*3.3. GR Scope and Planning Direction of the Selected Building*

Considering the utilization of the analysis results and the wide-ranging maintenance statuses of aged houses, the site and building type were based on the No. 4 case, but the aging performance of each item was analyzed as the aging performance with the highest ratio among the aging status survey results of the nine households. Table 5 (1) summarizes the average aging performance in terms of the building envelope (insulation, windows, doors), facility performance, indoor air quality, and user (elderly household) safety of the investigated buildings, (2) summarizes the problems in energy, air quality, and safety according to the aging performance of each item, and (3) explains the scope of improvement and method of remodeling for each item in terms of building envelope performance, interior and exterior finishing, facility performance, indoor air quality, and safety.


**Table 5.** Energy

performance

 of aged houses, health problems of residents, and

improvement

 directions according to the site survey.

#### **4. Economic Analysis Considering Social Cost**

#### *4.1. Analytical Procedures and Methods*

Regarding the analysis procedure and method, first, the energies before and after GR were analyzed by considering the spatial characteristics of the target building and the aging performances of the nine aged houses. The analysis tool was ECO-2, a Korean building energy efficiency rating program. For weather data of ECO-2, standard profiles were brought in from ECO-2 central server to allow selection of average data for 66 regions in Korea. Essentially, Korea has distinct climatic characteristics of four seasons: spring, summer, fall, and winter. Weather data of ECO-2 provide monthly average values calculated based on TMY (typical meteorological year data) weather data, which provides monthly average ambient temperature and monthly average solar intensity according to the incident angle by bearing. The target building of this study was located in Seoul. Accordingly, in ECO-2, Seoul was set out of 66 areas in Korea and analysis was conducted.

For the existing model (=building to be analyzed) and the improved model (=GR plan), the energy consumption was analyzed by preparing an improvement plan based on the aging performance and the renewal direction for each of items (1) and (3) in Figure 3 and Table 5. Second, the total construction cost was calculated per each item by dividing the aging performance (demolition cost, interior and exterior finishing, rest room renewal, etc.), health, safety, and energy performance of the improved model. Third, by comparing the energy and carbon generation of the existing model to the improved model in terms of ECO-2 analysis, the annual energy savings, greenhouse gas (CO2) savings, and air pollutant savings were derived, then converted into costs to calculate the annual benefits. Next, by calculating the benefits ((1) energy saving cost (resident benefit—1), (2) greenhouse gas reduction (social cost—1) and (3) air pollutant reduction (social cost—2)) of the improved model compared to the total construction cost (cost), the economic feasibility was analyzed using the net present value method (NPV). Based on this, in the discussion section of Section 5, a GR support policy concept for low-income elderly households was proposed by mixing the 'housing stability policy for low-income elderly people' and the 'urban energy transition policy' of Korea Government. Figure 4 depicts a schematic diagram of the analysis procedure detailing each step and method of the target building (existing model).

**Figure 4.** Problems considering elderly households in aged houses and improvement directions for each GR item.

### *4.2. Primary Energy Consumption Analysis for Existing and Improved Models*

#### 4.2.1. Primary Energy Consumption Analysis for Existing Model

As mentioned above, the primary energy consumption analysis for the existing model was conducted based on the architectural spatial properties (actual area and height) of the No. 4 case and the average aging performances of the nine aged houses. Tables 6 and 7 lists the key input values for energy performance analysis of the existing model as well as the reference notices and the energy performance result value output from ECO-2.

#### 4.2.2. Improved Model Analysis

The energy performance of the improved model was set at the recommended level of the GR technical reference notices [41], and external insulation (adding 100 mm of mineral wool and dry finish) was applied for insulation remodeling in consideration of thermal bridge improvement and fire safety. Further, to improve the airtight performance, by applying a first-grade window set with airtight performance as well as applying airtight tape to the window frame (wall joint) and hole portions of the ventilation device, the building's airtight performance was analyzed by assuming grade 3 (based on ACH 50). Tables 8 and 9 shows the key input value for ECO-2 and the analysis results for the improved model.

4.2.3. Calculation of Annual Energy and Greenhouse Gas Reduction from the Energy Analysis Results

ECO-2 (Energy) Result Analysis: Comparison before to after GR

The heating energy requirement of the existing model was 173.9 kWh/m2·y, and the heating energy requirement of the improved model was 60.4 kWh/m2·y, which represents a reduction to 1/3 of the original value. In terms of cooling, it slightly increased from 31.4 kWh/m2·y to 34.4 kWh/m2·y. This is an analysis result that is generally acquired in residential buildings with improved insulation, as the heat exchange of the indoor heat generating load becomes difficult as the building's thermal insulation and airtight performance are improved.

The primary energy consumption of the existing model was the lowest grade (grade 7) for the building energy efficiency of 413.1 kWh/m2·y, which indicated very poor energy performance. The primary energy consumption of the improved model was slightly lower than grade 3 for the building energy efficiency of 246.2 kWh/m2·y, which was similar to the level of a newly constructed building. Improvements could be made to a higher level than this. However, as the level of improvement was judged to be appropriate in consideration of the construction cost, the current legal standards, and recommended standards of the Ministry of Land, Infrastructure and Transport, no additional energy performance improvement was conducted.
