# A BIM–LCA integration technique to embodied carbon estimation applied on wall systems in Brazil

Julianna Crippa (Department of Civil Construction Engineering, Federal University of Parana, Curitiba, Brazil)
Letícia Cavassin Boeing (Department of Civil Construction Engineering, Federal University of Parana, Curitiba, Brazil)
Ana Paula Angonese Caparelli (Department of Civil Construction Engineering, Federal University of Parana, Curitiba, Brazil)
Marienne do Rocio de Mello Maron da Costa (Department of Civil Construction Engineering, Federal University of Parana, Curitiba, Brazil)
Sergio Scheer (Department of Civil Construction Engineering, Federal University of Parana, Curitiba, Brazil)
Aline Medeiros Ferreira Araujo (Department of Civil Construction Engineering, Federal University of Parana, Curitiba, Brazil)
Diogo Bem (Department of Civil Construction Engineering, Federal University of Parana, Curitiba, Brazil)

ISSN: 2044-124X

Publication date: 12 November 2018

## Abstract

### Purpose

Aiming to simplify the extraction of embodied carbon data using a building information modeling (BIM) software, the purpose of this paper is to present a framework that integrates BIM and life cycle assessment (LCA), which are useful to the architecture, engineer and construction (AEC) industry. As a further purpose, this study also tests four different wall systems.

### Design/methodology/approach

The study applies design science research and it presents a framework that integrates BIM and LCA. For analysis and validation, a case study features four different wall systems costs based on the Brazilian context. In the proposed framework, SimaPro8 accomplishes the LCA, while ArchiCAD 19 the modeling.

### Findings

The first analysis covers embodied carbon and the second covers the total cost of each m² of wall. The proposed framework performs well, and it is effective in the Brazilian context. Concerning the walls, the wood frame system is the most sustainable option within this analysis and the most financially feasible option in Brazil.

### Originality/value

The present study contributes to embodied carbon data analysis, ensuring that the best choice of elements and components is being used in the building project. This BIM–LCA integrated solution is valuable not only to the AEC industry and to professionals, but also to future researchers. This analysis is of great value to new ventures, since the society shows a great concern about reducing GHGs emissions.

## Keywords

#### Citation

Crippa, J., Boeing, L., Caparelli, A., da Costa, M., Scheer, S., Araujo, A. and Bem, D. (2018), "A BIM–LCA integration technique to embodied carbon estimation applied on wall systems in Brazil", Built Environment Project and Asset Management, Vol. 8 No. 5, pp. 491-503. https://doi.org/10.1108/BEPAM-10-2017-0093

### Publisher

:

Emerald Publishing Limited

## 1. Introduction

There is a worldwide need for investing in sustainable undertakings to reduce the global warming potential (GWP) and preserving the environment (Hertwich and Peters, 2009). Architecture, engineering and construction industries (AECs) consume around 50 percent of the natural resources used in the entire planet. One third of the greenhouse gases (GHGs) emissions originate from that same industry (UNEP, 2009). GHGs emissions are corresponding to carbon footprint that specifies an amount of carbon dioxide equivalent. The amount of low-carbon buildings and communities that generates a positive impact would increase, if innovation strategies were more applied in design, construction, operation and facility management. Therefore, researchers and professionals are exploring ways to improve built environment projects through a sustainability criterion. A technological improvement in building carbon footprint calculations by choosing the best materials and products shall be a great incentive for professionals to use this evaluation more often in their projects.

Life cycle assessment (LCA) is a technique regulated by ISO 14040 (2006) and ISO 14044 (2006) that allows the calculation of carbon footprint. LCA can enhance the control and comprehension of different alternatives and results presented in the projects (Jrade and Abdulla, 2012). According to Monich (2012), there are three phases in a building’s life cycle: pre-use phase, usage phase (operational) and post-use phase (or demolition recycling and reuse). Calculating the precise carbon footprint of buildings is not an easy task, and most assessments are cradle-to-gate. Only some cover the whole building life cycle and englobe all phases, from extracting raw materials, transportation, the pre-use and use phase until the material’s final disposal (Monich, 2012; Ortiz et al., 2009). This field of study is dynamic and its data is in constant evolution. According to Baitz et al. (2013), it is possible to perform easier analysis with generic data to identify trends, despite the lack of accuracy. LCA holds great potential to mitigate negative environmental impacts caused by construction sites. However, running a full LCA in a building project is a manual and repetitive way to calculate the carbon footprint. Once companies face the complexity of this task, they may have little interest in running a full assessment.

Besides that, there is building information modeling (BIM), standardized by ISO 12006-2 (2015). BIM is an intelligent 3D-based process that allows the inclusion of information related to a project into a model. It is a virtual representation of the physical and functional characteristics of a building, during its whole life cycle, serving as a collaborative platform for shared information. BIM should solve the lack of compatibility between projects, allowing the identification of future mistakes and delivery of positive impacts in the final project. According to Bynum et al. (2012), the use of BIM tools offered means to increase the overall quality of the project, providing precise quantities, a more accurate calendar and scheduling of the work process, and reducing the contingencies and total project cost.

The integration of BIM parametric models with LCA can allow designers, architects, engineers and managers to create solutions while still in project development stage, enabling it to be more efficient and sustainable. Therefore, aiming to simplify the extraction of carbon footprint data using a BIM software, this paper proposes a framework to integrate BIM and LCA in a Brazilian context. This technique should be able to improve calculation of building carbon footprint and to ensure that the elements and components are being chosen optimally. This BIM–LCA integrated solution has potential to be applied not only to AEC industry and professionals, but also to future researchers. For analysis and validation, this study presents a case study involving four different walls system: steel frame, wood frame, brick clay masonry and concrete block masonry. The carbon footprint data and the cost of the wall systems based on the Brazilian market provide the best environmental and economical option.

## 2. Literature review

A BIM–LCA process can be used to account for the carbon footprint in the chosen materials for the construction and the use of BIM tools to calculate both the energy used and the CO2 emitted during the operational phase of the buildings in the early stages of project (Stadel et al., 2011). From the standpoint of available techniques, it is easier to reduce and control embodied energy, which is more related to manufactory sectors than the operational one. Therefore, the government, enterprises and researchers must pay attention and put efforts to minimize it (Chang et al., 2010). The major goal is to add value to the product or service provided. Thus, some businesses, such as consulting firms, face the LCA from a practical point of view, being more interested in its implementation and results such as choosing the best products, providing scientific consistency toward sustainability, answering to questions posed by consumers, improving the corporate image and making them actually more profitable (Schatsky, 2011). According to Mao et al. (2013), the embodied emissions of building materials are responsible for approximately 85 percent of total GHGs emissions. Besides, choosing more sustainable materials in a building project can indirectly decrease GHGs emissions by 12 percent (Sandanayake et al., 2017). Therefore, many studies focused essentially on the project’s level of emissions estimation (Sandanayake et al., 2016).

According to Asdrubali et al. (2013), LCA is a complete method to assess the sustainability of a building over its life cycle. LCA is recognized as being a method, which analyzes all the phases of product and all its interactive processes (ISO 14040, 2006). In each life cycle phase of a product, all energy inputs and outputs, materials, processes and emissions are considered. LCA in the construction industry characterizes the resultant effects of the construction over the environment, considering all the impacts going from raw material extraction, transport, building conception, until finally the disposal of such materials. LCA of whole buildings is an exhaustive task due to its manual and repetitive nature. (Monich, 2012). There are four phases in an LCA study: the goal and scope definition phase; the inventory analysis phase; the impact assessment phase; and the interpretation phase (ISO 14040, 2006). However, the ISO 14040 lack consensus on the methodology to define the scope or system boundary for the considered study. Therefore, it is vital to address the system boundary before starting the analysis (Sandanayake et al., 2018).

Some attractive businesses related to LCA are the consulting services in the development of any project type, and even in the design of a software to work with it (Cherubini and Ribeiro, 2015). For Sandanayake et al. (2017), GWP is the main environmental impact category in a worldwide perspective. Hence, there is SimaPro, an LCA software that can calculate results of carbon footprint, including the 100-year time horizon GWPs relative to CO2 equivalent gases using the IPCC 2007 GWP 100a method. According to Intergovernmental Panel on Climate Change (IPCC, 2006), carbon footprint corresponds to GHGs emissions normalized to mass units of CO2 equivalent. There are three main GHGs: CO2, CH4 and N2O. They are equivalent to 1, 25 and 298 grams of CO2 each, correspondingly. Stadel et al. (2011) declares that SimaPro demands much time to data collection. However, it provides several sorts of environmental impacts allowing a better understanding of LCA data levels or further upstream.

BIM tools’ information delivery capabilities have been valued by their building’s sustainability trends, particularly according to decision-making processes in the early stages of planning and design, which can benefit design optimizations significantly by reducing energy consumption and, consequently, decreasing environmental impacts caused by the use of energy (Wong and Fan, 2013; Schade et al., 2011). Also, the use of BIM in AEC is growing and several papers have already emphasized the potentials of BIM to help with decision making in terms of environmental impact (Kreiner et al., 2015; Medas et al., 2015).

According to Kulahcioglu et al. (2012), the environmental performance of a building should be assessed at the project phase of construction because that is when changes can cause the biggest impact. In this phase, not only cost and constructability should be considered, but also how the environmental impact could be reduced. It is exactly in this phase that the BIM–LCA integration can show the biggest benefits. In spite of the fact that the integration BIM–LCA can reduce time and improve the application of environmental analysis, certain challenges still need to be overcome. The properly application of an LCA method to evaluate the environmental impacts of the project can be hindered due to lack of information in the database about the materials or due to fails in the interoperability between a BIM software and the LCA tool. (Jrade and Jalaei, 2013). Besides, LCA analysis tends to be extremely time-consuming, especially due to the amount of information needed and the difficulties to obtain them correctly (Diaz and Anton, 2014). However, it is recognized that the use of BIM for the LCA application can considerably reduce the necessity for data inputs (Soust-Verdaguer et al., 2016). It is very important that many researchers are concerned in developing and improving BIM–LCA methods. However, many factors can affect the validity of these developed methods. According to Tsikos and Negendahl (2017), one of these factors includes the precision of the BIM model, the material take-off precision and the accuracy of the database. At Basbagill et al. (2013) research and many others, the validation of the method is limited to a single case study involving a particular building type, size, location and geometry. So, additional case study applications are required to comment more generally on the performance of those methods.

According to Jrade and Jalaei (2013), besides the lack of interoperability between the design and analysis tools, there are other reasons why quantifying the environmental impacts of building is still so hard: the lack of information about the sustainable materials that are stored on databases. Most software packages already have their own database, or use impacts database and established methods. Impacts databases are calculated based in North America and Europe industry processes or based on industry-average values. Thus, it cannot account for differences in the impacts of specific materials from individual suppliers or locations. At Yang and Wang’s (2013) research, there are no standards or benchmarks for life cycle environmental impacts for buildings in China, and this problem also occurs all over the world. There is a large potential to improve the BIM–LCA tool by developing a user-friendly interface, completing the building material and components databases and setting benchmarks for different buildings according to national and local standards of each country.

## 3. Research method

This research presents a technique for carbon footprint calculation in building projects, using an LCA tool and a BIM software. Also, this method includes the extraction of quantities of materials to calculate costs through the parametric model, during project implementation. Once the several factors involved in the project were integrated, an analysis regarding the relationship between carbon footprint in each element and the amount of material for each square meter of the studied elements was carried out, enhancing the more sustainable option and also relating it to its total costs. Figure 1 shows the proposed framework elaborated by the authors.

The quantity of material that compound elements in the project could be found in the Brazilian Composition Table Prices Budgets, known as TCPO 13 (2008), published by PINI. However, since some information on material was not found in these charts, other sources were necessary, such as information provided directly by professionals, companies and even the library of the software used for running the LCA.

According to ISO 14040 (2006), “there are cases where the goal of an LCA can be satisfied by performing only an inventory analysis and an interpretation.” Therefore, for our LCA study, the chosen scope was cradle-to-gate, englobing equivalent embodied carbon present in materials before the construction phase in the buildings’ life cycle. This phase included data coming from the following steps of the life cycle: natural resource extraction and materials production, disregarding other phases of a building life cycle. This study has focused in execution LCA using SimaPro 8.0.4.30 Faculty license to measure environmental impacts caused by each material and product. Among the methods offered by SimaPro, IPCC 2007 GWP 100a technique was selected, since it calculates data considering all GHGs and converts all of them to carbon equivalent. For life cycle inventory, the Ecoinvent Database was used, which offers over 4,000 inventories, apart from the creation of some elements to maintain the study’s legitimacy.

Due to the need of a BIM platform compatible software, ArchiCAD 19 was selected, according to professionals’ recommendations. The tool has an easy and intuitive interface. Like other BIM authoring systems, this allows the user to enter information on carbon footprint in each input, modeled by the parameters of components.

From modeling, through ArchiCAD, one can extract all quantitative information and export them to an Excel sheet, making the budget calculation through the insertion of unit costs for materials and supplies. These values were obtained from the Brazilian National System of Costs Survey and Indexes of Construction (SINAPI, 2015) database provided by Caixa Econômica Federal, a Brazilian public bank. The system also provides average prices for labor and equipment, which were not considered in this study.

### 3.1 Case study definition – walls

The case study of this work applied the proposed method in four different types of interior walls. The created process can be applied to any other item of the project or even in the whole building. However, for calculation purposes, the study of this particular construction element was chosen, due to its high frequency in construction projects. Furthermore, it has greater magnitude when the different wall systems are opposed. As a research strategy, it was decided to design 1 m2 of four kinds of commonly used in internal walls, covering the most basic construction materials: Brazilian conventional masonry (clay brick), concrete block masonry, steel frame and wood frame. The first two were designed with a mortar finish and the remaining others were composed of plasterboard. In this study, the LCA scope was limited to embody GHGs emissions of building materials present in the walls, which has 3D models developed in a BIM Software.

## 4. Results

During the design phase, there were some observations concerning the proposed framework, which involved the model details’ level. Some inputs are not designed in everyday work, such as mortar, used to settle the masonry wall, and bolts of the frames, causing the template to be very heavy and demanding a long time to get the output result. Therefore, the carbon count and costs of these inputs were included within other elements, as they were very important for overall result indexes. The difference in units used in each software for counting the carbon footprint has prevented the automatic carbon data extraction from ArchiCAD. Consequently, LCA data were entered manually in the excel sheet. Through the application of sustainable methods and techniques over a period of time, there must be a considerable amount of changes resulting in lower environmental impacts, not only in construction sector but also in larger ecological scale.

### 4.1 Case study results

#### 4.1.1 Quantities of materials

Table I summarizes the amount of material used in each one of the four wall systems that were studied in the present paper.

Brazilian indexes provided by TCPO 13 (2008) database were used to determine the quantities of each material in masonry walls, both 19 cm thick. The dimensions of the clay bricks are equal to 9 cm × 19 cm × 19 cm while the concrete blocks are sized 19 cm × 19 cm × 39 cm. The mix ratio that represents the amount of consumed cement, lime and sand in volume used for the masonry mortar in both cases was standardized in 1:2:8. The undercoat plaster and the plaster were also considered as part of the wall system. The plaster mortar is the same as the masonry mortar, with a 1:2:3 mix ratio. The mortar that had been used for the undercoat plaster had a mix ratio of 1:3 (cement and sand proportions in volume). Those mortars were created and introduced into SimaPro data library by the authors.

The quantity of wood frame and steel frame was calculated directly from the model already found in the Ecoinvent Database. For checking purposes, a research into two other sources was carried out. As for steel frame, an adaptation was carried out on the quantitative accounted in TCPO 13 (2008). The wall stud selected for this study was a high-standard one, measuring 4,5 cm × 9,0 cm and the Oriented Strand Board, also known as OSB, was also included in the system (Table I).

The existing product in the library of SimaPro was then compared with the features of high-standard internal walls, and a similarity between these values was verified. Then, the usage of data from SimaPro was proceeded in order to facilitate the LCA calculation. The amount of materials included in the elements of the Ecoinvent library was considered in the LCA. As an example, data such as the quantity of bolts, which are important for the LCA calculation, were already included. However, they are barely relevant in the quantitative analysis in projects and would not be accounted in a practical application.

#### 4.1.2 Carbon footprint

Before calculating the carbon footprint of masonry walls, the whole composition of the walls was defined, as well as the quantitative based on the TCPO 13 (2008). Those were compared with the materials presented and created in the library of SimaPro. For both walls, the blocks, the grouting mortars, settlement and undercoat plaster were considered, as well as the waste of these materials. SimaPro allows to create products or make necessary changes through the insertion of components and their quantities, facilitating the LCA execution.

As stated earlier, the elements supplied by Ecoinvent database were used in the composition of the walls’ frames, as they already provide the complete information and manual filling was not necessary. According to the software, the wood frame is composed by plasterboard on the wall itself, by polystyrene foam on the covering, wooden for the beams and pillars, zinc bolts and the waste of all these materials. As for the steel frame, it is necessary to also note the use of plasterboard for the wall, polystyrene foam and rock wool for covering, steel and aluminum for the tabs, zinc bolts and the waste of all these materials.

Finally, when running the software, the carbon footprint per m² for each kind of wall was calculated using IPCC 2007 GWP 100a method. In addition to providing results to the entire wall, the software can also detail and show the amount of CO2 in each input and the percentage that it represents in whole. It is possible to compare all the kinds of created walls. These data follow, being shown through graphic and schematic layouts.

#### 4.1.3 Modeling

ArchiCAD 19 was the selected tool for modeling, in which there were designed walls that represent the four methods of construction, each one with its identity information, such as material and precise dimensions in their three dimensions.

The level of details when modeling a single square meter of a wall should be much larger than what is used every day in complete projects. However, due to software limitations, minor inputs had not been accounted for practical implementation, such nails and glue, but were incorporated into the cost and LCA.

In masonry walls, due to the level of details that the software provides, the individual masonry mortars were not designed. The most convenient solution, therefore, was to directly incorporate the values of mortar in blocks, as well as the carbon footprint mass and its cost. This adjustment was chosen because of its practical characteristics and easy application on projects and budgets.

In steel and wood frames, profiles and guides were first designed, since they had no default in the software library and were created from the function “complex profiles.” Profiles were designed for the steel frame and a rectangular profile, for the wood frame wall stud. That being finished, by adding the thermal and acoustic insulating material, as well as the plasterboard, the walls were completed (Figure 2).

The models discussed here were generic representations. As the structural load varies depending on the project, it is possible that more or less profiles in the square meter would be needed. Three-meters high by five in length walls were designed, of which only 1 m2 was considered.

#### 4.1.4 Obtaining costs and carbon footprint from quantities of material extraction

It is possible to extract quantitative elements’ properties from the model by pressing “Quantity Count” within “Project Map,” placed in ArchiCAD’s menu. From the table, in the software itself, data are obtainable to feed a support worksheet in Excel.

Within countless options of variables to be extracted from the model, for calculation purposes, it was only needed to extract variables of mass and area of each component present in the walls. ArchiCAD 19 also allows the user to insert a specific value for the amount of carbon footprint per kilogram in each material or using the available value in the software. However, in this work, the carbon footprint was deployed using the CO2 values obtained by SimaPro, considering the single square meter of the walls as a whole, and not as each individual element.

The values obtained through SimaPro were referring to the relation kg CO2/m² of a wall, unlike the ones presented in ArchiCAD, which worked with kg CO2/kg of material. Therefore, to simplify the process, a worksheet with the data obtained from the first software was used.

In order to obtain structure materials and elements’ prices, two SINAPI (2015) charts were used: one about inputs and another relative to cost breakdown. Both included taxes, with prices updated to the State of Paraná as for the month of August and September in 2015. However, wood frame and steel frame walls were not present in this chart, so there was a need to request budgets with companies specialized in these products.

For comparison purposes, Table II presents all data, both for carbon footprint and costs. In the columns layer/component and masses, it is possible to find the quantitative values extracted through ArchiCAD. The column “Carbon Footprint (kg)” displays the total amount of CO2 emitted for each wall type, in kilograms per square meter of wall, obtained through the SimaPro. The cost estimation of the walls was based on the Brazilian market; thus, the results are presented using the official currency of Brazil, known as Brazilian Real (R$). For calculation and analysis purposes, a simplified exchange rate can be estimated considering one Brazilian Real equivalent to US$0.30.

## 5. Discussion

### 5.1 Discussion of case study

Two analyses were conducted: one regarding carbon footprint, and the other, about the total cost of each m² of wall. However, it was not fully consistent to make a comparison between steel and wood frame methods with the masonry methods. The first ones have structural function, while the latter needed to add reinforced concrete in the project to have this purpose, which was not considered in this work. Thus, the comparison between both of them separated seemed to be more reasonable.

As noticed in Table II, the difference of prices and amount of carbon dioxide between the masonry methods is much the same. However, according to the achieved results, concrete block masonry provides more carbon emission savings and it is cheaper than clay brick masonry. Although, that difference is not very significant in each square meter of wall, which makes both options convenient and economical and environmentally competitive. By the time of choosing the best method, other factors should be considered, such as workers’ specialization, availability of materials and deadline.

The wood frame turned out to be the most sustainable option within this analysis and also the most economically feasible option. The steel frame was the most expensive among the four in Brazil, becoming a non-viable option when only execution costs and materials were considered. However, it should be remembered that the method is considered the faster and cleaner, which can decrease the total cost of the construction. In addition, within the sustainability analysis, the steel frame also stood out with a high value of carbon footprint. It is important to remember that, when it comes to carbon footprint, some economically irrelevant inputs become very significant, as, for example, the bolts, which possess a high carbon footprint, but a negligible cost compared to the total cost of wall.

### 5.2 Discussion of proposed BIM–LCA integration technique

Linking impacts databases with BIM is convenient to evaluate, during the design phase, building components’ emission and energy consumption. It also allows the prediction of environmental impacts in each phase of a construction. BIM provides opportunities to incorporate sustainability performance indicators in the building design process. However, it lacks interoperability with the LCA tools conventionally used. The proposed technique was able to improve the calculation of building carbon footprint and it showed potential to be applied not only by AEC industry and professionals, but also by future researchers.

Reproducing the proposed method combining BIM and LCA is feasible to both simple or complex projects. Linking environmental impacts databases with BIM is advantageous to evaluate, during the design phase, building components’ emission. It also allows predicting environmental impacts in all phases of a building. A BIM–LCA integration provides opportunities to incorporate sustainability performance indicators in the building design process. However, as a limitation, the studied framework analyses only embodied carbon of materials, disregarding other phases of a building life cycle.

By integrating these costs and carbon footprint in this work, it was possible to obtain results and compare them to the best environmental and economical choice. Commercially, this analysis is of great value to new ventures, since society shows increasingly concern about the future of the environment and, therefore, this sustainable appeal is effective at the time of the purchase of a project. For companies that provide this kind of service, the use of ArchiCAD showed itself suitable, once the software already presents carbon footprint data into its library materials, not requiring the extraction of them from SimaPro. In addition, it is possible to obtain each material’s quantitative in the entire design, copying that to support Excel spreadsheets, making the final budget easier.

Some large academic studies, for example, may require a higher accuracy level of data for carbon footprint. Therefore, it is suggested to obtain these data through an LCA. Following that, the SimaPro provides this information according to the inputs selected by the user, making more careful analysis. The applicability of the interaction between the two tools is highly beneficial to businesses in the area, to scientific research, the consumer and the environment. Therefore, the developed framework can influence the mitigation of problems related to sustainability in the construction industry.

This paper presented a method for estimation and comparison of incorporated emissions in wall systems at the project level. Further, the proposed framework has potential to evaluate cradle-to-cradle assessments, including circular economy concepts. The authors highlight the significance of performing a whole building embodied carbon analysis to gather more insights.

## 6. Conclusion, limitations and suggestion for future research

The integration of BIM parametric models with an LCA can allow designers, architects, engineers and managers to create solutions while still in project development stage, enabling it to be more efficient and sustainable. Therefore, aiming to simplify the extraction of carbon footprint data using a BIM software, this paper proposed a framework to integrate BIM and LCA in a Brazilian context, using TCPO 13 (2008) and SINAPI (2015). In the proposed framework, SimaPro8 was used to perform the LCA, while ArchiCAD 19 to modeling. The carbon footprint calculation was made using IPCC 2007 GWP 100a method together with Ecoivent database, both present in SimaPro. For analysis purposes and validation, this paper presented a case study that was applied involving four different walls system: steel frame, wood frame, brick clay masonry and concrete block masonry.

By integrating these costs and carbon footprint in this work, it was possible to obtain results and compare them to the best environmental and economical choice. Commercially, this analysis is of great value to new ventures, since the society shows increasingly concern about the future of the environment and, therefore this sustainable appeal is effective at the time of the purchase of a project. The developed BIM–LCA integration technique was able to improve calculation of building carbon footprint and it showed potential to be applied not only by AEC industry and professionals, but also by future researchers. Moreover, it is possible to reproduce the proposed method combining these two aspects to both simple designs and complex projects.

A considerable difficulty in this work was the early expiration date of SimaPro’s license. Therefore, LCA had to be conducted while this study was still in an early stage. With the development of the research, a misconception was identified and could not be corrected: both frames have structural function while masonry does not, what made impossible the initial idea of a fair comparison between the four walls. Also, as a limitation, LCA’s calculation components concerned only embodied GHGs emissions of building materials present in the walls, disregarding transportation and other phases as construction, operation, maintenance and demolition. Also, the TCPO 13 (2008) Brazilian database does not contain any specifications for wood frame quantities of materials. That induced the authors to look for more data, which were provided by a researcher and professor working on the construction material field and manufacturers. According to those sources, wood frame’s components depend either if the wall is internal or external and the material’s wall stud.

As a suggestion for future research, the method proposed by the authors should be applied in a real project with an architecture firm to better analyze the effectiveness of the procedure. Also, researchers could study a system to improve this method by developing an automation module, such as a plugin using application program interfaces.

## Figures

#### Figure 1

Proposed framework overview

#### Figure 2

Wall systems models, designed using ArchiCAD 19

## Table I

Quantities of materials for 1 m² of which type of studied wall

 Clay brick masonry wall (1 m²) Clay brick 51 units Masonry mortar (cement, lime and sand, 1:2:8 mix ratio) 0.042 m3 Undercoat plaster (cement and sand, 1:3 mix ratio) 0.005 m3 Plaster (cement, lime and sand, 1:2:8 mix ratio) 0.005 m3 Concrete block masonry wall (1 m²) Concrete block 13 units Masonry mortar (cement, lime and sand, 1:0.5:8 mix ratio) 0.018 m3 Undercoat plaster (cement and sand, 1:3 mix ratio) 0.005 m3 Plaster (cement, lime and sand, 1:2:8 mix ratio) 0.005 m3 Steel frame wall (studs placed 40 cm from each other’s center) Steel stud (C-shaped)Size: 90 mm×90 mm×90 mmthickness: 0.95 mm 3.996 Linear meter Rock wool 75 mm Gypsum plasterboard (2 units) 12.5 mm/each Wood frame wall (studs placed 40 cm from each other’s center) Wood studSize: 45 mm×90 mm 3.865 Linear meter Rock wool 75 mm OSB 11.1 mm Gypsum plasterboard (2 units) 12.5 mm/each

## Table II

Final results of carbon footprint and costs

Element (1 m²) Composition Layer area (m²) Mass (kg) Carbon footprint (kg CO2 eq) Unit cost (R$) Total cost (R$)
Clay brick masonry wall Plaster 1.0 8.5 50.3 17.01 17.01
Undercoat plaster 1.0 8.5 3.33 3.33
Clay brick 1.0 123.12 65.09 65.09
Undercoat plaster 1.0 8.5 3.33 3.33
Plaster 1.0 8.5 17.01 17.01
Total R$105.77 Concrete block masonry wall Plaster 1.0 8.5 45.3 17.01 17.01 Undercoat plaster 1.0 8.5 3.33 3.33 Concrete block 1.0 266 75.76 75.76 Undercoat plaster 1.0 8.5 3.33 3.33 Plaster 1.0 8.5 17.01 17.01 Total R$116.44
Drywall-steel framed system Gypsum plasterboard 1.00 11.25 159.0 230.00 230.00
Rock wool 0.96 1.01
Air volume 0.96 0.01
Steel stud 70.65
Gypsum plasterboard 1.00 11.25
Total R$230.00 Drywall-wood framed system Gypsum plasterboard 1.00 11.25 36.9 90.12 90.12 OSB 0.83 6.08 Rock wool 0.83 0.90 Air volume 0.83 0.01 Wood stud 11.25 OSB 0.83 6.08 Gypsum plasterboard 1.00 10.97 Total R$90.12

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## Corresponding author

Julianna Crippa can be contacted at: julianna.crippa@gmail.com