The built environment is responsible for approximately 42% of annual global CO2 emissions. During a building’s lifespan, half of these emissions come from its construction and demolition. Furthermore, the production of cement, concrete, and steel is also generating a massive amount of greenhouse gas emissions worldwide.
Research in Science Direct indicates that the carbon intensity for primary steel production is 1.9 tons of carbon dioxide per ton of steel from the burning of coke to reduce ore. The equivalent figure for 1 ton of cement is 1.25 tons of CO2 emitted from the combustion of fossil fuels and the calcination of limestone.
Global building floor area is projected to double by 2060, the equivalent of adding an entire New York City to the world, every month, for 40 years.
The rapid pace of urbanization is having a severe impact on the environment. Increasingly, cities globally are exploring more sustainable and eco-friendly approaches to urban development. Among the most promising of these is wood – a material largely overlooked in contemporary urban construction.
The built environment is responsible for approximately 42% of annual global CO2 emissions. During a building’s lifespan, half of these emissions come from its construction and demolition. Furthermore, the production of cement, concrete, and steel is also generating a massive amount of greenhouse gas emissions worldwide.
Research in Science Direct indicates that the carbon intensity for primary steel production is 1.9 tons of carbon dioxide per ton of steel from the burning of coke to reduce ore. The equivalent figure for 1 ton of cement is 1.25 tons of CO2 emitted from the combustion of fossil fuels and the calcination of limestone.
Global building floor area is projected to double by 2060, the equivalent of adding an entire New York City to the world, every month, for 40 years.
The rapid pace of urbanization is having a severe impact on the environment. Increasingly, cities globally are exploring more sustainable and eco-friendly approaches to urban development. Among the most promising of these is wood – a material largely overlooked in contemporary urban construction.
Wood structures at 25 King Street timber building, Australia.
Instead of emitting carbon, trees absorb and store a significant amount of carbon from the atmosphere during their growth process. On average, 50 percent of a tree’s dry weight is carbon. A single Douglas fir will sequester 966 kilograms of carbon over a 20-year span.
Throughout their life cycle, trees emit carbon as their parts decompose: needles and leaves fall to the ground; bark and dead branches are torn or blown off; and finally, when the tree itself dies, it begins to release carbon back into the atmosphere through decay. As long as wood products are not allowed to decompose, for example, by being used as building materials, their utility as a carbon sink remains intact for the entire life cycle.
For example, Stadthaus, London – a 9-story apartment building completed in 2009, considered a pioneer in paving the way for high-rise timber buildings, which has stored 185,000 kilograms of carbon dioxide equivalent (CO2 eq), compared to the 125,000 kilograms of carbon dioxide that would be released into the atmosphere had the building been constructed of concrete.
Similarly, by using wood rather than steel and concrete, the Ascent in Milwaukee, USA – a 25-story building completed in 2022 and currently the world’s tallest timber-concrete hybrid building, which has removed the equivalent of 2,400 cars from the road for an entire year.
Top 5 Tallest Timber Buildings in the World, as compiled by the Council on Tall Buildings and Urban Habitat (CTBUH)
These buildings were formed and set records thanks to mass timber – a technology for producing engineered wood products known for their strength, versatility, sustainability, and especially fire resistance.
Every building material will be negatively impacted by exposure to fire. Steel buckles, concrete spalls and wood, of course, burns. However, modern mass timber, a type of engineered wood made from pieces of lumber fixed together to create larger structural building components, behaves differently. Its thick layers of wood burn slowly, creating a charred layer that protects the inside and prevents complete combustion and structural deformation.
Research and analysis show that mass timber not only meets prescribed fire safety and safety codes but can exceed them. In a fire test, a 7-inch thick (about 18 cm) wall of plaster-coated Cross Laminated Wood (CLT) lasted 3 hours and 6 minutes. This result is an hour longer than current fire code requirements.
The Canadian Wood Council conducted a fire resistance test on a simulated mass timber building. The images show the building’s condition before and after a four-hour fire test, demonstrating significant structural integrity.
There are four common types of mass timber used in construction: Nail-Laminated Timber (NLT); Dowel-Laminated Timber (DLT); Glulam (GLT); and the most widely applied Cross-Laminated Timber (CLT).
Simulation of the structure of 4 common types of mass timber, with most wooden buildings in the world primarily using CLT and Glulam.
These materials can be used in various structural applications: beams, columns; floors, roofs, and walls; etc. As of 2022, mass timber technology has been used in 139 high-rise wooden buildings worldwide (counted from 8 stories and above) since the first project, the Stadthaus building, in 2009.
Governments and international organizations are also beginning to promote this trend, such as: Canada has implemented the Green Construction through Wood (GCWood) program, while the International Code Council (ICC) has also adjusted regulations to allow the construction of wooden buildings up to 80 meters.
The trend of “greening” is driving the development of timber high-rise buildings around the world. The use of wood is not merely a technical solution; researchers also emphasize that the timber used must come from planted forests that are sustainably managed to avoid depleting natural ecosystems.
Not only are there concerns regarding forest management, but for elevator manufacturers, wooden buildings also present new challenges, as traditional elevator shafts are made of concrete, brick, or steel. So far, the use of wood in elevator shafts has not become truly common.
An example is Mjøstårnet in Brumunddal, Norway, which was recognized by the CTBUH as the world’s tallest timber building upon its completion in 2019, standing at 18 stories and 85.4 meters high. The wooden components comprise glulam structures in the main load bearing, CLT in the elevator and staircase shafts, as well as wooden-based floor and facade elements.
Mjøstårnet was designed by Voll Arkitekter and developed by AB Invest, with elevator systems supplied by Starlift, Norway.
Tall timber not only poses challenges in terms of structure but also requires optimization in the design of elevator systems. With a lighter weight than concrete, wood can increase vibration, necessitating that elevator manufacturers ensure stability and safety. To keep vibrations in check, wooden elevator shafts typically need to be wider than their traditional, concrete counterparts.
Wooden elevator shaft at the Budakeszi Hospital construction site, Hungary.
To meet the growing trend of using wood in modern construction, many elevator companies have developed supporting solutions. These include establishing standards for wooden elevator hoistways and collaborating with timber companies that produce prefabricated hoistway modules. To further enhance fire resistance, these wooden hoistways are fully clad with fiber gypsum panels and equipped with smoke detectors, and more.
The future of wooden cities is not only a promising prospect but also an essential solution to address global climate change.
These efforts not only ensure that wooden buildings meet safety standards but also affirm the role of wood in the elevator industry as a sustainable material, catering to the increasing demand for environmentally friendly constructions and marking a new turning point in both technology and architectural design.
Editor: Phuong Linh
