Improvement Directions for the G-SEED System from the Resident's Perspective

1.1. Research Backgrounds and Objectives

Responding to aggravating depletion of energy and natural resources, and climate change including environmental pollution, global warming, and desertification since the 1990s, the international community has actively discussed environmentally friendly improvements such as the reduction of energy use and carbon emissions. The building section in particular is providing immediate causes for global climate change problems since it takes about 50% of carbon emissions, 20∼50% of waste discharge, 33% of energy consumption, 40% of resource use, and 17% of water consumption.¹⁾ So, many countries over the world have developed and implemented green building certification systems appropriate for their building environment to assess sustainable performances of buildings since the early 1990s. Among them, there are LEED (Leadership in Energy and Environmental Design) of the U.S., BREEAM (Building Research Establishment Environment Assessment Method) of the U.K., and CASBEE (Comprehensive Assessment System for Building Environmental Efficiency) of Japan. In Korea, the green building certification system targeting apartment buildings was first introduced in 2002 after incorporating systems operated by the Ministry of Construction and Transport and the Ministry of Environment. Since then, the green building certification criteria for mixed-use and office buildings was implemented in 2003, for school buildings in 2005, for retail buildings and hotels in 2006, and for small houses and existing buildings (apartment buildings and office housings) in 2011. In February 2013, under the Green Building Development Support Act, the green building certification system and the housing performance recognition system became the G-SEED (Green Standard for Energy and Environmental Design).

Though related studies have been conducted after the implementation and revision of the green building certification and G-SEED, most of them have focused on the summary of the system and status, or improvements. Also, many studies have focused on supplementation and improvement of the certification system after they compared other countries’ standards and criteria with those of Korea.²⁾ More recently, there has been a new research trend of studying improvements in scoring scale of the certification criteria based on surveys targeting specialists and engineers at architectural, construction, and consulting firms specialized in eco-friendly buildings.³⁾⁴⁾ However, the comprehensive and resident-oriented revision of G-SEED criteria including its assesment standards, which reflects residents’ opinions, has not been made.⁵⁾ Therefore, this study aims to examine scoring scales of the revised G-SEED criteria for apartment buildings and to examine the importance of each assessment standard based on the result of resident survey so as to provide references for future revisions of scoring scale and improvement directions.

1.2. Research Methods and Scopes

This research conducts a survey targeting residents in an apartment complex that was certified as a green building to examine the importance of assessment criteria and suggest improvement directions regarding changes in scoring scales of assessment standards, extra score, etc. The research methods are as below.

First, the definition of the G-SEED and recent revision and certification status were reviewed. In particular, assessment standards and scoring scales for apartment buildings were examined. Also, AHP (Analytic Hierarchy Process) method was explained. Then, a survey targeting residents in an apartment complex certified as a green building in Joong-gu, Daegu in 2013 was conducted in February, 2014. Lastly, based on the result of the survey, the importance of each standards were analyzed and compared with the scoring scales of the current certification criteria.

2.1. Introduction of G-SEED

The G-SEED⁶⁾ grants certification to an eco-friendly building that contributes to saving energy and reducing pollution throughout the entire construction process from design, construction to maintenance. Also, from selection of site and material, maintenance to destruction, it targets the life cycle of a building which is designed to harmonize humanity and nature with an aim to realize sustainable development and examines its environmental effects. Under the Green Building Development Support Act implemented in February, 2013, the G-SEED was revised with the incorporation of related legislations and regulations (the green building certification of the Building Act and the housing performance recognition system of the Housing Act). It comprehensively assesses eco-friendliness of a building. The revision includes that nine special sector categories were reorganized into seven, public buildings with the total floor area of over 3,000m2 are required to acquire the certification, the certification is valid for five years and will be renewed if necessary, explanation on giving extra scores when a person who received certain education from an expert institute participates in the design of a building or innovative design scheme is introduced is provided, and the English title of the G-SEED is confirmed for branding and PR.

2.2. Certification Status

The G-SEED has two steps consisting of pre-certification and main certification. Pre-certification grants a preliminary certificate based on a design layout, an assessment document by a design /construction company, and a document confirming that the design will be applied to a building. At the main certification stage, the official certificate is issued after inspection based on background materials and an assessment document by a company. According to the certification status of the G-SEED Online Total Operation System, the total of 3,923 buildings has obtained the certification among which 2,551 cases are pre-certification, and 1,372 are main certification. The number of certification has dramatically increased since 2006 (Fig. 1) implying that buildings have steadily acquired the certification. Also, 1,484 school buildings, 1,293 apartment buildings, 590 office buildings acquired the certification and they take up about 86% of the total certification. On the other hand, the number of certification for mixed-use buildings, retails, and hotels is relatively low. Fig 2 shows certification status of green buildings by use.

Fig. 1.

Certification Status of Green Building by Year

2.3. Certification Assessment Criteria and Points for Apartment Buildings

The assessment criteria of the G-SEED for apartment buildings were reorganized from nine categories to seven – land use & transportation, energy & environment pollution, material & resource, water circulation management, maintenance management, ecological environment, and indoor environment – with 24 assessment criteria and the total of 123 points. Table 1 shows assessment categories, criteria, points, and weights. The criteria and points are as follows: land use & transportation (4 items, 18 points), energy & environment pollution (3 items, 21 points), material & resource (4 items, 15 points), water circulation management (2 items, 15 points), maintenance management (4 items, 8 points), ecological environment (3 items, 18 points), and indoor environment (4 items, 28 points).

Table 1.

Certification Assessment Criteria, Points &　Weights(Apartment Buildings)

Fig. 2.

Certification Status of Green Building by Use

3.1. Introduction of AHP⁷⁾

The AHP (Analytic Hierarchy Process) is a decision making tool developed by Thomas Saaty in the early 1970s. It focused on the fact that the human brain utilizes analytic process step by step or hierarchically when making a decision. It helps reach a conclusion by systematically and hierarchically identifying the nature of a complex decision making process. The AHP is an effective tool to express various goals, assessment criteria, or elements in a hierarchical structure and to decide the relative importance of those elements and priority of alternatives by conducting pairwise comparison regarding the relation among the elements.

The AHP has four theoretical backgrounds for its application. First, elements of one level must have dependency on the higher level. Second, two elements in the same level can be compared, and they should meet reciprocal comparison to show preference between the two. Third, it has homogeneity that the preference between the two is expressed by a standard decided within a limited scope. Lastly, it has expectation that all alternatives and standards are perfectly included in a level to achieve the goal of decision making.

The application of the AHP is as follows. First, create a hierarchy of decision making elements related to each other. Second, calculate relative weight between the elements via pairwise comparison. As a standard for a quantitative judgment, 9-point standard (Table 2) is usually used. Third, relative importance or weight between the elements is calculated. Fourth, logical consistency of AHP survey respondents is checked. The consistency index (CI) and the consistency ratio (CR) can be used.⁸⁾ Lastly, priorities are decided by incorporating the relative importance of the decision making elements.

Table 2.

Rating Scale of Pariwise Comparison

3.2. Survey

The survey used in this research focused on the assessment criteria and standards of G-SEED for apartment buildings. The target was residents in an apartment building in Joong-gu, Daegu with 730 households, which acquired the certification in May, 2013. The perspective of the building is shown in Fig. 3.

Fig. 3.

Perspective of G-SEED Certified Building

The certification point and level of G-SEED certified building is shown in Table 3, and the final certification point is 68.56 implying that the building level is rated as good.⁹⁾ More specifically, the building obtained 13.40 points in land use & transportation, 33.54 in energy/resource & environment load, 6.27 in ecological environment, and 15.35 in indoor environment.

Table 3.

Certification Point and Level of G-SEED Certified Building

The survey was conducted in February, 2014 targeting the residents, and 19 out of 32 survey sheets were returned. Table 4 and 5 show survey categories of level 1 and 2 with a 9-point scale, and the importance was examined via priority between two elements. The lack of consistency means unreliable results in AHP, so 6 survey sheets with CR ratio of over 0.2 were excluded from the final analysis.

Table 4.

Survey Form of Level 1

Table 5.

Survey Form of Level 2「Land Use & Transportation」

3.3. Pairwise Comparison Matrix and Consistency Verification

To meet reciprocal comparison, this research used a geometric average by calculating geometric average of respondents’ values to each element of individual comparison matrix, incorporating them, and creating pairwise comparison matrixes by levels. Then, the consistency of these comparison matrixes were verified. The comparison matrix of level 1 is shown in Table 6, and the CR ratio was 0.016 meaning it is acceptable according to the Saaty’s suggestion. Comparison matrixes of land use & transport, energy & environment pollution, material & resource, water circulation management, maintenance management, ecological environment, and indoor environment are shown in Table 7 to 13, and all matrixes’ CR values are below 0.1 implying they have consistency.

Table 6.

Comparison Matrix of Level 1

Table 7.

Comparison Matrix of「Land Use & Transportation」

Table 8.

Comparison Matrix of「Energy & Environment Pollution」

Table 9.

Comparison Matrix of「Material & Resource」

Table 10.

Comparison Matrix of「Water Circulation Management」

Table 11.

Comparison Matrix of「Maintenance Management」

Table 12.

Comparison Matrix of「Ecological Environment」

Table 13.

Comparison Matrix of「 Indoor Environment」

4.1. Importance of Level 1 Criteria (X)

Level 1 criteria of G-SEED for apartment buildings consists of seven categories - land use & transport, energy & environment pollution, material & resource, water circulation management, maintenance management, ecological environment, and indoor environment. The results of survey on the importance of level 1 criteria (X) are 0.103, 0.137, 0.091, 0.102, 0.128, 0.201, 0.238 respectively as shown in Table 14. The total sum of the importance of level 1 criteria is 1, so each category takes up 10.3%, 13.7%, 9.1%, 10.2%, 12.8%, 20.1%, and 23.8%. Survey respondents consider level 1 criteria including indoor environment, energy & environment pollution, maintenance management, etc. as rather important. This shows that the respondents consider the creation of ecological environment via green network and habitat, the establishment of air environment and thermal environment which minimize hazards to residents to improve the quality of indoor environment, and acoustical environment related to sound insulation between units, which is a social issue, as important. Also, it means that the respondents recognize energy use and reducing carbon emissions which are directly linked to climate change and maintenance management through efficient building and unit management as important environmentally friendly performance factors. On the contrary, land use & transportation, material & resource, and water circulation management were less important.

Table 14.

Importance(X) & Ranking of Level 1

4.2. Importance of Level 2 Criteria (Y)

Table 15 shows the importance of level 2 criteria (Y). For criteria under the land use & transportation, ecological value takes up 19.1%, adjacent site 23.5%, occupancy environment 37.3%, transportation load 20.0%. This shows that occupancy environment establishment including plans for community centers and facilities inside a complex, pedestrian roads for comfortable walking environment and their links to resting facilities, and systematic linkages between internal and external facilities of a complex as well as transportation is the most important criteria. As for energy & environment pollution, energy saving takes up 39.2%, sustainable energy 31.1%, and global warming 29.8%, implying that energy saving related to pre-criteria of energy consumption that examines carbon emission reduction is the most important. In the material & resource category, resource saving accounts for 16.3%, waste minimization 20.3%, waste recycling 23.1%, and sustainable resource 40.2%, meaning sustainable resource recycling related to assessment on the use of certified sustainable product for resource recycling, information label about carbon emission of materials, and assessment on inherent carbon. As for water circulation management, water circulation system and water use saving take up 50.6% and 49.4% respectively. Under the maintenance management category, site management accounts for 26.1%, repairability 25.5%, unit management 24.5%, and building management 23.9% in the order of importance, but the difference is not so big. As for ecological environment, green space takes up 35.8%, ecological function 24.9%, and habitat 39.4%, showing that the quality improvement of ecological environment inside a complex by providing habitat. In the case of indoor environment, air environment accounts for 34.0%, thermal environment 14.0%, acoustical environment 20.4%, and light environment 31.6%, implying that air environment including the use of products with low indoor air pollutant emissions, natural ventilation providing fresh air from outside, which residents can control, and ventilation performance that can maintain fresh indoor air by emitting indoor air pollutants to the outside is the most important.

Table 15.

Importance(Y) & Ranking of Level 2

4.3. Composite Importance by Assessment Criteria (Z)

Table 16 shows the composite importance by assessment criteria (Z). The value of each item was calculated by multiplying the importance of level 1 criteria (X) by the importance of level 2 criteria (Y). In the indoor environment, air environment and light environment take up 8.1% and 7.5% respectively. In the ecological environment, habitat, green space, and ecological function account for 7.9%, 7.2%, 5.0% respectively. Also, in the energy and environment pollution, energy saving takes up 5.4%, in the water circulation management, water circulation system 5.2% and water use saving 5.0%. These eight items take up 51.3% of the composite importance, meaning they are considered important in the green building certification system for apartment buildings.

Table 16.

Comparison between Composite Importance(Z) and Certification Standard of Assessment Criteria

On the contrary, the respective shares of ecological value, transportation load, and adjacent site in the land use & transportation are 2.0%, 2.4%, 2.1%. Also, resource saving, waste minimization, waste recycling in the material & resource take up 1.5%, 1.8%, 2.1% respectively. It implies that those items are considered less important in the green building certification system for apartment buildings.

The comparison between the composite importance of assessment criteria drawn from the AHP survey and the importance of weighted points of the green building certification for apartment buildings shows that energy saving in the energy & environment pollution, water use saving in the water circulation management, ecological function in the ecological environment, and air environment in the indoor environment, which have higher importance with more than 5 points, have a similar order to that of the AHP result in terms of importance. However, occupancy environment of the importance of the land use & transportation, global warming of the energy & environment pollution, sustainable resource in the material & resource, and acoustical environment of the indoor environment was different when the assessment criteria was compared with the AHP result. Also, assessment criteria with higher importance in the current certification system have low composite importance in the AHP result. On the other hand, water circulation system in the water circulation management, green space and habitat in the ecological environment, and light environment of the indoor environment showed higher composite imoprtance in the AHP result. Therefore, the result of the AHP result of this research can be utilized when the assessment criteria points and weight of the green building certification system will be adjusted.