Addressing Energy Performance Challenges in a 24-h Fire Station Through Green Remodeling

Abstract

This study presents a comprehensive case of green remodeling applied to a local fire station in Seoul, South Korea. The project aimed to improve energy performance through an integrated upgrade of passive systems (exterior insulation, high-performance windows, and airtightness) and active systems (electric heat pumps, energy recovery ventilation, and rooftop photovoltaic systems), while maintaining uninterrupted emergency operations. A detailed analysis of annual energy use before and after the remodeling shows a 44% reduction in total energy consumption, significantly exceeding the initial reduction target of 20%. While electricity use increased modestly during winter due to the electrification of heating systems, gas consumption dropped sharply by 63%, indicating a shift in energy source and improved efficiency. The building’s airtightness also improved significantly, with a reduction in the air change rate. The project further addressed unique challenges associated with continuously operated public facilities, such as insulating the fire apparatus garage and executing phased construction to avoid operational disruption. This study contributes valuable insights into green remodeling strategies for mission-critical public buildings, emphasizing the importance of integrating technical upgrades with operational constraints to achieve verified energy performance improvements.

1. Introduction

As climate change intensifies, reducing carbon emissions has emerged as a central strategy for achieving global carbon neutrality. Among various sectors, the building sector plays a critical role due to its significant share of global energy use and emissions [1,2]. The building sector accounts for approximately 36% of global energy use and 39% of CO₂ emissions [3], making it imperative to enhance the energy performance of existing buildings to meet reduction targets. As part of the global push toward net-zero emissions by 2050, major economies have also set ambitious interim goals—such as the European Union’s target to cut emissions by 55% from 1990 levels [4] and the United States’ goal to reduce emissions by 50~52% from 2005 levels [1], further underscoring the urgency of nationwide and sector-specific actions. In this context, diverse strategies have been explored to enhance energy efficiency in the building sector, including renewable energy integration such as photovoltaic (PV) systems and energy storage optimization [5,6]. These studies highlight the growing role of renewable energy in decarbonizing building-related energy consumption.

South Korea has set a national goal to reduce building-related greenhouse gas emission by 40% from 2018 levels by 2050 [7]. In addition to mandating zero-energy standards for new constructions, a major strategy involves expanding green remodeling (GR) efforts for existing buildings [8]. Green remodeling refers to the renovation of aging buildings through a comprehensive approach that enhances envelope performance and active system efficiency, and integrates renewable energy technologies, thereby reducing energy use and carbon emissions. Various GR initiatives have been implemented since 2020 by the Ministry of Land, Infrastructure and Transport (MOLIT), the Ministry of Environment (MOE), and local governments. These initiatives have targeted daycare centers, community facilities, and health centers, yielding a growing body of performance data.

Empirical studies have demonstrated the effectiveness of green remodeling in reducing energy consumption and carbon emissions in aging public buildings. For instance, Cho et al. (2023) studied a public daycare center and reported a 48% reduction in primary energy use and a 46.7% cut in CO₂ emissions through the application of insulation, high-efficiency windows, and system upgrades [9]. Lee and Choi (2023) analyzed a remodeled community center and observed up to 35.4% electricity savings during winter months, with significant improvements in airtightness and reductions in heating and cooling loads [10]. Similarly, Lee and Kang (2024) reported a 71% reduction in heating energy consumption and approximately 10% overall energy savings in a public healthcare center after applying high-performance insulation and windows [11].

Table 1. Comparative summary of previous studies and this study on green remodeling.

Study	Building Type	Operational Type	GR Focus	Performance Evaluation
Cho et al. (2023) [9]	Public Daycare Center	Intermittent Use	Insulation, Window, HVAC	ECO2 simulation
Lee and Choi (2023) [10]	Community Center	Intermittent Use	Insulation, HVAC	Winter Season Monitoring
Lee and Kang (2024) [11]	Healthcare Center	Intermittent Use	Insulation, Window	1-Year Monitoring
This study	Local Fire Station	24-h Continuous	Insulation, Window, HVAC, PV	1-Year Monitoring

summarizes these previous studies in comparison to this study, highlighting differences in building type, operational characteristics, retrofit focus, and performance evaluation methods.

Despite these positive outcomes, most existing studies have focused on conventional buildings with intermittent use, offering limited insight into facilities that operate continuously, such as fire stations. These buildings have distinct occupancy patterns, higher standby energy demands, and functional constraints that differ from typical public buildings. Yoo et al. (2022) analyzed 19 fire stations and found that energy use patterns were largely unrelated to construction year and that heating systems were sometimes underutilized to avoid disrupting indoor comfort [12]. While subsequent studies have explored seasonal load variations and the impact of airtightness improvements [13], few have addressed the combined performance of passive and active systems under real operational conditions, or the practical limitations posed during remodeling, such as space constraints and the need for uninterrupted operation.

To address these research gaps, this study presents a comprehensive case of green remodeling applied to a local fire station in 24-h operation in Seoul. The project involved upgrades to both passive systems (e.g., 200 mm exterior insulation, airtight high-performance windows) and active systems (e.g., high-efficiency electric heat pumps, energy recovery ventilation units, and rooftop photovoltaic power), while ensuring continuous facility operation throughout the construction period. The study evaluates the project’s outcomes both quantitatively—through the analysis of utility-based energy savings and system performance—and qualitatively, by documenting construction-phase strategies for garage insulation, phased scheduling, and occupant impact minimization. By integrating technical performance evaluation with operational realities, this study contributes a practical framework for applying green remodeling to continuously occupied public buildings, which remain underrepresented in the current literature.

2. Building Description and Implementation Process

2.1. Studied Building

The subject of this study is a local fire station situated in Seoul. This facility operates 24 h a day as an emergency response station, characterized by continuous energy consumption. Although the building is relatively small, with a total floor area of 453.77 m², it consists of various spaces designed to support approximately 10 on-site personnel, as the facility is operated in three shifts with a total of 35 assigned firefighters.

Constructed with a reinforced concrete structure with masonry walls, the building received its construction permit in April 1995, was completed later that year, and received its occupancy permit in December. Detailed information about the building is summarized in

Table 2. Summary of the building.

Location	Seoul, Republic of Korea
Building Footprint	154.26 m2
Gross Floor Area	453.77 m2
Floors	B1, 1F, 2F, 3F, and Rooftop
Building Use	Local fire station
Building Permit Date	14 April 1995
Occupancy Permit Date	23 December 1995
Structure	Reinforced Concrete

. The building comprises one basement level and three above-ground floors, including a rooftop, as shown in Figure 1. The first floor houses office spaces and a fire truck garage; the second floor contains dormitories and shower facilities; and the third floor includes a dining area, fitness room, and the station chief’s dormitory.

2.2. Remodeling Process

The green remodeling project followed a four-stage process: planning, design, construction, and post-construction monitoring. An overview of the remodeling process is illustrated in Figure 2. This structured approach was adopted to enhance the building’s energy efficiency while accommodating the operational requirements of a continuously occupied public facility. To visually demonstrate the transformation achieved through the remodeling process, Figure 3 presents the exterior views of the building before and after the green remodeling.

In the planning stage, a target building was selected based on predefined criteria, which included buildings over 20 years old that failed to meet current energy-saving design standards. A local fire station in Seoul, completed in 1995, was ultimately chosen as the project site through collaboration with local government agencies. The building’s condition was assessed through a combination of floor plan reviews and on-site inspections. The remodeling target aimed at a 20% reduction in total building energy consumption, which was set as a voluntary goal for this project, referring to the energy performance improvement criteria commonly applied to private building remodeling projects in South Korea [14].

During the design stage, detailed drawings and technical specifications were developed to apply green remodeling technologies within the constraints of a limited budget. Material selection emphasized cost effectiveness and performance. Importantly, the building’s 24-h operational nature required that all construction be conducted without interrupting emergency services. As such, the design incorporated phasing strategies and noise/dust mitigation measures to minimize disruption to occupants and neighboring facilities. In the construction stage, efforts were focused on maintaining alignment between the design and on-site implementation. The architectural firm responsible for the design also supervised construction, ensuring that the intended performance outcomes were achieved. Unforeseen site conditions—such as the discovery of concealed piping during demolition—were addressed promptly through adaptive design revisions and field directives, enabling flexible problem-solving during execution.

The monitoring stage involved a comparative analysis of energy consumption before and after remodeling. Monthly electricity and gas usage were tracked using utility bills, allowing for a quantitative assessment of the remodeling’s impact. This analysis aimed to verify the tangible effects of the green remodeling and to generate valuable data for similar future projects.

3. Green Remodeling Design and Construction

3.1. Passive System Improvements

The passive system improvement strategy in this green remodeling project focused on enhancing the thermal performance of key envelope components—namely, the exterior walls, roof and ceiling slabs, windows and doors, and the garage area. To develop an effective intervention plan, a comprehensive diagnosis of the existing building conditions was conducted. This included assessing the original thermal performance at the time of construction (1995), and the characteristics of later renovations. A comparative summary of the building’s passive system components before and after green remodeling is provided in

Table 3. Comparison of building passive systems before and after green remodeling.

		Before Remodeling	Pre-GR U-Value [W/m2K]	Applied Technology	Post-GR U-Value [W/m2K]	Current Design Standard [15] U-Value [W/m2K]
Walls	Direct to outdoor	Dry exterior finish (metal, extruded cement board) + wall tile + cement brick + 50 mm Styrofoam + cement brick	0.61	Concrete brick finish + semi-noncombustible EPS 200 mm + wall tile + cement brick + 50 mm Styrofoam + cement brick	0.15	0.24
	Indirect to outdoor	Finish coat + cement brick + 50 mm Styrofoam + cement brick	1.53	Exterior finish + semi-noncombustible EPS 20 mm + vacuum insulation panel 10 mm + semi-noncombustible EPS 20 mm + cement brick + 50 mm Styrofoam + cement brick	0.13	0.34
Roof	Top floor	Waterproof coating + unreinforced concrete + reinforced concrete + Styrofoam 30 mm	0.48	Urethane top coating + polyurea waterproofing 3 mm + urethane waterproofing 1 mm + composite vacuum insulation board 23 mm + unreinforced concrete + reinforced concrete + Styrofoam 80 mm	0.13	0.15
	Garage ceiling	Reinforced concrete + Styrofoam 80 mm	0.45	Cement mortar 120 mm + reinforced concrete slab 150 mm + Styrofoam insulation 80 mm + flame-retardant rigid urethane foam spray 100 mm	0.13	0.21
Window		PVC frame with double glazing	3.6	47 mm low-e triple glazing aluminum curtain wall door	0.78	1.5
Door		Tempered glass and automatic doors	-	Low-e triple glazing aluminum curtain wall door	1.0	1.5
		Fireproof door	-	Insulated fireproof door	1.0	1.4

.

3.1.1. Exterior Wall Insulation

Although the building underwent an exterior finishing project in 2009, no thermal insulation improvements were made at that time (Figure 4a). The work focused solely on surface aesthetics, and the original 50 mm Styrofoam insulation, which falls significantly short of the current energy-saving design standards, was retained. To address this, the existing exterior finish was removed and an additional 200 mm of expanded polystyrene (EPS) insulation was applied to the original 1995 masonry walls with tile cover (Figure 4b,c). To mitigate potential fire hazards, semi-non-combustible EPS, certified under the national fire safety standards in Korea, was used for the exterior wall insulation [16]. The insulation thickness was determined based on structural conditions and spatial limitations.

During the construction phase, previously unidentified buried piping was found behind certain sections of the exterior walls after the removal of the existing cladding. In these localized areas, insulation thickness was adjusted from the specified 200 mm to 100 mm to accommodate these obstructions. Nonetheless, continuous insulation coverage was maintained to ensure overall thermal performance.

This upgrade significantly enhanced the wall’s thermal resistance and reduced heat loss. Following the application of the new insulation layer, the exterior wall was re-cladded using cement bricks, enhancing the building’s durability and providing a finished appearance (Figure 4d).

3.1.2. Roof and Ceiling Improvements

Thermal inspections revealed that the original insulation levels in both the roof and ceiling areas were far below the current standards, contributing significantly to heating loss (as shown in Table 2). The top floor ceiling was found to have only 30 mm of Styrofoam insulation, and the garage ceiling, which corresponds to the second-floor slab, contained only 80 mm of insulation.

To address this, different strategies were applied depending on the location and accessibility. On the main rooftop, external insulation and waterproofing were applied to improve thermal resistance from the outside (Figure 5a). In areas where the roof serves as a terrace with direct indoor access, interior spray foam insulation was applied to the ceiling from within, ensuring sufficient insulation while preserving usable outdoor space.

For the garage ceiling, internal spray foam insulation was selected (Figure 5b). This method allowed for a continuous and high-performance thermal barrier without removing or replacing the aging underfloor heating pipes embedded in the slab. This was particularly suited to the 24-h operational nature of the facility, avoiding extended downtime and minimizing disruption during construction.

3.1.3. Window and Door Upgrades

The original windows featured double-glazed PVC frames, but poor detailing—such as electrical conduits passing through window frames—resulted in thermal bridging and compromised airtightness (Figure 6a). Bloor door testing reveled a high air change rate (ACH = 9.16 h⁻¹), far exceeding recommended standards. All existing windows were replaced with high-efficiency, airtight units (Figure 6b), consisting of low-emissivity triple glazing and thermally broken aluminum frames. The new windows have a thermal transmittance (U-value) of 0.79 W/m²K, which is more than three times better than the previous installation. Thermal spacer bars and airtight tapes were also applied around window perimeters to further reduce thermal bridging and air leakage.

Although the post-remodeling ACH of 6.14 h⁻¹ remains above passive design benchmarks (typically 1.5~2.0 h⁻¹), it shows a clear improvement on the pre-remodeling value of 9.16⁻¹. The higher value can be attributed to testing constraints inherent in a 24-h emergency facility, where complete sealing was not feasible due to continuous operations. In particular, the large garage doors, which lack airtight design, significantly contributed to the residual air leakage. Nevertheless, the reduction confirms an improvement in overall airtightness. Further reductions in infiltration may be achievable in the future by replacing the garage doors with high-performance models or applying advanced sealing techniques as suitable technologies become available.

3.1.4. Insulation Strategy for the Apparatus Bay (Garage)

Although the apparatus bay in local fire station facilities is typically classified as a non-heated zone and is therefore not required to meet insulation standards in South Korea, the actual use of this space at the local fire station necessitated a different approach. In winter, the garage was routinely heated using a boiler system to prevent the firefighting water stored in the onboard tanks of fire trucks from freezing and to maintain operational readiness. This resulted in considerable energy loss, as the space was originally not designed to be heated.

In this remodeling, the garage walls were upgraded with the same level of insulation and window performance as the general occupied zones to minimize unnecessary energy loss. However, the garage door—which occupies a large portion of the wall surface—was not replaced, due to the absence of suitable high-performance industrial garage doors in the domestic market. Instead, the retrofit was designed to accommodate future replacement of the garage door once improved products become available.

Furthermore, because the garage door is frequently opened and closed during emergency dispatches, frequent air exchange with the outdoor environment is inevitable. This makes the garage a critical area for heat loss, reinforcing the importance of envelope-level upgrades in all surrounding components, even in traditionally non-heated spaces.

3.2. Active System Improvement Strategies

Active system improvements centered on replacing aging and inconsistent equipment to enhance the building’s operational energy efficiency. Prior to remodeling, the heating and cooling systems were a heterogeneous mix of hot water boilers, radiators, underfloor heating, and individual electric heat pumps (EHPs). Equipment had been replaced sporadically following failure, resulting in uneven performance across zones—for example, the first-floor office used radiators and EHPs and the second-floor dormitory relied on underfloor hot water heating and EHPs, while bathrooms were heated by radiators.

Although the coefficient of performance (COP) of the EHPs ranged from 2.6 to 4.1, the units varied in age (2015–2019), and overall system inefficiency was evident. During remodeling, all radiators and underfloor heating systems were replaced with new high-efficiency EHPs, while some functional units were retained as supplementary heating to minimize demolition and cost.

The domestic hot water system had also undergone makeshift modifications. Following a boiler breakdown in 2022, a dual setup was used—gas boilers for heating and electric on-demand heaters for hot water. This was resolved through the installation of new high-efficiency gas hot water boilers, restoring an integrated and reliable supply system.

For lighting, the garage still used fluorescent fixtures, while other interior areas had partial LED upgrades. The remodeling addressed this by replacing the remaining inefficient lighting with LED systems.

To meet ventilation requirements in the airtight indoor environment created through passive design improvements, energy recovery ventilation (ERV) units were installed in all occupied spaces (Figure 7a). Ceiling-mounted (250CMH) and wall-mounted (100CMH) units were selected according to room conditions, and each unit was equipped with individual controls to provide adequate fresh air while minimizing energy loss.

Additionally, a 3.6 kW rooftop photovoltaic (PV) system was installed to promote on-site renewable energy use (Figure 7b). Full rooftop coverage was not pursued due to spatial constraints and operational considerations, such as maintenance access. The generated electricity is consumed directly within the building without battery storage, contributing to reduced grid dependency and lower carbon emissions.

A summary of the system upgrades is presented in

Table 4. Comparison of building active systems before and after green remodeling.

		Before Remodeling	Applied Technology
Mechanical Systems	Cooling	Aging EHP	EHP system replacement
	Heating	Radiators, aging EHP, Underfloor hot water heating	Replaced with EHP
	Hot Water Supply	Electric on-demand water heater	Boiler replacement
Lighting System		LED light, fluorescent lights	LED lights
Ventilation System		N/A	Wall-mounted ventilation unit: 250CMH (70% heat recovery efficiency) Ceiling-mounted ventilation unit: 100CMH (72% heat recovery efficiency)
Renewable Energy		N/A	PV 3.6 kW, Southeast-facing, 15-degree angle

.

3.3. Predicted Energy Performance Based on ECO2 Simulation

To verify the energy-saving potential of the proposed remodeling measures during the design stage, a preliminary energy performance assessment was conducted using the ECO2 program, a simulation tool officially recognized in South Korea for building energy evaluations. ECO2 is based on ISO 13790 and DIN V 18599 standards [17,18] and calculates monthly primary energy demand using a static state simulation method. This tool estimates total primary energy consumption based on the combined energy demands of heating, cooling, domestic how water (DHW), lighting, and ventilation systems [19]. According to the ECO2 results, the building’s total primary energy consumption was expected to decrease from 290.9 kWh/m²yr before remodeling to 156.5 kWh/m²yr after remodeling—a reduction of approximately 46%. This validated that the proposed remodeling design significantly exceeded the initial target of a 20% reduction in total building energy consumption.

4. Results of Energy Improvement Measures

To evaluate the effectiveness of the passive and active system upgrades described in the previous sections, a quantitative analysis of energy performance was conducted using monthly utility billing data from the local fire station. Because the facility operates continuously in a compact and functionally consistent layout, occupancy-related variability in energy use is minimal, making this comparison method appropriate.

Data from 2023 were excluded due to the disturbance caused by renovation activities, including the frequent entry and exit of construction personnel and window and door openings for changing. Instead, the pre-green remodeling baseline was derived from the monthly average energy use between 2017 and 2022, and was compared with the 2024 data, for the first full year of post-green remodeling operation.

As shown in Figure 8, the building’s total energy use (electricity + gas) decreased by approximately 44%, significantly exceeding the initial goal of a 20% reduction in heating and cooling loads. Monthly savings ranged from 9.0% to 63.4%, with the greatest reductions observed in the winter months (see

Table 5. Energy usage and saving rate (%).

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sept	Oct	Nov	Dec	Total
Before GR (MWh)	23.97	20.20	14.43	11.61	6.80	5.15	5.17	4.95	4.18	6.25	11.92	18.17	132.81
After GR (MWh)	12.90	10.18	7.60	4.25	3.13	2.82	3.81	4.24	3.80	3.33	6.71	11.63	74.40
Reduction Rate (%)	46.2	49.6	47.4	63.4	54.1	45.2	26.5	14.5	9.0	46.7	43.6	36.0	44.0

). This demonstrates a substantial improvement in the building’s thermal performance and energy system efficiency.

4.1. Electricity Consumption

As shown in

Table 6. Electricity usage and saving rate (%).

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sept	Oct	Nov	Dec	Total
Before GR (MWh)	2.83	2.58	2.47	2.12	2.15	2.76	3.92	3.96	2.63	2.47	2.63	3.13	33.65
After GR (MWh)	4.60	3.75	3.01	1.97	1.79	1.86	2.97	3.50	2.96	1.97	2.46	3.63	34.46
Reduction Rate (%)	−62.5	−45.5	−22.0	7.0	16.7	32.7	24.3	11.7	−12.3	20.3	6.5	−16.1	−2.4

, the green remodeling resulted in a seasonal shift in electricity consumption patterns. During the winter months, January (−62.5%), February (−45.5%), and March (−22.0%), electricity usage increased compared to pre-remodeling levels, primarily due to the transition from gas-based heating to electrically powered systems. The newly installed electric heat pumps (EHPs) and energy recovery ventilation (ERV) now handle both heating and ventilation loads, replacing the previous gas-based systems and contributing to higher electricity demand during colder periods.

In contrast, during the transitional and cooling seasons, such as in May (32.7%), June (24.3%), and October (20.3%), electricity consumption decreased. These savings are likely due to the combined effects of improved insulation, more efficient cooling operation, and the contribution of the newly installed 3.6 kW photovoltaic (PV) system, which helped offset part of the building’s electrical demand during periods of higher solar irradiance.

This seasonal pattern is visually confirmed in Figure 9a, which presents monthly electricity consumption, showing increased usage in winter and reductions during warmer months. Additionally, Figure 9b, which plots electricity consumption against outdoor temperature, supports this interpretation. In the low-temperature range, the post-GR trend line exhibits a steeper slope, indicating increased electricity consumption during colder weather due to the operation of EHP and ERV systems. Conversely, in the high-temperature range, the post-GR trend flattens compared to pre-GR data, suggesting reduced electricity demand for cooling—a clear indication of enhanced energy efficiency during warmer periods.

While annual electricity consumption increased slightly by 2.4%, this should not be interpreted as reduced efficiency. Rather, it reflects a shift in energy source from gas to electricity for heating purposes. This trend is further explained by the significant reduction in gas consumption, as discussed in Section 4.2.

4.2. Gas Consumption

In contrast to electricity use, gas consumption showed a consistent and substantial reduction across nearly all months following the green remodeling. As shown in Figure 10a and

Table 7. Gas usage and saving rate (%).

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sept	Oct	Nov	Dec	Total
Before GR (MWh)	21.14	17.63	11.97	9.49	4.66	2.38	1.25	0.99	1.54	3.78	9.28	15.04	99.15
After GR (MWh)	8.30	6.44	4.59	2.28	1.34	0.96	0.83	0.74	0.84	1.36	4.25	7.80	39.93
Reduction Rate (%)	60.7	63.5	61.7	76.0	71.2	59.7	33.3	25.7	45.3	64.0	54.2	46.8	59.7

, monthly gas savings ranged from 25.7% to 76.0%, with the highest savings recorded in April (76.0%) and January (60.7%)—both during the heating season. These results highlight the impact of several retrofit measures, including enhanced insulation, improved airtightness, and, critically, the replacement of the gas boiler with an electric heat pump (EHP) system.

The scatter plot in Figure 10b further illustrates this improvement. In the low-outdoor-temperature range, the post-GR trend line is significantly flatter, indicating that gas consumption became less responsive to temperature drops. This reflects a reduction in heating-related gas use, achieved through better thermal envelope performance and the system shift from gas to electricity. In the higher temperature range (above ~20 °C), both pre- and post-GR trend lines remain nearly horizontal, confirming that gas consumption during these months is primarily associated with baseline non-heating uses, such as catering and domestic hot water, and is not significantly affected by outdoor temperature.

Overall, the reduction in gas consumption demonstrates the effectiveness of the passive measures and heating system changes in decreasing the building’s reliance on fossil fuels for space heating, contributing to lower energy costs and carbon emissions.

5. Discussion

5.1. Customized Remodeling Strategies for 24-h Operational Facilities

This study demonstrates that green remodeling of 24-h operational facilities requires a balance between improving energy performance and maintaining uninterrupted functionality. In this project, strategic insulation upgrades were applied even to non-heated zones like the fire apparatus bay, where operational requirements—such as preventing freezing of onboard firefighting water—necessitated localized heating. Although classified as a non-heated zone under regulations, the garage was treated with insulation and made airtight with high thermal performance windows, while the large garage doors, lacking suitable alternatives, remained unmodified. This case highlights the necessity of customized remodeling strategies that extend beyond regulatory classifications to address real-world operational demands.

Additionally, the project confirmed the feasibility of implementing significant energy remodeling without disrupting continuous public service operations. Staged construction, adaptive scheduling, and non-intrusive passive system upgrades were critical in minimizing disruptions. The discovery of previously unrecorded buried piping during construction further emphasized the need for thorough diagnostic assessments in early project stages to mitigate unexpected risks.

5.2. Energy Performance Outcomes and Validation with Simulation

Energy monitoring over one year confirmed a 44% reduction in total energy consumption, significantly surpassing the initial 20% improvement target. Passive upgrades, including high-performance insulation and airtight triple-glazed windows, combined with active system optimizations such as high-efficiency electricity heat pumps (EHPs), energy recovery ventilation (ERV), and rooftop photovoltaic (PV) generation, contributed to this achievement.

Additionally, an ECO2 simulation conducted during the design phase predicted a 46% reduction in primary energy consumption, which closely matched the actual reduction observed after remodeling. This consistency between simulation predictions and measured outcomes supports the reliability of the applied design strategies and validates the simulation approach for energy performance forecasting.

Seasonal energy behavior analysis further revealed the system-level impacts of the remodeling: gas consumption decreased substantially and became less dependent on outdoor temperatures, while electricity usage patterns shifted according to the electrification of heating system and improved cooling efficiency. The reduction in gas consumption is expected to lower direct carbon emissions from on-site fuel combustion, supporting the facility’s transition towards lower-carbon operations. As South Korea’ national grid continues to decarbonize, electrification strategies are anticipated to offer greater long-term benefits in terms of operational carbon footprint reduction.

5.3. Limitations and Future Research Directions

Despite the positive outcomes, this study’s findings are limited by its single case study approach, with applicability to other building types or climates requiring cautions interpretation. Although the remodeling framework—encompassing diagnostic evaluation, phased construction under occupancy, and envelope upgrades—can be adapted to other continuously operated public facilities, future studies should explore regional climate adaptations and validate its applicability across diverse building types to establish a broader evidence base.

In addition, the evaluation focused on the first year of post-remodeling operation. Long-term monitoring of energy consumption, photovoltaic system performance, and indoor environmental conditions would provide a more comprehensive assessment of remodeling outcomes over time. While this study focused on operational energy performance, future research should consider economic feasibility assessments to support decision-making in green remodeling projects.

6. Conclusions

This study demonstrated that a full-scale green remodeling of an aging, 24-h operational local fire station can lead to substantial improvements in energy performance and operational sustainability. Despite undergoing partial renovations in the past, the target building—originally constructed in 1995—significantly lagged behind current energy efficiency standards. Through a combination of targeted passive and active system upgrades, the project achieved a reduction of approximately 44% in total energy consumption. This result closely aligned with the 46% reduction predicted during the design phase using the ECO2 simulation tool, confirming the effectiveness of the applied strategies through one-year post-remodeling monitoring.

Key passive improvements, such as the installation of 200 mm EPS insulation, triple-glazed high-performance windows (U-value: 0.79 W/m²K), and airtight construction details, significantly improved thermal retention and reduced heating demand. Airtightness testing confirmed a reduction in the air change rate from 9.16 h⁻¹ to 6.14 h⁻¹, contributing to better thermal comfort and reduced energy loss.

Active system optimization, including the deployment of high-efficiency electric heat pumps (EHPs), energy recovery ventilation (ERV) units, and the integration of previously fragmented heating and cooling systems, further enhanced energy efficiency. The installation of a 3.6 kW rooftop photovoltaic (PV) system contributed to renewable energy generation and helped offset electricity demand.

Energy use patterns shifted as a result of these system changes. While electricity consumption increased modestly in winter due to the electrification of heating, gas consumption dropped by 63%, highlighting the impact of moving away from fossil fuel-based systems. In contrast, electricity use during the summer cooling period declined, reflecting the benefits of envelope improvements.

The remodeling was tailored to accommodate the unique operational needs of a 24-h local fire station. Strategic insulation of the fire apparatus bay—normally a non-heated zone—ensured thermal stability for vehicle readiness. Construction was carried out without interrupting building operations, underscoring the importance of careful planning and phased implementation in public facility remodeling.

This case study provides practical insight into the application of a green remodeling strategy for continuously operated public buildings. Future research should focus on long-term performance monitoring, replication across various building types, and integrated evaluations that consider indoor environmental quality and occupant satisfaction alongside energy metrics.