Sustainable Wooden Skyscrapers for the Future Cities

Abstract

At the time of writing, energy-saving and eco-friendly building materials have gained acceptance, recognition, and a strong foothold in the construction sector. There is an appreciable degree of congruence in the development of green buildings and bio-based building materials, making it imperative to promote and sustain the application of such materials. Wood is endowed with a host of favorable properties sought after in a building material—its organic warmth, softness, ability to control indoor moisture levels and act as a good insulator, malleability, and workability, to name a few. Wooden buildings blend perfectly into the surrounding landscapes much better than their counterparts. It facilitates design for lightweight and strength, is a renewable resource, and accords stability and seismic resistance to structures. The focus of this chapter is on wooden skyscrapers which promise to be a greener and eco-friendlier option vis-à-vis the conventional concrete high-rises.

1. Introduction

Modern architecture is changing the face of megacities, creating a more comfortable and prosperous environment for life. Leading architects are increasingly choosing those forms and materials that increase the energy efficiency of future buildings. Futuristic buildings coexist with the legacy of the past and harmoniously fit into the style of the area. And the plasticity of their facades reflects the dynamism of modern cities. These projects differ from traditional buildings not only in their architectural appearance but also in their rich infrastructure. In addition, they often embody the most daring and progressive ideas of their time. We are constantly in contact with building materials. Metal handles, wooden walls, and glass windows would create a completely different atmosphere if the handles were, say, glass, the walls were metal, and the windows were wooden.

And yet, before embarking on a detailed design of the future building, it makes sense to determine its style at least approximately. If it will be a fusion-style building (some experts consider the term “eclectic” already obsolete), then such a decision should not be spontaneous, but meaningful and justified. It is worth understanding what elements of which styles the country house will combine, whether one component will dominate the others, how harmony can be achieved in the resulting exterior, and so on. Separately, you need to think about the materials and technologies that will be used in the construction process: how to emphasize the creative idea with their help and facilitate its implementation, what new and unexpected esthetic solutions the material or technology itself can offer the architect (Figure 1). The material is as important to the building as its form, function, and location.

Figure 1.

The modern architecture between form and functions.

In the circular bio-economies which will gradually entrench themselves in many parts of the world, wood, as a renewable material of construction, will reign again as a dominant material in anthroposphere structures, supplanting the now-prevalent nonrenewable materials. Wood wastes generated in the forestry sector will lend themselves to being reworked and recycled back into the anthroposphere [1, 2]. It is not just the fact that it is renewable and abundant which makes wood a favorite in the architecture, building, and construction (ABC) sector of a circular bioeconomy. It is strong and light, has good thermal insulation properties [3], has the ability to resist shock loads without getting damaged, and dampens vibrations (thus resisting seismic shocks). It is highly malleable and workable and lends itself well to gluing, being joined by fasteners, etc. In Europe, wood found used in the past as the main building material for temples, towers owned by appanage princes, and peasants’ farmsteads and is more common within Europe, in Scandinavia. Many Finnish, Norwegian, and Swedish citizens expressed different views on the acceptability of the use of wood than their fellow-Europeans in Austria, Denmark, Germany, and the United Kingdom [4].

Expanding the scope of use of wood and finding creative and innovative ways of incorporating wood waste back into the anthroposphere supports the paradigms of circular bio-economies [5]. If the processing turns out to be complex, the wood itself can be modified and conferred with improved properties. Modified wood is a new material in which its anatomical structure is preserved, while its physical and mechanical properties are significantly improved. Various types of modified wood are used not only as substitutes but also as full-fledged, promising composite materials. The static flexural strength of Wood-Based Laminate Constructions comes in handy as they frequently experience static flexural and compressive deformation during service [6].

The mechanical properties of wood depend on a host of factors, the most important of which are the nature of the load, the direction in which it acts on the fibers, the speed and the duration of the load, as well as the structural defects in the wood, effects of humidity, etc. The mechanical and deformation characteristics are determined in the laboratory on small specimens made of defect-free wood, thus obtaining the standard strengths of the ideal wood under short loads. The modulus of rupture (MOR) and modulus of elasticity (MOE) are determined using nondestructive (NDT), semi-destructive (SDT), and destructive (DT) test methods [7]. The moisture content is also determined, as it must be remembered that variations in moisture content cause local swelling or shrinkage, thereby changing the distribution of stresses and impacting the strength and bearing capacity adversely [8]. Variation in the quality of wood is common, both within the same species and across different species; and the sources of such variations are diverse. It is found that most of the mechanical properties of the glued wood elements are superior to those of the wood in the component elements. This may be reasoned out as follows:

• Reduction of adverse effects due to eccentric defects, such as knots, which introduce bending stress on individual parts [9].

• Reduction of the weakening effect of nodes, by consolidation introduced by adjacent elements.

• Ensuring a more homogeneous element with a positive effect on the resistances and on the general density, which is very close to the average density of the component elements.

2. ABC¹ and wood

Wood, it goes without saying, is one of the oldest building materials. Houses, towers, and bridges of yore were built with wood. Special wooden structures—circles—were used in the construction of ancient arches [10]. Centuries of experience and scientific research have shown that during normal operation of wooden structures, their service life is measured in centuries. An example of this is the oldest wooden bridge in Europe—the Chapel Bridge in Lucerne, dating back to 1330. The use of wood and its derivatives in construction and especially for insulation and finishing depends to a large extent on its favorable thermal properties. By virtue of its low coefficient of thermal conductivity vis-à-vis other materials of construction, even a light/thin wood frame wall may provide a structure with adequate mechanical properties and an acceptable level of thermal insulation [11]. The interest in “zero-energy” or “low-energy,” or “climate-positive” constructions with a reduced demand for externally supplied heat energy has entrenched itself in academic, research, and ABC circles and is sure to be fueled into the future [12]. Talking of thermal conductivity, the coefficient λ of dry wood (at a moisture content below 20%), ranges between 0.14 and 0.21 W/m.K. It is noteworthy that thermal conductivity in a direction perpendicular to the fibers is lower than in a direction parallel to them (which is quite intuitive). It is dependent on the density and the moisture content of the wood. For densities in the range of 300–800 kg / m³, and moisture content lower than 40%, when heat flows perpendicular to the fibers, the thermal conductivity coefficient can be calculated as shown in Eq. (1):

$${\lambda }_0=\left[237+0.02{\rho }_0\left(1+2\omega \right)\right]{10}^{-4}$$E1

where

• λ_o—coefficient of thermal conductivity (W / m.K)

• ρ_o—wood density (kg / m³).

• ω—moisture content (%).

Experimental tests have shown that in the temperature range from 20–100°C, the thermal conductivity coefficient can be determined by the relation shown in Eq. (2):

$$\lambda ={\lambda }_0\left[1+\left(1.1-{10}^{-4}\rho \right)\left({\mathrm{\Theta }}_w-20\right)/100\right]$$E2

where

• λ—thermal conductivity coefficient at temperature Θ_w (W/m.K)

• λ_o—thermal conductivity coefficient determined with the aid of Eq. (1).

• ρ—density of wood determined at 20°C.

Among other things, sustainable construction is a strategy adopted these days to move steadily, surely, and slowly toward the goal of net-zero greenhouse gas emissions. Focusing merely on the use-phase and urging consumers to reduce their energy usage is necessary but not sufficient. It is here that a material like wood, adopted in the design stage itself, complements the efforts which the inhabitants of buildings would also make [13].

Like all materials in general, wood expands and contracts in response to temperature variations. This variation, which is expressed in terms of the coefficient of thermal expansion αT is not essentially the same along the three axes—longitudinal, tangential, and radial. Its value in the longitudinal direction (parallel to the fibers) lies between 3E6 and 6E6, while it is much higher in the tangential and radial directions perpendicular to the fibers—between 10E6 and 15E6. If one compares the coefficient of longitudinal thermal expansion of wood with those of steel and concrete (materials which wood can replace in structures), then wood is much lower. This implies that thermal expansion joints are not required for wooden constructions. This is also bolstered by the fact that temperature changes lead to variations in moisture content (water evaporating when it gets warmer, for instance), leading to contractions (or swelling) in directions opposite to the thermally induced deformations [2]. The specific heat (c) for wood (moisture content below 20%) is about 5.07 W/kg.K. It must be noted that the specific heat is quite sensitive to the moisture content of the wood:

$$c=1.16\left(0.324+u\right)/\left(1+u\right)\left[w/\mathit{kg}\bullet K\right]$$E3

Part 1.2 of the EUROCOD 5 standard proposes the calculation of specific heats, for a humidity ω and a wet bulb potential temperature, ${\mathrm{\Theta }}_w$with the relation [14]:

$$c=\left(c_{\theta }+{\omega }_{\mathit{cap}}\right)/(\left(1+\omega \right)\mathit{\text{for}}{\mathrm{\Theta }}_w\le {1000}^{°}C$$E4

$$c=c_{\theta }\text{for}{\mathrm{\Theta }}_w>{1000}^{°}C$$E5

where.

c_Ɵ = 1110 + 4.2 Θ _w (specific heat as a function of temperature).

c_water = 4200 J / kg K (specific heat of water).

2.1 Quality of wood

The market imposes several quality requirements on products made of wood. Every sector which finds use for wood has its own range of specifications when it comes to wood species and quality [15]. Wood demanded by the construction sector, thereby, is categorized into different quality classes, and the prices are proportional to the quality [16]. In the current international calculation standards for building structural elements, quality classes are associated with predefined values of mechanical strength at different stresses, or physical characteristics:

• Change—generating tissue: This consists of a single layer of cells located between the bark and wood, which causes an increase in thickness [17]. A new growth ring is added annually to the trunk of the tree, and the number of rings indicates the age of the tree.

• Intercellular canals: These are structural elements which can be resinous-to-resinous, gumiferous, or deciduous [18]. The resin channels contain only resins, while the rubber equivalents contain gums, resins, and oils.

• Load-bearing capacity: The property of a construction system or its element is able to withstand loads imposed by other elements of the structure/construction. This is dependent on the geometric characteristics of the section size that determine the load-bearing capacity and deformability [19].

The behavior of wooden structures over time needs to be monitored. Wooden structures are used in building coverings, agricultural construction, and rooms where there is a likelihood of exposure to aggressive chemicals [20]. Wooden structures are also widely used by landscape architects in the construction of pavilions, gazebos, bridges in parks, gardens, and other natural ensembles. In construction, coniferous wood is most often used [21, 22]. Elements of wooden structures are connected to each other by means of glue (glued structures) or with the help of nails, dowels, and other fasteners. The most widespread are glued structures—this technology allows you to create strong and durable elements of almost any shape and size.

3. SWOT² for skyscrapers in modern cities

Skyscrapers, being tall, inevitably become an important part of the cityscape. The world’s most iconic skyscrapers have silhouettes which people instantly recognize, like the peak of a popular mountain or the familiar face of a friend. It is unlike a sculpture or painting; in that it cannot be the work of a single artist. It is a product of teamwork, resulting from numerous collaborative exercises among architects and CEOs, steelworkers and engineers, bankers, and billionaires [23]. Architects mull over what a freestanding skyscraper would look like and how it would look alongside, behind, or in front of the surrounding buildings. All buildings together constitute the skyline of a city. Quite like the different buildings that make them up, the skylines of different cities are also different from each other, in general. Skyscrapers can be considered as reflections of the culture and values of the inhabitants of the city they belong to, and on account of their massiveness and by the tower over all other structures in their vicinity, they end up attracting attention invariably, and defining the city or becoming almost synonymous with it [24, 25]. The Makkah Royal Clock Tower in Mecca (Saudi Arabia), for instance, has a large clock which shows time—an important factor for Muslims—and is easily visible to the people of the city. Taipei 101, in Taipei (Taiwan), was designed in eight sections because “8”is a lucky number in China—the Chinese word for this number is homophonic with the word for prosperity. High-rise buildings must not only be viewed from an urban planning and architectural perspective, as the sociological perspective provides useful insights into the history of urban development. Towers, skyscrapers, and high-rises have been added to the cityscapes of the world over the last 100 years, to facilitate efficient land use and in response to the rising rate of urbanization worldwide. The earlier design approaches of high-rises were sheathed in the traditional fake clothing of postmodernity. However, the development of modern architecture was more inclined to modular repetitions and broad abstractions integrated into the international style [26]. The typical American high-rise construction developed from the 1880s onward, beginning in Chicago and New York. Chicago was, at that time, an important industrial and commercial city, next only to New York. Sustainable skyscrapers, while making economical use of available land, facilitate energy-saving and provide comfortable habitation for the urban denizens.

Veritably, they are the icons of modern cities. They inspire man to aspire for greater goals and keep aiming higher (readers may wish to read Ayn Rand’s The Fountainhead to understand the “spirit of the skyscraper,” so to say) [27]. The timid out-of-towner can suitably palpitate on entering the bright lobby, while Superman or Superwoman can aspire to the executive floor or even higher! [28]. Although people have mixed reviews of skyscrapers, it is undeniable that skyscrapers have played an important role in strengthening the vertical development of cities, preventing excessive horizontal expansion, multiplying the capacity of a city’s population, and shortening the distances people travel. It can be reiterated here that they have dominated the cityscapes ever since they came into being, visible to one and all, from both near and far [29]. However, if the race of skyscrapers were even a thousand times a vanity fair, their construction would not cease to be the most difficult engineering problem. There are parallel directions of development in the world. It starts with the development of large territories, including industrial zones, dilapidated housing stock, and places that are now turned off from the city’s work. In such cases, the urban planning task becomes primary—creating the right balance of the territory, an effective street-and-road network, transport accessibility, social infrastructure, and parks. Here, of course, there is really no desire for high-density development. The main goal is to include the place in the city’s “work” and activate it by creating jobs and infrastructure [30].

3.1 New code in an UN-sustainable building standard

The rapid urbanization of the planet and the imminent challenges of climate change compel us to reconsider the purpose and form of development of cities. Last year, the participants of the Third International Conference on Housing and Sustainable Development, organized by the UN-Habitat Center, adopted a new urbanization plan. Sustainable urban development means that we must make them comfortable not only for ourselves but also for future generations—including protecting them from the adverse impacts of climate change [31]. Yet, at the same time, cities themselves “contribute” to global warming by being the fount of greenhouse gas emissions.

In order to control the contribution of cities to global warming, energy efficiency is the watchword. New building construction should occur by new norms and standards that ensure energy efficiency, while ensuring comfort for residents, with a salubrious indoor climate [32]. City administrations must prioritize investments in public transportation, while residents themselves must take initiatives to drive less and walk or use their bicycles more. Greening the city is of paramount importance, with the setting-up of parks, planting trees adjacent to sidewalks, and preserving any sylvan surroundings which may exist near the cities as these are carbon-sinks—veritably, the lungs of the city. Development must be harmonious, without anything “good” being overly compromised to augment another. The focus must be on the resident, not on accommodating more and more people in the city come what may, and not certainly on increasing the profit margins of the builders.

3.2 Examples of sustainable wooden skyscrapers

Wooden structures remind one, at first thought of small, idyllic cottages in the “middle of nowhere” (in the “woods,” so to say), but wood will soon become the material of choice, as mentioned earlier for more and more structures in urban settings too. As referred to earlier in the chapter, wooden buildings in cities have been around in Scandinavia for quite some time, with Norway boasting of perhaps the tallest wooden building on date [33]. The penchant for including more and more wood in the housing stock of cities has now spread to other countries in Europe, Asia, and the USA. Of course, when one talks of skyscrapers built with wood, it must be remembered that it is always along with other materials like concrete. This ensures that some necessary properties like fire resistance and vibration damping are not unduly compromised. Concrete though is not environmentally friendly and is associated with high greenhouse gas emissions, with carbon dioxide being emitted not just owing to combustion of fossil fuels upstream but also released from the calcium carbonate which is the principal raw material for cement [34]. Researchers have been seeking solutions to tide over this issue, and there should be some on the horizon soon.

A solid wooden beam is covered with a thick, solid, white layer on top. Dry wood is not damaged by exposure to corrosive gases and chemicals, and in that regard, scores over metals and concrete. One however has to reckon with hygroscopicity, structure heterogeneity, and inflammability. The last-named property has been responsible for the destruction of several wooden structures constructed in the past.

3.2.1 Skellefteå cultural center: Sweden: 2019

The Swedish city of Skelleftea inaugurated a 20-story “skyscraper” built entirely of wood and other sustainable materials in September this year, the publication said. Construction has an important role to play: to provide environmentally sustainable alternatives. Skelleftea is a community of 30,000 people, just 200 kilometers south of the Arctic Circle. As the forestry sector is very well developed in this part of the world, the authorities resorted to wood. It is, in a way, as far as Scandinavia is concerned, as mentioned earlier, a kind of a déjà vu, a return to the past [35].

The 75-meter-high building is a cultural center that houses 6 theaters, several art exhibitions, a library, and a hotel with over 200 rooms (Figure 2). Above all, however, the role of the building is to abate pollution in the area. “The original idea was not a simple 20-story house in Skelleftea, but a strategy that meant that Skelleftea not only survived, but also developed.” The building is built with the help of over 12,000 cubic meters of timber, extracted from the immediate vicinity of the town, thus reducing transportation costs and, implicitly, pollution [36]. The cultural center is based on laminated wood pillars, thus completely avoiding the use of cement. The cement industry is responsible for about 7 percent of global carbon emissions, according to the International Energy Agency (as also mentioned earlier, carbon dioxide is emitted from calcium carbonate, in addition to from the fossil fuels which may be used as heat energy sources). The building is equipped with solar panels, storage batteries, and solar-powered heating systems. Even the building’s fire sprinkler system, which usually runs on fossil fuel elsewhere, is powered by renewable energy. The remaining energy, stored in the batteries, is then supplied to other usage points in the city, making the skyscraper a so-called prosumer.

Figure 2.

The design of the Skellefteå cultural center.

3.2.2 Trätoppen “tree top” Stockholm: Sweden: Proposed

This is a 40-story, 133-meter-tall, 35-meter wide, and 18-meter-deep wooden skyscraper with 850-square-meter apartments per floor, which could well become the tallest building in the Swedish capital city. The facades’ original “digital” decor is inspired by the numbers in the old car park, showing which floor the driver is on Treetop, which translates as “top of the tree.” This 40-story building will stand out surely as one of the many icons in Stockholm and will surely attract tourists who come to the city (Figure 3). It will be 25% lighter in mass than a similar skyscraper built with reinforced concrete and will necessitate a smaller and “shallower” foundation [37]. There, however, are challenges related to lack of durability which have to be overcome [38]. In recent years, significant advances have been made in wood-based composite materials, such as cross-laminated wood (CLT panel), consisting of cross-located sawn softwood and hardwood with fibers glued at a certain angle. And just as carbon fiber composites are used to make race cars, planes, and golf clubs stronger, CLT adds durability to wood structures.

Figure 3.

The “Trätoppen” tower in Stockholm—Sweden (proposed project).

3.2.3 Mjøsa tower: Norway: 2019

The 18-story Mjøsa Tower or Mjøstårnet (the tower of Lake Mjøsa) in Brumunddal, Norway, which is 85.4 meters tall. The base cross section of the building is a 37.5 x 17 meters rectangle and approximately 11,300 m². Adjacent to it is a 4700 m² swimming pool, also with a wooden structure (Figure 4). The supporting structure is made entirely of glulam beams and pillars, while the balconies, stairwell, and elevator are made of X-Lam structural wood panels. To maximize the project’s environmental sustainability, the wood used was obtained from local forests and two new trees were planted for each one cut down, reflecting the high Scandinavian standards of management in the forestry sector. Fire safety is taken care of, in this skyscraper [39]. Untreated solid wood creates its own fire-resistant surface as the outer layer chars in a fire, making the wood immune to further fire-induced damage. Fire safety regulations state that a building must withstand a full fire for at least 2 hours without collapsing. The floors of the first 11 floors are made of wood, while the floors of the last 7 floors of the tower are reinforced with concrete. Now, higher one is in a building, be the building made of concrete or wood, it sways. In the case of the Mjøsa Tower, the weight of the concrete on the upper floors dampens the tendency to sway, restricting it in the topmost floor to about 14 centimeters.

Figure 4.

The “Mjøsa” tower in Norway.

The facility includes home offices, a hotel, and apartments. The construction project is a testament to how more massive and less environmentally friendly concrete can be replaced with wood. This high-rise Mjøsa Tower was built from glued laminated timber, cross-laminated timber, and Kerto LVL [40]. To achieve the required load-bearing capacity, cross-glued Kerto-Q laminated veneer lumber panels are also used as the material for the floors. The plates are characterized by their robustness and resilience. The construction time thereby has decreased by 35–40% vis-à-vis working with cast-in-place concrete, thanks to the lightness of wood [41].

3.2.4 Multi-story wooden building “Treet” (Bergen, Norway): 2015

The building was recently built in the Norwegian city of Bergen—a 14-story, 52.8 meter-tall, 62-apartment high-rise residential building called Treet (which translates as “Tree”). The previous tallest wooden building was the 32-meter-tall Forte building in Melbourne, Australia. The load-bearing structures of the building are mainly made of glued laminated timber, a building material made by longitudinally gluing wooden boards (lamellas) with waterproof glue. Concrete was only used for the three main floors, which served as platforms for four tiers of stacked modular sections [42].

Treet, located near the Paddleford Bridge, is constructed as a wooden building with glulam beams as the outer and inner skeletons and has 14 floors above the plinth in concrete which includes parking spaces and the main technical installations. The 5th and the 10th floors of the building are more securely attached to the glulam beam skeletal structure, to dampen swaying when it is windy (Figure 5). The other floors consist of prefabricated modules. The main difficulty was to find a place for all the engineering systems. About 180 mm of space was allocated under the ceiling, in which it was necessary to fit the sprinklers and ventilation and lighting systems [42]. Therefore, when prefabricating the modules, the margin for error was very small. A special glued beam capable of withstanding fire for 90 minutes was used, without compromising the structural integrity in any way. Refractory paint was used for finishing work. In addition, the building was designed in accordance with stringent standards governing energy consumption in passive houses, which necessitated extra attention to be given to heat recovery in HVAC systems and associated piping. Separate sprinkler placement drawings were required, as they had to be installed in the balconies.

Figure 5.

The conceptual and execution phases of a “Treet” building.

3.2.5 HoHo tower: Vienna: 2018

The new 84-meter high 24-story HoHo tower in Vienna, Austria, which will be the tallest wooden building in the world, has been underway for over a year. Approximately 76% of the structure will be wooden [43].

Vienna is a city with numerous baroque buildings and architecture from the era of Grinders.

The HoHo skyscraper will house apartments and offices, spa and wellness centers, restaurants, and one hotel (Figure 6). Constructing such a tall structure in wood requires meticulous planning, a team of creative designers, architects and engineers, and appropriate building infrastructure This tower in Vienna is an exemplar of eco-friendliness and economy [43].

Figure 6.

The HoHo tower in Vienna.

In HoHo, massive cross-laminated wood elements and prefabricated concrete panels are combined. A deliberately “simple” system uses the laying of four prefabricated serial building elements: supports, ceilings, and facade elements. The novel wood-concrete composite ceiling elements reduce the proportion of steel fasteners in the construction. Prefabrication of wooden structures takes place under controlled conditions. The supports, in turn, form a single mounting element with similar prefabricated solid wood exterior wall modules. This modular design approach [44] decreases the working time on the construction site. It facilitates the avoidance of problems associated with adverse weather conditions and long drying periods. However, one needs to bear in mind that the visible wooden surfaces need to be handled carefully, as they would form the inner envelope for the houses and are meant to contribute to a feeling of coziness and not detract therefrom. The way space is engineered within the building is flexible and can be changed any time, without incurring high costs and extra effort. This contributes directly to the durability of the building.

3.2.6 W350 project: Japan: proposed

This project is a proposed wooden skyscraper in downtown Tokyo (Japan), which was announced in 2018. The Timber Interface consists of wood with a small cross section; thus, it can be used for renewing installations with a short lifespan, daily cleaning of windows, and general maintenance of buildings (Figure 7). About 70% of Japan’s land is forested, and 40% of the forested area, i.e., approximately 30% of the land, is artificially forested. The well-managed practice of tree planting, logging, building production, and replanting has favored the national environment of Japan’s lands, climate, cities, and forests, maintaining forestry and the surrounding area [45].

Figure 7.

The futurist tower “W350 project” in Japan.

The “W350 Plan” is an R&D concept that aims to further advance this technology and realize an “environmental wooded city with the goal of reducing the total greenhouse gas emissions of “embodied carbon“ during the construction phase of the life cycle, to curb climate change [46]. Many companies work to develop refractory materials and genome selection breeding to realize a highly durable and comfortable building space using wood. The skyscraper will be 90% wood, the rest being steel which will serve the purpose of providing the skyscraper with wind and seismic resistance. Wood too, for that matter, is known to be resistant to seismic shocks. The project requires 185,000 cubic meters of timber and plans to revitalize forestry and timber demand in Japan [47]. In addition to esthetics, the choice of wood is intended to “turn the city into a forest.” Wooden structures are also easier—when compared to concrete structures—to repair or replace if they collapse. It is estimated that the costs for fashioning wooden structures and incorporating them in buildings will continue to decrease due to technological advancement.

Eight years ago, a law was passed in Japan that requires construction companies to use wood in public institutions smaller than three stories [48]. There are other such constructions globally, although not as tall as the one proposed for construction in Japan. There is an 18-story wooden office building in Minneapolis and a 16-meter-tall student apartment building in Vancouver. Sumitomo Forestry, which develops businesses that utilize wood such as housing and building materials, has said that it looks forward to utilizing a lot of wood in the building and construction sector over time, in Japan.

3.2.7 The Chicago River beech tower—A vision of new building

It is a collaborative research effort aimed at identifying challenges and opportunities for the design of increasingly high-mass timber structures. The Chicago River Beech Tower is an 80-story, 300-duplex-unit residential building, which just about stays within the upper range established for residential towers in the city [49] (Figure 8). While the River Beech Tower structure is well balanced, an increase in material volume was expected as the design progressed.

Figure 8.

The Chicago River beech tower.

The River Beech Tower aims to provide the understanding necessary to design and build large buildings using next-gen engineered wood structures.

4. Results and conclusions

Climate change has been a key driver in the resurgence of wooden structures in building and construction in urban settings. Wood is a solid material made up of organic substances (cellulose, lignin, etc.) with carbon, hydrogen, and oxygen as the main constituent elements. From a microstructural point of view, it is made up of supporting and guiding tissues. The structure of the wood can be comprehensively studied by observing its cross section, the radial longitudinal section, and the tangential longitudinal section.

Wood has rarely been used in the construction of high-rises, but that is about to change, as the examples described in the chapter illustrate. Though it is inflammable and many old wooden buildings have been gutted down by fire, wood is essentially a carbon-sink (which stores up the carbon in it during its use phase as a building material for a long time), is hard and light, is easily workable, has very good acoustic and thermal properties, reduces the size and the cost of the foundations of a building, and provides occupants with a more comfortable and healthier indoor environment.

The wooden skyscrapers described, and those which may likely spring up in the years to come, in other cities of the world include many architectural functions such as offices, hotels, shops and residential units, garden roofs, terraces covered with greenery, water features, and huge interior spaces filled with natural light. The revolutionary construction is made of a durable material called glulam, which is made up of wooden planks that are glued together to form beams.

The use of wood essentially comes as a response to the need to rethink our approach to buildings in cities and pursuing the paradigm of zero-emission and energy-neutral buildings, toward the achievement of Sustainable Development Goal # 11—sustainable cities and communities. Indeed, they are not panaceas to all the challenges which humankind dwelling in cities faces on date, but surely, one step forward in the mitigation of and adaptation to the adverse effects of climate change.

Even if ultrahigh buildings are erected today for a different purpose—to display wealth, power, grandeur, and ambition, it would be wise to do that in a sustainable manner—and earn bonus points in the process!.