtainable insurance in the U.K., increasing efforts towards a collective underwriting approach are taking place. Aviva has launched a pilot program for insuring hybrid buildings and the Alliance for Sustainable Building Products will release a playbook for insuring mass timber buildings later this year.25
Additionally, Chase Underwriting International are stepping to the plate and launched a Mass Timber Construction Insurance Facility for projects that range between £10 to £200m.26 In 2021, the U.K. government’s Net Zero Strategy promoted growth in low-rise timber constructions as a critical component in reducing embodied carbon – another step in the right direction.27 At the end of the day, property and construction insurance costs will decrease if developers properly manage the risks of mass timber construction through strategies such as fire suppression technology, employing mixed or ‘hybrid’ structure, and conducting fire and water impact testing.
In demand
As companies seek to improve ESG performance and WLC assessments become more commonplace, mass timber buildings will become increasingly attractive to commercial occupiers and investors. They are already demonstrating early success in the office sector. The U.K.-based flex provider The Office Group, or TOG, completed London’s tallest mass timber office building in December 2022. The Black & White Building provides 38,315 square feet of office space to clients and boasts amenities including gym facilities, commuter facilities, and a rooftop terrace. Compared to similar office buildings with steel and concrete structures, it has 37% less embodied carbon and improved energy efficiency through passive solar technology and renewable energy sources.28 According to TOG, the building was 40% pre-let four months out from opening, which is unprecedented in the flex office sector, and TOG believe that the environmental credentials of the building are a primary driver.
Mass timber buildings will become increasingly attractive to commercial occupiers and investors.
Mass timber alone will not solve the challenge of decarbonizing construction, and no-one is suggesting that it is appropriate in every situation. But particularly when combined in hybrid structures alongside more conventional materials, it has a huge part to play in helping the real estate sector respond to the climate crisis.
1https://www.constructiondive.com/news/mass-timber-101-understanding-the-emerging-building-type/443476/
2 Karacabeyli, Erol; Douglas, Brad; Forest Products Laboratory (U.S.); FP Innovations (Institute); Binational Softwood Lumber Council (2019). CLT handbook: cross-laminated timber. Pointe-Claire, Québec
3 https://www.unep.org/news-and-stories/press-release/co2-emissions-buildings-and-construction-hit-new-high-leaving-sector
4 https://www.istructe.org/resources/guidance/carbon-embodied-operational/
5 https://www.chathamhouse.org/2018/06/making-concrete-change-innovation-low-carbon-cement-and-concrete-0/executive-summary
6 https://joint-research-centre.ec.europa.eu/jrc-news/eu-climate-targets-how-decarbonise-steel-industry-2022-06-15_en#:~:text=The%20steel%20industry%20is%20responsible,7%25%5B1%5D%20globally.
7 https://www.architecturalrecord.com/articles/15796-mass-timber-a-new-chapter-in-sustainable-forestry
8 https://www.rics.org/globalassets/rics-website/media/news/whole-life-carbon-assessment-for-the--built-environment-november-2017.pdf
9 https://eandt.theiet.org/content/articles/2022/08/switching-concrete-for-timber-in-construction-shown-to-yield-huge-carbon-savings/
10 Allied Market Research (2021). Alternative Building Materials Market by Material (Bamboo, Recycled Plastic, Wood and Others), End User (Residential and Non-residential) and Application (Construction, Furniture & Flooring): Global Opportunity Analysis and Industry Forecast, 2021–2030.
11 https://www.vox.com/energy-and-environment/2020/1/15/21058051/climate-change-building-materials-mass-timber-cross-laminated-clt
12 https://energysavingtrust.org.uk/passivhaus-what-you-need-know/
13 D’Amico, Bernardino; Pomponi, Francesco; Hart, Jim (2021-01-10). "Global potential for material substitution in building construction: The case of cross laminated timber". Journal of Cleaner Production. 279: 123487. doi:10.1016/j.jclepro.2020.123487. ISSN 0959-6526.
14 https://www.vox.com/energy-and-environment/2020/1/15/21058051/climate-change-building-materials-mass-timber-cross-laminated-clt
15 https://www.naturallywood.com/blog/coming-full-circle-wood-circular-economy/
16 https://www.fortunebusinessinsights.com/cross-laminated-timber-clt-market-102884
17 https://www.structurlam.com/whats-new/news/north-americas-mass-timber-industry-and-its-ascent-to-the-global-stage/
18 https://architecturetoday.co.uk/built-by-nature-fund-promoting-timber-buildings-europe/; https://eu.desmoinesregister.com/story/money/business/development/2022/05/27/usda-funds-eco-friendly-mass-timber-buildings-iowa-valley-junction/9949108002/
19 https://www.usda.gov/media/press-releases/2022/05/27/biden-administration-announces-32-million-advance-climate-smart
20 https://www.woodworks.org/resources/tall-wood-buildings-in-the-2021-ibc-up-to-18-stories-of-mass-timber/#:~:text=Solution%20PapersTall%20Wood%20Buildings%20in%20the%202021%20IBC%20%E2%80%93%20Up,18%20Stories%20of%20Mass%20Timber
21 https://www.architecturalrecord.com/articles/15813-mass-timber-on-the-rise
22 https://www.dezeen.com/2020/02/12/france-public-buildings-sustainability-law-50-per-cent-wood/
23 https://www.steelconstruction.info/images/8/87/Steel_construction_-_Fire_Protection.pdf
24 The Alliance for Sustainable Building Products. 2022 “Mass Timber: Challenges & Potential Solutions.”
25 https://www.ft.com/content/9db8d185-e0df-4fbf-9b91-b781a0e5182a
26 https://www.structuraltimbermagazine.co.uk/news/mass-timber-insurance-a-stock-take/
27 https://www.architectsjournal.co.uk/news/governments-promotion-of-low-rise-timber-long-overdue-say-architects
28 https://www.theofficegroup.com/stories/design/behind-the-scenes-the-black-white-building
