A Study on the Optimized Design for Responding to Climate Change Through Demonstration of Building Energy Cooling Load Element Technology

Abstract

This study proposes a building energy element technology system that addresses cooling loads, in response to rising average temperatures due to global warming caused by climate change. The study analyzes performance variations and energy-saving potential based on design parameters of individual element technologies, utilizing both simulation and field demonstration to derive an integrated Cooling Load Package System (CPS). The methodology comprises three key steps: (1) identifying and selecting element technologies suitable for optimal building design under subtropical climate conditions, (2) employing the building energy simulation software EnergyPlus v9.6.0 to evaluate the energy performance of each technology and establish prioritization based on energy-saving potential, and (3) conducting local climate validation through the construction of an outdoor demonstration site in northern Vietnam to assess the real-world energy-saving effectiveness of the proposed CPS.

1. Introduction

In recent years, the global community has established a common goal to reduce greenhouse gas emissions, which directly contribute to global warming. As the realization of carbon neutrality has emerged as an essential objective, reducing carbon emissions has become a key priority in the construction industry [1].

If the stages of improving energy efficiency in the building sector are divided into four phases (as illustrated in Figure 1), the initial focus is on enhancing the building envelope and adopting high-efficiency systems for “efficiency improvement”. The second phase emphasizes “demand management” technologies, such as passive building design and energy control and management strategies [2]. Once the industrial foundation and systems for efficiency improvement and demand management are established, the focus shifts toward the adoption of “new and renewable energy” solutions. Technologies and policies aimed at realizing zero-energy buildings—such as solar thermal systems, photovoltaics, and energy storage systems (ESS)—are being increasingly implemented. Finally, efforts to achieve the Green New Deal are accompanied by keywords such as convergence and digital architecture, targeting “zero energy” or “plus energy” technologies [3]. In addition, energy efficiency is one of the key national strategies for improving national economic competitiveness and sustainability, and the development of policies and interest in energy efficiency are closely related to the national economic growth rate. If we analyze the energy efficiency policies promoted at that time based on indicators such as the economic growth rate or income of advanced countries, we believe that we will be able to establish a more efficient industrial and policy foundation [4,5,6].

In particular, ASEAN countries with tropical climates are focusing on improving building energy efficiency as one of the main policies for reducing carbon emissions, as electricity and energy demand increases due to rapid economic development and urbanization [7,8,9]. Among them, Vietnam is currently the country with the highest construction market growth rate among ASEAN countries, at an annual average of about 7% (2019–2025), and has selected building energy efficiency policies as a priority to secure stability in energy supply and demand. A comprehensive reform of building energy efficiency regulations and support systems is underway [10]. In addition, the northern region of Vietnam is affected by a subtropical climate and can be compared to South Korea, which is changing to a subtropical climate, and the direct solar irradiance is also similar. In this study, Hanoi, Vietnam, was selected as a demonstration site for the application of building energy element technology [11].

Accordingly, this study aims to derive an optimal combination of technologies for reducing cooling load and enhancing energy efficiency.

As the average temperature increases due to climate change caused by global warming, the results of the comparative demonstration test in Vietnam are expected to serve as effective guidelines for reducing cooling energy in subtropical climates such as South Korea.

2. Derivation of Elementary Technology for Optimal Design in Subtropical Climate Response

Vietnam is a country centered on cooling loads, so it is necessary to select customized building energy efficiency items and technology levels. Therefore, through previous research [1,2,3,4,5], a building energy package element technology for responding to cooling loads was developed, as summarized in

Table 1. Building energy package technologies considering Vietnam’s climate and economic conditions.

Item	Purpose
Window and Film	Enhance thermal and optical performance to reduce cooling load
Insulation	Improve thermal performance of building envelope
Paint	Reflect solar radiation using low-emissivity materials
Air Conditioner	Apply an energy-efficient model (higher COP) to improve the indoor thermal condition
Lighting	Using LED to reduce lighting energy consumption
Ventilation	300 CMH class High Temperature and Humidity Climate Response Dehumidifying HRV System
Solar Photo Voltaic	Development of low-cost facility package linked to renewable energy (Solar PV)

. It includes radiant insulation materials with improved insulation performance and air thermal resistance, window films that can reduce solar heat loads, heat-insulating paints to reduce heat accumulation due to solar radiation, hidden-rail aluminum windows to respond to high-temperature and high-humidity environments, lighting that improves energy consumption efficiency, and high-efficiency inverter cooling equipment [12,13,14].

Performance Review of Building Energy Element Technology in Vietnam

Before applying the proposed package element technology to the outdoor demonstration test, two buildings to be demonstrated in Vietnam were selected to predict and derive priorities for energy-saving performance for each element technology [15]. Energy performance analysis was conducted focusing on the “passive system” element technology of buildings to be demonstrated using the EnergyPlus v9.6.0 program [16].

For the interpretation conditions of each building, the basic data values provided by the Vietnamese joint research institute were applied [17]. The total renovation of the building is limited, so one room size was selected for each site. The total floor area of buildings A and B to be demonstrated is 359.0 m² and 122.4 m².

As presented in

Table 2. Building energy package technology considering Vietnam’s climate and economic conditions.

Site	Category	Before Application	After Application
	Wall [W/(m2·K)]	1.264	0.500
	Roof [W/(m2·K)]	3.515	0.440
	Floor [W/(m2·K)]	3.515	0.440
	Window [W/(m2·K)]	5.300 Single-layer glass 5 mm	2.800 Double-layer glass 24 mm (film)
	Setpoint [°C]	22(Heating)/24(Cooling)	22(Heating)/24(Cooling)
	Light Density [W/m2]	5.0	5.0
	COP	2.0	2.0
[Site A]	Energy Demand [kWh/(m2·year)]	254.58	126.51
	Wall [W/(m2·K)]	0.904	0.500
	Roof [W/(m2·K)]	4.489	0.440
	Floor [W/(m2·K)]	4.489	4.489
	Window [W/(m2·K)]	5.300 Single-layer glass 5 mm	2.800 Double-layer glass 24 mm (film)
	Setpoint [°C]	22/24	22/24
	Light Density [W/m2]	5.0	5.0
	COP	2.0	2.0
[Site B]	Energy Demand [kWh/(m2·year)]	251.90	92.00

, Building A is expected to achieve an approximate 50.2% reduction in total energy demand, reaching 126.51 kWh/(m²·year), through enhanced performance of the external walls, roof, floor, and windows (including applied films). In addition, As shown on the left-hand side of Figure 2, improving the insulation performance of only the outer wall, roof, and floor results in about 36.4% reduction, and improving the insulation performance of windows and films shows a whopping 48.2% insulation effect. This is believed to be due to the high window-to-window area ratio in the case of Building A.

Building B can expect a reduction effect of about 63.5% compared to before the change, reducing energy use to 92.0 kWh/m²·year by changing the outer wall, roof, floor, and windows. In addition, As shown on the right-hand side of Figure 2, if the insulation performance of only the outer wall, roof, and floor is improved, about 52.3% reduction is achieved, and if the insulation performance of windows and films is improved, a reduction of 9.3% is observed. This includes the roof component, so it is concluded that a high energy-saving effect can be expected only by improving the insulation performance of the roof.

In the performance prediction through this simulation, it was possible to confirm the effect of reducing energy requirements by applying “passive system” element technology, and the priorities of energy-saving effects for each item were derived. Energy-saving effects were confirmed by improving insulation performance (supplementing insulation materials) and improving window performance (U-Value, SHGC improvement) according to the “characteristics of the building” being demonstrated.

However, this simulation analysis applies “active system” and “renewable” element technologies to predict performance and derive priorities for energy-saving effects for each element technology, and there will be some differences in energy consumption and performance during the actual demonstration.

3. Optimized Design and Verification of Building Energy Package Technology Through Demonstration Chamber

As a result of analyzing the energy saving performance according to the combination of element technologies through simulation of demonstration chamber and prior research [1,2,3], the optimized design element technologies for reducing the cooling load in response to subtropical climate are “passive system” windows, films, insulation, and paints; “active system” ventilation, lighting, and air-conditioning; and “renewable energy” solar cells. Therefore, this study proposes a Cooling Load Package System (CPS), which is the optimal design factor for responding to cooling load, and it is an organic combination design to cope with climate change, not just the application of advanced element technologies or the incorporation of integrated technologies. Although the proportion of each elemental technology may vary depending on the architectural design such as economic conditions and window area ratio, CPS intends to verify in this chapter by applying design technology with 60% for “passive system”, 30% for “active system”, and 10% for “renewable energy” [18].

3.1. Demonstration Outdoor Chamber Overview and Experimental Planning

The demonstration chamber is located at the Institute for Building Science and Technology (IBST), a research institute under the Vietnamese Ministry of Construction (MOC), in Hanoi, Vietnam.

Detailed specifications are shown in

Table 3. Demonstration chamber overview.

Location		Hanoi, Vietnam
Year of completion		April 2023
Floor number/total floor area		1st floor/18.3 m2 (detailed size: 3 m × 6.1 m × 2.5 m)
Structure		Sandwich Panel (PU)
Details	windows	5mm general glass (aluminum frame applied)
	walls	100 mm concrete + 10 mm insulation gypsum board 9.5 mm etc.
	air conditioning	Multi air conditioner
	lighting	LPD 13.11 W/m2 (fluorescent lamp applied)

and

Table 4. Demonstration chamber configuration and construction specifications.

Division	Construction Specification
Space unit chamber	- Dimensions: 3 m (width) × 6.1 m (length) × 2.5 m (height) - Exterior wall thickness and material: 150 mm, polyurethane (thermal conductivity 0.019 W/(m·k)) - Exterior finish: paint
Sample mounting frame	- Dimensions: 4.5 m (width) × 4.51 m (height) × 1.8 m (thickness) - Weight: approximately 1.78 tons - Opening for wall test installation (maximum size 3.3 m (W) × 3.1 m (H) × 0.25 m (D) - Detachable stud construction, anti-corrosive finish paint treatment
Measurement room (monitoring room)	- Dimensions: 2 m (width) × 2 m (length) × 2.5 m (height), container structure

. The demonstration chamber was constructed to simulate the actual environment, and the configuration of the measuring devices and the locations and number of installations for monitoring are shown in Figure 3.

Although the demonstration period was shorter than initially planned, efforts were made to collect reliable data by selecting periods with outdoor temperature distributions that were as similar as possible before and after the retrofit.

Table 5. Details before and after application of element technology.

Division		Before Construction(Baseline)	After Construction (CPS Application)
Passive system	windows	Aluminum frame, single layer glass 5 mm	Aluminum frame, double-layer glass 24 mm
	film	-	Attach low-emissivity film to glass
	insulation	PU Panel	Construction of low radiation insulation 40 mm
	paint	-	Apply the heat shield to the middle of the road and to the top
Active system	ventilation	-	Heat Recovery Ventilation (HRV) 1 EA
	lighting	Fluorescent light efficiency—55 (lm/W) Power consumption (30 W)	LED light efficiency—134 (lm/W) Power consumption (25 W, 20 W)
	air conditioning	EHP COP 3.0(-), 1EA	EHP COP 4.5(-), 1 EA
Renewable energy—PV		-	Single crystal capacity—3115 W Module efficiency 20.8%

summarizes the detailed technology application status before and after the implementation of CPS. Figure 4 presents the annual temperature distribution in Vietnam, and

Table 6. Demonstration period before and after CPS.

	Site and Duration	Outdoor Chamber (IBST) Demonstration Period
Category
Baseline period data		17 April 2023~2 June 2023 (47 days)
CPS installation		7 June 2023~30 June 2023 (24 days)
CPS period data		4 July 2023~26 September 2023 (85 days)

outlines the demonstration period details.

The indoor air conditioning setpoint was consistently maintained at 28 °C throughout all procedures. The power consumption of internal heat gains and lighting systems was measured in response to external environmental conditions, such as solar radiation, outdoor air temperature, and humidity [19,20]. Furthermore, the energy savings were analyzed using the International Performance Measurement and Verification Protocol (IPMVP), Option C [21], with appropriate modifications for the study context.

Figure 5 presents photographs of the test site before and after the implementation of the Cooling Load Package System (CPS).

3.2. Analysis of Savings from Demonstration Chamber Simulation

EnergyPlus is a representative dynamic building energy simulation tool developed by the US Department of Energy (DOE), and it can interpret energy consumption of various factors such as cooling and heating, ventilation, lighting, and renewable energy systems in detail. In addition, DesignBuilder was used for 3D modeling associated with EnergyPlus.

According to the energy analysis of the CPS before application (baseline energy), the heating energy demand per unit area was 6.26 kWh/(m²·year), and the cooling energy demand was 128.34 kWh/(m²·year) (Figure 6). Heating accounted for approximately 3.6% of the total energy demand, while cooling accounted for 73.4%, indicating that the cooling load was significantly higher due to the influence of local climatic conditions. Before applying CPS, the heating energy consumption per unit area was about 1.89 kWh/(m²·year), and the cooling energy consumption was 38.77 kWh/(m²·year), with cooling accounting for 44.1% of the total energy and lighting accounting for about 45.7%. Heating accounted for about 2.2%, which is completely different from the energy pattern of commercial buildings in Korea. The energy analysis results are shown in Figure 7.

As a result of energy analysis after applying CPS (package measured energy), the heating energy demand per unit area was 6.02 kWh/(m²·year), and the cooling energy demand was 72.58 kWh/(m²·year). Heating accounted for approximately 6.9% of the total energy demand, and cooling for 83.3%, indicating that the cooling load was significantly higher than before construction.

After applying CPS, the heating energy consumption per unit area was approximately 1.34 kWh/(m²·year), and the cooling energy consumption was 16.13 kWh/(m²·year), indicating that cooling accounted for 37.7% of the total energy and lighting for about 19.85%. According to the application of the total heat exchanger, the ventilation energy consumption per unit area was 10.1 kWh/(m²·year), which accounted for a relatively large proportion—23.6% of the total. The results of the energy analysis are shown in Figure 8.

As a result of the analysis of the energy-saving effect according to the application of CPS, the heating energy demand per unit area showed a slight saving rate of about 3.83%, while the cooling energy demand was 43.45%, and the lighting energy demand was 78.89%. The total energy demand was 174.80 kWh/(m²·year) before construction and 87.09 kWh/(m²·year) after construction, showing an energy-saving effect of about 50.18%.

As a result of the analysis of energy consumption per unit area, lighting was the highest at 78.89%, followed by cooling at 58.40% and heating at 29.1%. According to the application of the total heat exchanger, ventilation energy consumption per unit area was calculated as 10.08 kWh/(m²·year). However, since energy was saved in cooling and heating, the total energy consumption decreased by about 51.43%, from 88.01 kWh/(m²·year) before construction to 42.75 kWh/(m²·year). The results of the energy-saving effect analysis are shown in

Table 7. Results of energy demand and energy consumption analysis before and after CPS application.

Division	Energy Demand [kWh/(m2·year)]			Total Energy Demand [kWh/(m2·year)]	Energy Consumption [kWh/(m2·year)]					Total Energy Consumption [kWh/(m2·year)]
	Heating	Cooling	Lighting		Outlet	Heating	Cooling	Lighting	Ventilation
Before CPS	6.26	128.34	40.20	174.80	7.14	1.89	38.77	40.20	-	88.01
After CPS	6.02	72.58	8.49	87.09	6.71	1.34	16.13	8.49	10.08	42.75
Savings rate (%)	3.83	43.45	78.89	50.18	6.05	29.10	58.40	78.89	-	51.43

.

As a result of the analysis of energy-saving effects from CPS and the application of solar facilities, the annual solar power generation forecast is about 2572.46 kWh, and the primary energy consumption per unit area, including power generation, is about 23.01 kWh/(m²·year).

Table 8. Results of analysis of primary energy requirements according to solar power application.

Division	Primary Energy Demand [kWh/(m2·year)]	Solar Energy Production [kWh/(m2·year)]	Primary Energy Demand Including Power Generation [kWh/(m2·year)]
Before CPS application	242.03	-	242.03
After CPS application	117.56	140.57	−23.01
Savings rate (%)			109.51%

shows the results of calculating the primary energy consumption according to the application of solar PV.

3.3. Results of Empirical Application of Optimized Design Model

In order to secure as reliable data as possible by analyzing the monthly similar outdoor temperature distribution, the baseline period (18 April 2023~1 June), 45 days, and the package period (5 July 2023~18 August), also 45 days, were compared and analyzed under the same conditions.

As a result of energy analysis before CPS application (baseline energy), the average outside temperature for 45 days is 30.8 °C, the cumulative energy consumption is 551.33 kWh, and the energy consumption per unit area is 30.13 kWh/(m²·day). As a result of energy analysis after applying CPS, the average outside temperature for 45 days is 30.1 °C, the cumulative energy consumption is 141.57 kWh, and the energy consumption per unit area is 7.74 kWh/(m²·day), which is 74.3% lower than before applying CPS. In this way, the reliability could be increased by verifying the prediction results of the simulation model through outdoor demonstration tests. By comparing the results of the two methods in the future, the limitations of each method should be supplemented, and even if it takes more cost and time, it seems that long-term empirical tests should be conducted to secure reliable analysis results.

Table 9. Results of energy consumption analysis before and after the application of CPS.

Category		Data
Baseline Period	Average outdoor temperature	30.8 (°C)
	Average indoor temperature	28.2 (°C)
	45 days of cumulative energy consumption	551.33 (kWh)
	Energy consumption per unit area	30.13 (kWh/m2·day)
CPS Period	Average outdoor temperature	30.1 (°C)
	Average indoor temperature	28.3 (°C)
	45 days of cumulative energy consumption	141.57 (kWh)
	Energy consumption per unit area	7.74 (kWh/m2·day)
Energy saving		74.32%

shows the results of the energy-saving effect analysis through demonstration tests.

As a result of the analysis of the energy-saving effect of the application of CPS and solar facilities, solar power generation is 11.21 kWh/(m²·day), and energy consumption per unit area, including solar power generation, is −3.48 kWh/(m²·day), indicating a net energy gain of 11.5% when renewable energy sources are included. Even if the initial investment cost is high, the application of new and renewable energy is considered to have a great energy-saving effect.

Table 10. Results of energy consumption analysis according to CPS with solar PV application.

Division	Primary Energy Demand [kWh/(m2·day)]	Solar Energy Production [kWh/(m2·day)]	Primary Energy Demand Including Power Generation [kWh/(m2·day)]
Before CPS application	30.13	-	30.13
After CPS application	7.74	11.21	−3.48
Savings rate (%)			111.54%

shows the results of calculating energy consumption according to the application of solar power generation with CPS. Figure 8 shows the energy consumption according to the outside temperature during the baseline period, and Figure 9 shows the energy consumption according to the outside temperature during the CPS period. In addition, Figure 10 shows the amount of solar power generated according to the amount of insolation.

4. Conclusions

In this study, we propose building energy element technologies that address increasing cooling loads due to the rise in average temperatures caused by climate change. Through both simulation and field demonstration, we analyze performance variations and energy savings associated with design factors of each element technology, ultimately deriving a Cooling Load Package System (CPS) optimized for climte-responsive performance. Furthermore, the applicability and usability of the CPS-based optimized design configuration are evaluated.

The key findings of this study, based on the proposed element technologies, are summarized as follows:

The final selection of technologies aimed at reducing cooling loads includes passive system components such as high-performance windows, solar control films, thermal insulation materials, and heat-shielding coatings as well as active system technologies, including lighting, air-conditioning systems, and mechanical ventilation. Additionally, renewable energy components, such as photovoltaic (PV) solar panels, are incorporated.

Simulation-based performance prediction confirmed that the application of passive design technologies effectively reduced cooling energy demand. Moreover, the analysis enabled the identification of priority levels in energy-saving contributions from each individual element technology.

The simulation results for the demonstration chamber indicated that, compared to the baseline condition prior to the application of the package element technologies, the energy requirements were reduced by 3.8% for heating, 43.5% for cooling, and 78.9% for lighting. Overall, the total energy requirement—including that for ventilation—was reduced by approximately 55.4%. Furthermore, when renewable energy generated from solar photovoltaic (PV) systems was integrated, the total energy consumption showed a net reduction of 109.5%, indicating surplus generation beyond building demand.

The empirical analysis conducted after applying the Cooling Load Package System (CPS) revealed that the average accumulated energy requirement was 141.57 kWh, with a unit-area energy demand of 7.74 kWh/(m²·day). This represents an energy saving of approximately 74.3% compared to the pre-CPS condition. Additionally, the energy saving attributed solely to the application of solar PV systems demonstrated an improvement of approximately 115%, again indicating a surplus in energy generation.

The proposed building energy element technologies, developed in response to increasing cooling loads, were validated through both simulation and empirical testing. To ensure greater reliability and representativeness of the findings, future studies should incorporate long-term performance monitoring over periods exceeding one year. Given the ongoing rise in global temperatures due to climate change, the empirical results obtained from this Vietnam-based demonstration are considered valuable as practical guidelines for reducing cooling energy consumption in hot and humid climates.