Changyoon Ji

Assessment Model for Energy Consumption and Greenhouse Gas Emissions during Building Construction

Many studies use life-cycle assessment (LCA) as a tool to quantify the environmental impact of buildings. Most of these studies have focused on the maintenance and operation phases of construction projects, which account for the largest part of energy consumption during the life cycle of buildings. However, the construction phase may cause significant environmental impacts, so a detailed analysis on the construction phase is required to conduct a more accurate assessment of the energy consumption and environmental impact of a buildings entire life cycle. To assess energy consumption and greenhouse gas (GHG) emissions, this study developed a model using process-based LCA and input-output (I-O) LCA. This study divided the construction phase into material manufacturing, transportation, and on-site construction, and applied an appropriate methodology for each part. The analysis of an apartment building project using the developed model showed that the material manufacturing stage had the largest amount of energy consumption and GHG emissions. Quantitatively, material manufacturing, transportation, and on-site construction phases were responsible for 94.89, 1.08, and 4.03% of energy consumption, and 95.16, 1.76, and 3.08% of global warming potential, respectively. It is believed that the developed model would allow a more accurate assessment of energy consumption and GHG emissions during a buildings construction phase. DOI: 10.1061/(ASCE)ME.1943-5479.0000199.

CBR Revision Model for Improving Cost Prediction Accuracy in Multifamily Housing Projects

For any construction project to succeed, it is very important to accurately estimate the construction cost during the project’s initial stage. This is why there has been much interest lately in cost prediction models that use case-based reasoning (CBR). It has been pointed out, however, that existing CBR-based cost prediction models may yield inaccurate results even though they could survey optimal similar cases, if the number of cases in the case base is not enough. As opposed to the existing CBR-based construction cost prediction models, this study developed a CBR revision model that reflects the “revise” phase of the CBR cycle (retrieve, reuse, revise, and retain) based on nine multifamily housing projects executed recently by “A” Housing Corporation. To verify the developed model, a case study was performed using three case projects completed by “B” and “C” Housing Corporations. The result showed that the prediction error ratio after the Revise (I) phase decreased from 97.44 to 22.58%. This model can ...

Model for Evaluating the Financial Viability of the BOT Project for Highway Service Areas in South Korea

AbstractEvaluating the financial viability of a build-operate-transfer project for highway service areas (HSA BOT project) in South Korea is very important for the private sector because it does not have a risk-allocation agreement with the public sector, such as the minimum revenue guarantee. In this study, a model to evaluate the financial viability of a HSA BOT project is developed based on the discounted cash flow analysis and the real option valuation. The developed model can evaluate the financial viability of the HSA BOT project more robustly and comprehensively than existing methods by considering the characteristics of the HSA BOT project as well as the value of the HSA BOT projects due to the future uncertainty that the existing methods cannot consider. The case study shows that compared to the result from the existing methods, the result from the developed model is close to the actual results of the case project. It is expected that the private sector can use the developed model to determine th...

A model for evaluating the environmental benefits of elementary school facilities

In this study, a model that is capable of evaluating the environmental benefits of a new elementary school facility was developed. The model is composed of three steps: (i) retrieval of elementary school facilities having similar characteristics as the new elementary school facility using case-based reasoning; (ii) creation of energy consumption and material data for the benchmark elementary school facility using the retrieved similar elementary school facilities; and (iii) evaluation of the environmental benefits of the new elementary school facility by assessing and comparing the environmental impact of the new and created benchmark elementary school facility using life cycle assessment. The developed model can present the environmental benefits of a new elementary school facility in terms of monetary values using Environmental Priority Strategy 2000, a damage-oriented life cycle impact assessment method. The developed model can be used for the following: (i) as criteria for a green-building rating system; (ii) as criteria for setting the support plan and size, such as the governments incentives for promoting green-building projects; and (iii) as criteria for determining the feasibility of green building projects in key business sectors.

Predicting the CO 2 Emission of Concrete Using Statistical Analysis

Accurate assessment of CO2 emission from buildings requires gathering CO2 emission data of various construction materials. Unfortunately, the amount of available data is limited in most countries. This study was conducted to present the CO2 emission data of concrete, which is the most important construction material in Korea, by conducting a statistical analysis of the concrete mix proportion. Finally, regression models that can be used to estimate the CO2 emission of concrete in all strengths were developed, and the validity of these models was evaluated using 24 and 35MPa concrete data. The validation test showed that the error ratio of the estimated value did not exceed a maximum of 5.33%. This signifies that the models can be used in acquiring the CO2 emission data of concrete in all strengths. The proposed equations can be used in assessing the environmental impact of various construction structural designs by presenting the CO2 emission data of all concrete types.

Comparison of the CO 2 Emissions of Buildings using Input-Output LCA Model and Hybrid LCA Model

This study aims to determine whether or not the input output life cycle assessment (I-O LCA) model can be used to assess the carbon dioxide (CO2) emission of buildings in initial planning phase. To ensure this end, this study proposed I-O LCA model which is the simplified LCA model and Hybrid LCA model which is the detailed LCA model, and then assessed and compared the CO2 emission of six case projects (three apartment complexes and three educational facilities) using the two LCA model. The results of the case study showed that the CO2 emissions assessed by the I-O LCA is significantly similar to the CO2 emission assessed by the Hybrid LCA model. The similarity of results from both LCA models was 78.2-86.3% in apartment complexes and 59.9-84.8% in educational facilities. However, the CO2 emissions from I-O LCA model were smaller than the CO2 emissions from Hybrid LCA model in case study. Nevertheless, the case study showed that the I-O LCA model was capable of assessing the CO2 emission of buildings quite appropriately although the I-O LCA model is the simplified LCA model which considers only the construction cost. The I-O LCA model is expected to be a useful tool for assessing the CO2 emission of buildings in initial planning phase.

Environmental Impact Assessment of Buildings based on Life Cycle Assessment (LCA) Methodology

Most of the studies on reduction of buildings` environmental burden in the construction industry have been focused on carbon dioxide emission, although there are various kinds of environmental issues such as global warming, acidification, and etc. which are considered by many researchers. Therefore, this study defined and suggested six impact categories and the principles to assess each impact for the assessment of comprehensive environmental impacts of buildings. The six impact categories are abiotic depletion, global warming, ozone layer depletion, acidification, eutrophication, and photochemical oxidation. A case study has been conducted through comparative analysis of two structural design alternatives to confirm the necessity of assessing the six impact categories. That is, the results of global warming potential and the six impacts proposed in this study were compared. By comparing the results of only global warming potential, the second design alternative using 24MPa concrete was chosen as a better alternative, while the first design alternative using 21MPa concrete was resulted as a better alternative when six impact categories were considered. The results mean that the assessment of various environmental impacts is an appropriate and reasonable approach and the comprehensive assessment offers more reliable results of environmental impacts in the building construction.

Conversion Method for Obtaining CO2 Emission Data from the Life Cycle Inventory Database of Foreign Countries

AbstractThis study aimed to develop a method for converting CO2 emission data from the life cycle inventory (LCI) of foreign countries into the one that is suitable for one’s own country, to obtain CO2 emission data of products or materials. CO2 emission differs in the energy efficiency and the type of energy sources used in each country. The developed conversion method considered the average share of the energy sources that are used to manufacture products or materials, in addition to different energy efficiency. To verify the feasibility of the developed conversion method, the study applied it to steel rebar and the steel section of the European reference life cycle database (ELCD), which was established by the European Commission. The result was compared with the CO2 emission data from the LCI of the Ministry of Knowledge Economy (MKE) in South Korea. The result showed that the percent difference of the steel rebar and that of the steel section dropped from 36.29 to 12.28%, and 162.59 to 60.47%, respec...

An analysis on CO 2 emission of structural steel materials by strength using Input-Output LCA

Along with the increasing interest in environmental problems such as global warming, the South Korean government has established policies and regulations to reduce the amount of greenhouse gases, targeting a 30% reduction of compared to business-as-usual levels by 2020. Thus, there have been many studies in construction field to control and reduce the amount of emitted from buildings. emission from the building construction could be obtained by using the life cycle assessment(LCA) methodology. In LCA, it is essential to have life cycle inventory(LCI) data of construction materials consisting of emission data that have been defined and examined in a detailed way in order to obtain more accurate and detailed emission of buildings. To date, however, the LCI data have been acquired only for the representative materials. Accordingly this study aimed to propose detailed emission data for steel rebar and H-beam, which are the essential structural steel materials, by strength and type. To accomplish the objective, this study used Input-Output LCA methodology which is based on the Input-Output table. It is believed that the emission data of steel materials acquired from this study would allow a more accurate assessment of emission for diverse structural design alternatives.

Environmental Impacts Assessment of Elementary School Buildings and Establishment of the Reference Target using Life Cycle Assessment Model

In order to determine how much a new green building reduce the environmental impacts, it is necessary to establish the reference target for comparison. Therefore, this study aims to establish the reference target by evaluating the environmental impacts of existing buildings. To ensure this end, this study evaluated the environmental impacts(Global warming potential, ozone layer depletion potential, acidification potential, eutrophication potential, photochemical ozone creation potential, and abiotic depletion potential) of 17 existing elementary school buildings, which are located in Seoul, Busan, Daegu, and Gwangju, by using the hybrid LCA model. As a result, the environmental impacts of the case buildings were clearly distinguished in different regions. Therefore, this study presented the reference targets which are appropriate to each region. For example, the reference targets for global warming potential, which can be used in Seoul, Busan, Daegu, and Gwangju, are 3.76E+03, 1.90E+03, 2.63E+03, , respectively. The presented reference targets are expected to be useful for understanding how much environmental impacts can be reduced when a new green school building is constructed.