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Article

Sustainability Impacts of Wood- and Concrete-Based Frame Buildings

by
Edgaras Linkevičius
1,*,
Povilas Žemaitis
2 and
Marius Aleinikovas
2
1
Faculty of Forest Sciences and Ecology, Agriculture Academy, Vytautas Magnus University, Studentų 13, Akademija, LT-53362 Kaunas, Lithuania
2
Lithuanian Research Centre for Agriculture and Forestry, Instituto al. 1, Akademija, LT-58344 Kėdainiai, Lithuania
*
Author to whom correspondence should be addressed.
Sustainability 2023, 15(2), 1560; https://doi.org/10.3390/su15021560
Submission received: 8 December 2022 / Revised: 6 January 2023 / Accepted: 9 January 2023 / Published: 13 January 2023

Abstract

:
The European Commission adopted a long-term strategic vision aiming for climate neutrality by 2050. Lithuania ratified the Paris agreement, making a binding commitment to cut its 1990 baseline GHG emissions by 40% in all sectors of its economy by 2030. In Lithuania, the main construction material is cement, even though Lithuania has a strong wood-based industry and abundant timber resources. Despite this, approximately twenty percent of the annual roundwood production from Lithuanian forests is exported, as well as other final wood products that could be used in the local construction sector. To highlight the potential that timber frame construction holds for carbon sequestration efforts, timber and concrete buildings were directly compared and quantified in terms of sustainability across their production value chains. Here the concept of “exemplary buildings” was avoided, instead a “traditional building” design was opted for, and two- and five-floor public buildings were selected. In this study, eleven indicators were selected to compare the sustainability impacts of wood-based and concrete-based construction materials, using a decision support tool ToSIA (a tool for sustainability impact assessment). Findings revealed the potential of glue-laminated timber (GLT) frames as a more sustainable alternative to precast reinforced concrete (PRC) in the construction of public low-rise buildings in Lithuania, and they showed great promise in reducing emissions and increasing the sequestration of CO2. An analysis of environmental and social indicators shows that the replacement of PRC frames with GLT frames in the construction of low-rise public buildings would lead to reduced environmental impacts, alongside a range of positive social impacts.

1. Introduction

Carbon sequestration and carbon storage in wood products has been identified by the United Nations Framework Convention on Climate Change (UNFCCC) as a key GHG mitigation strategy. Thus, forest-based sectors play a crucial role in supplying a growing bioeconomy in Europe [1]. The forestry sector also contributes to the mitigation of climate change by carbon sequestration in forest plants biomass, soil, and carbon storage in harvested wood products [2,3]. Harvested timber holds a significant amount of carbon that can be stored in harvested wood products, including building materials, furniture, paper, etc. It is estimated that the EU forestry and the forest-based sectors currently mitigate net GHG emissions by a total of 13% [4], of which approximately 10% is stored in harvested wood products [5].
The EC’s initiative is to tighten the emissions reduction target from the current 40% to 55% in 2030, in addition to a strategic long-term vision, aiming for an economy with net-zero GHG emissions by 2050 [6]. This is a binding EU climate and energy legislation that requires the adoption of national energy and climate plans (NECP) by the member states for the period 2021–2030. As an EU member since 2004, Lithuania also ratified the Paris Agreement and is committed to reducing GHG emissions by at least 40% by 2030 [7].
Lithuania has a strong wood-based industry and abundant timber resources, which significantly contribute to the national bioeconomy [8,9]. Forest resources in Lithuania are gradually increasing, possessing 566.7 m3 of total growing stock in 2021 [8]. The two most important construction timber species grown in Lithuania are the Norway spruce (Picea abies (L.) H. Karst.) and the Scots pine (Pinus sylvestris L.); when combined, the total growing stock of both species accounts for approximately 334 million m3. In 2019, roundwood harvest in Lithuanian forests totalled 6.9 million m3, of which 1.26 million m3 was used for sawn timber production [10]. However, the annual industrial roundwood export from Lithuania reached 20–25%, and this complicates the use of wood in local manufacturing. Furthermore, Lithuania exports a considerable percentage of final wood products (plywood, particle board, fibreboard, glue-laminated timber (GLT)), that could be used in the national building sector. Thus, Lithuania reduces the potential to develop its own low-carbon construction sector.
In order to reach GHG emission targets, significant policy measures have been listed in the Lithuanian NECP in various areas, e.g., energy and equipment efficiency, such as the replacement of outdated boilers with more modern ones. However, relatively few measures target the construction sector. In Lithuania, the main construction material used is concrete. As a key input into concrete, cement is the most widely-used construction material in the world, and cement is a major contributor to climate change due to the chemical and thermal combustion processes involved in the production process. Annually, the global demand for cement is more than 4 billion tons, accounting for around 8% of global emissions caused by humans [11].
It is well known that a significant part of cement used in the construction sector could be replaced by wood. Timber, as a building material, has been increasingly used and has become more visible around the world. [12,13,14,15,16,17]. The prefabrication of wood-based building construction materials, including laminated veneer lumber, GLT, and cross laminated timber, allowed the increased use of timber in the construction sector [18,19,20,21,22,23]. The use of engineered wood products in construction enables the sector to build multi-storey public and commercial buildings, industrial and agricultural halls, bridges, sport centres etc. [12,18,21]. Still, the market share of wood-based constructions in Europe is below 10%; therefore, these materials possess great potential for substituting non-wood building constructions for wood alternatives, and thereby making the construction sector more sustainable [24]. Sikkema et al. [25] showed construction wood use intensity (expressed as the ratio of apparent national consumption of wood for construction (in m3) to the useful floor area of newly finished dwellings (in m2)) in Europe. Results showed that the ratio ranges from 0.01 in Cyprus/Malta to 0.32 in Estonia/Romania. The ratio found in Lithuania was 0.11, and was attributed to a high market share of wood-based constructions in dwellings and a relatively low market growth (maturity stage). However, the share of multi-floor annual buildings is currently less than 1% in Lithuania [26]. Therefore, a gradual increase in the share of wood-based construction can significantly contribute to reduced CO2 emissions in the national construction sector. Wood and wood-based materials have been shown to be environmentally beneficial in the environmental assessment of the full life-cycle of buildings [18,27,28,29,30]. The use of wood-based construction materials can lead to a lower environmental impact compared with non-wood alternatives [31,32,33]. A study presented by D’Amico et al. [34] showed that replacing concrete floors with steel-cross laminated timber lowers greenhouse gas emissions. More specifically, Saade et al. [35] presented the results of a systematic literature review of eleven case studies that ranked wood and concrete or steel framed buildings based on their sustainability performance; the study concluded that, in terms of climate change mitigation potential, wood-framed buildings performed better than concrete-framed buildings in all comparisons. However, Nässén et al. [36] highlighted the uncertainty of whether wood-framed buildings would be a cost-effective carbon mitigation option. Further, Cabeza et al. [37] came to the conclusion that most Life cycle assessments LCAs are performed in “exemplary buildings” that have been designed and constructed as low-energy buildings. However, only a few cases performed on “traditional buildings” were found in most cities. In addition, Amiri et al. [38] argues that carbon storage in the buildings is highly influenced by the volume of timber used and the number of timber elements used in the construction of the building; meanwhile, parameters such as building type, the size of the building or the sort of wood, have less significance. This leads to the assumption that building material value chains are influenced by country-related differences in raw material supply and manufacturing, and are highly dependent on the type of the specific construction material. Although studies that have been performed on GHG emissions generally focus on the manufacturing of construction materials, mostly varying in type of wood-based material [32,39,40,41], very few studies have focused on the comparison between GLT and other wood-based [26,40,42,43] or concrete-based alternatives [26,32,44]. GLT-based building materials shown advantages in comparison to non-renewable alternatives [26]. For example, Knauf et al. [45] presented a displacement factor of 1.3 tC/tC for use in softwood-based glued timber products (GLT, CLT) in place of steel, concrete, and bricks in Germany. However, there is a need to compare these construction materials under different conditions and scenarios.
This study was designed to assess the sustainability impacts of wood-based (GLT and sawn timber (ST)) and concrete-based (site-cast concrete (SCC) and precast reinforced concrete (PRC)) building frames under Lithuanian conditions. We designed two- and five-floor wood- and concrete-based building material alternatives in order to compare the impact of the construction size on sustainability values. For this purpose, a typical public building conception was chosen because of its wide application in, for example, kindergartens, schools, offices, etc. The data was collected during the project “BenchValue”, as part of the Lithuanian case study (http://benchvalue.efi.int/, accessed on 22 January 2018). In this study, we used a functional unit of indicators (calculated as per m3 of material), calculated in our previous research [26]. A functional unit was linked to the overall amount of material needed for the designed buildings and then expressed per one square meter of the building area. The research targets of this study were as follows: (i) to design two- and five-floor wood- and concrete-based public building frames for a “traditional building”, (ii) to quantify and to compare the sustainability impacts of wood- and concrete-based public building frames, and (iii) based on these findings, provide policy recommendations for GLT and PRC use in the construction sector.

2. Materials and Methods

2.1. Value Chain Topology, Assumptions and Sources of Data

All calculations and modelling were completed by using the ToSIA (a tool for sustainability impact assessment) approach [46]. The topology of wood-based (GLT and ST) and concrete-based (SCC and PRC) value chains involve three stages: (i) raw material supply, (ii) processing and manufacturing, (iii) transport to the building site. Figure 1 presents the wood-based value chain that combines seventeen processes (Figure 1). The value chain starts with the total growing volume of the forest and ends with the transport of final construction materials (GLT and ST) to the building site.
In this study, five concrete value chains were selected: four SCC and one PRC. C8–10, C20–25, C25–30 and C30–37 represent different strength classes of SCC. In our study, we used the recipe to produce 1 m3 of SCC as follows: C8–10—1 t sand, 1 t crushed stone, 0.2 t cement, 0.1 m3 water; C20–25—1 t sand, 1 t crushed stone, 0.26 t cement, 0.16 m3 water; C25–30—1 t sand, 1 t crushed stone, 0.3 t cement, 0.17 m3 water; C30–37—0.9 t sand, 1 t crushed stone, 0.35 t cement, 0.15 m3 water. The value chain starts with resource extraction and ends with the transport of the final construction materials to the building site (26 processes in total) (Figure 2). The topology of concrete-based chains involves three stages: (i) raw material supply, (ii) processing and manufacturing, (iii) transport to building site. The material flow through the production process was linked with the sustainability indicator values in each process. Material flows were calculated as per one cubic meter of final material produced.
Data sources and actual indicator values in each process and for one m3 of final produced material are presented by previous research by Žemaitis et al. [26]. Therefore, in this publication, we use aggregated values for one m3 of produced material and apply these values to calculate the sustainability indicator values for actual buildings. For a more detailed methodology on assumptions made, see Žemaitis et al. [26].

2.2. The Indicators Used

The indicators used are listed in Table 1. For a comparison of the sustainability impacts of wood-based and concrete-based building frames, eleven indicators were selected. The selection of indicators was made during a BenchValue project stakeholder workshop. For indicator selection, the Ketso method was applied [47,48]. The sustainability indicators were classified into environmental, economic and social indicators.
Seven environmental indicators were selected (Table 1). The indicator values are presented as per square meter of the building. The indicator GHG emissions quantifies the carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) emissions occurring in the processes along the estimated value chains. We used conversion factors to calculate the GHG emissions from diesel, CNG, and grid electricity used in the processes [26]. The indicators Energy consumption and Water consumption were calculated based on intake by industry throughout value chain processes. Generation of waste quantifies hazardous and non-hazardous waste in tons per reporting unit. Volume of non-renewable materials quantifies the volume of extracted non-renewable materials throughout value chain processes. The indicator only includes product components that are connected to the extraction of raw materials, resulting in land degradation. The wood-based chains were attributed to zero use of non-renewable materials, as Lithuanian forests are managed according to sustainable forest management principles and therefore, do not result in land degradation. Carbon inflow into the pool quantifies biogenic carbon storage in the wood (Hiraishi et al. [52]). The Wood displacement factor (WDF) was calculated according to the formula provided by Sathre and O’Connor [51]. This indicator is a measure of the GHG emission reduction when non-wood materials are substituted for wood-based alternatives. The concrete-based construction materials were considered to contain zero wood. The carbon content of GHG emissions was calculated as 12/44 CO2 eq. Currently, a carbon content of 50% in dry wood is widely accepted as a generic value. Therefore, we also used this value, and a wood density of 500 kg/m−3 was used. A positive WDF equation value means that the substitution of non-wood materials for wood alternatives results in GHG emission reduction.
Employment, wages and salaries and occupational accidents were selected as social indicators. Employment was estimated as a full-time equivalent (FTE) in total throughout value chain processes per production unit. The wages and salaries were calculated by summing all wages and salaries (EUR) throughout the value chain processes per production unit. Occupational accidents were calculated as fatal and non-fatal cases throughout value chain processes per production unit.
The production price was selected as an economic indicator. This indicator was calculated only for the final GLT, ST, PRC and SCC products.

2.3. Study Description

To compare the sustainability impacts of alternative construction material value chains, two standard public buildings were designed: two-floor (765 m2) and five-floor (1913 m2). Wood-based (GLT and ST) and concrete-based (SCC and PRC) building frames were compared. This style of construction was selected as it is commonly used and comparable in terms of sustainability parameters.
Wooden frame building. The two-floor and the five-floor wooden frame schematic plan and construction elements that were used are presented at Figure 3. The model is a wooden structural frame, made of GL28h class glued laminated timber. The frame consists of columns, main beams, distribution (secondary) beams, perimeter beams and deck beams. Deck beams installed on distribution beams are supported by main and perimeter beams, which are supported on columns. All frame elements are fixed to each other using hinged connections that simplify these joints. Constructions are connected by the steel plates and bolts. Portal steel trusses and monolithic wall shafts were used as they provide rigidity for the whole structure. The foundation is a drilled pile with a pile cap beyond the columns and reinforced concrete beams across the perimeter of the building. Reinforced concrete wall shafts were installed straight on the piles for the lift and stairs. Supplementary Material S1 and S2 details the two- and five-floor wooden frame building elements: foundations, the building frame, the specific dimensions of construction elements for each solution and detailed amounts of materials used for each element and building frame.
The two- and five-floor wooden-frame building aggregated material consumption values were calculated according to the structural dimensions (Table 2 and Table 3). In total, the two-floor construction used the following: 82.68 m3 of concrete, 9.10 tons of rebar, 7.50 tons of joint steel, 41.27 m3 of GLT and 28.93 m3 of ST. The five-floor building consists of the same elements and materials, except foundations were not made using C8-10 concrete. The five-floor construction used a total of 207.76 m3 of concrete, 23.15 tons of rebar, 21.32 tons of joint steel, 122.84 m3 of GLT and 70.75 m3 of ST.
PRC-frame building. The two-floor and the five-floor PRC-frame schematic plan and construction elements that were used are presented at Figure 4. The PRC building structural scheme consists of monolithic foundations and a frame of PRC elements. The columns were fixed on foundations using semi-rigid joints with anchor bolts. The PRC beams (forms of L and upside-down T) hinged, supported on columns via steel details inside of columns and at the ends of beams. Hollow core slabs hinged between L and T form beams, on their flanges. All spacings at the connection nodes were concreted at the construction site, using C30/37-grade concrete and S500-grade steel bar elements. Portal steel trusses were used in the middle and ends of the building, in addition to monolithic wall shafts which provided rigidity for the whole structure; this was the same as in the glulam frame building. The foundations were built up of drilled piles with pile caps beyond the columns, PRC beams across the perimeter of the building, and foundation slabs beyond PRC wall shafts for the lift and stairs. Supplementary Material S3 and S4 detail two- and five-floor PRC building elements: foundations, the building frame, the specific dimensions of the construction elements for each solution and detailed amounts of materials used for each element and building frame.
The two- and five-floor PRC-frame building aggregated material consumption values were calculated according to the structural dimensions and are provided in Table 4 and Table 5. For the two-floor building option, the PRC projected for the columns, beam header, supported slab, joist slab. The total amount of PRC materials was the following: 139.26 m3 of concrete, 10.58 tons of rebar, and 5.40 tons of joint steel. The total amount of SCC material was the following: 113.63 m3 of concrete, 11.02 tons of rebar, and 3.88 tons of joint steel. For the five-floor building option, the total amount of PRC material was the following: 376.57 m3 of concrete, 27.71 tons of rebar, and 13.50 tons of joint steel. The total amount of SCC material was the following: 301.39 m3 of concrete, 24.13 tons of rebar, and 7.84 tons of joint steel.

2.4. ToSIA Approach and Result Processing

In this study, we used indicator values of wood-based and concrete-based materials, calculated in our previous research [26]. The calculated indicator values were estimated along the production value chains by summing all processes and were presented as the total per one cubic meter production (GLT, ST, PRC and SCC, see Žemaitis et al. [26]). The processes were linked with a material flow for one cubic meter of final product (ST, GLT, PRC and SCC (C8-10, C20-25, C25-30, C30-37). Our previous research provides detailed information about value chain topologies, processes, assumptions made and indicator values in each process. In this study, the indicator values per one cubic meter of material were linked to the overall amount of material needed for building, and then expressed per one square meter of the building. This was performed by using ToSIA software. In ToSIA software, the sustainability indicators are linked to production processes. Indicator values in each process are linked to material flow and all calculated values are summed throughout the product value chain see [46].

3. Results

3.1. The Main Differences between Wood- and Concrete-Based Frame Buildings

In this section, we provide the main differences in aggregated material consumption values (m3) for designed two- and five-floor wood- and concrete-based frame building alternatives (Table 2, Table 3, Table 4 and Table 5). In the two-floor wooden frame building, only SCC (82.68 m3) was used, while in the concrete-based building alternative, PRC (139.26 m3) and SCC (113.63 m3) were used (total 252.89 m3). PRC was used in building frame elements in the concrete-based building, while GLT (41.27 m3) and ST (28.93 m3)) (total 70.2 m3) were used in the wood-based building alternative. Therefore, in the wood-based frame building, the amount of construction frame elements were 1.98-fold lower when compared to the concrete-based building alternative. In the five-floor wooden frame building, only 207.76 m3 of SCC was used, while in the concrete-based building alternative, 376.57 m3 of PRC and 301.39 m3 of SCC were used. PRC was used in building frame elements in concrete-based building, while GLT (122.84 m3) and ST (70.75 m3)) (total 193.59 m3) were used in the wood-based building alternative. Therefore, in the wood-based frame building, the number of construction frame elements was 1.94-fold lower when compared to the concrete-based building alternative. This leads to a significant reduction in the sustainability impact of the whole building. It is also important to note that the majority of the PRC used in the wooden frame building was used in the walls of the lift shaft and the stairs. Therefore, by using wood-based walls in the lift shaft and the stairs, a significant reduction in the sustainability impact could be achieved.

3.2. Environmental Impacts of Wood- and Concrete-Based Frame Buildings

In this section, we present results that describe the indicator values from whole value chain processes for two-and five-floor GLT, as well as PRC buildings frames. According to Table 6, wood-based construction materials have a more positive environmental impact, in absolute values, in comparison to concrete-based construction materials.
GHG emissions. The highest CO2 emissions were estimated for the five-floor PRC frame; this vale was 0.2190 t of CO2eq/m2. The construction of a two-floor PRC frame would lead to a slight reduction in emissions, to 0.2080 t of CO2eq/m2. On the contrary, to construct two- and five-floor GLT frames, only 0.0874 and 0.0899 t of CO2eq/m2 would be produced. Higher GHG emissions for concrete-based frame buildings, in comparison to wood-based frame buildings, are highly determined by cement and steel (for reinforcement) production.
The two- and five-floor GLT-frame buildings generate a 2.9 and 2.6-fold lower Waste in total, in comparison to the PRC-frame buildings. Waste is reduced because the wood residues are constantly used for biofuel purposes. The PRC-frame building waste is generated from gypsum extraction and steel production processes.
The two- and five-floor GLT-frame buildings quantify a 3.7- and 3.5-fold lower Water consumption rate, in comparison to the PRC-frame buildings. Of the total amount of water consumed during the manufacturing process, the majority goes into the production of the steel and concrete foundation materials. In comparison, water consumption, when constructing two- and five-floor PRC-frame buildings, is 0.85 and 0.84 m3/m2, while it is 0.23 and 0.24 m3/m2 for the GLT-frame buildings.
The two- and five-floor GLT-frame buildings quantify a 2.9-fold lower Energy consumption rate. To construct two- and five-floor GLT-frame buildings, 510 and 518 MJ/m2 of energy is consumed, while this value is 1482 and 1519 MJ/m2 for PRC-frame buildings. Cement production consumes the highest amount of energy along the concrete-based value chains.
The two- and five-floor GLT frame buildings quantify a 3.0- and 3.1-fold lower Volume of non-renewable material, in comparison to the PRC-frame buildings. To construct two- and five-floor PRC-frame buildings, 0.970 and 1.030 t/m2 of non-renewable material is consumed, while this value is 0.327 and 0.333 t/m2 for GLT frame buildings. All non-renewable raw materials used to produce GLT frame buildings go towards the construction of the foundation and steel production.
Carbon inflow into the pool was calculated for two- and five-floor wood-based frames: The two-floor GLT-frame buildings contained 0.0275, and the five-floor frame contained 0.0304 tC/m2.
WDF (GLT and ST) for the two- and five-floor GLT-frame buildings was 1.43 and 1.34 tC/tC. Consequently, for one tC in the two-floor GLT-frame building, substituted in place of PRC products, there is an emission reduction of 1.43 tC. Accordingly, for one tC in the five-floor GLT-frame building, substituted in place of PRC products, there is an emission reduction of 1.34 tC.

3.3. Social Impacts of Wood- and Concrete-Based Frame Buildings

Employment, Wages and salaries and Occupational accidents indicators were selected for the wood- and concrete-based frame buildings’ social impact assessment (Table 6).
The highest Employment was estimated for the two- and five-floor PRC-frame buildings; the values were 1.30 and 1.41 FTE/1000 m2. Meanwhile, the employment for the two- and five-floor GLT-frame buildings was 2.50- and 2.61-fold lower; the values were 0.52 and 0.54 FTE/1000 m2.
The highest Wages and salaries were estimated for the two- and five-floor PRC-frame buildings; the values were 16.53 and 17.89 EUR/m2. Meanwhile, the wages and salaries for two- and five-floor GLT frame buildings were 2.45- and 2.38-fold lower; these vakues were 6.94 and 7.29 FTE/1000 m2.
There were notable differences regarding the number of Occupational accidents when producing analyzed frames. To produce two- and five-floor PRC-frame buildings, 0.788 and 0.855 cases/1000 m2 were estimated. Accordingly, to produce two- and five-floor GLT-frame buildings, 0.012 and 0.011 cases/1000 m2 were calculated. The most important process influencing the rate of accidents was transportation distance and a lower wood-based materials weight, compared to concrete-based materials.

3.4. Economic Impacts of Wood- and Concrete-Based Frame Buildings

We analyzed the economic indicator Product price (Table 6). Results showed that the production of one cubic meter of GLT is twice as expensive as the production of PRC (471 and 241 EUR/m3, prices in 2017). However, the production price of two- and five-floor GLT-frame buildings is lower (48.05 and 46.93 EUR/m2) compared to the same PRC frames (74.00 and 68.68 EUR/m2). This is because the number of materials needed to produce two- and five-floor GLT-frame buildings is three times lower compared to PRC frames of the same price (see Table 2, Table 3, Table 4 and Table 5).

3.5. CO2 Emissions of Wood- and Concrete-Based Frame Buildings

A CO2 emission comparative analysis was carried out for two- and five-floor GLT and PRC-frame buildings (Table 7). Overall, the CO2 emissions of a two-floor frame building are reduced from 159.12 to 66.89 tC when a GLT frame construction is used as an alternative to a PRC-frame construction. Accordingly, CO2 production for a five-floor frame building is reduced from 418.18 to 171.98 tC.
Due to the Carbon storage properties of GLT, a two-floor GLT frame building stores 17.55 tC, meanwhile, a five-floor GLT frame building stores 48.39 tC. Thus, when compared, it is evident that GLT-frame construction offers a remarkably lower carbon emission output than PRC-frame construction.

4. Discussion

4.1. Sustainability Impacts of Wood- and Concrete-Based Frame Buildings

The results presented in this research article were collected during the BenchValue project (http://benchvalue.efi.int, accessed on 8 January 2023). The research aims of this study were as follows: (i) to design two- and five-floor wood- and concrete-based public building frames for a “traditional building”, (ii) to quantify and to compare the sustainability impacts of wood- and concrete-based public building frames, and (iii) based on these findings, provide policy recommendations for GLT and PRC use in the construction sector.
The main results of this study showed the advantages of constructed GLT-frame buildings over PRC-frame buildings in terms of various sustainability measures. This is especially relevant for environmental indicators: GHG emissions, Generation of waste, Water consumption, Energy consumption, Volume of non-renewable materials, Carbon inflow into the pool, WDF (GLT and ST). The results showed that the use of GLT-frame buildings can reduce carbon and transportation emissions during transportation to the construction site. This was also found by previous research [53].
Sathre and O’Connor [51] provided analyses of 21 different international studies of wood-based products displacement factors, compared with non-wood-based products. The average displacement factor was 2.1, while the ranges were from −2.30 to 15.00. A meta-analysis for structural constructions, performed by Leskinen et al. [54], presents displacement factors ranging from 0.9 to 5.5 tC/tC. A meta-analysis for structural constructions, performed by Myllyviita et al. [55], also presents comparable displacement factors ranging from 0.16 to 9.56 tC/tC. Knauf et al. [45] presented the displacement factor for softwood-based glued timber products (GLT, CLT) vs. steel, concrete, and bricks in Germany; this was 1.3 and corresponds to our study results (1.43 and 1.34 for two building alternatives). In Finland, 1.1 displacement factors were found for sawn wood and plywood in building construction [56]. Härtl et al. [57] presented a displacement factor for sawn logs, used in construction in Germany, that was 1.66. Some cases show negative values for displacement factors [39,58,59]. In general, our findings are in line with the previous findings of other researchers. For example, Gustafsson et al. [60] came to conclusion that wood-frame building constructions consume less energy, and emit less CO2 into the atmosphere, than concrete-frame constructions. In addition, the life cycle emission difference ranges from 30 to 130 kgC/m2 of floor area [60]. The results of Dodoo et al. [61], Nässén et al. [36] and Yadav et al. [62] also confirmed that a wood-framed building has remarkably lower life-cycle carbon emissions than a concrete-framed building. The use of wood-based building materials can be of benefit to resource-efficient systems with a low environmental impact [31]. The results of the cradle-to-grave assessment show that the timber-frame building, compared to concrete-masonry, generated the lowest impact in indicators such as GWP, human toxicity, ozone depletion potential, and acidification potential; however, it yielded the highest impact oneutrophication potential [63]. Finally, the aggregated results of Saade et al. [35], from eight previous case studies evaluating climate change potential, showed that wood-framed buildings performed better than concrete-framed buildings in all sustainability comparisons. Despite a remarkable number of studies concerning wooden and PRC building frames, and the life-cycle assessment, Cabeza et al. [37,64] argues that most-life cycle assessment studies were carried out with exemplary low energy buildings and there are very few studies on traditional buildings. Thus, our study focuses on this gap by providing valuable results regarding traditional low-rise public-type buildings.
The detailed planning of the selected buildings with GLT and PRC frames was performed by the professional architects. Thus, the amounts of material estimated for each building are realistic and based on detailed estimations (Supplementary Material S1–S4). As this study focuses upon simplistic low-rise public building designs, results should be easy to apply in countries of similar economic development. Further, it is worth highlighting that the assessment was performed on the sustainability of steps preluding the production phase (A1–A3); this was the largest contributor to full life-cycle impacts [65].

4.2. Benefits at the National Level

The strategic long-term vision of the European Commission for climate neutrality up to 2050, as well as the emissions reduction target from the current 40% to at least 55%, compared with 1990 levels, raises challenges for its member states [6].
Lithuania ratified the Paris Agreement in 2016, making a commitment to a 40% reduction in GHG emissions within all sectors of the economy by 2030 [7]. In detail, Lithuania was responsible for 20.6 MtCO2eq. of emissions in 2019, or 0.55% of total EU emissions that year [66]. Of the combined 20.6 MtCO2eq., energy industries produced 11%, manufacturing industries and construction produced 6%, industrial processes produced 16%, agriculture produced 21%, transport produced 31%, waste management produced 4% and others produced 12%. To reach the aforementioned targets, a remarkable number of policy measures are listed in the Lithuanian NECP; however, surprisingly few targets have been applied to the construction sector. For example, Hildebrandt et al. [24] assessed that the European building sector has a potential for a net carbon storage of approximately 46 million tons of CO2-eq. per year in 2030.
However, the lack of strategy and policies, relating to the bioeconomy, are probably some of the main reasons why opportunities to promote the local bioeconomy and simultaneously fulfil national commitments to cutting GHG emissions are being missed in Lithuania. To show the possible losses, we tried to upscale our findings to the national level. Since we do not have the average WDF for the Lithuanian construction sector, we calculated the WDF value (1.39) of GLT buildings substituted in place of PRC buildings; then, we adopted three possible assumptions for the increase in the Lithuanian annual market share of wood in structural frames of multi-floor residential buildings: (a) 1%, (b) 5%, (c) 20%. In 2018, the total area of newly-built multi-floor residential buildings was 0.315 million m2. Replacing 1% of the non-wood material-based building area with wood-based buildings would require approximately 3087 m3 of round wood or 1260 m3 of wood products (0.4 m3/m2 of wood needed according to Sathre and O‘Connor [51]), with a total 876 tC substitution value. To displace 5% of area annually, 15435 m3 of round wood or 6300 m3 of wood products are needed, with a total substitution value of 4378 tC. To displace 20% of the area covered by non-wood material-based building, 61740 m3 round wood or 25200 m3 of wood products are needed, with a total 17514 tC substitution value. These numbers would make 1.3, 6.5 and 6.1% of the GHG emissions assigned to the category of “manufacturing industries and construction” in 2019. The roundwood harvests in Lithuania totaled 6.9 million m3 in 2019, of which 1.26 million m3 was suitable for sawn wood production in Lithuania [10]. Considering that the accumulated volume increment part for final cutting in pine forests is 3 m3/ha, and in spruce forests is 4.1 m3/ha per year [8], 3087 m3, 15435 m3 and 61740 m3 of round wood could be restored in 1029, 5145 and 20580 hectares of pine forests or 753, 3765 and 15059 hectares of spruce forests.
More remarkable figures would be estimated if not only the frames, but also the walls of buildings would be displaced by wood-based materials. In addition, different building material (e.g., steel, bricks, silicate block) WDF value calculations are crucial to providing a more detailed and accurate view of wood-based buildings, substituted in place of non-wood building alternatives.
Further research must be conducted on the evaluation of economic indicators and especially the gross value-added EUR per m2. It would also be useful to perform the case study analysis with taller buildings. However, this could not be performed without a remarkable increase in the building design and planning costs.

4.3. Policy Recommendations Based on Our Study and Stakeholders’ View

Based on the stakeholder workshop held in Kaunas, 2018, the main findings of the construction sector wood-use sustainability impact assessment, suggest the following recommendations that are relevant to policy makers: (i) to create a monitoring system and a database on material use in the construction sector, (ii) to promote negative emission technologies, for example, carbon storage in wood-based construction, (iii) to initiate regulations for the public sector in order to promote building materials that have the lowest environmental impacts, (iv) to strengthen the education of the public, architects, designers and the construction industry on the environmental benefits of wood products, (v) to develop the national Bioeconomy Strategy, including the construction sector.

5. Conclusions

The two- and five-floor, and concrete-based public building frames for a “traditional building”, were designed by the professional architect; a sustainability impact assessment was performed by this study considering the environmental, social and economic indicators. An analysis of the environmental indicators shows that the replacement of PRC frames with GLT frames, in low-rise public-type buildings, would have lower environmental impacts; these would include lower greenhouse gas emissions, lower Waste in total, and lower Water consumption and Energy consumption rates.
However, while analyzing the social impacts, it was found that the highest employment levels, as well as wages and salaries, were estimated for the two- and five-floor PRC-frame buildings. We did not find remarkable differences regarding the occupational accidents.
An analysis of economic impacts and its indicator production price, revealed that the production of one cubic meter of GLT is twice as expensive as the production of PRC; however, the production price per one square meter of the two- and five-floor GLT-frame buildings is lower compared to the same PRC frames; this is due to the number of materials needed to produce two- and five-floor GLT-frame buildings.
The wood displacement factor for the two- and five-floor GLT frame buildings was 1.43 and 1.34 tC/tC. The two-floor GLT frame building stored 17.55 tC; meanwhile, a five-floor GLT frame building stored 48.39 tC.
Therefore, wood, as a national renewable resource, should be one of the key components in increasing the sustainability of the local construction sector. In Lithuania, the construction wood-based public low-rise buildings are still at the stage of society, policy, and political discussions. Therefore, we propose the following recommendations for policy makers: (i) to create a monitoring system for material use in the construction sector, (ii) to promote negative emission technologies, (iii) to initiate the required regulations in the public sector, (iv) to strengthen the education of the public, architects, designers, and the construction industry, and (v) to develop the national Bioeconomy Strategy.
In addition, although the authors acknowledge that the presented results of the study are country specific, they could be relevant in countries with comparable economic development levels to Lithuania.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/su15021560/s1. And detailed architectural drawings S1–S4, Restrictions apply to the availability of these data.

Author Contributions

Conceptualization, E.L., P.Ž. and M.A.; methodology E.L. and P.Ž.; validation E.L., P.Ž. and M.A.; investigation E.L. and P.Ž.; formal analysis E.L. and P.Ž.; data curation E.L. and P.Ž.; writing—original draft preparation E.L., P.Ž. and M.A.; writing—review and editing E.L., P.Ž. and M.A.; visualization E.L. and P.Ž.; project administration M.A.; funding acquisition E.L., P.Ž. and M.A. All authors have read and agreed to the published version of the manuscript.

Funding

The study was supported by the Ministry of Environment of the Republic of Lithuania in the frame of EU program 7BP ERA-NET SUMFOREST project BenchValue (2017–2019). This paper partly presents the findings obtained through the Long-term Research Programme “Sustainable Forestry and Global Changes” implemented by the Lithuanian Research Centre for Agriculture and Forestry (LAMMC).

Acknowledgments

The authors would also like to express their gratitude to the anonymous reviewers for their valuable and constructive comments. The authors would like to thank MSc Emilis Armoška (LAMMC) for valuable comments and checking the language of this manuscript.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. The topology of wood-based construction materials (sawn timber and glue-laminated timber) value chains. The value chain starts with the total growing volume of the forest and ends with the transport of the final construction materials (GLT and ST) to the building site (17 processes in total). The arrows linking processes represent the material flow for one cubic meter of final construction material.
Figure 1. The topology of wood-based construction materials (sawn timber and glue-laminated timber) value chains. The value chain starts with the total growing volume of the forest and ends with the transport of the final construction materials (GLT and ST) to the building site (17 processes in total). The arrows linking processes represent the material flow for one cubic meter of final construction material.
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Figure 2. The topology of concrete-based construction materials (site-cast concrete and precast reinforced concrete) value chains. The value chain starts with resource extraction and ends with transport of final construction materials to the building site (26 processes in total). The arrows linking processes represent the material flow for one cubic meter of final construction material. C8-10, C20-25, C25-30, C30-37 represent different strength class site-cast concrete.
Figure 2. The topology of concrete-based construction materials (site-cast concrete and precast reinforced concrete) value chains. The value chain starts with resource extraction and ends with transport of final construction materials to the building site (26 processes in total). The arrows linking processes represent the material flow for one cubic meter of final construction material. C8-10, C20-25, C25-30, C30-37 represent different strength class site-cast concrete.
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Figure 3. The wooden frame building structure and frame design for (A) two-floor and (B) five-floor public wooden frame building. K25 × 25–GLT column (250 mm); K32 × 32–GLT column (320 mm); PSPS220 × 360–GLT ceiling main perimeter beam; PSPV220 × 440–GLT ceiling main beam; PSSG220 × 320–GLT ceiling perimeter side beam; PSSV200 × 360–GLT ceiling side beam; Per_20–PRC stair landing (200 mm thick); Plokste25–PRC stair slab (average thickness 250 mm); ROS250 × 500–Reinforced concrete foundation beam; SSPS220 × 320–GLT roof main perimeter beam; SSPV200 × 400–GLT roof main beam; SSSG220 × 280–GLT roof perimeter side beam; SSSV200 × 320–GLT roof side beam; Siena_25–SCC stairwell/elevator shaft wall (250 mm thick); TRON 88 × 5–Round hollow bracing system pipe (88 mm diameter × 5 mm thick). Floor slab system consists of solid timber beams 64 × 150 mm + floorboards + thermal/acoustic isolation + floor decoration.
Figure 3. The wooden frame building structure and frame design for (A) two-floor and (B) five-floor public wooden frame building. K25 × 25–GLT column (250 mm); K32 × 32–GLT column (320 mm); PSPS220 × 360–GLT ceiling main perimeter beam; PSPV220 × 440–GLT ceiling main beam; PSSG220 × 320–GLT ceiling perimeter side beam; PSSV200 × 360–GLT ceiling side beam; Per_20–PRC stair landing (200 mm thick); Plokste25–PRC stair slab (average thickness 250 mm); ROS250 × 500–Reinforced concrete foundation beam; SSPS220 × 320–GLT roof main perimeter beam; SSPV200 × 400–GLT roof main beam; SSSG220 × 280–GLT roof perimeter side beam; SSSV200 × 320–GLT roof side beam; Siena_25–SCC stairwell/elevator shaft wall (250 mm thick); TRON 88 × 5–Round hollow bracing system pipe (88 mm diameter × 5 mm thick). Floor slab system consists of solid timber beams 64 × 150 mm + floorboards + thermal/acoustic isolation + floor decoration.
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Figure 4. The reinforced concrete frame building structure and frame design for (A) two-floor and (B) five-floor public reinforced concrete frame building. K30 × 30–PRC column; Per_20–PRC stair landing (200 mm thick); Plokste25–PRC stair slab (average thickness 250 mm); R300 × 400–Rectangle cross-section PRC perimeter side beam; R500 × 400–L cross-section PRC main perimeter beam; R700 × 400–Upside-down T cross-section PRC main beam; ROS250 × 500–reinforced concrete foundation beam; Siena_25–reinforced concrete stairwell/elevator shaft wall (250 mm thick); TRON 88 × 5–round hollow bracing system pipe (88 mm diameter × 5 mm thick). Floor slab system consists of prefabricated 200 mm thick prestressed reinforced concrete hollow core panels + thermal/acoustic isolation + 60 mm thick fiber-reinforced concrete levelling layer + floor decoration.
Figure 4. The reinforced concrete frame building structure and frame design for (A) two-floor and (B) five-floor public reinforced concrete frame building. K30 × 30–PRC column; Per_20–PRC stair landing (200 mm thick); Plokste25–PRC stair slab (average thickness 250 mm); R300 × 400–Rectangle cross-section PRC perimeter side beam; R500 × 400–L cross-section PRC main perimeter beam; R700 × 400–Upside-down T cross-section PRC main beam; ROS250 × 500–reinforced concrete foundation beam; Siena_25–reinforced concrete stairwell/elevator shaft wall (250 mm thick); TRON 88 × 5–round hollow bracing system pipe (88 mm diameter × 5 mm thick). Floor slab system consists of prefabricated 200 mm thick prestressed reinforced concrete hollow core panels + thermal/acoustic isolation + 60 mm thick fiber-reinforced concrete levelling layer + floor decoration.
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Table 1. Indicators used in the study. The table contains indicators definition and units.
Table 1. Indicators used in the study. The table contains indicators definition and units.
No.IndicatorUnitDefinition
Environmental
1.GHG emissionst CO2eq./m2Emissions expressed as GWP for 100 years. Values for CO2eq. were selected as presented in [49]. CO2, CH4, N2O emissions are converted to the CO2eq. by using GWP factors: CO2 = 1, CH4 = 25, N2O = 298. All emissions throughout value chain processes were included in calculation.
2.Energy consumptionMJ/m2All energy used in processes. This includes diesel, CNG, electricity from grid and heat. Conversion factors were used as presented in [50].
3.Water consumptionm3/m2Total freshwater intake by industry throughout value chain processes.
4.Generation of wastet/m2Generation of hazardous and non-hazardous waste in tons per reporting unit.
5.Volume of non-renewable materialst/m2Total volume of extracted non-renewable material throughout value chain processes.
6.Carbon inflow into the pooltC/m2Biogenetic carbon storage in the wood [definition presented in 49]. Carbon capture and storage in cement were not calculated.
7.WDF (GLT)tC/tCWDF definition used as presented in Sathre and O’Connor [51]. The indicator is a measure of tC emission reduction per tC contained in wood products.
Social
8.EmploymentFull time equivalent (FTE)/unitNumber of persons (expressed as FTE) employed in total throughout value chain processes per production unit.
9.Occupational accidentsCases/m2Total number of fatal and non-fatal occupational accidents. In this study indicator was calculated per 1000 employees per reporting unit (m2).
10.Wages and salariesEUR/m2Total wages and salaries (EUR) per reporting unit.
Economic
11.Product priceEUR/m2Average production price (EUR).
Table 2. The two-floor wooden frame construction elements and materials used chart.
Table 2. The two-floor wooden frame construction elements and materials used chart.
Construction ElementsMaterial
C8-10 (m3)C20/25 XC2 (m3)C25-30 XC2 (m3)C30-37 X0 (m3)Rebar S500 (t)Joints Steel S355 (t)GLT GL28h (m3)ST
C24 (m3)
Drilled piles foundation-16.03--2.56---
Basis for pile caps3.26-------
Pile caps-12.22--1.220.30--
Plinth beam--9.71-1.160.96--
First floor columns-----2.674.32-
Walls shaft for lift and stairs---41.474.150.20--
First floor beams-----0.5017.35-
First floor joist beams and decking beams-------13.94
Second floor columns-----1.584.12-
Steel (S355) joints-----0.79--
Second floor beams-----0.5015.48-
Second floor ceiling beams and decking beams-------14.99
Total material3.2628.259.7141.479.107.5041.2728.93
Table 3. The five-floor wooden frame construction elements and materials used chart.
Table 3. The five-floor wooden frame construction elements and materials used chart.
Construction ElementsMaterial
C8-10 (m3)C20/25 XC2 (m3)C25-30 XC2 (m3)C30-37 X0
(m3)
Rebar S500
(t)
Joints Steel S355 (t)GLT GL28h (m3)ST
C24 (m3)
Drilled piles foundation-48.06--7.45---
Basis for pile caps--4.56-----
Pile caps--23.94-2.390.40--
Plinth beam--9.33-1.120.96--
First floor columns-----3.597.38-
Walls shaft for lift and stairs---121.8812.191.00--
First-fifth floor beams-----2.1272.46-
First-fifth floor joist beams and decking beams-------55.77
Second-fifth floor columns-----9.6027.52-
Steel (S355) joints-----3.15--
Fifth floor beams-----0.5015.48-
Fifth floor ceiling beams and decking beams-------14.99
Total material0.0048.0637.82121.8823.1521.32122.8470.75
Table 4. The two-floor PRC-frame construction elements and material used chart.
Table 4. The two-floor PRC-frame construction elements and material used chart.
Construction ElementsMaterial
C8-10
(m3)
C20/25 XC2
(m3)
C25-30 XC2
(m3)
C30-37 X0
(m3)
Rebar
S500
(t)
Joints Steel S355
(t)
Precast Reinforced Concrete Material
First floor columns---8.830.881.44
First floor beam header---19.762.371.26
First floor supported slab---39.901.99-
Second floor columns---7.580.761.44
Second floor beam header---20.132.421.26
Second floor joist slab---43.052.15-
Subtotal material---139.2610.585.40
Site-cast concrete material
Drilled piles foundation-25.64--4.10-
Basis for pile caps3.66-----
Pile caps--13.66-1.370.36
Plinth beam--10.09-1.210.96
First floor columns monolitization---0.44--
First floor steel joints-----0.68
Walls shaft for lift and stairs---28.902.891.20
Monolitization of supported slab---4.500.45-
First floor topping of supported slab--21.60-0.53-
Monolitization of the columns---0.44--
Steel joints-----0.68
Monolitization of joint slabs---4.700.47-
Subtotal material3.6625.6445.3538.9811.023.88
Total material3.6625.6445.35178.2421.609.28
Table 5. The five-floor PRC-frame construction elements and material used chart.
Table 5. The five-floor PRC-frame construction elements and material used chart.
Construction ElementsMaterial
C8-10 (m3)C20/25 XC2 (m3)C25-30 XC2
(m3)
C30-37 X0
(m3)
Rebar S500
(t)
Joints Steel S355
(t)
Precast Reinforced Concrete Material
First floor columns---8.830.881.44
First-fourth floor beam header---97.059.495.04
First-fourth floor supported slab---177.609.78-
Second-fourth floor columns---22.322.234.32
Fifth floor column---7.580.761.44
Beam header---20.132.421.26
Joist slab---43.052.15-
Subtotal---376.5727.7113.50
Site-cast concrete material
Drilled piles foundation-25.64--4.102-
Basis for pile caps-9.97----
Pile caps--55.82-5.5820.48
Plinth beam--10.09-1.210.96
First floor columns monolitization---0.444--
First floor steel joints-----0.68
Walls shaft for lift and stairs---106.510.653.0
Second-fourth floor supported slabs topping--86.40-2.12-
Second-fifth floor columns monolitization---1.824--
Steel joints-----2.72
Monolitization of joint slabs---4.70.47-
Subtotal-35.61152.31113.4724.137.84
Total-35.61152.31490.0451.8421.34
Table 6. Environmental, social and economic indicators values (calculated per useful floor area (m2)). Indicators values calculated by using ToSIA model. Results presented for two- and five-floor GLT-frame buildings, and two- and five-floor PRC-frame buildings.
Table 6. Environmental, social and economic indicators values (calculated per useful floor area (m2)). Indicators values calculated by using ToSIA model. Results presented for two- and five-floor GLT-frame buildings, and two- and five-floor PRC-frame buildings.
IndicatorUnitsTwo-Floor
GLT
Five-Floor
GLT
Two-Floor
PRC
Five-Floor
PRC
Environmental
GHG emissionst CO2eq/m20.08740.08990.20800.2190
Generation of wastet/1000 m20.00090.00100.00260.0026
Water consumptionm3/m20.230.240.850.84
Energy consumptionMJ/m2510.0518.01482.01519.0
Volume of non-renewable materialst/m20.3270.3330.9701.030
Carbon inflow into the pooltC/m20.02750.030400
WDF (GLT and ST)tC/tC1.431.3400
Social
EmploymentFTE/1000 m20.520.541.301.41
Wages and salariesEUR/m26.947.2916.5317.89
Occupational accidentsCases/1000 m20.0120.0110.7880.855
Economic
Production priceEUR/m248.0546.9374.0068.68
Table 7. Total CO2 emissions produced and conserved in two- and five-floor GLT and PRC-frame buildings.
Table 7. Total CO2 emissions produced and conserved in two- and five-floor GLT and PRC-frame buildings.
Building TypeConcrete-Based Building, tCWood-Based Building, tCC Contained in the Wood-Based Frame Building, tCC Contained in Concrete-Based Frame Building, tC
Two-floor (765 m2)159.1266.8917.550.00
Five-floor (1913 m2)418.18171.9848.390.00
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Linkevičius, E.; Žemaitis, P.; Aleinikovas, M. Sustainability Impacts of Wood- and Concrete-Based Frame Buildings. Sustainability 2023, 15, 1560. https://doi.org/10.3390/su15021560

AMA Style

Linkevičius E, Žemaitis P, Aleinikovas M. Sustainability Impacts of Wood- and Concrete-Based Frame Buildings. Sustainability. 2023; 15(2):1560. https://doi.org/10.3390/su15021560

Chicago/Turabian Style

Linkevičius, Edgaras, Povilas Žemaitis, and Marius Aleinikovas. 2023. "Sustainability Impacts of Wood- and Concrete-Based Frame Buildings" Sustainability 15, no. 2: 1560. https://doi.org/10.3390/su15021560

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