Green Remodeling: Empirical Study of Thermal Insulation Improvement Remodeling of Public Healthcare Center

Abstract

This study investigates the energy performance improvement in an aging public healthcare center in South Korea through a comprehensive “Green Remodeling” project. The building, originally constructed in 2001 before the establishment of national energy-saving standards, exhibited substandard insulation performance in its walls, roof, floors, and windows. The remodeling was designed to meet the highest current energy-saving criteria, incorporating advanced insulation techniques and energy-efficient systems. The remodeling process achieved a significant improvement in heating efficiency, with the ECO2 simulation predicting a 50% reduction in energy consumption. However, actual post-remodeling savings were approximately 10%, influenced by factors such as varying occupancy patterns and construction challenges. Despite these obstacles, the project demonstrated the effectiveness of targeted energy-saving measures in enhancing the overall performance of the building. This research underscores the importance of green remodeling as a viable strategy for improving energy efficiency in aging buildings, particularly in the context of South Korea’s carbon reduction goals. This study provides practical insights into the design and implementation of energy-saving technologies, offering a model that can be adapted for similar projects in other contexts.

1. Introduction

Frequent and severe weather events are ongoing challenges that result from rising global temperatures. The shift from global warming to what is now being termed “global boiling” is increasingly apparent [1]. Since 1981, the rate of temperature increase has accelerated significantly, more than doubling from the previous rate to reach 0.18 °C per decade [2]. To mitigate the most severe impacts of rising global temperatures, urgent and collective action is imperative. In pursuit of the 2050 net-zero emission goals, major countries have set reduction targets for 2030: the European Union aims to reduce emissions by 55% from 1990 levels [3], while the United States’ target is a reduction of 50~52% from 2005 levels [4].

Achieving carbon neutralization in the building sector is vital to minimize the environmental impact of CO₂ emissions. Over one-third of CO₂ emissions from energy usage can be attributed to buildings [4,5]. As buildings age, energy improvement remodeling becomes increasingly important not only for existing structures but also for newer constructions. In South Korea, the proportion of buildings over 30 years old has steadily risen, having reached 37.8% by 2019 [6]. As time progresses, the number of aging buildings continues to grow, and many of these older structures fail to meet the energy-saving standards necessary for carbon neutrality. South Korea, for instance, has set a target to reduce emissions in the building sector by 35.0 million tons, representing a 40% reduction from 2018 levels [7].

A comprehensive national strategy for carbon emission reduction includes the necessity of green remodeling as much as enhancing the energy performance of new buildings. In South Korea, specific measures have been established in the building sector to achieve carbon neutrality: (1) enhancing the energy performance of new buildings, and (2) implementing “Green Remodeling” for existing old buildings [8]. The term “Green Remodeling” in South Korea refers to the renovation and retrofitting of buildings aimed at improving their energy performance. To concretize this, efforts are being made to promote and mandate “Green Remodeling” support for existing public buildings [9].

Research underscores the effectiveness of green remodeling in achieving substantial energy savings and emission reductions. Lee et al. [10] examined the effects of retrofitting on energy performance and sustainability in a public office building, finding that green remodeling can significantly improve energy efficiency and contribute to the sustainability of public infrastructure. Their energy simulation results indicated an expected reduction in energy consumption of 20% or more. Cho et al. [11] conducted a detailed analysis of the energy and economic effects of green remodeling in a public daycare center. Their energy simulation results revealed that green remodeling reduced primary energy consumption by approximately 48% and CO₂ emissions by 46% in this facility. A study by Lee and Choi [12] applied green remodeling to a community center in South Korea. They observed that green remodeling led to a significant 17.4% average monthly reduction in energy consumption, with the most substantial savings of 35.4% occurring in February, despite higher outdoor temperatures.

Theoretically, replacing components with higher-performing alternatives is expected to improve a building’s energy consumption. However, empirical studies that validate these outcomes through actual application remain limited. Moreover, even in the context of remodeling aging buildings, the effectiveness of applied technologies can vary significantly depending on factors such as building usage and the condition of the structure. In this study, we conducted an empirical investigation of green remodeling applied to a public healthcare center in South Korea. A comprehensive energy performance enhancement encompassed diagnosis, design, construction, and subsequent performance monitoring before and after the remodeling.

2. Methods

2.1. Subject Building

The building we selected for the empirical study of green remodeling is a public health center, originally constructed in 2001. It provides medical services such as internal medicine, oriental medicine, physical therapy, and dental care to the local community. The building’s specifications are detailed in

Table 1. Summary of building attributes.

		Contents
	Location	Incheon-si, South Korea
	Building use	Public medical service
	Year of completion	2001
	Building footprint	912.89 m2
	Gross floor area	3698.88 m2
	Floor	B1, 1F, 2F, 3F, and rooftop
	Structure	Reinforced concrete

. It consists of a basement and three above-ground floors. As shown in Figure 1, the basement houses a parking lot and a mechanical room, while the first and second floors contain examination rooms, treatment rooms, and testing facilities. The third floor is dedicated to administrative offices for public health services. Approximately 100 staff members work in the building, which operates from 8:00 AM to 6:00 PM on weekdays, serving local residents throughout the day.

2.2. Study Process

In this study, the implementation of the green remodeling project was carried out through the following steps: (1) diagnosis of the current status of the target building, (2) energy-efficient design development, (3) construction supervision and design modifications based on on-site conditions, and (4) post-construction monitoring of building energy consumption.

The timeline for the green remodeling project is outlined in

Table 2. Timeline of the green remodeling process.

Phase	Date
Pre-diagnosed site	September 2020
Conceptual design	October 2020
Design development	June 2021
Re-diagnosed site	March 2022
Construction document	June 2022
Start of construction	August 2022
End of construction	December 2022
Energy monitoring	January 2023~present

. Following the completion of the conceptual design in October 2020, the construction was originally planned to commence in 2021. However, the onset of the COVID-19 pandemic led to an indefinite postponement. During this period, the building’s occupancy doubled, and the front yard of the building was frequently used for COVID-19 testing, creating a crowded and urgent environment. As a result, the green remodeling project could not proceed as initially planned.

The delayed construction timeline resulted in increased labor and material costs, necessitating modifications to the design. The final construction drawings were completed in June 2022. The remodeling commenced in August 2022 and was completed by December 2022. Monitoring of the building’s energy consumption has been ongoing since January 2023.

2.3. Subject Building Condition and Green Remodeling Strategy

To assess the degree of aging and performance of the target building, we conducted a comprehensive collection of basic architectural drawings and an on-site investigation. Unfortunately, no detailed drawings were available that could provide insights into the current thermal performance of the building. Despite various repair and replacement operations being undertaken over the years since its completion, there was a lack of architectural documentation for these modifications, making on-site diagnostics essential. For aspects that remained unclear during the on-site investigation, assumptions were made based on the building’s condition at the time of its completion.

South Korea has established energy-saving design standards aimed at enhancing the efficient energy management of buildings, including measures to prevent heat loss [13]. These standards, first enacted in 2001, have undergone continuous revisions with the addition of new requirements and the elevation of existing criteria. As the building under study was constructed in 2001, just before the energy-saving design standard was first enacted, it did not benefit from these guidelines, resulting in its energy performance significantly lagging behind current standards.

This remodeling project was carried out with consideration of the potential future elevation of energy-saving design standards to meet Zero-Energy Building performance levels. The design was implemented to reflect the highest standards currently required. The energy-saving design requirements of insulation performance are presented in

Table 3. Subject building performance and energy-saving design criteria.

Building Element	U-Value of Pre-Remodeling	U-Value of Energy-Saving Critera 1 (≤0.0 W/m2K)
		Required Standard 2	Highest Required Standard 3
Wall	0.57	0.24	0.15
Roof	0.42	0.15	0.15
Floor	4.0	0.29	0.24
Window	3.6	1.5	0.9

¹ Amended Standards for Energy-Saving Design of Buildings, Article 2, Clause 1, Table 1 [13]; ² Non-Residential/Central Region 2; ³ Residential/Central Region 1.

. The domestic energy-saving design standards in South Korea differentiate performance requirements based on climate zones and building characteristics, such as exposure to external elements and the building type. Although the subject building is located in Central Region 2 and is classified as a non-residential building, the remodeling targeted the highest standards, which are typically applied to buildings located in Central Region 1 and residential buildings.

3. Final Implementation of Green Remodeling

3.1. Wall System Enhancements

In this remodeling study, the building’s thermal insulation performance was enhanced by applying an external insulation system over the existing walls.

Table 4. Remodeling of the wall system.

Building Element		Existing Layer	Remaining Layer	New Application	U-Value (W/m2K)
					Pre	Post
Wall	Front Façade	AL sheet panel + concrete wall + 50 mm insulation + masonry structure	Concrete wall + 50 mm insulation + masonry structure	Granite stone finish + 80 mm PF (phenolic foam) board	0.57	0.15
	Back Façade	EIFS (exterior insulation and finish system) + concrete wall + 50 mm insulation + masonry structure		Stucco finish + 20 mm semi-noncombustible EPS (expanded polystyrene) insulation + 10 mm vacuum insulation panel + 20 mm semi-noncombustible bead method insulation	0.57	0.13

outlines the changes in wall composition and thermal performance before and after the remodeling. Prior to the renovation, the building’s wall finishes comprised two types: the front façade was finished with aluminum panels, while the back façade was finished using the Dryvit system. Since the insulation within the walls could not be verified on-site, it was assumed that a 50 mm expanded polystyrene (EPS) board, consistent with the insulation thickness requirements at the time of construction, had been applied [14]. Based on this assumption of a concrete wall structure, the thermal performance of the original walls was estimated to have a U-value of 0.57 W/m²K.

For the façade, esthetic considerations were paramount. To achieve the desired appearance, the aluminum panels were removed, and an 80 mm PF (phenolic foam) insulation board was installed, followed by the installation of a frame to secure stone panels, as shown in Figure 2a. On the back façade, an additional external insulation system was applied over the existing Dryvit finish. Due to the narrow gap between the building and the adjacent structures, a thin yet highly efficient 50 mm vacuum insulation composite board, as shown in Figure 2b, was utilized to meet the required thermal performance.

3.2. Roof and Floor System Enhancements

The roof insulation of the building was installed as internal insulation, allowing for the identification of the insulation type, thickness, and other details during the on-site inspection, as shown in

Table 5. Remodeling of the roof and floor system.

Building Element		Existing Layer	New Application	U-Value (W/m2K)
				Pre	Post
Roof	Rooftop Floor	30 mm protective mortar over urethane waterproofing + concrete slab + 80 mm EPS (expanded polystyrene) insulation	Urethane-based top coating + polyurea waterproofing + 10 mm protective insulation (hardboard) + 15 mm vacuum insulation panel + 5 mm PF (phenolic foam)	0.42	0.10
	2nd-floor Ceiling		Sprayed 150 mm fire-resistant rigid polyurethane foam	0.4	0.11
Floor	Basement Ceiling	Vinyl title + cement mortar + concrete slab	Sprayed 100 mm fire-resistant rigid polyurethane foam	4.0	0.19

. Both the ceiling of the third floor, which serves as the roof, and the ceiling of the second-floor director’s office were found to contain 80 mm expanded polystyrene (EPS) board insulation. Since floor insulation was not required by the construction standards at the time of the building’s completion, no insulation material was indicated in the plans, and on-site inspection confirmed the absence of insulation in the floors.

For the uppermost roof, an external insulation system was implemented using a vacuum insulation composite board applied to the rooftop floor, as shown in Figure 3a. However, the ceiling of the second floor, which is located beneath a rooftop garden on the third-floor terrace, could not accommodate the same external insulation as the uppermost roof. Consequently, a 150 mm spray-applied internal insulation was used on the second-floor ceiling, as shown in Figure 3b.

Regarding the first-floor slab, it is adjacent to the unheated underground parking garage. This garage is affected by external temperatures due to the ramp that allows for vehicle access. To enhance the insulation of the heated spaces on the first floor, the ceiling of the underground parking garage was insulated with a 100 mm layer of spray-applied polyurethane foam, as shown in Figure 3c.

3.3. Window and Vestibule Enhancements

Among the building’s exterior elements, the windows exhibited the lowest thermal performance, consisting of 16 mm double-glazed units with aluminum frames. Due to the inability to verify the exact performance, the thermal transmittance (U-value) of similar windows, as specified in design standards, was estimated to be around 3.6 W/m²K [13]. As shown in

Table 6. Window system after remodeling.

Type	Glazing	U-Value (W/m2K)	Airtightness (m3/(h·m2))
Sliding Window	39 mm triple glazing (LE 5 mm + Ar 12 mm + CL5 mm + Ar 12 mm + LE 5 mm)	1.19	0.66
Fixed and Projected Window	24 mm double glazing (LE 5 mm + Ar 14 mm + CL5 mm)	1.19	0.00
Curtainwall Window	24 mm double glazing (LE 5 mm + Ar 14 mm + CL 5 mm)	1.16	0.01
Fixed Window at Vestibule	26 mm double glazing (LE 5 mm + Ar 16 mm + CL 5 mm)	1.16	0.01

, all windows, including glass curtain walls, were replaced with high-seal aluminum-framed windows featuring low-emissivity (low-E) glass with argon-filled cavities. Although the project aimed to incorporate high-performance windows with U-values below 0.9 W/m²K, this objective was constrained by increased costs resulting from construction delays caused by the COVID-19 pandemic.

Most of the entrance doors were made of glass, which contributed to low thermal and airtight performance. This design made the first-floor lobby, along with the areas in front of the traditional medicine treatment and dental treatment rooms, particularly susceptible to heat loss. To address this issue, the main entrance was upgraded with a vestibule that included airtight frames and high-performance glass. For the secondary entrance, which previously consisted solely of glass doors without a vestibule, new vestibule systems of the same specification were installed, as illustrated in Figure 4.

3.4. Active Systems and Others

The building’s active systems primarily consist of the FCUs (fan coil units) installed during the original construction, with additional stand-alone air conditioners installed in some rooms. Additionally, certain spaces are equipped with radiators that utilize off-peak electricity. The building’s floor heating and hot water supply are provided by a boiler system. Due to budget constraints, a full replacement of the active systems was not feasible for this project; instead, the HVAC systems on the first and third floors were upgraded to EHP (electric heat pump) units.

Prior to the green remodeling study, energy-efficient upgrades had already been made. These included the replacement of all lighting fixtures with LED lights and the installation of a 27 kW photovoltaic (PV) system on the roof. As a result, no additional work was needed for the lighting or renewable energy systems.

The complete overhaul of the passive systems significantly improved the building’s thermal insulation and airtightness, leading to plans for the installation of energy recovery ventilation (ERV) units. However, during the construction process, structural challenges arose, preventing the installation of ceiling-mounted ERV units due to insufficient ceiling height. The increased costs associated with resolving these issues led to a design change, ultimately forgoing the installation of ceiling-mounted ERV units.

4. Energy Performance

4.1. Simulation Results

The building’s energy performance before and after remodeling was evaluated using the ECO2 simulation program, a tool officially recognized in South Korea for building energy assessments. ECO2 is based on ISO 13790 and DIN V 18599 standards [15,16], ensuring that the evaluation adheres to international norms for building energy performance. This program was selected due to its ability to reduce evaluator variability by employing a static state simulation that calculates primary energy demand using monthly average data [17]. The focus of this analysis was on the monthly heating and cooling energy demands, as these are critical indicators of a building’s energy efficiency.

Figure 5 and

Table 7. Annual heating and cooling energy demand and reduction rate.

Energy Demand	Pre (kWh/m2a)	Post (kWh/m2a)	Reduction Rate (%)
Heating	63.9	18.5	71
Cooling	15.1	21.4	(42)
Total	79	39.3	49

provide a comparative analysis of heating and cooling energy performance before and after remodeling. The remodeling resulted in a substantial reduction in annual heating energy demand, from 63.9 kWh/m²a to 18.5 kWh/m²a, representing a 71% decrease. This significant improvement can be attributed to the enhanced insulation and other energy-saving measures implemented during the renovation. However, the cooling energy demand exhibited a 42% increase, rising from 15.1 kWh/m²a to 21.4 kWh/m²a. This increase was primarily due to the improved insulation, which, while effective in reducing heating losses, also traps radiant heat entering through windows, thereby increasing the cooling load.

Additionally, the lack of energy recovery ventilation (ERV) units further contributed to the rise in cooling demand. Although the initial renovation plans included the installation of ERV units, structural challenges during construction—specifically, insufficient ceiling height—prevented the installation of ceiling-mounted ERV units. The absence of ERV units, which would have helped in mitigating the cooling load by expelling excess heat while maintaining indoor air quality, thus played a significant role in the increased cooling energy demand post-remodeling.

When evaluating the overall energy performance, the total monthly heating and cooling energy demand combined showed a reduction of approximately 49%, from 79 kWh/m²a to 39.9 kWh/m²a post-remodeling. This indicates that while the cooling demand increased, the overall energy efficiency of the building improved significantly, highlighting the effectiveness of the remodeling efforts. Future considerations may include exploring additional strategies to mitigate the increased cooling demand, such as optimizing window shading or enhancing ventilation strategies.

During the on-site diagnostics, certain assumptions were made regarding the thermal insulation properties of the existing walls and floors due to a lack of detailed architectural drawings. These assumptions, while grounded in standard practices, may introduce uncertainties in the pre-remodeling energy performance estimates. Specifically, it was assumed that the building’s insulation adhered to standards in place at the time of construction. As the insulation could not be verified in some areas, these assumptions may result in a slight over- or underestimation of the building’s initial energy performance.

4.2. Energy Consumption Results

To evaluate the effectiveness of the remodeling, we conducted an analysis of the actual electricity and gas energy bills, comparing pre- and post-renovation periods. The pre-remodeling data, drawn from January 2017 to December 2019, excluded the years 2020 to 2022 due to disruptions from the COVID-19 pandemic and ongoing construction activities. Post-remodeling data were collected from January 2023 to June 2024, immediately following the completion of the remodeling.

Figure 6 presents the analysis of electricity and gas consumption. The annual electricity usage dropped from 292,670 kWh pre-remodeling to 236,656 kWh post-remodeling, reflecting a 19.14% reduction. The post-remodeling electricity consumption decreased across most months, though there was an increase during the summer months of May to July due to a higher cooling demand. This increase aligns with the simulation findings and can be linked to the higher cooling demand due to the use of the electric heat pump (EHP) system, which operates on electricity. In contrast, gas consumption significantly declined from 1,174,326 MJ to 639,765 MJ, representing a 45.52% reduction, corresponding to the decreased heating demand. These figures demonstrate that the remodeling substantially improved overall energy efficiency, particularly in reducing heating energy consumption.

When we converted gas consumption into an equivalent electricity usage unit (Figure 7 and

Table 8. Annual energy usage of electricity and gas.

Annual Usage	Pre (2017–2019)	Post (2023–2024)	Reduction Rate
Electricity (kWh)	292,670	236,656	19.14%
Gas (MJ)	1,174,326	639,765	45.52%
Gas and electricity (kWh/m2a)	83.69	75.37	10%

), the average annual energy consumption decreased from 83.69 kWh/m²a before the remodeling to 75.37 kWh/m²a afterward, indicating an overall reduction of approximately 10% in total energy usage. This decrease underscores the energy-saving benefits of insulation improvement green remodeling, particularly in reducing heating demand. However, the increase in summer electricity consumption points to a potential area for further improvement.

Despite the seemingly modest 10% reduction in actual energy consumption, it is crucial to consider the broader context. The remodeling not only improved the building’s thermal performance but also significantly enhanced occupant satisfaction with the indoor thermal environment, as shown by the survey results in Figure 8. The improved insulation, while contributing to increased cooling loads, has created a more comfortable living space, which is a vital outcome of the renovation efforts.

5. Discussion

The green remodeling of the public healthcare center resulted in a significant reduction in energy demand, particularly in heating, where a 71% decrease was observed. However, the cooling demand increased by 42%. Overall, the total energy usage was reduced by approximately 10%, demonstrating the effectiveness of the effectiveness of the implemented strategies while also highlighting areas for improvement.

The substantial reduction in heating demand in our study can be attributed to enhanced insulation and the other energy-saving measures implemented during the remodeling process. This is consistent with the findings of Lee at al., who emphasized the importance of building envelope improvements in reducing energy consumption [10]. However, the increase in cooling demand highlights a common challenge in energy efficient remodeling: while insulation reduces heat loss, it can also trap heat inside the building during warmer months, increasing the cooling load. This phenomenon was also observed by Cho et al., who noted an increase in cooling demand post-remodeling [11].

Our study faced limitations similar to those reported in other research. The inability to install ceiling-mounted energy recovery ventilation (ERV) units due to structural constraints likely contributed to the increased cooling demand. Lee et al. similarly noted that limited remodeling interventions without effective ventilation systems, including mechanical ventilation with heat recovery (MVHR), did not generate increased energy savings [10].

Future research should explore the integration of advanced ventilation systems that can enhance cooling efficiency without compromising the gains in heating energy reduction. Additionally, studies that examine the long-term performance of remodeled buildings, particularly in varying climatic conditions, would provide a deeper understanding of how different retrofitting strategies perform over time. The development of more adaptable and cost-effective green remodeling solutions could further support the achievement of carbon neutrality in the building sector.

The green remodeling of the public healthcare center demonstrates the potential for substantial energy savings in aging buildings, though it also highlights the need for the careful consideration of both heating and cooling demands. By addressing these challenges, further remodeling projects can more effectively contribute to carbon reduction goals and the overall sustainability of public infrastructure.

6. Conclusions

To effectively mitigate carbon emissions from buildings, it is crucial to focus on energy improvement strategies for both new and existing constructions. This study underscores the potential of green remodeling as a viable approach to enhance the energy performance of aging buildings. By applying comprehensive energy-saving measures to a public health center built before the establishment of modern energy standards, significant improvements were observed, particularly in heating efficiency.

However, this study also revealed the complexities involved in green remodeling, particularly when dealing with unforeseen challenges, including those caused by external factors such as the COVID-19 pandemic and the limitations of existing building structures. The insights gained highlight that building managers and policymakers need to recognize that unforeseen obstacles may impede progress towards desired goals and acknowledge the potential for deviations from initial energy-saving targets due to unexpected challenges.

The green remodeling model presented in this study offers a valuable framework for similar projects, especially in public buildings that contribute significantly to national carbon emissions. Its applicability extends beyond the local context, providing a blueprint for energy efficiency improvements in diverse settings.

Future research should expand the scope to include a variety of building types and geographical locations, which would help in refining the model’s applicability and effectiveness. By addressing these areas, we can move closer to achieving the ambitious carbon neutrality goals set by nations worldwide, ensuring that our built environment contributes positively to the global effort against climate change.