Energy Efficiency Analysis of Building Envelope Renovation and Photovoltaic System in a High-Rise Hotel Building in Indonesia

Abstract

The development of high-rise buildings worldwide has given rise to significant concerns regarding their excessive electricity consumption. Among the various categories of high-rise structures, hotels used for business and conferences stand out as particularly extravagant in their energy use. The consequence arising from excessive energy usage is an escalation in carbon emissions, which is a primary driver of global warming. Therefore, this study aims to investigate the energy use intensity (EUI) of a hotel building located in Jakarta, Indonesia. In order to improve energy performance, this study explored various options for renovating the building envelope, such as incorporating insulation and a roof covering, as well as implementing building-integrated photovoltaics (BIPV). The building envelope renovations demonstrated a notable reduction in energy use by 15.8–27.7% per year. BIPV, such as curtain walls and double-skin façades, generated an energy use reduction of 4.8–8.6% per year. Remarkably, by combining the two approaches (i.e., adding insulation and a roof covering in the building envelope and adopting BIPV as double-skin façades), the potential reduction in energy use reached up to 32.2% per year. The findings can assist decision-makers in developing building renovation strategies for high-rise buildings while considering energy conservation.

1. Introduction

Buildings use a significant amount of energy, comprising approximately 40% of overall energy usage [1]. The 2021 United Nations Climate Change Conference (COP 26) highlighted the crucial role of buildings in climate action, emphasizing the requirement to cut emissions by 50% by the year 2030 through building energy efficiency [2]. In particular, high-rise buildings require enormous electricity consumption throughout operational periods, which increases carbon emissions, leading to environmental issues [3]. Among the various types of high-rise buildings, hotels are ranked as the highest energy-intensive structures, alongside shopping centers and office buildings [4]. As hotels use more energy compared to other commercial buildings [5], it is essential to improve energy performance in hotels to minimize their environmental impacts.

Two main strategies that can be implemented for such buildings are building envelope renovation and building-integrated photovoltaics (BIPV) installation. Building envelope renovation aims to reduce the energy demands of buildings, while BIPV installation aims to provide additional opportunities for energy generation. BIPV has the potential to transform the hotel industry by lowering energy expenses; enhancing hotels’ sustainable image, giving them a competitive edge; and contributing additional value towards achieving green building certification

Typically, the evaluation standard for investigating building energy use is the Energy Use Intensity (EUI) value, which is the ratio of energy used to the building’s gross floor area [3]. The EUI value, expressed in units of (kWh/(m²·year)), quantifies the annual energy used (kWh) per square meter of building area (m²) [6]. The impact of both strategies on influencing the EUI value is commonly assessed using building information modeling (BIM) tools such as Revit for building modeling and Insight 360 for EUI value analysis [7]. BIM enables the rapid analysis of energy performance across numerous design alternatives, proving particularly advantageous during the initial design phase of new buildings or the retrofitting design phase of existing buildings [8].

The approaches of these two renovation strategies differ significantly, with building envelope renovations focusing on enhancing thermal performance to resist heat transfer between the warmer and colder environments within a building [9], while BIPV installation hinges on the self-generation of renewable energy. These two strategies can function independently or in combination. As per Ochoa and Capeluto [10], integrating both passive building envelope renovations and BIPV strategies can yield a reliable energy reduction ranging from 50% to 55%, surpassing the savings achieved by implementing individual active features or passive design strategies alone. Therefore, this study aims to explore the potential for reducing EUI values by considering building envelope renovation and BIPV strategies independently and in combination.

1.1. Building Envelope Renovation Strategies

A building envelope consists of elements such as the walls, fenestration, foundations, roof, shading devices, etc., which separate indoor and outdoor environments [11]. The building envelope plays a vital role in regulating the temperature within indoor spaces [12]. Among the modifiable components of a building envelope, insulation stands out as the most effective and primary contributor to energy savings [13,14].

Correct utilization of thermal insulation within the building envelope proves to be the most efficient approach in diminishing the heat transmission rate and lowering energy consumption for heating and cooling internal spaces [15]. Adequate thermal insulation can notably decrease the annual cooling load and peak cooling demands for buildings situated in hot regions (both dry and humid) [16]. The factors considered in choosing insulation materials include material properties, material thickness, availability, ease of application, life-cycle cost, climate condition, and energy-saving rate [17].

The properties that influence insulation materials include thermal conductivity, thermal resistance, thermal transmittance, etc. [18]. The U-value (thermal transmittance), measured in W/m²·K, represents the overall heat flow coefficient, indicating the rate of heat transfer through one square meter of a building component with a 1-degree Kelvin temperature gradient. On the other hand, the R-value (unit: m²·K/W), the thermal resistance, is the inverse of the U-value and is crucial in insulation selection [19]. To be effectively integrated and operate efficiently within the building’s design, it is essential to attain low U-values in the building envelope [20].

In tropical climates, thermal insulation can be advantageous by maintaining cooler indoor temperatures through the reduction of heat transfer from the outside to inside [21]. Insulation helps in reducing the load on cooling systems, leading to energy savings. This is particularly relevant in regions with hot climates where air conditioning is commonly used [22].

Currently, there are many types of insulation materials on the market, each with distinct thermal properties, material composition, and associated costs. Their application methods vary depending on the overall structures of walls and roofs. Some studies conducted analysis using various insulation materials in tropical climate [23,24,25]. A study conducted in Maldives examined the potential for cost savings and emission reductions through the installation of various insulation materials at the optimal thickness in building walls [23]. The research revealed that using fiberglass (rigid) and fiberglass urethane (roof deck) at their ideal thicknesses could decrease fuel consumption by over 77%. Another study explored the application of extruded polystyrene (XPS) in two common wall structures, concrete blocks and compressed stabilized earth blocks, in Cameroon [24]. The research revealed that the orientation of the walls significantly influenced the optimal insulation thickness, consequently impacting energy savings.

A research project in Malaysia assessed the impact of ten different thermal insulation materials, including urethane, fiberglass, and XPS, on air-conditioning energy consumption for cooling purposes, considering the tropical climate [25]. The findings showed that energy savings ranged from 85 to 92%/m² depending on the insulation material at its optimal thickness. Finally, a study carried out in Iran focused on optimizing the thicknesses of various insulation materials and assessing them through life-cycle cost analysis [26]. Despite Iran not being situated in a tropical region, buildings in the country face substantial cooling demands. The study determined that as the thermal resistance of the insulation material increased, the cost of insulation also increased, but the cooling expenses decreased.

Roof technologies, alongside insulation, play a significant role in enhancing energy efficiency. Recent innovations, such as cool roofs and green roofs, have been employed in roof design to reduce cooling needs in buildings [27]. These strategies not only aid in conserving energy but also contribute to providing thermal comfort for occupants. One current approach suggests an optimum combination of surface reflectivity and insulation to maximize energy savings in buildings [28]. Among the various cool roof technologies and methods are reflective coatings, light-colored roofing materials, metal roofs, asphalt shingles, and roof ventilation.

1.2. BIPV Strategies

BIPV is an energy efficiency strategy that complements primary electrical energy with electricity generated from solar panels through energy conversion, which can reduce the use of fossil fuels and greenhouse gas emissions [29,30]. In its installations, BIPV integrates solar panels into building envelope components such as façades, roofs, and shading devices, rather than using separate mounting materials and spaces [31]. BIPV functions not only as an on-site electricity generator but also as an envelope material that can decrease the room temperature and save energy consumption for indoor lighting [32]. BIPV may act as additional layer, providing shading which therefore lowers the building’s cooling demand [33].

Currently, semi-transparent BIPV modules are frequently employed to curtain walls and façades to allow sunlight into the building interior while still fulfilling their role in generating electricity [34]. Semi-transparent BIPV curtain walls and BIPV double-skin façades (DSF) are two examples of BIPV. Apart from preserving the amount and intensity of natural light that goes in, semi-transparent solar panels also increase the aesthetic value of buildings. Semi-transparent BIPV can be accomplished either by using transparent thin film or spacing opaque solar modules [35]. BIPV modules are comprised of PV cells arranged with gaps between them, enabling a portion of solar radiation to penetrate. This feature proves particularly valuable in situations where there is a need for decreased or filtered sunlight [36].

The use of BIPV on building envelopes has been proven to reduce building energy consumption. Several studies have incorporated BIPV into the curtain wall. Chen et al. [37] presented evidence that the incorporation of BIPV into building windows could mitigate cooling loads, resulting in substantial energy savings of up to 63.71%. An et al. [38] showed that BIPV on building windows reduced the heating and cooling load by 18.2% when compared to double-layer windows.

Regarding BIPV DSF, some studies have investigated its energy performance. Peng et al. [39] provided evidence demonstrating that implementing a BIPV double-skin façade (DSF) featuring semi-transparent PV modules resulted in a significant reduction (of approximately 50%) in net electricity usage. Additionally, Peng et al. [40] illustrated that a BIPV DSF comprising a translucent amorphous silicon (a-Si) PV module and inward-opening windows offers a low solar heat gain coefficient (SHGC). Furthermore, Italos et al. [41] analyzed the energy performance pre- and post- an energy renovation that incorporated a BIPV DSF. The BIPV system contributed to around 26,706 kWh of electricity generation annually, covering 63% of the building’s projected energy use. Lastly, a study by Aguacil et al. [42] evaluated a combination of passive, active, and BIPV strategies for energy saving using a multi-criteria evaluation approach. This research revealed that the combined implementation of these strategies achieved energy savings of over 89%.

1.3. Aims and Scope

Few studies have focused on the impact of retrofitting strategies for high-rise hotel buildings, which are among the most energy-intensive buildings worldwide. One novel aspect of this research is that it addresses the existing gap in the literature, focusing specifically on the relatively limited retrofit studies of hotels. Another novel aspect of this study is the hotel building’s location and Indonesia’s unique climatic conditions as an equatorial country. In such regions, due to the consistent cooling demands throughout the year, the potential to minimize energy use through retrofitting strategies (both passive and active) is underrepresented in the existing literature. This makes the research a valuable contribution to reducing the energy demand in buildings located in equatorial countries. Therefore, this study aims to investigate the potential for reducing EUI in a high-rise hotel building in Indonesia through building envelope renovation and BIPV strategies. Three strategies were defined: (1) building envelope renovation by adding insulation materials to walls and roof; (2) semi-transparent BIPV installation in the form of curtain walls and double-skin façades; and (3) the combination of the first and second strategies.

Each strategy was subdivided into multiple sub-scenarios, with slight variations introduced in each of the sub-scenarios. The results of this study are expected to assist designers in planning the optimum building envelope renovation strategies for high-rise buildings while attaining the ideal EUI value for low-carbon buildings.

The structure of this paper is outlined as follows: Section 2 includes data from a hotel building case study along with the process of developing building envelope and BIPV installation strategies. Section 3 presents the resulting EUI values for each scenario and their comparison. Section 4 discusses the results and possibilities for future studies. Section 5 presents the conclusions of the research.

2. Methodology

2.1. Case Study Hotel

Indonesia, situated in Southeast Asia, possesses a tropical rainforest climate characterized by consistent high temperatures, humidity, and abundant rainfall throughout the year. The temperature typically ranges from 23 °C to 32 °C. Due to the hot and humid conditions, a significant portion of electricity, approximately 50–60%, is consumed for cooling and ventilation purposes [43]. Urban areas such as Jakarta heavily rely on heating, ventilation, and air conditioning (HVAC) systems, which contribute substantially to electricity consumption.

The selected case study is a high-rise hotel located in Jakarta, Indonesia, which was chosen due to Jakarta having 11% of the total hotel units in Indonesia [44]. Figure 1 shows the hotel from front and rear views. The selected hotel consisted of 21 floors, and the total building area of 9320 m² (44.4 m in length and 26.35 m in width) served as a suitable representative of Indonesian hotels. The guest rooms, lobby, and convention hall of the hotel were designed to use a centralized air conditioning system for temperature control convenience. The remaining spaces utilized a single-mounted or exhaust fan due to lower population density, making a targeted cooling approach more feasible and effective.

The initial modeling of the case study was referred to as the base case, representing the existing condition without any improvement. The building components of the hotel were assembled in Revit using the default settings, with slight adjustments made to comply with Indonesia’s standards.

Table 1. Initial characteristics of building components of the case study.

No.	Building Part	Building Products
1	Basement wall	Cement plaster 15 mm
		Cast in situ 400 mm
2	Interior walls	Light brick 100 mm
		Cement plaster 15 mm
		Frame partition with 19 mm gypsum board Adding soft board for both inner coverings
3	Exterior walls	Lightweight concrete 200 mm—no insulation
		Cement plaster 15 mm Adding aluminium composite panel for outer coverings panel and soft board for inner coverings
4	Curtain wall	Double glazed with reflective coating 30 mm
5	Ceilings	Lightweight concrete 200 mm—no insulation
		Cement plaster 15 mm
		Frame partition with 19 mm gypsum board
6	Flat roof deck	Cement plaster 15 mm
		100 mm lightweight concrete-no insulation
7	Room floor	Cement plaster 15 mm
		100 mm lightweight concrete—no insulation Adding ceramic tile and carpet tile

presents the characteristics of the building components of the case study.

2.2. Research Framework

The framework of this study is outlined in Figure 2. The workflow consists of three steps: (1) model preparation of initial design, (2) development of renovation scenarios related to passive building envelope and BIPV strategies, (3) combination scenario of passive and BIPV strategies. In the first step, the base case was built using BIM software (Autodesk Revit 2023.1). Material type and thickness, building dimension, building location, and weather data were obtained from the existing data of the hotel building study case. After the BIM model was developed, the EUI of the initial design was calculated using Insight 360. Then, renovation scenarios were developed, which were denoted as Scenarios A, B, and C for passive renovation strategies and Scenario D for BIPV installation. Scenario A emphasized adding building envelope insulation to walls, Scenario B focused on the addition of a roof covering, Scenario C was a combination of Scenarios A and B, and Scenario D was the implementation of BIPV installation. Lastly, optimal passive strategies were combined with BIPV application to obtain the maximum possible EUI reduction. This combination strategy was referred to as Scenario E.

2.3. Scenario Development

As mentioned earlier, the developed scenarios for this study are the base case, four individual scenarios, and one combination scenario. The EUI calculation for the base case was conducted in three phases: modelling, zone setting, and EUI calculation. In the modelling phase, the model was built based on existing data for the hotel building (see Table 1) and also from studies conducted by Fitriani et al. [45] and Berawi et al. [46]. In the zone setting phase, each room (or thermal zone) in the building was defined by its type, such as guest room, meeting room, etc. In the third phase, the EUI calculation was performed using Insight 360.

Scenarios A, B, and C were related to building envelope renovation, whereas Scenario D was related to BIPV application. Scenario A involved the addition of insulation to the building envelope, where the building envelope was modified by incorporating an additional insulation layer with three different material types (all having the same thickness): A1, A2, and A3. These insulations were 50 mm of polyurethane foam (PU), fiberglass batt, and extruded polystyrene (XPS) for A1, A2, and A3, respectively. The thickness of 50 mm was chosen to maintain the thickness of the existing wall. If the insulator was thicker than 50 mm, it would reduce the room size. Furthermore, in Scenario A, the previous curtain wall was replaced with triple energy-efficient glazing to improve energy performance.

Scenario B concentrated on building envelope renovation through the addition of roof coverings. Two types of renovation were developed in Scenario B: the application of reflective white paint and the incorporation of asphalt, designated as Scenarios B1 and B2, respectively. Meanwhile, Scenario C was a combination of Scenarios A and B, which entailed the installation of building envelope insulation and improvement of the roof coverings. As a result of Scenarios A and B being integrated, six distinct renovation configurations (3 × 2) were obtained in Scenario C.

Scenario D involved the application of an integrated solar panel system, referred to as BIPV, at two distinct building parts, namely the southeast (SE) and northeast (NE) sides of the hotel. BIPV was only modeled on the SE and NE sides of the building due to surrounding buildings that had been built on the west side of the building. The calculation of PV generation was performed using the solar analysis feature of Revit. A 13.3% panel efficiency was set due to the use of semi-transparent solar panels. The average efficiency value of 13.3% is derived from the efficiencies reported in two studies: 12.4% in the study by Zhao et al. [47] and 14.3% in the study by Wong et al. [48]. Lastly, the average for solar radiation was set to 2–6 kWh/m² [49].

Scenario D encompassed two primary configurations: semi-transparent BIPV integrated within curtain wall panels and semi-transparent BIPV employed as a double-skin façade, designated as Scenarios D1 and D2, respectively. Within Scenario D2, an aluminum mullion frame was utilized as the second façade layer, assuming its robust capacity to sustain the semi-transparent solar panels, which were attached to the glazing panels. Both D1 and D2 utilized the exact same dimensions of semi-transparent solar panels, measuring 1 m × 2 m. Moreover, Scenarios D1 and D2 shared an equivalent installation area of 882 m² for the NE side and 360 m² for the SE side. The depiction of BIPV installation for Scenarios D1 and D2 is shown in Figure 3.

Finally, the best passive strategies (from Scenario A to Scenario C) were merged with the most effective BIPV strategies (Scenario D) to form a combined scenario, called Scenario E.

2.4. EUI Calculation

For the renovation scenarios of the building envelope (Scenarios A, B, and C), the final EUI is obtained by conducting simulation in Insight 360 3.0. The software directly displays the final EUI results by doing calculations as shown in Equation (1). Equation (1) achieves EUI calculation (kWh/m²·year) by considering annual energy use (kWh/year) and total area of building (m²).

$${EUI}_{scenario}=\frac{Annual Energy Use}{Area}$$

(1)

For the analysis, EUI percentage reduction is calculated by comparing the EUI results from each scenario with the EUI value of the base case. The calculation is conducted by dividing the difference between the EUI of each scenario and the EUI of the base case by the EUI of the base case, as shown in Equation (2).

$${EUI}_{\% reduction}=\frac{{EUI}_{base case}-{EUI}_{scenario}}{{EUI}_{base case}}\times 100\%$$

(2)

Meanwhile, EUI calculation for Scenario D, which implements BIPV, requires several steps. The first step is to determine the building’s electricity consumption after installing solar panels, which might differ from the EUI of the base case. The calculation is performed using Equation (1). The second step is finding the production of solar panels. Equation (3) shows PV output (kWh/m²·year) considering energy production (kWh/year) and area of building (m²).

$${PV}_{output}=\frac{{Energy}_{production}}{{Area}_{building}}$$

(3)

Third, the final EUI of the BIPV scenario was obtained by subtracting the building’s electricity consumption from the solar panel production, as shows in Equation (4). Finally, the reduction percentage compared to the base case was calculated as shown in Equation (2).

$${EUI}_{final}={EUI}_{initial}-{PV}_{output}$$

(4)

3. Results

After establishing the baseline condition, the simulation outcomes for the base case yielded an EUI value of 336.7 kWh/m²·year. This value acted as a base value for the EUI reduction percentage of the four analyzed scenarios (Scenarios A–D).

Scenario A involved the addition of building insulation material, with 50 mm PU foam in A1, fiberglass batt in A2, and XPS in A3. The thermal conductivity (unit: W/m·K) of these insulation materials is considered to be 0.022 [50], 0.032 [51], and 0.036 [52,53], respectively.

The EUI results, calculated using Equation (1) by dividing the annual energy consumption by the total building area, are shown in Insight 360 and summarized in

Table 2. Thermal conductivity, U-value, and EUI calculation results of Scenario A.

Scenario	Material	Thermal Conductivity (W/m·K)	U-Value (W/m2·K)	Annual Energy Use (kWh/year)	EUI Value (kWh/m2·year)	EUI Reduction to Base Case (%)
A1	Polyurethane foam	0.022	0.155	2,570,456	275.8	18.1%
A2	Fiberglass batt	0.032	0.199	2,582,572	277.1	17.7%
A3	Extruded Polystyrene (XPS)	0.036	0.213	2,585,368	277.4	17.6%

. The selected hotel has a total building area of 9320 m². From Scenario A, Scenario A1 (addition of 50 mm PU foam) achieved the lowest EUI value (275.8 kWh/m²·year). Using Equation (2) to compare the EUI value with the EUI of the base case, Scenario A1 achieved the highest percentage reduction in EUI, which was 18.1%. This suggests that the use of PU foam, which has the lowest thermal conductivity value, produced the lowest EUI value among other scenarios related to building wall renovation. The low thermal conductivity of PU foam enables the minimization of transmission losses and thus results in a lower U-value, even when using the exact same thickness. Scenario A1, A2, and A3 yielded a U-value of 0.155, 0.199, and 0.213 W/m²·K, respectively.

The roof coverings used in Scenario B were a reflective coating in B1 and asphalt shingle in B2. The results of the EUI calculation for scenario B are summarized in

Table 3. Thermal conductivity, U-value, and EUI calculation results of Scenario B.

Scenario	Material	Thermal Conductivity (W/m·K)	U-Value (W/m2·K)	Annual Energy Use (kWh/year)	EUI Value (kWh/m2·year)	EUI Reduction to Base Case (%)
B1	Reflective coating	0.630	0.549	2,595,154	278.45	17.3%
B2	Asphalt shingle	1.594	0.553	2,644,643	283.76	15.8%

. The thermal conductivity (unit: W/m·K) of these roof coverings is 0.63 [54] for reflective coating and 1.594 for asphalt shingle [55]. The EUI value for Scenario B1 demonstrated the reflective capabilities of using a reflective coating, efficiently deflecting heat from sunlight. Meanwhile, the asphalt layer in Scenario B2 tended to absorb solar heat due to its higher emissivity compared to Scenario B1. This indicates that energy demand is affected not only by material thickness and thermal conductivity but also by the material’s capacity to reflect solar heat. As a result, the reflective coating from Scenario B1 yielded a lower EUI value and a higher EUI percentage reduction than the asphalt shingle from Scenario B2. Furthermore, Scenario B1 yielded a U-value of 0.549 W/m²·K, while Scenario B2 showed a U-value of 0.553 W/m²·K. Consistently with Scenario A, a lower U-value for roof coverings also resulted in a higher EUI reduction.

Scenario C is the combination of Scenarios A and B; the results are summarized in

Table 4. EUI calculation results for Scenario C.

Scenario	Description	Annual Energy Use (kWh/year)	EUI Value (kWh/m2/year)	EUI Reduction to Base Case (%)
C1	PU foam + reflective coating	2,268,488	243.4	27.7%
C2	PU foam + asphalt	2,280,604	244.7	27.3%
C3	Fiberglass + reflective coating	2,307,632	247.6	26.5%
C4	Fiberglass + asphalt	2,311,360	248.0	26.4%
C5	XPS + reflective coating	2,315,088	248.4	26.2%
C6	XPS + asphalt	2,326,272	249.6	25.9%

. There was no notable difference in the EUI values between Scenarios A and B. However, combining Scenarios A and B into Scenario C resulted in a significantly reduced final EUI value when compared to the base case’s EUI value. Scenario C1, which was the combination of PU foam insulation on the walls and roof and a reflective coating, produced the lowest EUI of 243.4 kWh/m²·year and an EUI reduction percentage of 27.7%. This was due to both materials having the lowest thermal conductivity.

In Scenario D, BIPV was implemented as curtain walls (Scenario D1) and as double-skin façades (Scenario D2); the results are summarized in

Table 5. EUI calculation results of Scenario D.

Scenario D	Description	PV Output (kWh/m2·year)	Initial EUI Value (kWh/m2·year)	Final EUI Value (kWh/m2·year)	EUI Reduction to Base Case (%)
D1	BIPV as curtain walls	15.24	335.6	320.3	4.8%
D2	BIPV as double-skin façades	15.24	322.9	307.6	8.6%

. The PV output results for both scenarios are the same because they use the same type of panels and the same area of coverage. The BIPV system generated 142 MWh annually. Dividing this by the building’s area (9320 m²) yields a PV output of 15.24 kWh/m²·year. The distinction between Scenarios D1 and D2 lies in their initial EUI values. Scenarios D1 and D2 yield initial EUI values of 335.6 and 322.9 kWh/m²·year, respectively. The lower initial EUI value in Scenario D2 is due to the shading caused by the solar panels acting as façades being more impactful compared to the solar panels acting as curtain walls. The final EUI values for the BIPV scenarios were calculated by considering the initial EUI value and the energy generated from BIPV, as outlined in Equation 4. Therefore, Scenarios D1 and D2 yielded final EUI values of 320.3 kWh/m²·year and 307.6 kWh/m²·year, respectively. This corresponds to EUI reductions of 4.8% for D1 and 8.6% for D2 compared to the base case.

The EUI values for Scenario C can be further reduced with the implementation of BIPV, as demonstrated by the results of Scenario D. To achieve the maximum EUI reduction, this study combined the optimum scenarios from both passive building envelope strategies and BIPV strategies. Specifically, the optimal among the passive strategies is Scenario C, particularly Scenario C1, while the best among the BIPV strategies is Scenario D2. In the calculation of the combined scenario, named Scenario E, the final EUI value of Scenario C1 was adjusted with the PV output from Scenario D2, resulting in 228.16 kWh/m²·year. When compared to the EUI value of the base case (336.73 kWh/m²·year), this equates to a 32.2% reduction in energy use.

Figure 4 and Figure 5 display the compilation of EUI values and the percentage reduction in EUI from Scenarios A–E compared to the base case’s EUI value. From Figure 4 and Figure 5, it is evident that renovating building walls or roof coverings individually has a more significant impact on reduction of EUI than installing BIPV alone. However, when these efforts are combined in Scenario E, the maximum reduction in energy use is achieved. This phenomenon can be attributed to several factors. Firstly, renovating the building envelope can address all sides of the building, whereas BIPV installations are limited to the NE and SE sides due to the proximity of adjacent buildings. Secondly, given the extensive building area of 9320 m², the energy production from BIPV, when divided by the total building area, results in a PV output of 15.24 kWh/m²·year. This output does not significantly offset the hotel’s high energy demand.

4. Discussion

The energy analysis results showed differences in approaches between passive envelope renovation strategies and BIPV implementation in reducing EUI values in a high-rise hotel building in Indonesia. Passive renovation minimizes heat transfer and, thus, energy use through wall insulation and roof coverings. Additionally, insulating the building envelope can mitigate structural damage risks from moisture, reduce material waste, and extend building lifespan, as shown by Cusenza et al. [56]. Meanwhile, integrating PV systems into a building not only generates clean energy and reduces electricity usage but also enhances property value and elevates architectural appeal, as demonstrated by Polo López et al. [57]. The combination of passive strategies and BIPV implementation, as explored in this study, yielded the most significant EUI reduction. Specifically, integrating 50 mm PU foam insulation into the building envelope, applying a reflective coating on the roof, and implementing BIPV as a double-skin façade emerged as the most effective strategy, achieving up to a 32.2% reduction in EUI.

A direct relationship was observed between the thermal properties of materials and EUI reduction. Thermal properties influence U-values, which regulate heat transfer and, consequently, lower EUI. In Scenario A, PU foam stood out for its heat transfer control, leading to a considerable EUI reduction. Scenario B benefited from reflective coating that, due to low emissivity, effectively reflected heat. As a result, the combination of PU foam insulation in the building envelope and a reflective coating on roof in Scenario C showed the most substantial EUI reduction, though this finding requires experimental validation. Future research could thus include prototype testing to evaluate the performance of various insulation materials and roof coverings.

Incorporating a PV system into the northeast and southeast of the building, as seen in Scenarios D1 and D2, contributed to a reduction in the building’s EUI. BIPV, by efficiently generating electricity, present a practical alternative to conventional energy sources. Specifically, in Scenario D2, utilizing BIPV as a double-skin façade (DSF) was more effective in lowering EUI than its application on the curtain wall in Scenario D1. The enhanced efficiency observed in Scenario D2 is primarily due to the shading conferred by the additional layer of BIPV as double-skin façade, which effectively mitigates solar heat gain, thereby lowering the building’s cooling demands. In contrast, Scenario D1, featuring BIPV on the curtain wall, fails to offer sufficient shading, which could have contributed to a reduction in cooling and energy demands. Thus, utilizing a BIPV double-skin façade in Scenario D2 leads to a more significant reduction in EUI, despite using the same solar panels and the same area for installation.

Nonetheless, installing BIPV on all sides of a building poses significant financial considerations. Solar panel initiatives demand substantial investment, as reported by Hajir et al. [58], who spent approximately 635 million IDR on 80 solar panel modules for a manufacturing facility. Based on this investment, the current study, which used nearly 600 semi-transparent panel modules, would face renovation expenses of around 4.7 billion IDR for BIPV installation. Additionally, Gholami et al. [59] highlighted the lengthy payback period for BIPV projects, which can extend up to 22 years. Given that the PV output from BIPV fell short of meeting the building’s energy demands, the main challenge with BIPV lies in its high investment costs and a prolonged payback period. Hence, further research is required to explore the life-cycle cost–benefits of BIPV as well as the combined life-cycle cost–benefits of integrating passive strategies with BIPV.

5. Conclusions

This study highlights the advantages of BIPV applications and building envelope renovations that use insulation materials and roof coverings to reduce energy use for a high-rise hotel building in Indonesia. Scenarios A1–A3 explored different insulation materials, including PU foam, fiberglass batt, and XPS, while Scenarios B1–B2 investigated roofing materials such as reflective coatings and asphalt shingle. The findings indicated that PU foam (used in Scenario A) was the most effective insulation material for building envelopes for minimizing heat transfer, and reflective coating (used in Scenario B) was identified as the optimal roofing material due to its high sunlight reflectivity. U-values, significantly affected by thermal properties and material emissivity, were key in determining EUI outcomes. The study found that combining 50 mm PU foam in the building envelope with a reflective coating on the roof yielded the lowest EUI value for the building case in Scenario C. Regarding renewable strategies, the study analyzed the integration of PV systems on the building’s curtain wall in Scenario D1 and as a double-skin façade in Scenario D2. The results demonstrated that while both scenarios produced the same amount of energy (15 kWh/m².year), integrating BIPV as a double-skin façade achieved a more substantial reduction in EUI value (8.6%) compared to the curtain wall BIPV. This significant reduction was attributed to the shading benefits provided by the double-skin façade BIPV, which effectively minimized solar heat gain and, consequently, the building’s cooling demand. Finally, to explore the maximum EUI reduction for the case study building, the most effective passive strategy from Scenario C was combined with the leading renewable strategy from Scenario D. This synergistic strategy involved incorporating 50 mm PU foam insulation into the building envelope, applying a reflective coating on the roof, and installing BIPV as a double-skin façade on the building’s northeast and southeast faces. This holistic approach led to a significant EUI reduction of 32.2%.