Low-Carbon Emissions and Cost of Frame Structures for Wooden and Concrete Apartment Buildings: Case Study from Finland

: To date, the existing literature lacks any studies that compare timber and concrete apartment buildings in the Finnish context regarding their carbon footprint, handprint, and the cost of frame structures. This study rigorously analyzes and calculates the carbon footprint, carbon handprint, and costs associated with various structural solutions in a proposed multi-story building located in Laajasalo, Helsinki, Finland. While the primary focus is on wooden frame construction, exploring both its challenges and opportunities, this study also includes a comparative assessment with concrete frame construction. In Finland, regulations require a sprinkler ﬁ re extinguishing system to be installed inside. Also, weather protection is typically added to the top of building in connection with the construction of wooden apartment buildings. When the costs of a sprinkler system and weather protection are taken into account, the cost of achieving positive climate e ﬀ ects through a concrete frame is 290% higher than that of a solid wood frame. Our ﬁ ndings will provide a robust basis for assessing the sustainability and feasibility of construction methods, o ﬀ ering valuable insights into environmental and economic considerations for decision-makers in Finland and beyond as regulations evolve and awareness of climate impacts grows.


Introduction
In the realm of low-carbon construction, the assessment of environmental merits and drawbacks spans the entirety of a building's life cycle [1].The favorable ecological influence is quantified as a negative carbon handprint, while the adverse impact is gauged as a positive carbon footprint, with both conveyed in units of kg CO2e/m 2 /a.This measurement signifies the quantity of carbon dioxide equivalents per square meter of the building's heated space annually [2].Specifically, carbon handprint is indicated by a negative numerical value, whereas carbon footprint is represented by a positive number.A construction is deemed low-carbon when it demonstrates a minimal carbon footprint coupled with a substantial carbon handprint [3].
In the 2020s, Finnish building regulations are integrating the evaluation of lowcarbon considerations, with the finalization of regulations for climate assessments and material descriptions expected by 2023 [4].A draft regulation outlining thresholds and their corresponding impact assessment is scheduled to be developed in 2024.These thresholds play a pivotal role in guiding construction practices toward low-carbon methodologies, ensuring that calculations encompass both the environmental drawbacks and benefits throughout the entire life cycle of a building [5].The planned introduction of thresholds in 2025 is perceived as a dynamic process, with regular updates synchronized with the carbon neutrality target set for 2035 in Finland [6,7].
The selection of building materials plays a crucial role in influencing the overall life cycle carbon footprint of a building [8].To strategically address and mitigate climate impact, it is essential to target the reduction in emissions associated with these materials [9].This reduction can be accomplished by implementing measures such as adopting manufacturing processes with lower emissions or substituting environmentally unfriendly materials with eco-friendly alternatives [10].By concentrating on the emissions embedded in building materials, substantial progress can be achieved in making a positive impact on the climate within the construction industry [11].
Strategies such as bio-based carbon capture and storage, timber construction, and the utilization of wood products emerge as crucial measures for mitigating net greenhouse gas emissions [12].Timber construction, specifically, holds the potential to sequester carbon within buildings, thus contributing to the expansion of Finland's existing carbon sink and facilitating progress toward national carbon neutrality [13].Presently, only approximately 3% of raw timber employed in domestic construction serves as a prospective long-term carbon store or sink [14].Maximizing the effectiveness of this carbon sink necessitates preventing the release of carbon dioxide into the atmosphere during the demolition of old structures [15].Techniques like biochar production from demolition wood, coupled with the incorporation of biochar into the soil, can effectively curb CO2 emissions, establishing a continuous carbon sink and nearly permanent carbon storage in the soil [16][17][18][19].
In Finland, timber is predominantly used in constructing single-family homes (constituting 80% with wooden frames) and row houses (making up 60% with wooden frames) [20].Despite the established tradition of timber construction and abundant forest resources in Finland, the utilization of timber in multi-story buildings like apartments is still in the early stages, with relatively low market share [21][22][23].Nevertheless, there is growing momentum and support for the adoption of wooden multi-story buildings as an innovative building technology, receiving attention from both the public and political spheres in Finland and other forest-rich European countries [24].
There is rising interest in assessing and mitigating environmental impacts related to climate change and other adverse environmental factors.The focal point at this juncture revolves around the challenge of quantifying and minimizing environmental burdens [25].In recent times, scholars, organizations, and various stakeholders have been actively engaged in formulating concepts and methodologies to gauge environmental sustainability.The environmental footprint, a significant topic addressed at the Habitat Conferences [26,27], has gained prominence and is playing a crucial role in sustainability assessments and research [28,29].Environmental footprints serve as quantitative metrics for human utilization of natural resources [30].These footprints are categorized into environmental, economic, and social dimensions and can also be combined to form integrated environmental, social, and/or economic footprints [31].The foundational idea of the footprint concept stems from the ecological footprint introduced by Rees [32] and Fang et al. [33].Notably, in recent years, the carbon footprint has been predominantly utilized as an indicator for environmental protection, e.g., [34][35][36][37].
Numerous studies have investigated the life cycle assessment (LCA) and carbon footprint of timber in contrast to conventional construction materials like concrete, such as [38][39][40][41][42]. Currently, there is a noticeable absence of studies in the existing literature that specifically examine the carbon footprint, handprint, and frame structure costs of timber and concrete apartment buildings within the context of Finland.The objective of this study is to address this gap by analyzing and calculating the carbon footprint, carbon handprint, and costs associated with wooden and concrete structural solutions in a proposed multistory building located in Laajasalo, Helsinki.
Notably, hybrid construction is intentionally omitted from this investigation, guided by prior research findings suggesting that hybrid buildings may potentially exhibit higher carbon intensity than concrete construction [43].In this paper, the term 'hybrid building' denotes a structure primarily constructed with reinforced concrete load-bearing elements, except for the top floor, which is framed with timber.Additionally, the exterior facade of the building is composed of timber framing and cladding.The deliberate exclusion of hybrid construction underscores a concentrated examination of wooden and concrete frame constructions.It is also important to note that this article does not address the implications of design choices on future repair needs or the potential reuse of structural elements post-demolition [44].

Materials and Methods
This study revolves around scrutinizing and computing the low-carbon characteristics and corresponding costs of structural alternatives for multi-story building construction in Laajasalo to provide a thorough comprehension of the intricacies and subtleties associated with low-carbon construction, evaluating two alternative structural solutions: a concrete frame and a massive wood frame.
To ensure the objectivity and comparability of results, the structural design, cost estimations, and quantity calculations for both frames were delegated to a third-party consulting service.This outsourcing strategy was implemented to uphold a standardized and unbiased approach to the assessment.The evaluations concentrated on the primary structure of the building, maintaining consistent content across both alternatives to facilitate precise and meaningful comparisons.
The main goal is to quantify the expenses related to the positive climate impacts associated with each of the structural solutions.This computation is guided by the results of both cost assessments and evaluations of low-carbon properties.The objective is to furnish a dependable and nuanced assessment of a construction approach that is not only environmentally sustainable but also economically viable.

Apartment Building Initial Information
The development of the residential complex in Laajasalo is a component of the Helsinki City's Developing Apartment Building initiative, designed to lead pioneering ventures in apartment construction and enhance the overall standard of apartment living.The site (Figures 1 and 2) is positioned within a residential apartment block zone established by the zoning plan ratified on 24 April 2019.The building permit determined for the parcel is 11,250 m 2 , and the number of floors allowed is 7.The distance to Helsinki's city center is approximately 10 km, and the existing public transport travel duration is about half an hour.A new tram route through Kruunusillat is presently under construction, with the commencement of operations between Laajasalo and Hakaniemi expected in 2027.This infrastructure improvement is foreseen to considerably improve transportation links between Laajasalo and the city center.
In contrast to the specifications delineated in the zoning plan, Figure 3 proposes a departure from the initial plan.Rather than building two separate donut-shaped apartment structures, the revised proposal introduces a more illuminated and expansive design that diverges from the prescribed zoning directives.The architectural concept for the Developing Apartment Building initiative incorporates the fusion of articulated and straight segments, resembling frames of bookshelves.Adhering to zoning regulations, the design includes a gallery on the side facing the courtyard.
The depiction of the building's street-facing facade emphasizes elements like glazed balconies and steel profiles, enhancing the overall visual allure of the structure.This alternative design aims to bring in a more luminous and expansive approach while maintaining compliance with zoning regulations, achieved through the incorporation of the gallery on the courtyard side.

Alternatives for the Apartment Building's Structural Solution
Three structural alternatives for the ground floor of the apartment building in the early stages of project planning, as illustrated in Figure 4, underwent evaluation.It was recognized that a solution in line with the zoning plan requirements could be achieved through solid wood, frame construction, or traditional concrete methods.However, considering the project's ambition to lead innovations in apartment building construction, conventional concrete methods were deemed inappropriate for meeting the criteria outlined in the plot transfer conditions.
As a result, the decision was made to implement the Developing Apartment Building using timber construction, thereby creating an extraordinary pioneering project that considers structural innovations, floor plans, and a substantial potential for carbon sequestration.Although the apartment building could have been constructed using a frame structure, preference was given to a cross-laminated timber (CLT) structural solution due to its significantly higher capacity for carbon sequestration.It was recognized in the project planning phase that opting for a CLT-framed building would yield considerably greater climate benefits throughout the building's life cycle through the sequestration of carbon over an extended period.

Scope of Quantity, Cost, and Low-Carbon Calculations
As a crucial facet of the development process for the Developing Apartment Building initiative, the goal is to assess the environmental impact stemming from the selection of structural materials for the apartment building.In endeavors of this scale, the environmental consequences, encompassing both positive and negative aspects, are particularly significant.A comparative evaluation was carried out between the structural components and roof of a CLT apartment building, characterized by an identical floor plan design, and those of a conventionally designed concrete apartment building.
This analysis focused specifically on the structure and roof of the building, as these elements play a substantial role in carbon dioxide emissions during the product phase (A1-A3), which includes the extraction, manufacturing, and transportation of construction materials.Furthermore, emissions arising from on-site activities and transportation (A4-A5) during the construction phase are essential aspects of the evaluation.Through a detailed examination of these components, this study seeks to identify the environmental benefits and drawbacks associated with the selection of construction materials, considering their impact on the overall life cycle of the building.

Structural Design and Cost Estimation of the Structural Elements
The structural designs for both concrete and CLT structures were developed to replicate each other in terms of content and quantity, ensuring a meaningful foundation for comparison.A professional engineering and design firm was tasked with the responsibility of conducting the structural design for both alternatives, adhering to the primary principle of ensuring realistic constructability.Detailed information regarding the structural types, components, and quantities for both the concrete and CLT alternatives can be found in Appendices A-C.
To ensure consistency in this study, external entities were assigned the task of conducting cost assessments for the structural contracts.An experienced construction engineer carried out the cost estimation process for the concrete frame using the project planning-phase materials.Concurrently, another experienced consultant performed the cost estimation process for the CLT frame, also relying on the project planning-phase materials.The cost calculations were carefully harmonized in terms of content and carried out using a methodology for building component cost calculation.
The self-cost estimation for the concrete apartment building, which includes five floors and the roof structure, as per the cost estimate for the concrete frame's building components, is EUR 8,150,378 (Appendix C).In contrast, the self-cost estimation for the CLT apartment building, covering the same number of floors and roof structure, based on the frame cost estimate, is EUR 9,114,500.These cost assessments encompass various structural elements for the specified floors and roof, incorporating expenses for frame installation, labor and project management, element design, element installation work, crane operation, rental, and supplies.All calculations were performed with a 0% VAT rate.

Carbon Footprint and Handprint of Structural Elements
Assessing low-carbon impacts involved the use of building component estimates, structural designs, and quantity calculations for both timber and concrete frame contracts.Microsoft Excel (Microsoft 365) was used to calculate quantities and masses of various construction materials, facilitating a comprehensive low-carbon assessment.Quantities of building materials were obtained from the basic cost calculation of building components.Material masses were then determined from these quantities to perform mass-based lowcarbon calculations.Detailed information on the quantities of building materials and calculated masses is available in Appendix A (concrete frame) and Appendix B (wooden frame).The computation of material masses relied on values provided by material suppliers, expressed in kg/m 2 or kg/m 3 .
Upon determining the material weights, carbon footprints, and handprints for the five floors and the roof, the Ministry of the Environment's building carbon footprint calculation tool was employed.Rather than relying directly on the tool's values, the calculations incorporated material data or more detailed figures sourced from the Finnish Environment Institute's construction emissions database version 1.01.000(dated 29 June 2023) or values extracted from the environmental product declarations (EPD) of material suppliers.The specific sources and links for the refined emission values utilized in the calculation of each building material are comprehensively outlined in Appendices D and E. In the calculation process, refined values from the material suppliers' own EPDs or environmental product declarations were preferred when available; otherwise, refined emission values from the Finnish Environment Institute's emission database were utilized.

Results
The choice of the structural frame material for the apartment building stands as a pivotal element with extensive ramifications for the overall climate impact of the construction project.Figure 5 shows the scale of this impact, accentuating the substantial influence that the selection of building material wields in shaping the environmental footprint of the structure.
Various structural materials, including concrete and wood, exhibit distinct carbon footprints and environmental implications across their life cycles, spanning extraction and production to construction and eventual end-of-life considerations.The choice of a specific material can impact factors such as carbon emissions, energy consumption, and resource utilization.Choosing a concrete frame as the load-bearing structure for the upcoming apartment building yields immediate and environmentally adverse consequences.Over a 50-year analysis period, this decision contributes to over 2.2 million kilograms of carbon dioxide equivalent compared to opting for a massive wooden load-bearing frame.Precisely, the concrete frame in the Developing Apartment Building initiative building results in 3,060,000 kg CO2e/50 years, representing a 270% increase in carbon dioxide emissions compared to the 830,000 kg CO2e/50 years associated with a massive wooden CLT frame, as delineated in Equation (1): This comparison underscores the considerable environmental advantages of selecting a wooden CLT frame over a concrete frame, particularly in terms of mitigating carbon emissions and advocating for a more sustainable and eco-friendly construction approach.The provided figures underscore the noteworthy influence that material choices can exert on the overall carbon footprint of a building over an extended period, underscoring the importance of integrating environmental considerations into construction decision-making processes.
From a low-carbon perspective, another crucial aspect to consider in selecting the structural frame material is the carbon handprint, which measures the positive climate impacts stemming from building construction.Choosing a CLT frame as the load-bearing structure for the upcoming apartment building leads to the creation of over 3.67 million additional kilograms of carbon dioxide equivalent in positive climate impacts over a 50year analysis period compared to selecting a concrete load-bearing frame.The climate benefits associated with the massive wooden frame are, remarkably, 420% greater than the positive climate impacts caused by the concrete frame, as expressed in Equation ( 2 This assessment highlights the substantial benefits of choosing a massive wooden CLT frame in terms of carbon handprint, signifying a noteworthy net positive contribution to climate mitigation.It reinforces the idea that the selection of construction materials extends beyond simply reducing negative environmental impacts; it can actively contribute to positive climate outcomes, aligning with sustainability goals and promoting environmentally responsible building practices. Comparing the costs associated with these two distinct framing methodologies in relation to their positive climate impacts is of significance.According to the construction estimate for the concrete frame, the self-cost of the frame contract is EUR 8,150,000.Conversely, the self-cost of the frame contract for the CLT frame is EUR 9,110,000.By utilizing the cost estimates and low-carbon computations, we can juxtapose the cost per kilogram of carbon dioxide equivalent (kg CO2e) sequestered between the implementations of concrete and massive wooden CLT frames.
The cost of positive climate impacts resulting from the construction of the concrete frame in the developing apartment building, per kilogram of carbon dioxide equivalent (kg CO2e) over a 50-year analysis period, is EUR 9.34/kg CO2e (=8,150,000 €/870,000 kgCO2e).In contrast, the positive climate impacts associated with constructing the massive wooden frame in the developing apartment building, per kg CO2e over the same analysis period, amount to € , resulting in EUR 2.01/kg CO2e.
Consequently, the cost of positive climate impacts for a concrete frame is significantly higher, precisely 364.68% higher, compared to the cost associated with massive wooden construction.These calculations reveal that carbon sequestration in the building's structure and the positive climate impacts resulting from construction are approximately 365% more expensive with concrete construction than with the use of CLT in massive wooden construction.
It is worth noting that in Finland, regulations mandate the installation of a sprinkler fire extinguishing system in wooden apartment buildings, incurring construction costs of approximately EUR 100 per square meter of apartment space.Similarly, due to the country's climatic conditions, weather protection is typically added on top of the building frame during construction, also amounting to around EUR 100 per square meter of apartment space.Thus, the sprinkling system and weather protection will add an additional EUR 1,840,000 to the construction costs of this project.It means that when the cost of sprinkling and weather protection is considered, the cost of the positive climate effect of the concrete frame of the apartment building studied is 290% more expensive than the cost of a massive wooden frame.

Discussion
Presently, there is a growing interest in expanding the utilization of wood in the construction industry [45][46][47].Various companies, ranging from large corporations to medium-sized enterprises in the construction sector, are diversifying their focus toward wood construction, indicating a strategic shift in their business approach.Drawing upon emission data and comparative analyses, it is observed that wood, when used as a structural building material, currently exhibits a reduced carbon footprint in comparison to alternative materials.As a result, the increasing prevalence of wood construction is considered a significant achievement in the realm of climate action.
Our study underscores a deficiency in existing environmental certifications, revealing their inadequacy in adequately addressing the low-carbon attributes of buildings.These certifications primarily focus on energy efficiency and the carbon footprint throughout a building's life cycle, providing a limited perspective on low-carbon considerations.To enhance the significance of the findings, the suggestion is made that environmental certifications at various levels should include mandatory limits on carbon footprints.
As the importance of energy efficiency diminishes over a building's life cycle due to reduced emissions from energy production, it is crucial to implement stringent regulations, comprehensive accountability reporting, and sustainability reporting obligations for both companies and public entities.This approach aims to prevent greenwashing and promote a genuine and robust transition toward environmental sustainability.The proposal seeks to ensure that certifications go beyond superficial assessments and actively contribute to meaningful progress in reducing carbon footprints in the construction and building sectors.
As the transition progresses toward low-carbon and, ultimately, fully carbon-neutral energy production, the direct contribution of building energy use to emissions is expected to decline [48][49][50].Instead, indirect impacts may arise from potential replacements of energy-related building components.Consequently, the forthcoming emphasis will shift toward the material phase (A1-A3) of building materials and the emissions stemming from construction transport and on-site activities (A4-A5).This shift is driven by the decreasing operational carbon dioxide emissions (B1-B7) over the life cycle.
It is argued that the implementation of mandatory limits for emissions during the building material phase (A1-A3) and construction transport and on-site activities (A4-A5) is unavoidable.Without these limits, the perpetual shifting of responsibility among financiers, clients, and construction companies cannot be halted.Limits are seen as the most effective means to systematically guide the reduction in buildings' carbon footprints.Diminishing the carbon footprint of construction, both during the construction process and throughout the building's life, is considered an essential measure to counteract the accelerating pace of climate change.
Recent research in the field provides significant insights into the environmental impact of structural materials in multi-story buildings [51][52][53].A thorough analysis of comparative projects indicates that the carbon footprint (A1-A5) associated with concreteframed buildings surpasses that of massive timber CLT-framed buildings by approximately 40%.This substantial difference highlights the considerable environmental advantage of opting for timber-based construction methods in the context of multi-story buildings.
Furthermore, a more detailed examination of carbon handprints in these structures reveals that CLT-framed buildings exhibit notably larger carbon handprints, ranging from 330% to 890%.The extent of this variation depends on various factors, including the specific structural solutions and foundation methods employed.This nuanced perspective underscores the multifaceted environmental benefits associated with choosing CLTframed constructions over concrete-framed alternatives in the realm of multi-story buildings.The findings suggest that not only is there a reduced carbon footprint with timber-based construction, but there are also additional positive environmental implications that contribute to the overall sustainability of such structures.
Currently, wood construction stands out as the most economically viable and environmentally friendly option for low-carbon building practices [54][55][56].In particular, the use of massive CLT for the building frame is highlighted as an exceptional choice, offering a compelling combination of advantages in terms of carbon footprint, carbon handprint, and carbon storage potential.This emphasizes the pivotal role of wood, especially massive CLT, in promoting a greener and more sustainable future for construction projects aiming to minimize their carbon impact.
A comprehensive analysis of an upcoming multi-story building project in Laajasalo, comprising five floors and a roof, indicates that selecting a concrete frame would have detrimental climate consequences, emitting over 2.2 million kilograms of carbon dioxide equivalent over a 50-year timeframe, 270% higher than the emissions associated with a substantial CLT frame.To thoroughly evaluate low-carbon and climate-friendly construction, it is essential to consider both the carbon footprint and carbon handprint.Choosing a massive CLT frame results in substantial positive climate impacts, exceeding 3.67 million kilograms of carbon dioxide equivalent over a 50-year period, 420% more than what would be achieved with a concrete frame.This underscores the critical significance of opting for construction methods that positively contribute to climate outcomes.
A thorough examination of the costs related to the positive climate impacts resulting from the adoption of these two framing methods reveals a significant economic disparity.When meticulously considering the financial aspects involved in the construction of a multi-story building, it becomes apparent that the expenses associated with the positive climate impacts incurred by a concrete frame are notably elevated.To be precise, the cost of positive climate impacts linked to a concrete frame construction is a staggering 370% higher compared to the construction of a massive CLT frame in this specific scenario.This sharp contrast underscores the economic advantage and affordability inherent in choosing environmentally sustainable and low-carbon massive wood CLT construction over the conventional concrete frame alternative.As was already pointed out in the results section, in Finland, regulations mandate the installation of a sprinkler fire-extinguishing system in wooden apartment buildings, incurring construction costs of approximately EUR 100 per square meter of apartment space.Similarly, due to the country's climatic conditions, weather protection is typically added on top of the building frame during construction, also amounting to around EUR 100 per square meter of apartment space.Thus, the sprinkling system and weather protection will add an additional EUR 1,840,000 to the construction costs in this project.It means that when the cost of sprinkling and weather protection is taken into account, the cost of the positive climate effect of the concrete frame of the apartment building studied is 290% more expensive than the cost of a massive wooden frame.
In the face of escalating climate change impacts and declining biodiversity, relying on future generations to bear the burden of significant carbon emissions from construction materials is considered unsustainable.Projections suggest that with increasing carbon dioxide emissions, natural carbon sinks on land and in oceans are expected to diminish.Consequently, there is an urgent imperative to promptly reduce carbon emissions.The implementation of stringent regulations and laws becomes crucial to guide market economies toward low carbon intensity.Such measures are essential to ensure the potential for future generations to inhabit and thrive on this planet while fostering sustainable and environmentally conscious practices.
Moreover, there is a compelling need for an in-depth exploration of the relationship between calculated and actual emissions throughout the life cycle of building energy usage.Preliminary findings underscore significant divergences, especially in relation to electricity consumption.An essential avenue for further investigation involves a thorough examination of the use of local emission factors for district heating in carbon neutrality calculations.The integration of local emission factors is anticipated to align seamlessly with the low-carbon objectives of municipal and city district heating providers, enhancing the regional relevance of the results and extending their significance beyond reliance on national averages.

Conclusions
The findings of this study shed light on crucial aspects of construction methods and their implications for environmental sustainability, particularly in the Finnish context.
Firstly, this study underscores the inadequacy of existing environmental certifications in capturing the full extent of low carbon content in buildings, highlighting a gap in current assessment methodologies.Secondly, it elucidates the evolving role of energy efficiency in mitigating carbon dioxide emissions across a building's lifecycle, emphasizing the need for nuanced strategies amid changing energy production landscapes.Notably, the comparison between conventional concrete and CLT structures reveals substantial disparities in carbon footprint and handprint, with CLT outperforming concrete in both categories.The stark contrast in emissions between the two materials underscores the significant climate benefits achievable through wooden frame construction.Moreover, the analysis of costs unveils a compelling economic case for solid wood frames, with the cost of achieving positive climate effects substantially lower compared to concrete frames, particularly when factoring in additional requirements such as sprinkler systems and weather protection.
These findings provide a robust foundation for decision-makers to assess the feasibility and sustainability of construction methods, offering valuable insights into the environmental and economic considerations inherent in building design and material choices.As regulations evolve and awareness of climate impacts grows, this study serves as a timely resource for guiding future construction practices toward more environmentally responsible and cost-effective solutions in Finland and beyond.This does not include the procurement or installation of windows.There is no initial information about the quality/size/surface area of the windows.

Figure 1 .
Figure 1.The location of the site in Laajasalo, Helsinki, on the map.

Figure 2 .
Figure 2. Map extract from the zoning plan (image by authors).

Figure 3 .
Figure 3. Structural principle of the Developing Apartment Building initiative (image by authors).

Figure 4 .
Figure 4. Apartment distribution diagram for the base floor of the studied apartment building (image by authors).

Figure 5 .
Figure 5.The impact of material selection for the load-bearing structure of a Developing Apartment Building initiative building on carbon footprint and handprint (image by authors).

Table A2 .
Quantities and masses of the solid wood frame and roof of a mass timber apartment building.

Component-Based Cost Estimate for the Concrete Frame Structure Figure A1.
Apartment distribution diagram for the base floor of the studied apartment building (image by authors).Estimated Total Price: Self-cost price is EUR 9,114,500, with VAT of 0% Calculation content based on architectural plan drafts are dated 24 May 2023.The basic floor area has been calculated for five levels, resulting in a total residential floor area of approximately 9677 m 2 in the timber-built floors.The discrepancies in ground floor layouts and the spaces in concrete floors have not been accounted for.According to the architectural plans, the area is 8678 m 2 because part of the ground floor consists of other spaces.
Project: Wood Builders, Developing Apartment Building in Yliskylä Contents of Cost Estimate: Residential Apartment Building Timber Frame Contract, including CLT AKU and PALO surface structures indoors, as well as exterior cladding.Details of the cost calculation are provided below.

Table A8 .
Sources of detailed emissions data for solid wood structures.