The air emission assessment of a South Korean traditional building during its life cycle

Building and Environment 105 (2016) 283e294

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Building and Environment journal homepage: www.elsevier.com/locate/buildenv

The air emission assessment of a South Korean traditional building during its life cycle Jaehun Sim a, Jehean Sim b, * a b

Busan Techno-Park, Center for Integrated Logistics Management, Busan, Republic of Korea Department of Architecture, Pusan National University, Busan, Republic of Korea

a r t i c l e i n f o

a b s t r a c t

Article history: Received 12 March 2016 Received in revised form 25 May 2016 Accepted 6 June 2016 Available online 8 June 2016

During its entire life cycle, a Korean traditional building produces various types of air emissions from the building material production, construction, operation, maintenance, demolition, and recycling and disposal stages, along with related transportation activities. This study investigates the life cycle air emissions of a building of this type located in Seoul, South Korea. The results of this study demonstrate that it produces 143,843.7 kg of CO2, 1466.01 kg of CO, 686.22 kg of NOX, 475.99 kg of SO2, 280.59 kg of NMVOC, 274.44 kg of CH4, and 1.26 kg of N2O during its 30-year life span. In comparison with an apartment building, a traditional building significantly reduces about 98% of CO, 87% of CO2, 78% of CH4, 62% of NOX, 45% of N2O, and 36% of SO2, except NMVOC emissions, in terms of life cycle air emission productivity. In addition, an environmental impact analysis of the building materials used finds that the roof tile has the largest impact on global warming potential, while the cement has the largest impact on ozone depletion potential. © 2016 Elsevier Ltd. All rights reserved.

Keywords: Air emission Air emission productivity Environmental impact analysis Energy simulation

1. Introduction Since the international Kyoto Protocol treaty talks, the South Korean government has realized its responsibility for decreasing the annual carbon emissions in major industries, as this nation is the ninth largest source of carbon emission in the world [1]. To fulfill its responsibility, the South Korean government has assigned specific carbon emission reduction targets to each industry [2]. At the national level, the construction industry in particular consumes about 40% of the total raw materials and about 30% of the total energy [3]. Within the construction industry, the building sector contributes a large portion of the total carbon emissions produced. As a result, the South Korean government has established and implemented various polices to achieve a 48 million ton carbon emission reduction in the building sector by the year 2020 [4]. Residential buildings are major consumers of raw materials and energy, as well as producers of carbon emissions during their life cycle. Therefore, most efforts to mitigate the environmental impact of the entire building sector focus on the residential building segment [5]. Through the life cycle assessment approach, the

* Corresponding author. Pusan National University, Department of Architecture, Busandaehak-ro 63 beon-gil, Geumjeong-gu, Busan, 609-735, Republic of Korea. E-mail address: [email protected] (J. Sim). http://dx.doi.org/10.1016/j.buildenv.2016.06.007 0360-1323/© 2016 Elsevier Ltd. All rights reserved.

environmental impacts of a residential building in South Korea are usually investigated in terms of energy consumption and carbon emission production in the five stages of the life cycle of a residential building e building material production, building construction, building operation, building demolition, and building material recycling and disposal e along with related transportation activities [6]. In addition to enacting various policies to decrease carbon emissions in the building sector, the South Korean government has recently promoted the potential of the traditional Korean building, or Han-ok, as an eco-friendly building. This type of building is constructed primarily by manpower with natural building materials e clay, stones, and wood e and is based on a passive solar design [7]. Since the surface area of the Korean peninsula is mainly covered by mountains, traditional buildings have been built in harmony with Korea’s natural and geographical characteristics at the site, with rivers to the front and mountains to the back [8]. Called Hanok, the house is a single-story timber framework building, elevated on an architrave stone block to protect the building from rainwater and moisture, with a multilayered timber roof covered by baked brick tiles [8]. The cooled spaces provide a cool indoor climate with a well-ventilated timber floor and high ceilings for summer, while the heated spaces provide a warm indoor climate with a traditional floor heating system for winter [8]. Since this is an eco-friendly

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building in terms of architectonic methods, building materials, and landscaping techniques, the South Korean government has recently made an effort to revitalize interest in this type of building as an alternative for new residential building [7]. Due to the South Korean government’s concerns about carbon emissions, most of the existing research has focused on carbon emissions produced from the building sector. To date, little research has been conducted specifically to investigate a Korean traditional building’s air emissions from the life cycle perspective. However, the studies that have been conducted indicate the production of not only carbon emissions but also other air emissions to the atmosphere, namely carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), nitrogen oxides (NOX), sulphur dioxide (SO2), nonmethane volatile organic compounds (NMVOC), and nitrous oxide (N2O), during the entire life cycle. The first step toward mitigating the environmental impact of the residential sector as a whole is to quantify the environmental impacts of various types of residential buildings [6]. Thus, the objective of this study is to analyze seven types of air emissions in the entire life cycle of a traditional building in South Korea, from a building production stage to a building material disposal and recycling stage, including transportation activities. By comparing the amount of air emissions between an apartment building and a traditional house, this study will provide the amount of air emission reduction possible by replacing the construction of apartment buildings in Korea with the more traditional and eco-friendly alternative. Further, this study can be used as reference data for environmental policy makers to estimate air emission quantity generated from the traditional buildings and to expedite the construction of more of these to improve the sustainability of the residential sector. 2. Literature review A review of relevant research has been conducted to evaluate the environmental impacts of a wood frame building over its entire life cycle. In respect to energy consumption and greenhouse emissions, two studies indicate that a wood frame building generally consumes lower embodied energy and generates fewer carbon emissions than concrete or steel frame buildings. Furthermore, the results of these studies indicate that a concrete frame building consumes about 60%e80% higher total energy than a wood frame building at a building material production stage [9], while the wood frame building produces 20%e25% fewer total greenhouse emissions than the concrete frame building and the steel frame building [10]. In respect to the energy consumption and carbon emissions of a timber building, several studies indicate that a timber building generally consumes less energy and produces less carbon emissions than a non-timber building [11e15]. Not only does the wood frame building produce fewer carbon emissions than the concrete frame building, but there is also no cost difference between wood materials and concrete materials [16]. Among three types of timber buildings e a cross-laminated timber building, a beam-and-column building, and a prefabricated module building, the beam-andcolumn building contributes the largest impact on total carbon emissions, while the cross-laminated timber building has the least impact on total carbon emissions [17]. In the context of South Korea, most research on the environmental impacts of residential buildings focuses on the carbon emissions generated from apartment buildings [18e20]. However, other studies have looked at emissions in non-residential buildings. For example, one study investigated the environmental impacts of an elementary school, considering global warming, ozone layer depletion, acidification, eutrophication, photochemical ozone

creation, abiotic depletion, and human toxicity [6]. Using the concept of life cycle air emission productivity, one study looking at seven types of air emissions generated from an apartment building during its entire life cycle finds that carbon emissions are the major source of air pollution and that nitrous oxides are the smallest source [21]. To date, little research has been conducted in terms of the environmental impacts specifically of the Korean traditional building. One study comparing three types of residential dwellings in terms of energy requirements and carbon emissions finds that the apartment building has a larger amount of carbon emissions per unit building than a single-family house or a Han-ok [22]. By only investigating greenhouse gas of a Korean traditional building, one study indicates that natural gas for heating is the major source of consumption, accounting for about 70% of total greenhouse gas production [7]. A review of the relevant literature on air emissions from wood frame buildings shows that most of the research does not include the entire life cycle of a building, from building material production to building material disposal. In South Korea, the research focuses on the environmental impact of buildings in terms of carbon emissions. In order to further the South Korean government’s goal of improving the sustainable practices of the residential building industry, it is useful to comprehensively investigate the entire life cycle of a traditional building in terms of seven types of air emissions, along with the environmental impact analysis in the context of South Korea. 3. Methodology To estimate the life cycle air emission productivity during the life cycle of a traditional residential building, this study investigates the quantity of seven types of air pollutants e carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), nitrogen oxides (NOX), sulphur dioxide (SO2), non-methane volatile organic compounds (NMVOC), and nitrous oxide (N2O). These seven types of air pollutants are emitted from the six stages of the life cycle e building material production, construction, operation, maintenance, demolition, and material recycling and disposal, along with associated transportation activities. In the life cycle air emission assessment, this study utilizes an attributional life cycle approach which investigates consumption-based emissions using average emission intensity data to gain an understanding of a system [23]. Based on the air emission estimation methodology from the Sim, Sim and Park study of a Korean apartment building [21], this study first investigates the amount of air emissions produced at each stage of the life cycle of a Korean traditional building over its 30-year life span by multiplying an amount of energy consumed in an activity by an air emission density factor of required energy in an activity at each stage of the entire life cycle. In the next step, the life cycle air emission productivity is calculated using the total air emissions generated and the economic value of the traditional building. In the last step, this study utilizes the life cycle assessment software to analyze the environmental impact analysis of the building material used. 3.1. Description of a case study In order to exemplify the application of the air emission estimation method in the case of a traditional building, this study considers one with traditional mud-plaster walls located in the Bukchon Han-ok village in Seoul. This Han-ok consists of two buildings with two main halls, five bedrooms, one kitchen, and two bathrooms over the area of 77.13 m2, while each building has 4.9 m of height, 3.6 m of width, and 11.1 m of length [7]. The plane

J. Sim, J. Sim / Building and Environment 105 (2016) 283e294

drawing of the building under the case study is shown in Fig. 1. The basic information for the Korean traditional building is summarized in Table 1. Based on the previous studies, the basic information on thermal characteristics for the traditional building is summarized in Table 2. It is assumed that the building under the case study has a 3.5 W/ m2 K of U-value for an external mud-plaster wall [24], a 1.64 W/ m2 K of U-value for a separation wall, a 0.21 W/m2 K of U-value for a wooden window, and a 2.4 W/m2 K of U-value for a wooden frame door [25], along with a natural ventilation.

Table 1 The basic information for the building of the case study. Building specification

Value

Building specification

Value

Area Structure Envelope Aboveground storey

77.13 m2 Wood Mud-plaster 1

Height Width Length Service life

4.9 m 3.6 m 11.1 m 30 years

Table 2 The thermal characteristics for the Korean traditional building (Source: [25]). Thermal specification

3.2. Life cycle air emission assessment The total air emissions of seven types of air emissions produced during the building’s life cycle AHO, are calculated by the summation of air emissions at the stage of construction material production AHO,P, building construction AHO,C, building operation AHO,O, building maintenance AHO,M, building demolition AHO,D, and building material recycling and disposal, AHO,R as following. At each stage, the seven types of air emissions are calculated by multiplying the consumption of energy required for an activity by the air emission density of energy used in that activity.

AHO ¼ AHO;P þ AHO;C þ AHO;O þ AHO;M þ AHO;D þ AHO;R

AHO;P ¼

(1)

285

Roof External wall Separating wall Internal floor Ground floor

Value 2

0.32 W/m K 3.5 W/m2 K 1.64 W/m2 K 0.22 W/m2 K 0.22 W/m2 K

Thermal specification

Value

Windows Doors Air infiltration Natural ventilation

2.1 W/m2 K 2.4 W/m2 K 1.9 ac/h 10 ac/h

of the energy used in the production activity. The air emissions of construction material production AHO,P, are estimated as shown in Equation (2). In the transportation activity associated with this stage, the seven types of air emissions are estimated by multiplying the energy consumption of each truck type by the air emission density of energy type over the traveled distance. The number of trucks required is estimated by dividing the total amount of volume transported by truck capacity in Equation (2).

X

air emission density of product type  production of product type ðkgÞ X þ air emission density of truck type ðkg air emission=kmÞ  the required number of truck type  distance ðkmÞ (2)

3.2.1. Building material production In the building material production phase, ten types of construction materials are considered: baked roof tile, cement, clay, concrete, granite, gravel, sand, steel, stone, and wooden materials [7]. Seven types of air pollutants are generated in the process of building material production, which includes the transportation activities of construction materials from each manufacturer site to a construction site. The densities of seven types of air emissions from the major construction materials are tabulated in Table 3. In this stage, the seven types of air emissions of each building material are calculated by multiplying the energy consumption required to manufacture each material by the air emission density

In the transportation activity, the air emissions are produced from the diesel fuel consumption of the trucks used. It is assumed that a concrete truck consumes 0.41 l/km of diesel fuel for the transportation of concrete from a concrete manufacturer site to a construction site. An 8-ton truck consumes 0.22 l/km of diesel fuel for the transportation of cement and steel products from each manufacturer site to a construction site. A 20-ton trailer consumes 0.32 l/km of diesel fuel for the transportation of other building materials from a manufacturer site to a construction site. The density of seven types of air emissions of three energy sources e diesel, electricity, and natural gas e are tabulated in Table 4.

Fig. 1. The plane drawing of the traditional building under the case study.

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Table 3 The air emission density of major construction materials (Source: [27]). Material

CO2

CH4

N2O

SO2

CO

NOX

NMVOC

Baked roof tile (kg/kg) Cement (kg/kg) Clay (kg/kg) Concrete (kg/m3) Granite (kg/m3) Gravel (kg/m3) Sand (kg/m3) Steel (kg/kg) Wood (kg/kg)

0.2387 1.049 3.45E-06 419.57 11.15 5.02 3.58 0.34,047 0.01382

0.00025 0.00034 1.87E-06 0.44,378 0.00809 0.00364 0.00272 0.00056 0.00001

6.79E-06 1.58E-06 9.76E-08 0.00069 0.00003 0.00002 0.00075 0.00101 4.12E-08

0.00027 0.0003 4.31E-06 0.26,173 0.00012 0.00006 0.00066 0.00001 4.50E-06

0.00005 0.00054 0.00001 34.88 0.00137 0.00061 0.00201 0.00021 0.00012

0.00043 0.00142 0.00003 0.62,439 0.02807 0.01263 0.01471 0.00109 0.00013

0.00223 0.00016 4.98E-06 0.00806 0.0003 0.00013 0.00195 0.00005 0.00002

Table 4 The air emission density of major energy sources (Source: [26]). Energy

CO2

CH4

N2O

SO2

CO

NOX

NMVOC

Diesel (kg/l) Electricity (kg/KWh) Natural Gas (kg/ton)

0.06805 0.48,722 536.4

0.00001 0.00035 2.74

2.75E-08 1.53E-06 0.00234

0.0001 0 5.75

0.00001 0.00005 1.35

0.00006 0.00012 7.72

2.00E-07 0.00002 0.0142

Table 5 The air emission density of each truck type (Source: [21]). Truck type

CO2

CH4

N2O

SO2

CO

NOX

NMVOC

Concrete Truck (kg/km) 8-ton truck (kg/km) 20-ton truck (kg/km)

0.0279 0.01497 0.02178

2.58E-06 1.39E-06 2.02E-06

1.13E-08 6.06E-09 8.81E-09

0.00004 0.00002 0.00003

0.00001 3.17E-06 4.61E-06

0.00002 0.00001 0.00002

8.20E-07 4.40E-08 6.40E-08

Table 5 shows the density of seven types of air emissions of each truck type, estimated from the air emission density of the major energy sources shown in Table 4. For instance, the density of the carbon emissions of a concrete truck, 0.0279 kg CO2/km, is estimated by multiplying the fuel consumption of a concrete truck, 0.41 l/km, by the carbon emission density of diesel, 0.06805 kg CO2/l. 3.2.2. Building construction In the building construction stage, nine types of construction processes e site preparation work, foundation work, stylobate work, foundation stone work, wooden framework, roofing work, interior finishing work, and plaster work e are considered [27]. Unlike other residential building construction in South Korea, most construction activities of the traditional building are conducted by manpower [7]. Therefore, this study assumes that the air emissions are generated from the diesel fuel consumption of the construction equipment used in five types of construction activities: excavation, backfilling, grading earth work, compaction, and the pouring and lifting of concrete. The energy density of major construction processes is calculated by dividing the total energy consumption of construction equipment by the total amount of area involved. The energy density of these processes is tabulated in Table 6. This study assumes that, during the construction of this building, an excavation activity uses a backhoe to remove soil, rock, and other materials to prepare for the slab foundation of a building,

Table 6 The energy density of major construction processes (Source: [6]). Construction activity

Construction equipment

Energy density

Excavation Backfilling Grading earth work Compaction Pouring and lifting of concrete

Backhoe Bulldozer Loader Plate compactor Concrete pump truck

0.3536 0.2579 0.2224 0.1032 0.7692

l/m3 l/m3 l/m2 l/m3 l/m3

while a backfilling activity uses a bulldozer to push soil and stones back into the trench to roughly level out the construction area in the site preparation process. The grading earth work uses a loader to elevate, and the compaction work uses a plate compactor to compress and smooth the soil over the construction area in the foundation process. In the stylobate process, a concrete pump car pours concrete into a foundation form to make the slab foundation of a building. After the pouring and lifting of concrete activity, only manpower is used for the remaining construction activities. In the stone foundation process, a stone masonry activity constructs a structural masonry foundation over the slab foundation to support the weight of the wooden structure of the building. In a wood framework process, wooden columns are set up on the stone masonry, then connected by horizontal lintels to stabilize the building, while woodblocks are placed at the tops of the wooden columns [28]. The wooden doors and wooden windows are placed between the columns. In the roofing process, transverse beams and purlins are connected above the horizontal lintels to connect the building and to support a roof structure, while rafters are joined to the transverse beams and covered with wooden panels and clay to support the building’s roof load [28]. Roof tiles are placed over the wooden panels, and the space between rafters is filled with clay. In the interior finishing process and the plaster work, the space between columns is filled with clay, and an under-floor heating system with a heating water pipe for inner rooms and a wooden floor for outer rooms are installed. At the building construction stage, the seven types of air emissions of each construction activity are calculated by multiplying the energy used in each construction activity by the air emission density of the energy type used. Based on the energy density of construction activities shown in Table 6, using Equation (3), the density of air emission of each construction activity is calculated as shown in Table 7. For example, the density of the carbon emissions

J. Sim, J. Sim / Building and Environment 105 (2016) 283e294

287

Table 7 The air emission density of major construction processes (Source: [21]). Construction stage

CO2

CH4

N2O

SO2

CO

NOX

NMVOC

Excavation (kg/m3) Backfilling (kg/m3) Grading (kg/m2) Compaction (kg/m3) Pouring concrete (kg/m3)

0.02406 0.01755 0.01514 0.00702 0.05235

2.23E-06 1.62E-06 1.40E-06 6.5E-07 4.85E-06

9.73E-09 7.10E-09 6.12E-09 2.84E-09 2.12E-08

0.00003 0.0003 0.00002 0.00001 0.00007

0.00001 0 0 1.49E-06 0.00001

0.00002 0.00002 0.00001 0.00001 0.00005

7.07E-08 5.16E-08 4.45E-08 2.06E-08 1.54E-07

of an evacuation activity, 0.02406 kg CO2/m3, is calculated by multiplying the energy density of excavation, 0.3536 l/m3, in Table 6 by the carbon emission density of diesel, 0.06805 kg CO2/l, in Table 4. The air emissions of construction activity AHO,C, are calculated as shown in Equation (3).

AHO;C ¼

X

90.1e2010. The DesignBuilder is a well-validated simulation model tool for estimating the energy consumption and the carbon emissions of design alternatives in the early design phase [29]. EnergyPlus uses the heat balance model to estimate the thermal performance of buildings based on weather data [30]. The building under the case study is located in Seoul, which has a humid con-

air emission density of constuction process type ðkg air emission=kgÞ

 the quantity used at each construction process type ðkgÞ

3.2.3. Building operation This study assumes that all the air emissions in the building’s operation stage are generated from the electricity consumption for cooling, heating, lighting, and appliance use, along with natural gas consumption for heating. In order to extrapolate the total amount of seven types of air emissions produced during the building’s entire life (on average 30 years), this study first estimates the amount of seven types of air emissions produced in a one-year operation period. At the building operation stage, the seven types of air emissions of each operation activity are calculated by multiplying the energy consumed in an operation activity by the air emission density of the energy type used in an operation activity. The air emissions of building operation AHO,O, are estimated as shown in Equation (4). For instance, the carbon emission generated from the electricity consumption for appliance use is calculated by multiplying the carbon emission density of electricity in Table 4 by the electricity consumption for appliance use

AHO;O ¼

X

(3)

tinental climate. As shown in Table 8, the operation energy simulation model considers the weather data of Seoul. This building uses a hydronic radiant heating system with a natural gas boiler for heating, which is modeled in DesignBuilder with a HVAC system using a heating floor, boiler hot water, and natural ventilation template [32]. The study assumes that the heating system is scheduled to operate in a full operation system from 9 a.m. to 8 p.m. and in a setback system from 8 p.m. to 9 a.m. everyday. In addition, the building uses a residential air conditioner for cooling, which is modeled with a packaged terminal air conditioner template without a heating operation schedule in DesignBuilder [32]. In compliance with the Korean building energy code [33], this study assigns 22 C as the set-point temperature for the bedroom and living area heating and 26 C for the bedroom and living area cooling. In addition, the energy simulation model uses a 0.054 person/m2 occupancy density, a 3.88 W/m2 lighting power density, and a 5.38 W/m2 electric equipment density.

air emission density of building operation type ðkg air emission=kwhÞ

 energy consumption at building operation type ðkwhÞ

This study develops an operation energy simulation model using an energy simulation software tool, DesignBuilder with EnergyPlus simulation engine, in compliance with ASHRAE standard

(4)

3.2.4. Building maintenance Since all maintenance activities for the building are conducted by manpower using natural building materials, the air emissions

Table 8 The basic climate information for the Korean traditional building location [31]. Climate specification

Value

Climate specification

Value

Latitude Longitude Average annual temperature Average max annual temperature Average min annual temperature Average annual relative humidity

37 570 N 126 970 E 12.5  C 17  C 8.6  C 64.4%

Average vapor air pressure Average solar radiation Average annual wind speed Average annual cloud cover Elevation above sea level Average annual precipitation

3.4 hpa 10.1 MJ/m2 2.3 m/s 4.9 (1/10) 38 m 1.4 m/yr

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Table 9 The air emission density of major demolition processes (Source: [21]). Demolition stage

CO2

CH4

N2O

SO2

CO

NOX

NMVOC

Backhoe & Crusher (kg/kg) Aggregate loading (kg/kg)

0.00009 2.79E-06

8.00E-09 2.58E-10

3.50E-11 1.13E-12

1.24E-07 3.99E-09

1.83E-08 5.90E-10

7.67E-08 2.48E-09

2.54E-10 8.20E-12

are generated solely from the building materials used for maintenance. In this stage, the seven types of air emissions of each operation activity are estimated by multiplying the energy required in an activity by the air emission density of the energy type required in a maintenance activity. For its entire life cycle, the traditional

AHO;D ¼

activity, 0.00009 kg CO2/kg, is calculated by multiplying energy density, 0.00127 l/kg, by the carbon emission density of diesel, 0.06805 kg CO2/l, shown in Table 4. The air emissions of building demolition AHO,D, are calculated as shown in Equation (6).

X

air emission density of demolition process type ðkg air emission=kgÞ X  the quantity of building material demolished ðkgÞ þ air emission density of truck type ðkg air emission=kmÞ

 the required number of truck type  distance ðkmÞ (6)

building under the case study requires 50,420 kg of roof tiles, 49,610 kg of clay, and 60 kg of wood at the building maintenance stage [7]. The air emissions of building maintenance, AHO,M, are calculated as shown in Equation (5).

X AHO;M ¼ airemissiondensityof producttypeðkgairemission=kgÞ therequirednumberof producttype (5) 3.2.5. Building demolition This study assumes that all air emissions in the building demolition stage are generated from the diesel fuel consumption of the demolition processes, along with transportation of wooden and masonry stone materials from a building site to a warehouse facility site and other demolished building materials from a building site to a landfill site. In this stage, it is assumed that a backhoe and crusher consume 0.00127 l/kg of diesel fuel for a demolition activity, and a loader consumes 0.00004 l/kg of diesel fuel for a loading activity [20]. Based on the energy density of the demolition and loading activities, the air emission density of each demolition process is

AOH;R ¼

X

3.2.6. Building material recycling and disposal In the building material recycling and disposal stage, the air emissions are generated from the diesel fuel consumption of the disposal process. In this stage, the wooden materials e columns, doors, lintels, rafters, transverse beams, and doors e and masonry stones are the only recyclable materials produced. The wooden materials and the masonry stones are recycled in an as-is condition, so there are no air emissions generated from the recycling stage. In the disposal stage, it is assumed that a dozer consumes 0.00015 l/kg of diesel fuel for a burial activity [20]. The air emission density of the disposal activity is estimated as shown in Table 10. In the building material recycling and disposal stages, the seven types of air emissions of each activity are estimated by multiplying the energy consumed in each activity by the air emission density of the energy used in a recycling and disposal activity. For instance, the carbon emission density of a burial activity, 0.00001 kg CO2/kg, is calculated by multiplying the energy density of a burial activity from diesel fuel consumption, 0.00015 l/kg, by the carbon emission density of diesel, 0.06805 kg CO2/l, in Table 4. The air emissions of building recycling and disposal AOH,R, are calculated as shown in Equation (7).

air emission density of recycling and disposal process type ðKg air emission=kgÞ

 the quantity of building material recycled and disposed ðkgÞ

shown in Table 9. In the building demolition stage, the seven types of air emissions of each demolition activity are estimated by multiplying the energy used in a demolition activity by the air emission density of the energy type used in a demolition activity. For instance, the carbon emission density of a backhoe and crusher

(7)

3.3. Life cycle air emission productivity Similar to the concept of eco-efficiency, which is a sustainable indicator to measure the degree of sustainable development of a product and service [34], the concept of eco-productivity can be

Table 10 The air emission density of major recycling and disposal processes. Disposal stage

CO2

CH4

N2O

SO2

CO

NOX

NMVOC

Burial (kg/kg)

0.00001

9.45E-10

4.13E-12

1.46E-08

2.16E-09

9.06E-09

3.00E-11

J. Sim, J. Sim / Building and Environment 105 (2016) 283e294

Fig. 2. The air emissions of the material production stage in one-year building operation.

used to measure the level of sustainable development by comparing the environmental impact of a building with its economic output [21]. The economical output can be represented by the residential building’s life cycle economic value in terms of the product of the space in volume and the service life span [5], while the environmental impact can be represented by the residential building’s life cycle environmental value in terms of the total air emissions produced during its entire life cycle [21]. Thus, the life cycle air emission productivity AEPHO, of a Korean traditional building is calculated as shown in Equation (8):

AEPHO ¼

AHO;P þ AHO;C þ AHO;O þ AHO;M þ AHO;D þ AHO;R Area  Storey Height  Service Life

(8)

where AHO,P is air emissions generated from the construction material production stage, AHO,C is air emissions generated from the building construction stage, AHO,O is air emissions generated from the operation stage, AHO,M is air emissions generated from the maintenance stage, AHO,D is air emissions generated from the demolition stage, and AHO,R is air emissions generated from the material recycling and disposal stage. 4. Results and discussion Using the air emission estimation method from a study by Sim et al. [21], this study estimates a Korean traditional building’s air emissions during its entire life cycle. The building under the case study is located in Seoul, South Korea. South Korea’s capital and its largest metropolitan city, Seoul is located in the northwest of the Korean peninsula. Seoul has a continental climate with a humid and hot summer and a freezing winter. In this study, the air emission estimation methodology investigates seven types of air emissions e carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), nitrogen oxides (NOX), sulphur dioxide (SO2), non-methane volatile organic compounds (NMVOC), and nitrous oxide (N2O) e during the studied building’s entire life cycle, along with related transportation activities. Finally, the total air emission amounts of an apartment building and a traditional building are compared in terms of square meter per year during their entire life cycles.

Fig. 3. The air emissions of the construction stage in one-year building operation.

the building material production stage to the building material recycling and disposal stage, along with related transportation activities. 4.1.1. Building material production Based on the study of Kim [7], this study considers ten types of construction materials e baked roof tile, cement, clay, concrete, granite, gravel, sand, steel, stones, and wooden materials e to estimate seven types of air emissions. As shown in Fig. 2, using Equation (2), the seven types of air emissions of each construction material are calculated. According to the study of Kim [7], the Korean traditional building requires 91,520 kg of clay, 84,640 kg of stones, 72,290 kg of baked roof tile, 27,210 kg wooden materials, 7860 kg of cement, 30 kg of steel, 38.57 m3 of concrete, 36.34 m3 of granite, 21.18 m3 of gravel, and 18.75 m3 of sand. From Fig. 2, the building material production activities release 42,648.63 kg of CO2, 1357.47 kg of CO, 163.83 kg of NMVOC, 74.21 kg of NOX,32.51 kg of SO2, 21.63 kg of CH4, and 0.58 kg of N2O to the atmosphere. In this stage, roof tile, concrete, and cement contribute approximately 40%, 38%, and 19%, respectively, of the total CO2 at the building material production stage, while clay, granite, gravel, sand, stone, and wood produce an almost negligible amount of carbon emissions. Two materials, roof tile and cement, contribute about 84% and 12% of the total CH4 at the building material production stage, respectively; clay, granite, and wood account for about 4% of the total CH4. In addition, roof tile contributes about 84% of the total N2O at

4.1. Results of life cycle air emission assessment Using the air emission estimation methods in the previous section, this study estimates the seven types of total air emission amounts generated from the Korean traditional building’s 30 years life span, while considering the six stages of its entire life cycle from

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Fig. 4. Operation energy usage per month.

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Fig. 5. The air emissions of the operation stage in one-year building operation.

the building material production stage, and concrete and steel account for about 10% of the total N2O. Roof tile and concrete produce about 60% and 31% of the total SO2 at the building material production stage, respectively; cement and clay account for 7% and 1% of the total SO2, respectively. Concrete produces about 99% of the total CO at the building material production stage. Roof tile, concrete, and cement contribute about 42%, 32%, and 15% of NOX at the building material production stage, respectively. In respect to NMVOC, roof tile contributes about 98% of the total NMVOC. The results show that roof tile is the major source of air emissions at the building material stage of this building.

4.1.2. Building construction In the building construction stage, this study investigates nine types of construction processes e site preparation work, foundation work, stylobate work, foundation stone work, wooden framework, roofing work, interior finishing working, and plaster work, based on the findings of Kim et al. [25]. Since most construction processes of Han-ok are accomplished solely by manpower [7], this study uses Equation (3) to estimate the air emissions generated from the diesel fuel consumption of five types of construction activities e excavation, backfilling, grading earth work, compaction, and pouring and lifting of concrete. As shown in Fig. 3, the major source of air emissions is CO2, with 5.33 kg released. Other air emissions are almost negligible in this stage. The results demonstrate the pouring and lifting of concrete produce the largest amount of CO2 among the five major types of construction activities.

Fig. 6. The air emissions of the maintenance stage in one-year building operation.

4.1.3. Building operation This study utilizes an energy simulation software tool, DesignBuilder, to estimate four types of energy usage in the building operation stage e cooling, heating, lighting, and appliance use. For one year of operation, the building under the case study requires 3166.29 m3 (35,977.49 KWh) of natural gas and 29.13 KWh of electricity for heating and 198.89 KWh of electricity for cooling. This building also requires 2645.43 KWh of electricity for appliance use and 478.81 KWh of electricity for lighting. As shown in Fig. 4, the two largest periods of energy consumption are for heating in January and for cooling in August. For validation purposes, the results of the developed energy simulation model are compared with the results of Kim’s study in terms of total annual energy consumption per square meter [7]. Using the percentage error value method, the comparison shows that the percentage error value between the actual value, 42.3 KWh/m2, and the estimated value, 43.9 KWh/m2, is 3.78% for electricity, and the percentage error value between the actual value, 40.8 m3/m2, and the estimated value, 41.1 m3/m2, is 0.73% for natural gas. Since the percentage error values for electricity and natural gas are less than 5%, it is reasonable to validate our developed energy simulation model. As shown in Fig. 5, using Equation (4), the air emissions in the building operation stage are estimated. For example, the carbon emission generated from the electricity consumption for cooling is calculated by multiplying the carbon emission density of electricity, 0.48,722 kg CO2/KWh, by the electricity consumption for heating, 198.89 KWh. From Fig. 5, for one year of operation, the major source of air emissions is the CO2 emission, which produces 4603.17 kg of CO2. In addition, 20.03 kg of NOX, 14.32 kg of SO2, and 9.19 kg of CH4 are released. The results demonstrate the heating load requires the largest amount of energy e 3166.29 m3 (35,977.49 KWh) of natural gas and 29.13 KWh of electricity e and releases 1349.83 kg of CO2 to the atmosphere. During the building’s 30-year life span, it is expected to release 89,067.52 kg of CO2, 588.76 kg of NOX, 429.53 kg of SO2, 240.1 kg of CH4, 105.5 kg of CO, 1.9 kg of NMVOC, and 0.32,837 kg of N2O.

4.1.4. Building maintenance During the traditional building’s entire life cycle, maintenance is performed by manpower using three types of building construction materials: roof tiles, clay, and wood. Using Equation (5), the air emissions of the building maintenance activities are calculated. As shown in Fig. 6, for the life span of 30 years, the building emits 12,036.25 kg of CO2, 112.68 kg of NMVOC, 23.18 kg of NOX, 13.83 kg

Fig. 7. The air emissions of the demolition stage in one-year building operation.

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calculated. As shown in Fig. 8, in this stage the noticeable pollutant of air emission is CO2 emissions, at 4.11 kg CO2. The other air emissions are negligible in the recycling and disposal stage.

Fig. 8. The air emissions of the recycling stage in one-year building operation.

Fig. 9. The air emissions of the transportation stage in one-year building operation.

of SO2, and 112.70 kg of CH4 to the atmosphere in the maintenance stage. 4.1.5. Building demolition Since the Han-ok is constructed mainly of wooden materials, dismantling is done by manpower in order to recycle the wooden materials and masonry stones. Subsequently, in the demolition stage, the combination of backhoe and crusher is used to demolish the concrete slab foundation. Through the concrete demolition activity, the volume of the demolished concrete materials is assumed to increase by a volume increase rate factor of 1.5 [20]. A 20-ton dump truck transports the dismantled wooden materials and masonry stones from the building site to a wood warehouse facility, and transports the demolished building materials to a landfill site. Using Equation (6), the air emissions of building demolition activities are calculated. As shown in Fig. 7, the noticeable air emissions produced in the building demolition stage are CO2 emissions, at 35.91 kg. The other air emissions released in this stage are negligible. 4.1.6. Building material recycling and disposal As stated above, the wooden material and the masonry stone are the only recyclable materials from the building. The other demolished building materials are transported to a landfill site for a burial activity. The dismantled wooden materials and the masonry stones are recycled in an as-is condition. At the landfill site, the demolished building materials are buried using a dozer. Using Equation (7), the air emissions of the recycling and disposal activities are

4.1.7. Transportation In the life cycle of a traditional building, there are three transportation activities. The first is the transportation from each building material production site to a construction site using a concrete truck, an 8-ton truck, and a 20-ton truck for specific building materials. The second is the transportation of recyclable materials from a construction site to a wood warehouse facility using a 20-ton truck. The last route is the transportation of other demolished materials from a construction site to a landfill site using a 20-ton truck. As shown in Fig. 9, in the transportation activity, CO2 emissions and NMVOC emissions are the only noticeable pollutants, accounting for 45.94 kg CO2 and 2.18 kg of NMVOC, respectively. Fig. 10 shows that seven types of air emissions are estimated for the six stages of a traditional building’s entire life 30-year life span, along with the transportation activity. At the different stages of the building’s life cycle, various pollutants are produced in larger proportions. The operation stage produces about 62% of the total CO2 emissions, the building material production stage produces about 30% of the total CO2 emissions, and the maintenance stage produces about 8% of the total CO2 emissions. The operation stage again contributes the largest amount of the total CH4 emissions, about 87%, while the building material production stage produces about 8% and the maintenance stage produces 5%. The building material production stage has the largest portion of the N2O emissions, accounting for about 46% of the total, and the maintenance stage and the operation stage contribute about 27% and 26%, respectively. The operation stage also has the largest influence of SO2 emissions, accounting for about 90% the total, while the building material production stage and the maintenance stage together produce 10% of the total SO2 emissions. The building material production stage has the largest portion of CO emissions, accounting for 93% and the building operation stage has the largest influence in terms of NOX emissions, with about 86% of the total. The building material production stage has the second largest influence, with about 10% of the total NOX emissions. In respect to NMVOC emissions, the building material production stage and the building operation stage have the largest and the second largest influence, accounting for 58% and 40% of the total NMVOC emissions, respectively. 4.2. Results of life cycle air emission productivity Using Equation (8), the traditional building’s life cycle air emission productivity is estimated. The results show that the major source of air emissions is carbon dioxide, at 12.69 CO2 kg per cubic area per year. The building’s yearly production of emissions per cubic area are as follows: 0.13 kg of CO, 0.06 kg of NOX, 0.04 kg of SO2, 0.02 kg of CH4, 0.02 kg of NMVOC, and 0.00011 kg of N2O. In order to investigate the decreased air emissions in the case of the replacement of the apartment building with the traditional building, the two types of residential buildings are compared in terms of life cycle air emission productivity. This study uses the results of the authors’ previous study on the yearly production of emissions per cubic area of an apartment building [21]: 101.35 kg of CO2, 7.43 kg of CO, 0.1581 kg of NOX, 0.112 kg of CH4, 0.0657 kg of SO2, 0.0087 kg of NMVOC, and 0.0002 kg of N2O. By comparing the value of life cycle air emission productivity, this study finds that the traditional building reduces about 98% of CO, 87% of CO2, 78% of CH4, 62% of NOX, 45% of N2O, and 36% of SO2 emissions over the apartment building. However, the amount of

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Fig. 10. The air emissions of the Korean traditional building’s life cycle.

NMVOC emission is higher due to the roof tile, which produces a relatively large amount of this pollutant to the atmosphere. The results of the comparison indicate the potential of the more traditional building as an environmentally friendly building. However, the results of this study indicate that, in order to improve the potential of the traditional building, it is necessary to make improvements to the building material production and operation stages. It is especially recommended to develop an environmentally friendly roof tile, as the current style contributes the largest portion of NMVOC emissions, while increasing renewable energy usage to decrease the air emissions generated from the building operation stage.

4.3. Embodied energy assessment In response to the increased importance of sustainable building in the building sector, this study utilizes the life cycle assessment software, GaBi, to further investigate the embodied environmental impacts of ten types of building materials, along with related transportation activity. This study analyzes four types of environmental impact e global warming potential, acidification potential, eutrophication potential, and ozone depletion potential. Fig. 11 illustrates the global warming potential of the ten types of building materials in terms of global warming potential 100. The global warming potential 100 is estimated by measuring the amount of

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Fig. 11. The potential environmental impacts of a Korean traditional building.

heat released by a greenhouse gas into the atmosphere [35]. In the case of the building in the study, the roof tile is the major contributor, at approximately 61.21% of total global warming potential. The concrete and the cement have the second and third largest impact, contributing 10.55% and 8.27% of total global warming potential, respectively. The acidification potential of the building materials is also analyzed, as shown in Fig. 11. The transformation of air emission pollutants into acid causes the acidification potential [35]. The transportation activity has the largest portion, contributing 19.27% of the total acidification potential, while the roof tile, cement, and concrete have the second, third, and fourth largest portions, contributing about 16.55%, 15.15%, and 11.39% of the total acidification potential, respectively. Further, the eutrophication potential of the building materials is analyzed. Air pollutants, wastewater, and fertilization in agriculture cause eutrophication potential by enriching nutrients at certain places [35]. The transportation activity associated with the building in the study has the largest impact, accounting for approximately 39.32% of the total eutrophication potential. The concrete and cement have the second and third largest impact, accounting for approximately 10.86% and 9.45% of the total eutrophication potential, respectively. Unlike its other environmental potential, the roof tile has little impact on eutrophication.

Finally, the ozone depletion potential of the ten types of building materials is analyzed. The ozone depletion potential is measured in terms of the relative amount of degradation in the ozone layer [35]. The cement has the largest potential for ozone depletion, contributing approximately 87.41%, while the clay and roof tile contribute approximately 8.39% and 4.05%, respectively. In summary, the results of environmental impact analysis of the ten types of building materials used in the Korean traditional building case, along with the related transportation activities, show that the roof tile is the major sources of potential environmental impact in terms of global warming potential and cement is the major environmental impact source of ozone depletion potential, while the transportation activity is the major environmental impact source of both eutrophication and acidification potentials. 5. Conclusion Since the construction of residential buildings is expected to increase in South Korea, the related environmental impact of these buildings is likewise expected to increase. Thus, it is important to analyze their air emissions and the environmental impact of residential buildings. In recent years, the wooden framed traditional building has emerged as an alternative building to mitigate the environmental impact of the building sector. In order to investigate

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the building’s life cycle assessment of terms of air emissions, this study analyzes this type of building’s life cycle e building material production, construction, operation, maintenance, demolition, and recycling and disposal, along with related transportation activity. After estimating the seven types of air emissions produced from the entire life cycle, this study compares the rate of generation of seven types of emissions between a Korean traditional building and a typical Korean apartment building in terms of life cycle air emission productivity. The results show that, during the traditional building’s entire life cycle, the operation stage produces 4603.17 kg of CO2, 20.03 kg of NOX, 14.32 kg of SO2, and 9.19 kg of CH4 to the atmosphere, while the material production stage produces 42,648.63 kg of CO2, 1357.47 kg of CO, 163.83 kg of NMVOC, and 74.21 kg of NOX, 32.51 kg of SO2, 21.63 kg of CH4, and 0.58 kg of N2O to the atmosphere. As a major pollutant of carbon emissions, the building produces 12.69 kg CO2 per cubic area per year. In addition, in terms of life cycle air emission productivity, the traditional building reduces all emissions except NMVOC e approximately about 98% of CO, 87% of CO2, 78% of CH4, 62% of NOX, 45% of N2O, and 36% of SO2 e in comparison with the apartment building. In the environmental impact analysis, the roof tile contributes 61.21% of the global warming potential and cement contributes 87.41% of the ozone depletion potential, while the transportation activities contributes 39.32% of the eutrophication potential and 19.27% of acidification potential. Through the life cycle air emission assessment, it is evident that the traditional building is an environmentally friendly building which significantly reduces various types of air emissions except NMVOC emission, compared with the most popular residential building in South Korea, the apartment building. In order to enhance the more traditional building’s ecofriendliness, it is recommended to make a concerted effort to produce environmentally friendly roof tiles, as well as to promote more sustainable, reusable energy usage. Based on the results of this study, we are planning to further expand our research to estimate total air emissions generated from a commercial building and a public building in the Korean building sector. References [1] Final Report-reduction Potential Analysis of National Greenhouse Gases, Korea Energy Economic Institute (KEEI), Republic of Korea, 2009. [2] J. Sonnenschein, L. Mundaca, Decarbonization under green growth strategies? The case of South Korea, J. Clean. Prod. (2015), http://dx.doi.org/10.1016/ j.jclepro.2015.08.060. [3] EPA, Greenhouse Gas Emission Data, Environmental Protection Agency, 2006. [4] Greenhouse Gas Inventory and Research, http://www.gir.go.kr. [5] D. Li, H. Chen, E. Hui, J. Zhang, Q. Li, A methodology for estimating the lifecycle carbon efficiency of a residential building, Build. Environ. 59 (2013) 448e455. [6] M. Jang, T. Hong, C. Ji, Hybrid LCA model for assessing the embodied environmental impacts of buildings in South Korea, Environ. Impact Assess. Rev. 50 (2015) 143e155. [7] S. Kim, A study on the estimation method of the environmental load intensity for analyzing GHG reduction effect of Han-Ok, Archit. Res. 15 (3) (2013) 143e150.

[8] J. Choi, J. Chun, H. Hong, S. Kang, D. Kim, C. Min, H. Oh, Y. Park, Hanoak, Traditional Korean Homes, Hollym International Corporation, USA, 1999. €rjesson, L. Gustavsson, Greenhouse gas balances in building construction: [9] P. Bo wood versus concrete from life-cycle and forest land-use perspectives, Energy Policy 28 (2000) 575e588. [10] B. Upton, R. Miner, M. Spinney, L. Heath, The greenhouse gas and energy impacts of using wood instead of alternatives in residential construction in the United States, Biomass Bioenergy 32 (2008) 1e10. [11] B. Lippke, J. Wilson, J. Perez-Garcia, J. Bowyer, J. Meil, CORRIM: life-cycle environmental performance of renewable building materials, For. Prod. J. 54 (6) (2004) 8e19. [12] B. Lippke, L. Edmonds, Environmental performance improvement in residential construction: the impact of products, biofuels and processes, For. Prod. J. 56 (10) (2006) 58e63. [13] X. Gong, Z. Nie, Z. Wang, S. Cui, F. Gao, T. Zuo, Life cycle energy consumption and carbon dioxide emission of residential building designs in Beijing: a comparative study, J. Industrial Ecol. 16 (4) (2012) 576e587. [14] B. Lippke, E. Oneil, R. Harrison, K. Skog, L. Gustavsson, R. Sathre, Lifecycle impacts of forest management and wood utilization on carbon mitigation: knowns and unknowns, Carbon Manag. 2 (3) (2011) 303e333. [15] A. Petersen, B. Solberg, Greenhouse gas emissions and costs over the life cycle of wood and alternative flooring materials, Clim. Change 64 (1/2) (2004) 143e167. [16] A. Dodoo, L. Gustavsson, R. Sathre, Lifecycle carbon implications of conventional and low-energy multi-storey timber building systems, Energy Build. 82 (2014) 194e210. €sse n, F. Hedenus, S. Karlsson, J. Holmberg, Concrete vs. wood in buildings [17] J. Na e an energy system approach, Build. Environ. 51 (2012) 361e369. [18] K. Lee, S. Tae, S. Shin, Development of a life cycle assessment program for building (SUSB-LCA) in South Korea, Renew. Sustain. Energy Rev. 13 (2009) 1994e2002. [19] S. Tae, S. Shin, J. Woo, S. Roh, The development of apartment house life cycle CO2 simple assessment system using standard apartment house of South Korea, Renew. Sustain. Energy Rev. 15 (3) (2011) 1454e1467. [20] S. Shin, S. Tae, J. Woo, S. Roh, The development of environmental load evaluation system of a standard Korean apartment house, Renew. Sustain. Energy Rev. 15 (2011) 1239e1249. [21] J. Sim, J. Sim, B. Park, The air emission assessment of a South Korean apartment building’s life cycle, along with environmental impact, Build. Environ. 95 (2016) 104e115. [22] K. Lee, J. Yang, A comparative study on the carbon-dioxide emission of the Han-Ok, the single family housing, and the apartment, J. Regional Assoc. Archit. Inst. Korea 42 (2010) 151e160. [23] M. Brander, R. Tipper, C. Hutchison, G. Davis, Consequential and Attributional Approaches to LCA: a Guide to Policy Makers with Specific Reference to Greenhouse Gas LCA of Biofuels, Ecometrica Press, 2008. [24] H. Choi, Comparison Study on the Eco-friendly Elements of Hanok and Green Building Certification Criteria, Master thesis, Hannam University, 2014. [25] H. Lim, A Study on Design Supports to Improve Han-ok Productivity e Focusing on Analyzing Han-ok Components Manufacturing Process in Practice, Master thesis, Hanyang University, 2013. [26] Korea LCI Database Information Network, http://www.edp.or.kr/lci/lci_db.asp. [27] M. Kim, H. Kim, J. Ryu, Y. Jung, New building materials and methods for modernized Korean housing (Hanok), Korea Inst. Constr. Eng. Manag. 15 (2) (2014) 23e32. [28] I. Cho, An overview of Korean wooden architecture, in: International Conference on Sustainable Building Asia, Seoul, SB10 Seoul, 2010. [29] A. Kirimtat, B. Koyunbaba, I. Chatxikonstantinou, S. Sariyildiz, Review of simulation modeling for shading devices in buildings, Renew. Sustain. Energy Rev. 53 (2016) 23e49. [30] OpenStudio, http://www.openstudio.net. [31] Korea Meteorological Administration, http://www.kma.co.kr. [32] DesignBuilder, http://www.designbuilder.co.uk. [33] Korea Energy Agency, http://www.energy.or.kr. [34] World Business Council for Sustainable Business (WBCSD), Measuring Ecoefficiency: a Guide to Reporting Company Performance, WBCSD, Geneva, 2000. [35] GaBi Paper Clip Tutorial, PE International, 2011.