Towards Sustainable Cities—Selected Issues for Pro-Environmental Mass Timber Tall Buildings

Abstract

The paper undertakes considerations and research into the implementation of mass timber tall buildings in shaping sustainable built environments. The investigated issues arise from contemporary challenges in shaping sustainable built environments, including the implementation of selected aspects of Sustainable Development Goals 11 and 13 relating to the need to meet the needs of an increasing urban population while limiting urban sprawl; the use of nature-based development solutions regarding materials and access to green spaces to ensure a high quality of life for residents, as well as the need to reduce the negative environmental impact of development. The aim of this article is to present building construction that is at the forefront of implementing pro-environmental solutions and contributing to sustainable urban development. Using a research method based on a case study with an analysis of the available literature, the study covered 109 tall mass timber buildings erected worldwide since 2009. General analyses of the urban context of the buildings in question were carried out in terms of accessibility to leisure and recreation areas and to urban greenery, public transport, as well as functional and material solutions for the structure and interior and facade design.

1. Introduction

The 2030 Agenda for Sustainable Development [1] sets out goals for the sustainable development of cities and communities among others, namely Goal 11 ‘Make cities inclusive, safe, resilient and sustainable’ and Goal 13 ‘Climate action’. Actions have been identified to achieve Goal 11, including ensuring access to adequate, safe, and affordable housing for all; intensifying efforts to protect the natural environment; reducing the negative impact of cities on the environment; etc., and Goal 13, including requirements to reduce global emissions of greenhouse gases across all sectors of the economy. The Sustainable Development Goals Report 2023 [2] reports on analyses of the current functioning of cities among other things. The document states that, e.g., 55% of the world’s population lived in cities as of November 2022 and projections in this regard indicate that the percentage of the world’s population living in urban areas will increase to around 70% by 2050. In addition, data on the 681 cities surveyed over the last 30 years is provided, showing that the global physical expansion of cities has outpaced the population growth of these cities. The conclusion was drawn that as cities grew, their population density decreased. This fact has been identified as detrimental to sustainable urban development.

Furthermore, it should be mentioned that the construction sector has a significant impact on the environment, e.g., it is responsible for 40% of global energy consumption, more than one-third of global CO₂ emissions, and 50% of waste in accumulated landfills [3]. With regard to climate action, Goal 13 promotes, e.g., actions that influence the shape of the built environment, including the sustainable use of natural resources, i.e., promoting the use of low-carbon materials (including construction) and technologies that do not have a negative impact on the environment, rational use of existing housing resources through sustainable renovation procedures [4,5,6], etc.

The above data and information have important implications for the ongoing discussion and consequently the shape of future cities and how they are governed, e.g., [7,8], including the use of artificial intelligence [9]. They inspire consideration of development prospects and the widespread implementation of sustainable pro-environmental construction in line with residents’ expectations and aspirations, creating sustainable relationships between the city and the environment [10].

The paper [11] emphasises that cities—due to the fact that they concentrate the majority of the world’s population—will be the focus of activities related to the implementation of sustainable development goals involving, among other things, the rational use of resources while reducing the negative impact of urban areas on the environment. For these reasons, expectations are being formulated regarding the unique role of cities in protecting the planet’s resources, and solutions are being sought to contemporary urban-environmental problems, e.g., related to the phenomenon of urban sprawl.

Based on a study of 282 European cities, the determinants of urban sprawl have been characterised, e.g., in [12]. It is recognised, e.g., in [13,14], that urban expansion restricted through an intensification, consolidation, and concentration of development results in urban areas that are more environmentally, economically, and socially sustainable. The discussion on increasing development density as one of the necessary tools to achieve sustainable urban development is the subject of many research papers [15,16,17]. Emphasis is placed on the positive aspects of increasing density but also on the negative effects on the shape of cities and the wider satisfaction and quality of life of their inhabitants.

An attempt to define the directions of urban development with a view to meeting the needs and expectations of residents was made in, e.g., [18]. Issues relevant to human needs were identified, e.g., happiness, well-being, and quality of life. Many research institutions are carrying out scientific studies on the impact of the possibility of using various types of green areas located in the proximity of their place of residence and communing with nature on the happiness and health of city inhabitants. In [19], the results of a study conducted on a significant sample of 250,782 people indicate a significant positive impact of the presence of green areas in close proximity to their place of residence on their overall health. This impact is stronger in the case of people with lower socio-economic status and in certain age groups—the elderly and young people—and also increases with the density of development. Similar relationships were confirmed in [20], which presented the results of a study carried out in the Netherlands on a sample of 10,000 people concerning the impact of green areas in the vicinity of their place of residence on their health and self-assessment of happiness. A positive correlation was found in this area and furthermore that the impact was greater for people who were more dependent on the local environment, e.g., older people and people with lower levels of education.

The paper [11] synthesises contemporary urban sustainability policy as ‘dense, green urbanism’.

Due to the trend and promotion of the phenomenon of urban concentration and reduction in the built-up area of cities [2], there is an emerging need to construct tall buildings with residential and public functions using materials with the least possible negative impact on the environment.

Opinions vary, and both positive and negative aspects of vertical urban development, including high-rise development, are accentuated. Consideration is given to the problems of high-rise construction during wartime conflicts, fires, and other hazards, e.g., [21]. In the face of the aforementioned problems, arguments and views are being formulated that suggest a ‘crisis of verticality’.

Among the negative effects of vertical urban development, the most acute include taking away or limiting access to daylight and sunlight and restricting the view from windows—consequently worsening the living conditions of neighbouring residents and making them feel isolated from the outside world [22]. The perceived consequences of this type of urbanisation lead to inconsistencies and asymmetries in urban development, as well as a sense of harm and trauma for many of the inhabitants [22].

Research is being conducted on the impact of living in tall buildings on the quality of life of their residents [23]. This research shows that residents of tall buildings are more susceptible to mental illness, including depression, in particular, and more frequent mental development disorders among children. It has also been found that flats in high-rise buildings are often perceived by their residents as cages/prisons, which on the one hand provide comfort and access to all utilities but, on the other hand, separate and alienate them from society. As a result, living in such buildings often leads to a lack of ties and sense of belonging to the community/society, feelings of isolation and loneliness, a fear of crime, a fear of contact with the outside world, and dissatisfaction with life. Further consequences often include a reduction in residents’ outdoor physical activity, resulting in overweight and an increasing number of residents with obesity and metabolic disorders. These kinds of problems have led to attempts to improve living environments and eliminate the negative effects of living in tall buildings by providing residents with greater access to green spaces, recreational areas, and playgrounds and increasing the number of meeting places and opportunities for local communities to integrate [23]. An important factor influencing the quality of such buildings is also their biophilic design through the wider use of natural materials, e.g., wood for their construction, and integration with the natural environment within the buildings by creating green spaces on balconies, terraces, and roofs, which provide opportunities for residents to integrate and reduce stress and fatigue.

The accumulation of the aforementioned problems is characterised using the example of uncontrolled vertical urbanism in the city of Chongqing [24]. The strange relationship between the existing and newly erected urban fabric has been presented, playing out at different levels of this city and affecting the inhabitants’ daily lives. The extreme case of the urbanisation of the city of Chongqing—interspersing residential spaces at different heights with public spaces, e.g., transport infrastructure ‘piercing’ the body of the residential buildings with the communication infrastructure of the monorail [24]—contributed to the consideration of the determinants of urban spatial design.

Despite the many negative phenomena accompanying vertical urbanisation, there is an enduring imperative for ever-taller buildings that constitute enclaves of wealth and luxury [25] and contrast—in many respects—with neighbouring developments, e.g., the Shard in London [26], but also often present pro-environmental solutions—material, technological, architectural, and structural.

Cultural heritage is an important factor that is increasingly recognised as stimulating sustainable urban development. It constitutes a value, a kind of ‘brand’, as well as an element that is recognisable and identified with a given space. The revitalisation and respect for cultural heritage sites, and the creation of new spatial contexts based on their value, ensures their continued functioning and adaptation to contemporary requirements. On the one hand, this approach enables the sustainable use of existing resources; on the other hand, it ensures the continuity of the ‘life’ and survival of heritage sites. As a result, it enriches a given space, improves its aesthetics, and may even lead to additional benefits, e.g., resulting from the development of tourism [27]. The positive effects of conservation or appropriate management of cultural heritage sites leading to sustainable urban development are presented, among others, in [28,29,30].

According to the provided results of the analysis, it can be concluded that the choice of intensive land-use and of building materials based on natural raw materials obtained from renewable or low-emission sources, ease of reuse or recycling, suitable aesthetic properties, durability, as well as a positive influence on users, significantly influence the reduction in the negative impact of the construction industry on the environment while meeting increasing housing needs. Mass timber produced from certified timber from sustainably managed forests meets these requirements.

1.1. Historical Outline of the Development of Timber Construction

Timber is one of the first materials used in construction for building structures and their fittings, as well as bridges and footbridges with small spans. Initially, low- and medium-rise buildings were constructed from this material [31]. However, as early as the 6th century, the first techniques for constructing tall buildings out of wood were developed in Japan. In 725, the 50 m high pagoda of a Buddhist temple was erected in Nara, and the 57 m high pagoda of the Tō-ji temple was built in the 9th century [32].

The development of timber construction—due to the disadvantages and limitations of the material, i.e., solid wood, mostly including its anisotropy, susceptibility to permanent deformation under long-term loads, limited possibility to form structural elements with significant lengths and cross-sections, lack of resistance to the effects of fire or susceptibility to biological corrosion, etc.—was significantly hampered in the 20th century, while research and design interest was focused on structural materials, primarily steel, concrete, and masonry.

At the end of the 19th century, due to the damage caused in cities by frequent fires, legal conditions were introduced in many countries to prohibit the use of timber as a structure for tall buildings. It was not until the end of 1980 that the European Commission confirmed the possibility of implementing timber in high-rise construction as a load-bearing structure, subject to the requirements included in the building regulations of specific countries [33].

In 1906, the technology was implemented for glueing wood lamellae together and creating a new material in which many of the limitations and disadvantages of solid wood were eliminated. Glued laminated timber (GLT) has been widely and extensively implemented for nearly 100 years for the manufacture of load-bearing members of bar structures, i.e., beams, columns, frames, etc.

In the 1990s, intensive research undertaken in collaboration with the industry [31] led to the expansion of the application of the wood glueing technology to surface elements (floor slabs, wall panels) mainly made of cross-laminated timber (CLT) and subsequently to the implementation of the prefabrication of cubic modules shaped from CLT surface elements.

CLT was initially used as a load-bearing structure material in low-rise buildings up to three storeys above ground and, after 2000, also in medium-rise, high and high-rise buildings [31]. The technology for the production of the new CLT construction material is developing most in countries with a high availability of raw material, i.e., sustainably managed timber, including primarily the Alpine countries, especially Austria, but also Scandinavia and Canada.

Different varieties of mass timber construction (MTC) are available these days, i.e., glued laminated timber (GLT), cross-laminated timber (CLT), laminated veneer lumber (LVL), nail-laminated timber (NLT), and dowel-laminated timber (DLT). For more than a century, DLT and NLT have been used for the structural design of low- and medium-rise buildings having no more than eight storeys above ground [34], while the first decade of the 21st century saw the beginning of high and high-rise buildings constructed primarily from CLT, GLT, and LVL. MTC elements are also prefabricated to a significant degree and, consequently, have short assembly times, low dead weight and are easy to assemble, usually requiring no heavy equipment. For these reasons, there is no dust pollution of the air and construction site during the construction of the building, which results in limited nuisance to the surrounding area.

1.2. Pro-Environmental Benefits of Mass Timber

Mass timber is characterised by favourable strength and deformation properties and higher resistance to moisture and the impact of fire than in the case of solid wood. Important advantages of this material include low dead weight and, consequently, relatively easy assembly of mass timber elements; a reduced need for heavy construction equipment and machinery; reduced transport costs; the possibility of assembly in various thermal conditions; the possibility of prefabrication in the form of rods, surface, or volume elements [35]; high quality and aesthetics of the surface finish of prefabricated elements and, consequently, the possibility of resignation from finishing layers; as well as the positive impact of natural materials on the well-being of users. An important advantage of assembling prefabricated mass timber buildings is the significant reduction in waste and air and site pollution with particles in the course of the works, as well as limited noxiousness to users of neighbouring buildings or spaces thanks to the rapid assembly.

Important advantages of wood include its ease of recycling or reusability, i.e., the resulting possibility of implementing such elements in a so-called closed loop economy [36,37]. Investments implemented according to a circular economy model have a significant impact on reducing the negative environmental impact of construction materials thanks to their sustainable use (continuous flow of materials, independence from new products) [38].

The popularity of this mass timber is also strongly influenced by non-technical aspects, i.e., the will of investors and users of buildings to manifest environmental protection through the choice of pro-environmental material, construction, and architectural solutions.

It should be mentioned that, due to the relatively short period of use of mass timber, concerns have also been expressed about the need to characterise, in depth, the rheological properties of mass timber products, i.e., the behaviour over time of the wood/adhesive composite material, and to determine the durability of such solutions.

The reduction in CO₂ emissions is a tangible benefit of implementing mass timber in construction. The results of design analyses of a six-storey building with three variants of the construction material solution—reinforced concrete, steel, and CLT mass timber—showed that a building with either steel or reinforced concrete construction accumulates similar amounts of CO₂ of 1984 t each, while one made of CLT accumulates 727 t [34].

The paper [39] reports, among other things, that the energy consumption and greenhouse gas emissions resulting from the production of building materials for the construction of a multi-storey building (using the Wälludden building project as an example) with a mass timber frame structure is 60–80% lower than that of a corresponding building with a reinforced concrete frame structure.

The authors of the paper [40] carried out a comparative analysis of greenhouse gas emissions for multi-storey buildings with a structure made in three material options, i.e., steel, reinforced concrete, and mass timber, in the life cycle of these buildings. Mass timber-framed buildings were found to have 34–84% lower greenhouse gas emissions compared with the aforementioned traditional material solutions. The smallest emissions occur in buildings with smaller heights of 3 to 12 storeys, and higher emissions occur in taller buildings of 12–21 above-ground storeys.

It should be noted that due to the short service life of tall buildings made of mass timber (the first building of this type was erected in 2009, i.e., it is 16 years old), there is a lack of experience regarding their full life cycle, including, among other things, the durability of the solutions adopted, the environmental costs of renovations and repairs, the scope of possible recycling, etc. For these reasons, the examples cited in the literature concern the environmental impact of the buildings in question at various stages of their life cycle or forecasts for their entire life cycle. For these reasons, it is necessary to gradually verify the forecasts throughout the entire period of operation of the buildings under study.

It can therefore be concluded that the appropriate choice of materials for building construction can have a significant impact on reducing the negative environmental impact of the construction industry.

The main advantages of tall construction using mass timber are the pro-environmental aspects mentioned above, as well as all the benefits of prefabrication. However, prefabrication, modularity, repeatability, and the limited range of structural timber elements available also impose restrictions on architectural design in terms of the freedom to shape buildings and functional and spatial limitations. These types of buildings usually have cuboid shapes or are formed from a system of cuboids [41]. Due to the mechanical properties of mass timber and the technology used to construct such buildings, tall buildings made of mass timber are characterised by low slenderness. For buildings up to 50 m high, the slenderness ratio ranges from 1 to 2, and for buildings over 50 m high, the slenderness ratio ranges from 2.41 to 4.97 [41].

1.3. Selected Health-Promoting Aspects of Wood

The selection of natural materials in the decoration of interior surfaces in buildings and their impact on humans are the subject of many interdisciplinary studies and analyses. The results of these studies agree in their general conclusions and confirm the beneficial effects of natural materials, including timber, on human well-being [42].

Close contact with natural materials and the natural environment has the effect of reducing stress, triggering positive emotions and an appropriate heart rate, improving human concentration, etc. In general, materials identified with the natural environment have a positive effect on many human physiological indicators, i.e., electrocardiogram measurements, electro-dermal activity, oxyhaemoglobin saturation, and skin temperature, measured both at rest and at work. Consequently, they affect the autonomic nervous system, the respiratory system and the visual system of the human being, as well as improve mood and reduce stress [43]. It is worth mentioning that the visual experience is also important, with the aesthetics of the wood surfaces or the tactile perception of the natural material with its varied grain or texture highly valued by users.

The research results [34] showed a lower activation of the sympathetic nervous system (sympathetic nervous system) of people staying in rooms with exposed wooden surfaces compared with rooms with plasterboard walls, as well as a positive effect on blood pressure.

The paper [44] reports the results of a study conducted on a group of 119 students in order to diagnose the stress-reducing effects of different interior office space arrangements, including an environment equipped with wooden elements and vegetation, wood and no vegetation, vegetation with no wood, and no wood with no vegetation. A positive effect of wooden furnishings was found, pointing to an activation of the human sympathetic nervous system manifested in the results of measurements of skin conductance levels and frequencies of non-specific skin conductance responses, as well as in the absence of such effects on humans in a vegetation-only indoor environment. In [44], it was confirmed that wood had a soothing and stress-reducing effect on humans, and its practical use was recommended in biophilic designs, i.e., primarily in hospitals, offices, schools, etc.

The papers [45,46,47,48] identify contemporary trends of exposing the surfaces of timber structural elements that show their natural beauty while positively affecting the occupants’ well-being. The biophilic style often forms the basis of interior design and the design of user-friendly spaces nowadays.

1.4. Contemporary Views on the Prospects for Development of Tall Buildings Made of Mass Timber

As the number of tall buildings made of mass timber is still small, there is a research gap and a lack of comprehensive information on the successful use of this material in the construction industry and no outlined prospects for its wider implementation. Attempts are underway to diagnose this problem, e.g., on the basis of the results of statistical and survey research.

The paper [34] reported the results of a statistical survey conducted in the USA in order to diagnose the reasons for the still-low use of mass timber in that country. It was determined as a result of that research that as many as 55% of the respondents who were designers and construction contractors demonstrated low levels of knowledge and experience in the implementation of mass timber; it also pointed out the high cost of mass timber elements or design problems due to insufficient legal and factual conditions for the implementation of mass timber in construction among other things. It should be mentioned that respondents rated the aesthetic qualities of wooden elements significantly higher than those of steel or concrete. In addition, the pursuit of appropriate state policies coupled with the implementation of economic, legal, and research and development tools and simplification of legal procedures were identified as key, having a direct impact on the popularisation of mass timber in high-rise construction.

Some of the reasons identified as the main constraints to the wider implementation of mass timber [34] included the lack of tradition and comprehensive standards for the design and technology of the construction of this type of structure; the lack of experience and sufficient knowledge among representatives of the construction industry; the small number of factories producing assorted mass timber and, consequently, high transport costs due to long distances between the prefabrication plants and the investment sites; as well as the high cost of elements made of mass timber. The following factors were identified as key factors that could contribute to increased acceptance and wider use of mass timber in the US: the need to popularise the awareness of implementation examples and expand information about the new building material, i.e., mass timber—22%, increasing the number of prefabrication facilities and consequently the availability of these products—20%, reducing their cost—13%, expanding standard conditions and procedures for this material—6%, etc.

The results of a study on the integrated ‘holistic design of taller timber buildings’ were presented [49] as part of the World Conference on Timber Engineering Oslo 2023. It was reported that the design and erection of tall mass timber buildings required an interdisciplinary approach covering simultaneous analyses of structural statics and dynamics, fire protection, acoustics, occupants’ health and welfare, comfort of use, proper use and maintenance of buildings, as well as durability, repair, or recycling.

In [50], the results were presented of a survey conducted among stakeholders and participants in the construction process of tall mass timber buildings in order to identify the main factors and considerations that had the greatest influence on the choice of this type of solution. It has been found that the motivations depend on the type of stakeholders but that the dominant factors are the high prestige of companies introducing new solutions, i.e., innovative techniques, products and design concepts, shorter investment times compared with traditional construction materials (e.g., reinforced concrete) thanks to the significant share of prefabricated timber elements, competitiveness of investment costs—with a holistic approach to determining investment costs including the whole life cycle of the building, energy efficiency, and efficiency in terms of reducing CO₂ emissions.

However, barriers affecting the still unsatisfactory use of mass timber in high-rise construction were also defined, most notably relating to the more complex design process requiring integrated design in interdisciplinary teams bringing together, among others, designers; specialists in the prefabrication of structural elements, logistics, and site supply; and the 3D numerical modelling of investments and requiring cooperation with research centres. It was further noted that the legal procedures associated with the final inspections and commissioning of such buildings were more complicated and required more agreements compared with traditional solutions. Furthermore, the sharing of knowledge and experience in the design and construction process and in the operation of such buildings has been identified as a key factor influencing the wider uptake of such solutions [50]. It has been found that a significant impact on the quality of use, durability, and reduction in repair or renovation costs is caused by educating the occupants on the use of the systems and installations in buildings, which typically meet Passive House standards. Respondents confirmed that displaying wood in interiors had a positive impact on the well-being of the occupants.

The use of mass timber for the construction of tall buildings has been practised for less than 20 years and the solutions implemented provide a basis for in situ observation and research into their behaviour under various influences, including wind, seismic loads, and fire conditions.

The issue of seismic resistance of tall mass timber buildings has been addressed in the following publications, which present the results of laboratory tests or 3D numerical analyses, e.g., in [51].

The paper [52] summarises the results of test studies and numerical analyses of the impact of seismic interactions on CLT wall structures and concludes that their behaviour under seismic conditions is satisfactory.

A major issue in designing tall buildings made of mass timber is their low dead weight, ensuring resistance to dynamic wind loads and ensuring comfort of use [53,54,55]. For these reasons, the tallest buildings of this type are most often designed as hybrid reinforced concrete and mass timber structures, although there are also rare cases of above-ground structures made entirely of mass timber [41].

Fire safety issues are a significant constraint on the development of tall timber construction, primarily due to the lack of legal regulations and still insufficient results of full-scale and laboratory tests [56,57].

The design of buildings made of mass timber in this regard should take into account, among other things, the determination of the required fire resistance time and the assessment of fire risk, which is influenced by many factors, such as the functional solution adopted, the height of the building, the anticipated fire protection measures or extinguishing systems, the use of non-combustible cladding for timber elements—leading to their encapsulation from the dynamics of the fire, as well as the anticipated evacuation strategy in the event of a fire.

The spatial and functional solutions and material and structural solutions for buildings should be adopted as a result of an analysis of probable scenarios for the occurrence and development of a fire, as well as a thorough assessment of the risk of a fire occurring and its consequences. Consequently, the solutions adopted in the event of a fire should ensure the safe evacuation of users, convenient access for fire crews, limiting the spread of fire within a given building to the area directly affected by it, as well as limiting the spread of fire outside the zone to neighbouring buildings and structures.

Fire protection in buildings can use active systems—early fire detection and extinguishing systems including smoke detectors, alarms, sprinkler systems, etc.—or passive systems—including, among other things, the appropriate division of the building into fire zones, the possible introduction of non-combustible cladding or fire-resistant coatings (intumescent coatings and nano-coatings, fire-resistant varnishes or impregnants), as well as the accounting of the possibility of protecting wooden elements by charring their surface in the design. In the case of tall wooden buildings, both active and passive fire protection systems are usually used simultaneously. Fire-protected connections, fasteners, and nodes of the load-bearing structure (usually steel) should be noted [58].

When exposed to fire, mass timber undergoes surface charring. The charred outer layer naturally insulates against heat transfer and oxygen access, thus creating a barrier that slows down the spread of fire and protects unburned timber [59]. It should be noted that the protective properties of the charred layer depend on the volume density of the timber. Mass timber with a higher volume density forms a more compact protective layer when exposed to fire, providing better protection for the unburned cross-section.

The use of surface charring of cross-sections as a fire protection measure is still relatively poorly understood, and the construction of tall wooden buildings, due to the flammability of wood and the availability of ‘combustible fuel’ located in the structure, still raises a lot of controversy and has an impact on relatively few investments of this type. The results of experimental studies of buildings with CLT wall structures show that the fire resistance of this type of structure (depending on the type and thickness of CLT structural elements) ranges from 1 to 3 h [60].

It should be noted that research is being conducted on the occurrence, under specific conditions of exposure to fire (with external radiation of a critical value of at least 40 kW/m²), of spontaneous extinguishing as a result of surface charring [61,62], as well as on determining the minimum thickness of the pre-charred surface layer of a cross-section to ensure its specific fire resistance. For selected wood species, ref. [63] states that adequate fire resistance can be achieved with a minimum charred layer thickness of 6 +/− 1 mm. When designing a timber cross-section with regard to protection against surface charring, the thickness of this charred layer should also be taken into account [57,64,65].

2. Materials and Methods

2.1. Aim of the Paper

The first construction of a tall building made of mass timber took place in 2009 [66,67]. By March 2025, approximately 109 such buildings have been erected worldwide, an average of 7.3 buildings per year. The dataset of buildings was determined based on an analysis of the Council on Tall Buildings and Urban Habitat (CTBUH) database [66] and the literature [67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106]. Basic information about the buildings is summarised in

Table A1. Summary of basic data concerning the architectural, functional, and spatial solutions of the buildings under research.

No.	Name of Building	Location	Year of Completion	Height (Above Ground Level), [m].	No of Floors Above Ground	Type of Utility Function (1)	Interior Decoration/Wall Coverings/Ceilings	Exterior Decoration—Facade	Public Transport Within a Walking Distance Along the Street of 500 m	High-Capacity System Public Transport a Walking Distance Along the Street of 1000 m	Local/Pocket Open Public Spaces Within a Walking Distance or 400 m	Neighbourhood Public Open Spaces Within a Walking Distance or 400 m	District/ City Open Spaces or City Open Spaces 800 m or 10 min Walking Distance	Regional Open Space/ Larger City Parks Up
1	Holz 8 [68]	Bad Aiblng, Germany	2011	25	8	R and O	Timber and other materials	Wooden cladding	Yes	No	Yes	Yes	Yes	Yes
2	Heartwood [69]	Seattle, USA	2023	25.5	8	R	Timber and other materials	Cladding	Yes	Yes	Yes	Yes	Yes	Yes
3	Cradle [70]	Düsseldorf, Germany	2023	25.7	7	O	Timber and other materials	Glass and timber	Yes	Yes	No	No	Yes	Yes
4	Marselle Condos [66]	Seattle, USA	2009	25.9	7	R	-	-	-	-	-	-	-	-
5	Emmons on 3rd [71]	Seattle, USA	2014	26	8	R	-	-	-	-	-	-	-	-
6	T3 Minneapolis [72]	Minneapolis, USA	2016	26	7	O	Timber and other materials	Wooden cladding	Yes	Yes	Yes	No	Yes	Yes
7	Carbon 12 [73]	Portland, USA	2018	26	8	R	Timber and other materials	Glass curtain wall (south and north elevations) and other ‘green walls’ with climbing plants	Yes	No	Yes	No	Yes	Yes
8	T3 West Midtown [68]	Atlanta, USA	2019	26	7	O	Timber and other materials	Glass and metal cladding	Yes	Yes	Yes	Yes	No	Yes
9	Cirrus [68]	Denver, USA	2022	26	7	R	Timber and other materials	Cladding	Yes	Yes	Yes	Yes	Yes	Yes
10	Limnologen [74]	Vaxjo, Sweden	2009	27	7	R	Timber and other materials	CLT panels with facade cladding and plaster	Yes	No	Yes	Yes	Yes	Yes
11	Portvakten Söder [67]	Vaxjo, Sweden	2009	27	8	R	Timber and other materials	CLT panels with facade cladding and plaster	Yes	No	Yes	Yes	Yes	Yes
12	Bridport House [66]	London, UK	2010	27	8	R	Timber and other materials	Brick cladding	Yes	Yes	Yes	Yes	Yes	Yes
13	LCT One [75]	Dunrobin, Austria	2012	27	8	O	Timber and other materials	Cladding	No	Yes	Yes	Yes	No	Yes
14	Pentagon I [68]	As, Norway	2013	27	8	R	-	-	-	-	-	-	-	-
15	Strandparken Building B [76]	Stockholm, Sweden	2024	27	8	R	CLT wood panels or plasterboard	Cedar wood shingles	Yes	Yes	Yes	Yes	Yes	Yes
16	Residences J.Ferry [66]	Saint-Dié-des Vosges, France	2014	27	8	R	Timber and other materials	Wooden and brick cladding	Yes	Yes	Yes	Yes	Yes	Yes
17	Nautilus Hotel [66]	Pesaro, Italy	2016	27	8	H	Timber and other materials	Cladding	No	Yes	Yes	Yes	Yes	Yes
18	Wood City Apartments [66]	Helsinki, Finland	2017	27	8	R	Timber and other materials	Wooden cladding	Yes	Yes	Yes	Yes	Yes	Yes
19	Dramsvegen [66]	Tromso, Norway	2017	27	8	R	-	-	-	-	-	-	-	-
20	Highpoint Terrace [66]	London, UK	2017	27	8	R	Timber and other materials	Cladding	-	-	-	-	-	-
21	Lucien Cornil Student Residence [66]	Marseilles, France	2017	27	8	R	Timber and other materials	Wooden cladding	Yes	Yes	Yes	No	No	Yes
22	The Macarthur Gardens [77]	Sydney, Australia	2018	27	8	R	-	-	-	-	-	-	-	-
23	Maskinparken TRE [78]	Trondheim, Norway	2018	27	8	R	Timber and other materials	Cladding	Yes	No	Yes	Yes	Yes	Yes
24	Frostaliden [79]	Skövde, Sweden	2018	27	8	R	Timber and other materials	Wooden cladding	Yes	No	Yes	Yes	Yes	Yes
25	Puukuokka One, Two, Three [80]	Jyväskylä, Finland	2018	27	8	R	Timber and other materials	Wooden cladding	Yes	No	Yes	Yes	Yes	Yes
26	Docenten [66]	Vaxjo, Sweden	2018	27	8	R	-	-	-	-	-	-	-	-
27	Jo & Joe [66]	Paris, France	2019	27	8	R	Timber and other materials	Wooden cladding	Yes	Yes	Yes	Yes	Yes	Yes
28	Das Kelo [66]	Rovaniemi, Finland	2019	27	8	R	Timber and other materials	Cladding	Yes	No	Yes	Yes	Yes	Yes
29	Arbora Condominium [73]	Montreal, Canada	2019	27	8	R	Timber and other materials	Cladding	Yes	Yes	Yes	Yes	Yes	Yes
30	Trummens Strand [66]	Vaxjo, Sweden	2020	27	8	R	Timber and other materials	Wooden cladding	Yes	No	Yes	Yes	Yes	Yes
31	Cirerers [81]	Barcelona, Spain	2022	27	8	R	Timber and other materials	Cladding	Yes	Yes	Yes	No	Yes	Yes
32	Moholt 50/50 [82]	Trondheim, Norway	2016	28	9	R	Timber and other materials	Wooden cladding	Yes	Yes	Yes	Yes	Yes	Yes
33	EDGE Suedkreuz [83]	Berlin, Germany	2022	29	8	O	Timber and other materials	Glass and cladding	Yes	Yes	No	No	No	Yes
34	Wood Innovation Design Centre [66]	Prince George, Canada	2014	29.5	8	E and O	Timber and other materials	Glass curtain wall; LVL mullions	Yes	Yes	Yes	No	Yes	Yes
35	Stadthaus [66]	London, UK	2009	30	9	R	Timber and other materials	Painted wooden cladding	Yes	Yes	Yes	Yes	Yes	Yes
36	Patch 22 [66]	Amsterdam, Netherlands	2016	30	7	R	Timber and other materials	Wooden cladding	Yes	No	Yes	Yes	Yes	Yes
37	International House South [66]	Sydney, Australia	2017	30	7	O	Timber and other materials	Glass	Yes	Yes	Yes	Yes	Yes	Yes
38	Daramu House [66]	Sydney, Australia	2020	30	7	O and C	Timber and other materials	Glass	Yes	Yes	Yes	Yes	Yes	Yes
39	Timber Pioneer [66]	Frankfurt am Main, Germany	2023	30	8	O	Timber and other materials	Glass and cladding	Yes	Yes	Yes	Yes	Yes	Yes
40	Cenni di Cambiamento [66]	Milan, Italy	2013	31	9	R	Timber and other materials	Wooden cladding	Yes	No	Yes	No	Yes	Yes
41	Press house [66]	London, UK	2017	31	8	R	Timber and other materials	Brick cladding	-	-	-	-	-	-
42	Vallen [66]	Vaxjo, Sweden	2018	31	9	R	-	Wooden cladding; cedar wood shingles or plaster	Yes	No	Yes	Yes	Yes	Yes
43	Immeuble ‘Perspective’ [67]	Bordeaux, France	2018	31	7	O	Timber and other materials	Glass curtain wall with wooden elements	Yes	No	No	No	No	Yes
44	Kajstaden [66]	Vasteras, Sweden	2019	31	9	R	Timber and other materials	Wooden cladding	Yes	Yes	Yes	Yes	Yes	Yes
45	Botanikern [66]	Uppsala, Sweden	2019	31	9	R	Timber and other materials	Wooden cladding	Yes	No	Yes	Yes	Yes	Yes
46	Caisse d’Epargne Bourgogne-Franche-Comté Headquarters [66]	Dijon, France	2022	31	7	O	Timber and other materials	Glass and timber	Yes	No	No	No	Yes	Yes
47	Forte [66]	Melbourn, Australia	2012	32	10	R	Timber and other materials	Wood and other cladding materials	Yes	Yes	Yes	Yes	Yes	Yes
48	Tamedia Office [84]	Zurich, Switzerland	2013	32	7	O	Timber and other materials	Glass	Yes	Yes	Yes	Yes	Yes	Yes
49	The Cube Building [66]	London, UK	2015	33	10	R	Timber and other materials	-	Yes	Yes	Yes	Yes	Yes	Yes
50	Dalston Works [85]	London, UK	2017	34	10	R	Timber and other materials	Brick cladding	Yes	Yes	Yes	Yes	Yes	Yes
51	Kringsja Studentby [66]	Oslo, Norway	2018	34	10	R	-	-	-	-	-	-	-	-
52	Jakarta Hotel [66]	Amsterdam, Netherlands	2018	34	9	H	Timber and other materials	Glass	Yes	Yes	Yes	No	No	Yes
53	Skaio Wooden Apartment Building [68]	Heilbronn, Germany	2019	34	10	R	Timber and other materials	Concrete cladding	Yes	Yes	Yes	Yes	Yes	Yes
54	Opalia [68]	Paris, France	2017	35	8	O	Timber and other materials	Glass and wooden cladding	Yes	Yes	Yes	No	No	Yes
55	Green Office ENJOY [66]	Paris, France	2018	35	8	O	Timber and other materials	Metal cladding	-	-	-	-	-	-
56	Pont de Flandres Batiment 007 [66]	Paris, France	2019	35	8	O	Timber and other materials	Glass and wooden cladding	Yes	Yes	Yes	Yes	Yes	Yes
57	Palazzo Meridia [66]	Nice, France	2020	35	10	O	Plasterboard and timber	Glass and aluminium truss	Yes	Yes	Yes	No	Yes	Yes
58	Supercell Headquarters [66]	Helsinki, Finland	2020	35	10	O	Plasterboard and timber	Glass and timber	Yes	Yes	Yes	Yes	Yes	Yes
59	Apex Plaza [66]	Charlottesville, USA	2022	35	8	O	Timber and other materials	Cladding	Yes	No	No	No	No	Yes
60	Suurstoffi 22 [86]	Risch-Rotkreuz, Switzerland	2018	36	10	O	Plasterboard and timber	Glass	Yes	Yes	Yes	No	No	Yes
61	Aveo Bella Vista [66]	Sydney, Australia	2018	36	11	R	-	-	Yes	No	No	No	Yes	Yes
62	Trafalgar Place [68]	London, UK	2015	36.6	10	R	-	Brick cladding	Yes	Yes	Yes	Yes	Yes	Yes
63	Sensations [87]	Strasbourg, France	2019	38	11	R	Plasterboard and timber	Perforated steel mesh	Yes	Yes	Yes	Yes	Yes	Yes
64	Fyrtornet [66]	Malmo, Sweden	Under construction	38	11	O	Timber and other materials	Glass	Yes	Yes	Yes	Yes	Yes	Yes
65	Monterey [88]	Brisbane, Australia	2021	39	12	R	Timber and other materials	Metal, wooden, and glass cladding	Yes	Yes	Yes	Yes	Yes	Yes
66	Auckland City Mission [89]	Auckland, New Zealand	2022	39	10	R	Timber and other materials	Cladding, wood and metal	Yes	No	Yes	Yes	Yes	Yes
67	INTRO Residential Tower [90]	Cleveland, USA	2022	39.6	9	R and C	Timber and other materials	Glass	Yes	Yes	Yes	No	Yes	Yes
68	Klein Veldekens [68]	Geel, Belgium	2020	40	10	R	Timber and other materials	Wooden cladding	Yes	Yes	No	No	Yes	Yes
69	T3 Sterling Road [66]	Toronto, Canada	Under construction	40	8	O	Timber and other materials	Glass and metal cladding	Yes	Yes	No	Yes	No	Yes
70	Origine [72]	Quebec, Canada	2017	40.9	13	R	Plasterboard and timber	Steel and aluminium cladding	Yes	No	Yes	Yes	Yes	Yes
71	Blindern Studenthus [66]	Oslo, Norway	2019	41	12	R	-	-	-	-	-	-	-	-
72	Tallwood I [91]	Langford, Canada	2022	41	12	R	Timber and other materials	Glass curtain wall	Yes	No	Yes	No	Yes	Yes
73	Spor X [92]	Drammen, Norway	2021	41.4	10	O	Plasterboard and timber	Wooden cladding and glass	Yes	Yes	Yes	Yes	Yes	Yes
74	T3 Bayside [67]	Toronto, Canada	2023	42	10	O	Timber and other materials	Glass curtain wall with wooden elements	No	Yes	Yes	Yes	No	Yes
75	Hoas Tuuliniitty [66]	Espoo, Finland	2021	44	13	R	Plasterboard and timber	Wood panel cladding	Yes	Yes	Yes	Yes	Yes	Yes
76	Obayashi Training Facility/Port Plus [46]	Yokohama, Japan	2022	44	11	O	Plasterboard and timber	Glass	Yes	Yes	Yes	Yes	Yes	Yes
77	Cederhusen [79]	Stockholm, Sweden	2023	44	13	R	Plasterboard and timber	Wooden cladding—cedar shingles	Yes	Yes	Yes	Yes	Yes	Yes
78	Holz-Hybrid-Hochhaus CARL [66]	Pforzheim, Germany	2024	45	14	R	Plasterboard and timber	Wooden cladding	Yes	Yes	Yes	Yes	Yes	Yes
79	2150 Keith Drive the Hive [93]	Vancouver, Canada	Under construction	45	10	O	-	Glass and metal cladding	Yes	Yes	Yes	Yes	Yes	Yes
80	25 King [93]	Brisbane, Australia	2018	46.5	10	O	Plasterboard and timber	Glass	Yes	Yes	No	No	Yes	Yes
81	Baker’s Place [66]	Madison, USA	Under construction	47.4	14	R	-	-	Yes	No	Yes	No	Yes	Yes
82	Lighthouse Joensu [66]	Joensuu. Finland	2019	48	14	R	Plasterboard and timber	Fibre cement boards	Yes	Yes	Yes	Yes	Yes	Yes
83	Proud Kanda Surugadai [66]	Tokyo, Japan	2021	48.3	14	R	-	-	-	-	-	-	-	-
84	Treet [94]	Bergen, Norway	2015	49	14	R	Plasterboard and timber	Wood and metal cladding; glass	Yes	No	Yes	Yes	Yes	Yes
85	Sawa [66]	Rotterdam, Netherlands	Under construction	50	16	R	-	-	Yes	Yes	Yes	Yes	Yes	Yes
86	503 on Tenth [93]	Portland, USA	Under construction	50	10	O	-	--	-	-	-	-	-	-
87	Wurriki Nyal Civic Precinct—Ngytan Koriayo [93]	Greater Geelong, Australia	Under construction	52	11	O	Timber and other materials	Glass	Yes	Yes	Yes	Yes	Yes	Yes
88	Limberlost Place [95]	Toronto, Canada	Under construction	52.5	10	E	Plasterboard and timber	Glass and wooden cladding	Yes	No	Yes	Yes	Yes	Yes
89	Albizzia [96]	Lyon, France	2023	53	16	R and C	Plasterboard and timber	Concrete cladding	Yes	Yes	No	No	Yes	Yes
90	Brock Commons Tallwood House [91]	Vancouver, Canada	2017	53	18	R	Timber and other materials	Glass curtain wall with wooden elements	Yes	Yes	Yes	Yes	Yes	Yes
91	Hyperion [97]	Bordeaux, France	2021	55	16	R	Plasterboard and timber	Timber and basalt facade panels	Yes	Yes	No	No	Yes	Yes
92	Eunoia Junior College [93]	Singapore, Singapore	2019	56	12	E	-	-	-	-	-	-	-	-
93	Stories [66]	Amsterdam, Netherlands	2021	56	13	R	Timber and other materials	Glass and metal cladding	Yes	No	Yes	Yes	Yes	Yes
94	Arbo [98]	Lucerne, Switzerland	2019	60	15	O	Timber and other materials	Glass curtain wall	-	-	-	-	-	-
95	T3 Collingwood [99]	Melbourn, Australia	2023	63	15	O	-	Glass; brick cladding	Yes	Yes	Yes	Yes	Yes	Yes
96	ANDYS at 1510 Webster Street [66]	Oakland, USA	2024	65	19	R	Plasterboard	Glass and cladding	Yes	Yes	Yes	Yes	Yes	Yes
97	Roots [66]	Hamburg, Germany	2024	65	19	R and O	-	-	Yes	Yes	Yes	Yes	Yes	Yes
98	Brunfaut Tower [66]	Brussels, Belgium	2023	69.3	22	R	-	-	Yes	Yes	Yes	Yes	Yes	Yes
99	55 Southbank [68]	Melbourne, Australia	2020	69.7	19	O and H	-	Glass	Yes	Yes	Yes	Yes	Yes	Yes
100	De Karel Doorman [100]	Rotterdam, Netherlands	2012	70.5	22	C and R	-	Glass	Yes	Yes	Yes	Yes	Yes	Yes
101	Haut [101]	Amsterdam, Netherlands	2021	73	21	R	Timber and other materials	Glass curtain wall	Yes	Yes	Yes	Yes	Yes	Yes
102	Kaj16 [66]	Gothenburg, Sweden	Under construction	78.5	16	O and C	-	-	-	-	-	-	-	-
103	Sara Kulturhus Center [102]	Skelleftea/Sweden	2021	80	20	C and Cu	Timber and other materials	Glass curtain wall with wooden elements	Yes	No	Yes	Yes	Yes	Yes
104	TRÆ [68]	Aarhus, Denmark	Under construction	81.7	20	O	Plasterboard and timber	Glass and wooden cladding	-	-	-	-	-	-
105	HoHo Vienna [103]	Vienna, Austria	2019	84	24	C	Timber and other materials	Wooden cladding	Yes	Yes	Yes	Yes	Yes	Yes
106	Mjøstårnet [104]	Brumunddal, Norway	2019	84.5	18	C and R	Timber and other materials	Wooden cladding	Yes	Yes	Yes	Yes	Yes	Yes
107	Tilia Tower [66]	Lausanne, Switzerland	Under construction	85	28	R	-	-	-	-	-	-	-	-
108	Ascent MKE [105]	Milwaukee, USA	2022	86.6	25	R	Timber and other materials	Glass curtain wall	Yes	Yes	Yes	Yes	Yes	Yes
109	Atlassian Central [106]	Sydney, Australia	Under construction	182.6	42	O and H	-	Glass	-	-	-	-	-	-

⁽¹⁾ C—commercial, Cu—cultural, E—educational, H—hotel, O—office, R—residential.

in Appendix A.

This paper aims to investigate the current state of mass timber high-rise construction by analysing case studies to identify trends, challenges, and opportunities for sustainable urban development.

Despite the significant advantages of this type of solution and the need for sustainable urban design, there is still a research gap and a lack of comprehensive information on the use of this material in construction.

The focus of the research—presented in the paper—on tall mass timber buildings is a direct result of contemporary challenges in shaping sustainable built environments, including the following:

-

the need to meet the housing needs of urban residents efficiently while limiting urban sprawl; limiting the conversion of natural land, limiting the area of development, and, consequently, limiting interference with natural green spaces;

-

the use of nature-based development material solutions and access to green spaces to ensure a high quality of life and well-being for residents;

-

the limited negative impact of investment on the environment, e.g., due to the choice of wood as the basic construction material and furnishing of a building, characterised by its origin from renewable sources, carbon capture during tree growth, CO₂ storage in the embedded material of the construction and furnishings of the building.

2.2. Study Area

The subject of the study covers tall buildings with a structural system of the above-ground part made of mass timber. The article defines a tall building as having a height of at least 25 m above ground or a residential building of at least nine storeys above the ground level. It should be mentioned that there is no clear, internationally accepted definition of a tall building. Usually, the basic criteria for the classification of buildings in this area are their height, the number of overground storeys, or the proportion of the overall dimensions, i.e., the quotient of the smallest dimension in the ground plan and the height (slenderness). At the same time, the values of these criteria relating to the different building categories vary.

Selected aspects of the urban context of the tall mass timber buildings in question, that is, the residents’ access to green spaces and public transport, were subjected to a general analysis. Scientific literature is missing topics that combine aspects of urban context and the architectural and structural design of tall buildings made of mass timber. For these reasons, the article presents the authors’ own analyses concerning the care taken in the design of the buildings in question, both in terms of the well-being of residents—thanks to the choice of a convenient location close to green public spaces, natural areas, attractive spaces for recreation, leisure, as well and transport accessibility—in terms of care for the natural environment, thanks to the choice of mass timber as the basic construction material for these buildings, as a renewable material that also stores CO₂ in its mass.

It has been assumed according to [60] that the term ‘mass timber construction’ (MTC) covers many types of timber products, including cross-laminated timber (CLT), glued laminated timber (Glulam), nail-laminated timber (NLT), dowel-laminated timber (DLT), as well as structural composite lumber (SCL)—which includes laminated veneer lumber (LVL) and laminated strand lumber (LSL). Among the aforementioned types, GLT, CLT, and LVL are the primary types of mass timber used in tall buildings.

Analyses were carried out of the functional–spatial and material–construction solutions of 109 buildings, whose documentation or basic technical parameters—in varying degrees of detail—were available in the literature and internet sources, including databases, e.g., the Council on Tall Buildings and Urban Habitat (CTBUH), websites of designers, contractors, investors, and users of the buildings in question, etc.

An attempt has been made to give an overview of what has been achieved to date in the use of mass timber in high-rise construction.

The timeframe for the analyses is from the date of commissioning of the first building of its kind in 2009 to March 2025.

2.3. Methodology

A research method based on a case study with a comprehensive analysis of the available literature, peer-reviewed scientific publications, and internet sources was used. The earth.google application was used to analyse the urban context of the buildings in question, in general, and, in particular, the availability of leisure and recreational areas, urban greenery, and the accessibility of urban infrastructure.

3. Results and Discussion

In relation to the total number of 109 buildings, the following aspects were analysed: location, height and number of overground storeys, functional and spatial solutions, material and construction solutions, and method of finishing internal surfaces and facades, and in the case of 90 buildings (out of 109), also accessibility to green areas and transport infrastructure (Table A1).

The article attempts to analyse the mentioned aspects of their design in the case of all 109 buildings completed to date. For these reasons, the level of detail of the research is limited. The accessibility of public and transport spaces for residents of the buildings surveyed was assessed in general terms by analysing the locations of the buildings surveyed on the basis of Google Earth maps.

Measuring tools—within the Google Earth application—were used for each building location to determine the distance of accessibility to public transport and public spaces.

Thanks to its measurement tools, high-resolution satellite images, and street view photos, Google Earth is a convenient tool for determining the distance of a given building from open public spaces and the distance from various types of public transport or long-distance transport stops. It is recommended for this type of application by UN Habitat [107] and is also implemented as one of the tools for easy, quick, and remote determination of the quality of public spaces [108]. In this article, Google Earth was used to determine the accessibility of public spaces in the following areas:

-

measurement of the distance between buildings and open public spaces—measuring tool;

-

analysis of satellite images, street view images, and virtual walks through each public space for the purpose of a general assessment of its accessibility and attractiveness to residents, particularly in terms of the layout of the entrance area, spatial development and provision of footpaths and cycle paths, playgrounds, benches and small architectural elements, ponds, etc.

3.1. Analysis of Material and Structural Solutions

The beginning of tall mass timber construction is represented by the four buildings commissioned in 2009, with a significant increase in the number of buildings by 2019 (Figure 1). The highest number of such buildings—15—was put to use in 2019. A slight pause in the upward trend occurred in the period 2020–2022, which can be attributed to the constraints of the COVID-19 pandemic period, while the number of these construction projects has now increased again, amounting to 12 in the first quarter of this year. This fact confirms the increased use of mass timber and the interest in the wider implementation of material solutions with limited negative environmental impact in tall buildings.

Buildings with heights of up to 35 m (20 buildings out of 23) prevailed in the initial period up to 2016, while from 2017 to the present, there has been a clear trend towards an increase in the number of developments and the number of buildings with heights of more than 35 m (Figure 2). It is worth mentioning that the tallest timber buildings, i.e., over 80 m, are currently being erected—7 such buildings, including one with a record height of 182.6 m, i.e., Atlassian Central, which is currently under construction.

3.2. Analysis of Functional Solutions

The utility function of 109 buildings was analysed, and the percentage of buildings with a specific function in relation to the entire study group was determined. On the basis of these analyses, it was determined (Figure 3) that the predominant functional solution was the residential function present in 66 buildings (which accounts for 60% of the buildings under research), the office function in 28 buildings (26%, as above), or the residential function with services in the lower storeys—in 6 buildings (6%, as above). In addition, rarer cases of educational, office/residential, office/commercial, commercial, and utility functions were identified in nine buildings (8%, as above).

When analysing the locations of these buildings and utility functions carried out in them, we can say (Figure 3) that mass timber buildings are residential in a majority of countries and this function is predominant in the USA, Sweden, Norway, UK, Finland, Netherlands, Italy, Belgium, Spain, and New Zealand. In the case of France, Australia, Canada, Germany, Switzerland, Japan, Austria, Singapore, and Denmark, office, commercial, educational, and other public utility functions and, to a lesser extent, residential functions are carried out.

3.3. Analysis of the Interior Design and the Facade

An important aspect of the design of the buildings in question is the use of wood in the shaping of the facade, as well as the prominence of this material in the interior design. In the 109 buildings analysed (c.f., Table A1 in Appendix A), timber was the most common interior decoration material; the predominant use of timber in the decoration and a minor amount of other finishing materials occurred in 66 buildings under analysis (which accounts for 61% of all analysed buildings); the predominant use of plasterboard elements and a minor amount of timber occurred in 16 buildings (15% as above); finishings with plasterboard elements occurred in 1 building (1% as above); no information—26 buildings (23%, as above).

The aesthetic qualities of wood and the ease with which this material can be integrated into and harmonised with its surroundings, especially in park spaces, is widely used by architects and also appreciated by urban residents. Despite the relatively small representation of related information in the literature concerning the buildings under research, a significant proportion of timber in the facade decoration was identified in as many as 40 cases, accounting for 37% of the buildings in question. In most cases, the documentation does not specify precisely the material of the facade cladding. For these reasons, it can be assumed that the above defined proportion of 37% of timber as the dominant facade material of the buildings under research may actually be higher.

3.4. Analysis of Transport Accessibility

One of the priorities of sustainable development is the introduction of appropriate urban development integrated with communication infrastructure to ensure that citizens can access goods, services, etc., using public transport and active modes of transport such as walking and cycling.

In order to estimate the transport accessibility of the surveyed buildings, selected basic criteria for a sustainable city included in [107] were used, in particular,

-

convenient access to low-capacity public transport (e.g., bus, bus rapid transit)—if a stop is available within 500 m;

-

convenient access to a high-capacity public transport system (e.g., rail, metro, ferry)—if a stop is available within 1 km.

For 90 of the 109 buildings in question, it was possible to estimate the availability of low- and high-capacity public transport. These analyses were carried out using Google Earth maps.

These analyses show the distance to public transport stops (Figure 4):

-

Low capacity—For 88 buildings (out of 90), it is no more than 500 m and more than 500 m for 3 buildings. It follows that 97.8% of buildings have low-capacity public transport accessibility.

-

High capacity—It is no more than 1 km for 65 buildings (out of 90), and more than 1 km for 25 buildings. It follows that 72.2% of buildings have high-capacity public transport provision.

Figure 4. Accessibility to low- and high-capacity public transport of the surveyed buildings expressed as a percentage.

Figure 4. Accessibility to low- and high-capacity public transport of the surveyed buildings expressed as a percentage.

It is worth mentioning that reducing individual transport in favour of environmentally friendly public transport has the effect of significantly reducing CO₂ emissions.

3.5. Analysis of the Accessibility of Public Spaces

One of the actions necessary to achieve ‘Goal 11’ of sustainable development [107] is to ensure the quality of the residential environment capturing, among other things, universal access to safe, inclusive, public spaces.

In urban areas, according to [107], the percentage of open public spaces should be 15–20%. Public space, described in [107] as an ‘outdoor living room for city dwellers’, should, among other things, provide conditions conducive to improving the physical and mental health of city dwellers and tourists, providing places for meeting and recreation, walking and playing, relaxing in attractive green spaces, and other outdoor activities.

Public spaces in [107] are classified according to their size and the distance necessary for a resident to travel to reach them:

• Local/pocket public open spaces—that is, small parks for recreation, located within 400 m, i.e., within a 5 minutes’ walking distance. The average area of these spaces is 0.03–0.04 ha.
• Neighbourhood public open spaces—i.e., larger spaces for recreational needs, sports, nature conservation, etc., with an area of up to 0.4 ha, easily accessible within 400 m.
• Neighbourhood or city open spaces—mainly for organised sports for residents of several neighbourhoods. They cover an area of 0.4–10 hectares and are accessible within a walking distance of 10 min, i.e., a distance of up to 800 m.
• Regional open spaces/larger urban parks—for organised sport, play, social interaction, relaxation, and enjoyment of nature of 10–50 ha.

For 90 buildings (out of the 109 buildings in question), access to various types of public open spaces was estimated using Google Earth maps and the following was found (Figure 5):

-

a total of 88.9% of the buildings analysed (80 buildings) have access to local/neighbourhood public open spaces;

-

a total of 74.4% of the buildings analysed (67 buildings) have access to neighbourhood public open spaces;

-

a total of 87.8% of the buildings analysed (79 buildings) have access to neighbourhood or urban public open spaces;

-

all buildings analysed (90 buildings) have access to regional open spaces/larger urban parks.

Figure 5. Accessibility of public spaces for the surveyed buildings expressed as a percentage.

Figure 5. Accessibility of public spaces for the surveyed buildings expressed as a percentage.

In light of the estimates carried out on the availability of green public spaces for the residents of the 90 buildings surveyed, it can be confirmed in the vast majority of buildings that they are conveniently located based on nature in various types of public spaces and consequently provide favourable conditions for leisure and recreation for residents.

4. Conclusions

Tall mass timber buildings are a relatively ‘young’ urban development built since 2009 and in greater intensity after 2019. This development is in the vanguard of the implementation of pro-environmental solutions and a contribution to sustainable urban design.

The high-rise development in question has been designed with care for the environment on both an urban and architectural scale, including, but not limited to, the following:

-

the use of wood—a natural, renewable material—in both the design of the load-bearing structure and the interior and exterior elements;

-

very good accessibility of public transport, including low capacity in 97.8% of the surveyed buildings and/or high capacity in 72.2% of the surveyed buildings;

-

very good accessibility of public open spaces, with all analysed buildings having access to regional/major city parks, 88.9% of analysed buildings having access to local/neighbourhood public open spaces, 74.4% of analysed buildings having access to neighbourhood public open spaces, and 87.8% of analysed buildings having access to neighbourhood or city public open spaces.

In light of the analyses carried out on the availability of green public spaces—for the residents of the buildings in question—it can be confirmed that the vast majority of them are conveniently located, based on nature, in proximity to various types of attractive spaces for recreation and leisure.

The predominant functional solution is the residential function; the residential function with services in the lower storeys; or, less frequently, educational, office, and residential functions.

An important aspect of the design of these buildings is to take advantage of the biophilic properties of wood and to display this material in the interior and exterior design of the facade.

It was concluded on the basis of own research that there was an increasing interest in the use of mass timber in construction and in an expansion of its implementation as well as for the shaping of load-bearing systems of tall buildings. There is a trend towards ever greater heights for this type of development, with the current tallest completed mass timber building being the Ascent MKE in Milwaukee (USA) with a height of 86.6 m and 25 storeys above ground, the tallest under construction being the Atlassian Central in Sydney, (Australia) with a height of 182.6 m and 42 storeys above ground, and the tallest in the design concept phase being the Oakwood Tower in London (United Kingdom) with a height of 300 m [109].

The key motivations for implementing mass timber in the construction in question include pro-environmental aspects and, above all, concern for the high quality of urban areas and the quality of life of their inhabitants.

The main advantages of high-rise construction using mass timber are the pro-environmental aspects mentioned above, as well as all the benefits of prefabrication. However, prefabrication, modularity, repeatability, and the limited range of available mass timber elements also impose restrictions on architectural design in terms of the freedom to shape buildings and functional and spatial limitations. Such buildings usually have cuboid shapes or are formed from a system of cuboids and are characterised by low slenderness.

It should be noted that due to the short service life of tall buildings constructed from mass timber, there is a lack of experience regarding their full life cycle, including, among other things, the durability of the solutions adopted, the environmental costs of renovations and repairs, the scope of possible recycling or the possibility of adaptation to new functions after the original function has been exhausted, etc. For these reasons, forecasts of the environmental impact at different stages of a building’s life should be verified throughout its entire life cycle.