Reaching Near-Zero Environmental Impact in Heritage Buildings: The Case of the Wine Cellar of Rocafort de Queralt

Abstract

In the current context of a necessary reduction in environmental impact, the reuse of heritage buildings is key. Although architectural rehabilitation already significantly reduces this impact, thermal comfort facilities present several challenges, both due to the huge visual impact they entail, compromising buildings’ historical values, as well as the environmental impact due to machines and ducts and the operating energy consumption. This paper demonstrates, through the case study of the Rocafort de Queralt Wine Cellar, that it is possible to reduce to nearly zero the thermal comfort facilities of converted heritage buildings for public cultural use. This historic building, considered one of the “Wine Cathedrals” in Spain, was built in 1918 and is characterized by its architectural style typical of Catalan modernism. The method applied was in situ monitoring, combined with dynamic simulation with DesignBuilder v7 software and NECADA software v2024, considering four different scenarios of the building: (1) the current state; (2) after passive improvements; (3) after architectural rehabilitation; and (4) subject to the climatic conditions expected for 2050 according to IPCC AR4 A2. The conclusions are surprising. In Scenario 2, 87% thermal comfort is reached with zero facilities, and 100% thermal comfort is reached when the location of cultural activities within the building is changed according to geographical orientation and the season of the year.

1. Introduction

1.1. Legislation on Energy Efficiency and Heritage Buildings

Research on the energy efficiency of historic buildings is increasing, with a particular focus on those with heritage protection. This is due to several reasons, primarily because they constitute a substantial portion of the built environment in Europe and hold significant reuse potential. Additionally, there is a lack of technical and professional knowledge about their thermal behavior, which is essential to establish intervention solutions that improve their efficiency while preserving their main cultural values [1].

In March 2024, the European Union published its latest directive on energy efficiency, stating that buildings considered part of cultural and historical heritage may be exempted from the regulations derived from this directive in each Member State.

In Spain, since 2012, energy efficiency requirements for building renovations have been mandatory, except for those listed for their heritage values. This approach is similar in other EU countries, as legislation recognizes that historical values are the priority [2,3].

Despite this legal “exclusion”, experts agree that heritage buildings cannot remain outside the scope of energy sustainability, as the consequences could be dire. This includes historical areas at risk of abandonment due to energy inefficiency and high rehabilitation costs [4]. Building owners and managers are the main stakeholders in designing solutions that allow the preservation of heritage values while making them more sustainable [5]. Therefore, the sustainable and comfortable reuse of heritage buildings is essential [6].

1.2. Conflicts Arising from Improving Energy Efficiency and Preserving Cultural Values

Common strategies to improve the energy efficiency of existing buildings often have a high, generally negative impact on the historical documented values of the building [7] and its surroundings [8]. As a result, either the preservation of these values is prioritized, or new materials and technologies that reduce energy demands and environmental impacts are given precedence. But as we have seen, legislation leans towards preservation.

To date, a typical strategy to improve thermal comfort in historic buildings has been to rely indiscriminately on mechanical systems [9], which often focus primarily on preserving the building and its artworks rather than user comfort [10].

Additionally, because the envelope of historic buildings is often considered their most inefficient element in terms of energy performance [11], modern building layering systems have also been applied. However, adding thermal insulation to the envelope is rarely compatible with preserving historical values [12]. In Mediterranean climates, it can even increase the need for cooling in summer [13].

Nonetheless, various researchers have opted for other passive strategies that do not create an impact while improving the energy performance of historic buildings in Mediterranean climates. These include night-time ventilation [14,15] or thermal mass [16], though it should be noted that calculating thermal transmittance accurately is challenging, as it varies depending on the building’s location [9,17].

Some authors prioritize replacing carpentry and glazing over any other passive intervention strategy, depending on the window-to-wall ratio (WWR) [18]. Fouseki [19] established that balancing thermal comfort improvement and heritage preservation is a socio-cultural practice. It depends on original materials, restoration professionals’ skills, costs, historical–cultural values, interior thermal and luminous environments, and the time users have been living in the building.

Ultimately, it is essential to consider that restoration interventions in historic buildings do not have the same objectives as modern building construction. They must consider additional requirements, such as using materials compatible with the originals and maintaining authenticity criteria to ensure the preservation of historical, artistic, and cultural values for future generations [20].

It may be time to consider that some sustainability improvements in buildings can be compatible with their cultural values and should be understood as the added value of our era—the 21st-century layer [12].

1.3. The Specificity of Historic Industrial Buildings

Historic industrial buildings are characterized by large interior air volumes, minimal decoration, and low thermal mass [21]. These features result in complex airflow movements, creating thermally stratified environments with vertical temperature differences [22,23,24].

Additionally, these buildings require functional reconversion and in-depth research on their energy behavior. However, there is limited specific research on this topic [22,25]. An example is the research conducted in the Falset cellar (Spain) [26], also designed by architect César Martinell, where the focus has been primarily on architectural and constructive restoration. Here, there is already a noticeable concern for preserving this type of agricultural building intended for new uses, through conservation and functional rehabilitation, prioritizing passive strategies before incorporating active systems. A similar approach is used in the wine cellars and oil mills of southern Italy [27], based on bioclimatic principles to enhance environmental comfort and natural light intake. In fact, the restoration of such buildings is occurring throughout the Mediterranean basin [28], where the wine culture is deeply ingrained, with an emphasis on future climate scenarios and their social, economic, and environmental implications [29].

1.4. Comfort in Historic Buildings: A Different Perspective

Furthermore, it is worth considering whether thermal comfort should be measured in the same way for new and heritage buildings. It has been demonstrated that users’ perceptions and the heritage values of the buildings influence their understanding of the building’s conservation, energy use, and thermal comfort. Thus, user perception of thermal comfort and expectations must be integrated into studies on the energy efficiency of these buildings through user-centered strategies [30].

Murillo Camacho [31] conducted a study on user comfort in heritage buildings, concluding that while users recognized the initial environmental shortcomings of the building, they preferred adaptive comfort rather than invasive interventions that could jeopardize the building’s historical–cultural values.

Lucchi in Italy [32] observed that users behave differently in these types of buildings due to cultural and experiential factors, exhibiting distinct comfort preferences.

1.5. Thermal Comfort Dynamic Simulation Through DesignBuilder

Considering the above, it is possible to establish comfort limits based on user understanding and the type of use: permanent or sporadic.

The PMV/PPD (Predicted Mean Vote/Predicted Percentage of Dissatisfied) model is mainly used to evaluate thermal sensation [33]. Various authors propose raising Fanger’s PMV to −1/+1 [25,34], which accepts up to 20% of users feeling some discomfort.

Dynamic simulations to study the hygrothermal behavior of historic buildings allow for the consideration of the indicated PMV and the investigation of various rehabilitation scenarios based on boundary conditions. In fact, the issue of simulations is extensively addressed in the scientific literature: from the definition of a comprehensive framework for building energy simulation, ensuring model credibility through dynamic modeling, calibration, and validation, which enhances the usefulness of the final results [35], to integrated systems for decision making [36], and experiences in historical and heritage buildings [37,38], such as the San Salvatore hospital in L’Aquila (Italy) [39].

Approximately half of the published research on dynamic energy simulation has used the EnergyPlus v7 calculation engine [1]. However, some authors argue that further research is needed on Fanger’s models applied to historic buildings with large interior air volumes [10,30]. Limitations include a lack of knowledge about the thermal–physical parameters of the envelope and difficulties in representing complex geometries [1].

1.6. The Future Already Present

(a)

nZEB and heritage

Achieving an nZEB (nearly Zero-Energy Building) is challenging for protected historic buildings [40], although some authors have developed possible scenarios [41]. These scenarios often end up including photovoltaic panels, as it is rarely feasible to act on protected envelopes due to their cultural and architectural values. Despite the technical and economic feasibility of renewable energy systems, especially solar, to achieve near-zero emissions by 2050, their integration into historic neighborhoods and buildings presents various barriers [4]. Only some buildings are more likely to be modified rather than fully preserved [42].

Another option is to place photovoltaic panels nearby, rather than on top of the monument, and to study the integration of the panels into the landscape [43]. However, even if renewable energy exceeds consumption, nZEB status is not achieved unless all required parameters are met. The premise is not just to use renewable energy but to require very low or almost zero energy.

(b)

Environmental impact

Despite the European Commission establishing in its 2011 roadmap, A Roadmap for moving to a competitive low-carbon economy in 2050, that the European construction sector must reduce greenhouse gas emissions by 90%, the criteria for greenhouse gas reduction and energy management in historic buildings have been little explored [20]. This is despite knowing that mitigating climate change also depends on the energy efficiency of historic buildings, which cause more CO₂ emissions than new buildings [44].

Mamo Fufa [45] conducted a study on the restoration and adaptive reuse of existing buildings, including heritage buildings, from a lifecycle perspective. The study concluded that extending the service life of existing buildings reduces greenhouse gas emissions by 50%, while preserving cultural values and saving scarce raw material resources:

“Given most of the world’s building stock for the next 30 years already exists today, consideration of refurbishment and adaptive reuse of existing buildings, in general, and historic/heritage buildings, in particular, is considered as the way towards a sustainable future” and “Findings in the literature support the conclusion that the refurbishment of existing buildings”, including buildings with historic/heritage values, is preferable in the 30-year time frame up to 2050, as it can take from 10 to 80 years before the embodied GHG emissions arising from a new building are compensated for.

(c)

Climate change

Although the impact of climate change on heritage buildings is little explored [46], it is expected that for the Mediterranean climate, climate change will cause overheating during summer periods, increasing energy loads and carbon emissions from cooling systems [47].

For historic buildings, this will affect the preservation of artworks and the thermal comfort of users. A comparative study conducted by Muñoz-González [34] shows that comfort will increase by 10–20% during the cold months but decrease by 20–30% during the warm months. Meanwhile, legislation in most EU countries continues to prioritize only the preservation of cultural values.

This literature review has identified a lack of scientific literature about thermal comfort in heritage industrial buildings with interior spaces of great height and huge air volumes. These are buildings with extraordinary reuse potential, warranting further investigation to fulfill the goals of this research.

The objective is to explore whether it is possible to reduce the energy demand of a historic building with large interior air volumes, used for cultural purposes, to the point that relocating some activities according to the season could eliminate the need for HVAC systems, achieving an nZEB but also a nZEIB (near-Zero Environmental Impact Building) while preserving cultural values.

2. Materials and Methods

2.1. Case Study

The Rocafort de Queralt Winery, located in a rural setting, represents a significant example within the context of Catalonia’s so-called “Wine Cathedrals”. It serves as a model that intertwines winemaking activities with rural tourism and the preservation of cultural heritage. This space not only embodies the history and architecture of the region but is particularly noteworthy for being the first work of renowned Catalan architect Cèsar Martinell dedicated to agricultural use, further enhancing its historical and cultural value. The winery remains operational, producing wines and sparkling cavas, highlighting its potential to evolve into a center promoting wine culture, enotourism, and cooperative practices (Figure 1).

The structure achieves a balance between functionality, economy, and aesthetics. As wineries, these buildings needed to maximize production efficiency (functionality), be constructed using local and accessible materials (economy), and simultaneously inspire pride among the farmers who worked there (aesthetics). Martinell, influenced by one of his great mentors, Antoni Gaudí, incorporated the use of parabolic arches or inverted catenaries (Figure 2). He also designed large openings in the spandrels (the areas between arches, walls, and ceilings) and employed Catalan vaults for both the roof and the bases of the fermentation vats.

The primary materials used were brick and terracotta, leveraging the region’s clay resources to promote local employment and reduce construction costs. Additionally, tiles and ceramics were incorporated as decorative elements, enhancing the aesthetic appeal without significantly increasing the budget.

Currently, the winery is undergoing a transition where its historic, rural, and industrial character is being complemented by new activities, including recreational events, gastronomy, guided tours, and wine tastings.

The integration of mechanical systems to provide thermal comfort for future users, aligned with the requirements of these new activities, poses several challenges. These systems can visually impact the structure and compromise the historical values of the building. Moreover, the maintenance costs of such systems add a financial burden to the conservation of heritage buildings.

The interplay between humans and space, framed by a contemplative architecture imbued with meaning, underscores the complex task of achieving comfort without compromising the building’s historical memory or the surrounding natural environment.

The design of passive solutions and the building’s historical-material capacity to support new activities, combined with an analysis of the climatic context where the structure is situated, form the foundation of this research. The aim is to determine the building’s specific suitability and adaptability across different scenarios, throughout the year, during critical periods, and at specific times of the day.

2.2. Method for Assessing Thermal Comfort Conditions

The research develops a methodical approach to evaluating the thermal comfort of historic buildings with special characteristics, particularly those with large volumes. The process begins with an initial phase involving an extensive literature review that encompasses the building’s history, construction techniques, and the analysis of relevant historical climate data using models such as ERA5T and NEMSGLOBAL. These models provide high spatial and temporal resolution information on temperatures, winds, humidity, and other atmospheric factors.

In the second phase, a comprehensive characterization of the building is conducted, analyzing aspects such as its construction properties, orientation, envelope, ventilation systems, and climatic conditions. This phase includes on-site visits to perform surveys, take measurements, and create detailed photographic records of both internal and external features, supported by drone technology. This stage also involves understanding the building’s future activities and, consequently, the clothing of its users.

The third phase involves on-site monitoring of hygrothermal data. Here, the modeled climate data are compared with observed climate data to calibrate the climatic file, a resource that will simulate the climatic characteristics of the area.

Finally, this study concludes with a thermal comfort analysis based on Fanger’s mathematical model, utilizing key indicators such as the Predicted Mean Vote (PMV) and the Predicted Percentage of Dissatisfied (PPD). The DesignBuilder software, powered by the EnergyPlus engine, is employed for this purpose, enabling precise modeling and simulation of scenarios while integrating variables such as materials, occupancy, and climatic conditions.

2.2.1. Data Collection on the Building and Users

The Celler Cooperatiu is located in the town of Rocafort de Queralt, within the Conca de Barberà region in the province of Tarragona, Spain. The site is situated on a sloped parcel covering approximately 3109.32 m², with a built area of approximately 2600 m² (Figure 3).

Architecturally, it comprises a set of three naves constructed in different periods (1918, 1931, and 1948, respectively), all sharing the same material, construction, and formal characteristics (Figure 4).

The main façade faces north with a slight tilt towards the west. The naves forming the façade share a uniform design and aesthetic, characterized by a large three-section window. The central section features a semi-circular arch, while the lateral sections follow the roof’s slope, and are constructed with exposed brick.

On the southern side, there is a fourth nave added in the last construction phase, used as a loading and unloading area.

The eastern façade combines exposed brick for the cornices and windows with stucco as a finish for the masonry walls. The southern and western façades follow the same design, but the western façade features a lower section clad in stone (Figure 5).

For decorative purposes, ceramic pieces featuring motifs related to wine agriculture, such as grape clusters, have been used on the windows, cornices, and façades.

The building also includes a basement beneath the three main naves (Figure 6).

Inside, the geometry of the arches forming the transverse porticoes varies across the naves. The dimensions of these arches, which define the building’s cross-section, are as follows:

Left nave (A): b = 11.50 m, h = 9.90 m;

Central nave (B): b = 10.60 m, h = 9.60 m;

Right nave (C): b = 11.10 m, h = 9.60 m.

The winery is built with stucco masonry walls, except for the door and window arches, as well as the parabolic arches and cornices, which are made of exposed bricks measuring 27 × 13 × 5 cm.

The roofs of the naves and the loading dock are gabled with a 30% slope. They consist of wooden beams supporting wooden ties, topped with ceramic elements and traditional Arab tiles.

Interior finishes include walls coated with mortar and painted, while the flooring is a smooth mortar finish.

Occupancy and thermal comfort—beyond the building’s technical and physical characteristics, another key factor in determining user thermal comfort is occupancy based on time of day. The Celler has defined a schedule for future activities, specifying hours and occupancy data, along with zoning into four areas (

Table 1. Opening Hours and Occupancy Data.

Zone	Type of Use	Summer Schedule	Rest of the Year Schedule	Occupation
1	Restoration Space, Intensive use air conditioning	every day from 12:00 to 24:00	Friday night, Saturday all day, Sunday half day	80 People
2	Welcome of Visitors, Wine Bar, Restaurant	every day from 10:00 to 22:00	every day from 10:00 to 18:00	50 People
3	Multipurpose space, sporadic air conditioning, intensive use	on demand	on demand	200 People
4	Meeting and Tasting Space	from Monday to Friday	Friday night, Saturday all day, Sunday half day	TBD

). Additionally, temperature setpoints were established (

Table 2. Temperature Setpoints.

Heating Design Data Heating
BS Nominal Temperature with 99% Percentile
Minimum Dry Bulb Temperature °C	−5
Coincident Wind Speed	3.0
Refrigeration Design Data
BS Nominal Temperature with 1% Percentile
Maximum Dry Bulb Temperature °C	29.5
Wet Bulb Coincident Temperature °C	24.5
Minimum Dry Bulb Temperature °C	18.0

).

Temperature setpoints define the desired comfort range for HVAC systems. The heating set point is 21 °C, while the cooling setpoint is 25 °C. These systems maintain interior temperatures within this range: heating activates below 21 °C, and cooling activates above 25 °C. Within this range, both systems remain inactive.

Activity and Clothing; the user activity level and its associated physical movement must also be specified. In this case, a light activity level was considered, involving standing and a relaxed visit where guests walk slowly through the winery. This level correlates to a metabolic rate of 93 W/m².

Finally, clothing levels, which depend on the climate, were defined. For summer, a clo value of 0.5 (light clothing) was assumed, while winter clothing was set at 1.5 clo (thick jacket). For the rest of the year, intermediate values were interpolated.

2.2.2. Onsite Monitoring

These conditions are evaluated by sampling with 12 thermal sensors installed in the building, with a time cut, for data analysis between February and July 2023, on its facades and in the internal part of the building (Figure 7). The hygrothermal analysis of the Celler Rocafort de Queralt provides a detailed view of its behavior during the months studied, offering information on the cold, warm, and spring periods.

The building generally maintains a cool indoor environment, with relative humidity levels ranging from 50% to 70%, depending on the season. During February and March, corresponding to the winter season, indoor temperatures averaged 10 °C, with relative humidity ranging from 60% to 65%, creating relatively humid conditions. Solar radiation on the southeast façade, in particular, reached significant peaks, approaching 30 °C, highlighting considerable daytime solar incidence.

As spring progressed in April and May, indoor temperatures increased slightly, averaging 15 °C in April and rising to 20 °C in May. Relative humidity showed a stable decline, settling around 60%. During June and July, the warmest months of this study, indoor temperatures rose significantly, averaging 24 °C, while relative humidity dropped to 50%. Solar radiation had a notable impact on the building’s most exposed façade, with southeast-facing surfaces experiencing peak temperatures exceeding 40 °C.

This drop in relative humidity is typical of warmer, drier climates, potentially contributing to higher thermal discomfort under conditions of intense solar radiation. The southeast façade, receiving the highest solar exposure, emerges as the most critical area in this regard.

2.2.3. Dynamic Simulation

The dynamic simulation software used was DesignBuilder, operating with the EnergyPlus calculation engine. Data were progressively entered in the following sequence: first, the building configuration; followed by user occupancy, activity, and clothing; then climatic data; and finally, simulation scenarios. Each of these phases is detailed below.

The initial step involved modeling the building, specifying the surfaces of envelope elements responsible for thermal exchange, as well as materials and their theoretical thermal performance, as shown in Figure 8 and

Table 3. Parameters of the Envelope Elements in the Current State.

Envelope Elements	Theoretical Thermal Transmittance, U (W/m2 C)	Enclosure Thickness (cm)	Solar Heat Gain Coefficient
Stone Wall	1.2	60
Brick Wall	1.2	60
Brick Wall	1.2	42
Ceramic Tile Roof	3.77
Concrete Floor and Roof	1.62
Metal Door	5.8
Wooden Door	2.67
Single Glass Window	5.80		0.847

.

Next, occupancy data were introduced based on projected activities and the potential number of future visitors, as well as user activity and clothing (Table 1).

Subsequently, climatic data were input and calibrated using three sources: climatic data (T, RH) provided by a nearby weather station, modeled climate data from ERA5T and NEMSGLOBAL, and in situ monitoring data collected outside the winery. The latter considers the following parameters: Theoretical Thermal Transmittance, which refers to the measure of heat transfer through building elements per unit of time and surface area. The term “theoretical” is used because the envelope of historical buildings is heterogeneous and requires specific monitoring to determine its approximate average value; Inertia, which indicates the amount of heat a body can retain and the rate at which it transfers or absorbs heat from the environment; Solar Heat Gain Coefficient, which corresponds to the percentage of radiation that the glass allows to pass through; and Dry/Wet Bulb Temperature, where the former measures temperature without considering the Relative Humidity of the environment, while the latter does take it into account.

Lastly, simulation scenarios were defined to establish the degree of thermal comfort for users, simulating various conditions to evaluate their impact on thermal comfort, while maximizing energy efficiency and environmental performance.

This approach aims to thoroughly analyze both the architectural envelope and the mechanical climate control systems of the winery, a building with unique characteristics, such as its large-volume spaces.

Through real-time dynamic simulations using hourly climate files, the building’s energy demands and consumption are calculated, along with the thermal comfort or discomfort of its users.

Passive climate control strategies are evaluated in this process, including natural ventilation, solar heat gain utilization, strategic shading, and the use of thermal mass or inertia. These solutions are analyzed under different scenarios to optimize thermal performance without altering the building’s historic essence. Additionally, the heating and cooling systems are sized based on climatic design conditions defined through ASHRAE’s Heat Balance Method, ensuring technical coherence in the results.

The results are presented in various time intervals (annual, monthly, daily, hourly, and sub-hourly), facilitating analysis through both graphical representations and spreadsheets. These outputs detail the thermal comfort variable based on thermal sensation estimation using Fanger’s method and table, first obtaining the Predicted Mean Vote (PMV) and then calculating the Percentage of People Dissatisfied (PPD).

The first developed model, referred to as Scenario 1 or the current situation, considers the original state of the building with its primitive materiality, incorporating the projected activity schedule for its future use. This baseline model establishes a solid reference for comparison with improved scenarios.

In Scenario 2 or passive improvements, changes are introduced in the construction materials to optimize their thermal transmittance coefficient, maintaining the inertia of the walls as a key factor (

Table 4. Parameters of the Envelope Elements in the Passive Improvement State (Scenarios 2, 3, and 4).

Envelope Elements	Theoretical Thermal Transmittance, U (W/m2 C)	Enclosure Thickness (cm)	Solar Heat Gain Coefficient
Stone Wall	1.2	60
Brick Wall	1.2	60
Brick Wall	1.2	42
Ceramic Tile Cover + EPS 10 cm	0.33
VentilatedCover + Wooden Deck	0.28
Wooden Door	2.67
Glass Guardian TEX 62 low E 5 mm glazing	0.98		0.474

). These improvements do not alter the built volume, but rather optimize its thermal performance, seeking to reduce hours of discomfort. Thermal insulation was incorporated into the roofs (10 cm EPS). Additionally, the carpentry was replaced. Originally, the cellar windows featured a single 4 mm-thick glass pane. For the window retrofit, Guardian TEX 62 Low E glass was selected, which breaks thermal bridges. It consists of 5 mm inner glass, a 12.7 mm air gap, and 5 mm outer glass.

In Scenario 3, the integration of a contemporary architectural project introduces a large glazed volume to the historic building, establishing a symbiotic connection with the surrounding vineyards.

To complete the scenarios, a theoretical future climate was projected based on the IPCC AR4 A2 [49] predictions, enabling an evaluation of how climate change might impact this particular building (Scenario 4). The comparison across all four scenarios was conducted by analyzing results obtained using the Fanger method, while adjusting the variables according to the theoretical understanding of the model.

In the results analysis, a graphical model was developed, allowing clear visualization of variations in temperature, humidity, and the Percentage of People Dissatisfied (PPD), alongside the Predicted Mean Vote (PMV) values. This provides a global overview of the situation while also focusing on critical conditions throughout the year, including the weeks with the highest and lowest temperatures during summer and winter, as well as the design day. Graphs for these scenarios were also exported for detailed examination.

These graphs, respectively, display the average thermal sensation inside the building and the percentage of people likely to feel discomfort. A PPD < 6% was considered equivalent to a PMV close to 0, representing very strict thermal comfort. A PPD < 10% corresponds to a PMV between −0.5 and +0.5, representing ideal thermal comfort. A PPD < 20% aligns with a PMV between −1 and +1, signifying acceptable thermal comfort. This last threshold was deemed appropriate for this case study, as it reflects a reasonable level of comfort for short stays, such as cultural visits or attending a church service. Additionally, it was considered that users would understand that achieving stringent thermal comfort in a historic building of cultural value is not comparable to the conditions achievable in a modern building.

The study of thermal comfort behavior according to the Fanger model and the acceptability levels mentioned above was contrasted with temperature setpoints of 21–25 °C to establish a parallel analysis regarding the use of HVAC systems and their future energy consumption.

3. Results

3.1. Scenario 1: Current Situation (Table 3)

At an annualized building level, the analysis reveals a significantly high level of discomfort during winter, as the building fails to maintain adequate comfort levels. However, the summer period appears to benefit from the building’s thermal inertia, suggesting that during warmer months, it performs more efficiently, maintaining more pleasant indoor temperatures compared to the exterior (Figure 9).

When examining extreme winter and summer weeks or specific days, the situation becomes more complex. In both periods, the Celler experiences discomfort levels far exceeding expectations. PMV indices surpass the limits of +1 and −1, which mark the threshold where 20% of occupants are considered to be in discomfort. During extreme weeks, PPD levels reach up to 90%, with PMV values approaching +3 and −3, indicating that nearly all users experience severe discomfort, whether due to oppressive heat and humidity in summer or extreme cold in winter.

These discomfort conditions, particularly during peak periods of public attendance, are critical when deciding on the implementation of improvement strategies. The analysis indicates that the internal climatic conditions are unsuitable for ensuring occupant thermal comfort during critical periods, underscoring the need for mitigation measures to optimize the Celler’s interior conditions and minimize the impact of external climatic variations on the building.

During the summer period, the first two morning hours after the Celler opens achieve acceptable comfort levels (PMV +1), but the rest of the day exceeds acceptable PPD thresholds. Conversely, during critical winter days, the Celler fails to reach acceptable comfort levels at any hour of the day.

This does not imply that the thermal inertia of the walls is irrelevant in this building. On the contrary, it plays a role, as evidenced in Figure 9. It manifests in two phenomena: the damping of temperature fluctuations, with an indoor-outdoor temperature difference of 4–5 °C, and a delay of 2–3 h in indoor temperature changes compared to outdoor conditions. The shortcomings of Scenario 1 are primarily due to the lack of airtightness in the windows, but more significantly, the extensive roof area (1704 m²) remains uninsulated. As is well known, in Mediterranean climates, the roof is the least efficient building element in terms of energy performance. In winter, it fails to retain heat due to the low angle of the sun, while in summer, it absorbs excessive heat because of prolonged direct exposure to the sun. Furthermore, the dark red ceramic tiles exacerbate the issue by increasing the surface temperature of the roof.

Exporting the results to a spreadsheet allows for more precise analysis of the Celler’s operating hours and its compliance with PMV comfort standards. The data show that out of the 4015 annual operating hours, approximately 30.83% occur under optimal PMV conditions between +0.5 and −0.5, with a 10% PPD. This percentage rises to 62.22% when the comfort range is expanded to +1 and −1, with a 20% PPD.

In summary, this first scenario reveals that 40% of the Celler’s annual operating hours take place under conditions far from admissible thermal comfort (PMV +1 and −1) (

Table 5. Hours of Comfort at the Building Level; the Current State Average Values.

	PMV	Scenario 1: Current Situation
Total hours of use		4015
Hours of use with 90% compliance	−0.5 < X > 0.5	1238
Hours of use with 80% compliance	−1 < X > 1	2526
Hours of use that exceed admissible comfort	>−1+1	1489
90% compliance, PMV +0.5 and −0.5	%	30.83%
80% compliance, PMV +1 and −1	%	62.91%
Percentage out of admissible comfort	%	37.09%

).

3.2. Scenario 2: Passive Improvement (Table 4)

The analysis of annualized graphs (Figure 10) reveals a significant improvement in the building’s thermal comfort conditions due to the implementation of passive design strategies. Percentage of People Dissatisfied (PPD) levels are practically acceptable throughout the year. However, while summer remains within the acceptable PPD range of 20%, corresponding to PMV values between +1 and −1, winter still shows peaks of 40% PPD, falling below the acceptable PMV threshold of −1.

This global analysis provides a positive initial indication of improved user comfort, suggesting that the applied solutions have been effective, though there is room for experimentation with variables not considered in this scenario.

A deeper analysis of critical weeks shows significant progress in PMV values, particularly during winter. Acceptable PMV levels of −1 are almost universally achieved, and while some peaks of discomfort are still detected, they do not occur during the Celler’s operating hours. This indicates a consistent improvement in comfort. A 20% PPD is observed in the early morning hours, with PMV levels nearing −0.5 after 11:00 a.m., persisting throughout the day.

Conversely, during the summer, where initial observations suggested total compliance, elevated discomfort levels occur, with PMV values exceeding +2 and PPD reaching nearly 70%. These discomfort conditions arise after 11:00 a.m. and persist until 9:00 p.m., at which point PMV levels return to an acceptable range of +1. While the implemented solutions have successfully improved thermal comfort in winter, they fall short in guaranteeing comfort during the most critical hours on the hottest summer days.

The critical days of both summer and winter can be seen in Figure 11.

This is likely due to the same source of discomfort identified in Scenario 1: the poor thermal performance of roofs in Mediterranean climates. While Scenario 2 incorporates 10 cm of thermal insulation into the Celler’s roofs, this measure is still insufficient, and a greater insulation thickness would be required, similar to in cold climates but for the opposite purpose.

The challenge with increasing insulation lies in its impact on the building’s historical and cultural values. Thermal insulation must remain invisible both from the interior and the exterior, and it must be installed between the ceramic layer resting on the beams and the outer ceramic tiles. However, this creates a noticeable edge visible from the roof’s profile, which needs to be minimized to preserve the visual integrity of the heritage building.

Analyzing operating hours and PMV levels (

Table 6. Hours of comfort at the building level; passive improvement average values.

	PMV	Scenario 2: Passive Improvement
Total hours of use		4015
Hours of use with 90% compliance	−0.5 < X > 0.5	2016
Hours of use with 80% compliance	−1 < X > 1	3489
Hours of use that exceed admissible comfort	>−1+1	526
90% compliance, PMV +0.5 and −0.5	%	50.21%
80% compliance, PMV +1 and −1	%	86.90%
Percentage out of admissible comfort	%	13.10%

) reveals a clear improvement over Scenario 1, with 86.9% of hours achieving PPD acceptance within a PMV range of +1 to −1. Additionally, 50% of the time falls within the ideal comfort range, with PMV values between +0.5 and −0.5.

However, the goal of fully optimizing the Celler’s thermal performance has not been entirely achieved, as 13.10% of PPD values still exceed the acceptable discomfort threshold. This underscores the need to continue improving mitigation strategies, particularly for the hottest periods, or to explore alternatives to reduce this percentage. For example, segmented summer operating hours could be considered, as conditions in the morning are acceptable, while afternoon conditions are not.

3.3. Scenario 3: Passive Improvement and Architectural Rehabilitation (Figure 10)

This scenario is the result of the Rehabilitation Project (Mercè Zazurca i Codolà and César Sánchez), which focuses on, among other things, maximizing biophilic design (Figure 12). The aim is to create a harmonious and symbiotic connection between the historic building and the surrounding natural environment while prioritizing occupant comfort. The psychological factor is particularly notable, as the visual and spatial connection to greenery and vineyards contributes to a certain degree of spatial appreciation and comfort.

To draw a parallel with previously simulated scenarios and considering that the architectural and restoration project originates from a space already incorporated into the Celler’s morphology, shading elements such as eaves and vegetation included in the final project were excluded from the simulations. These elements could further enhance thermal comfort performance.

The annualized building-level analysis (Figure 13 and Figure 14), taking into account the anticipated impact of the glazing and its orientation, shows a notable increase in PPD levels, peaking at 60% during winter and 50% in summer. These values exceed the PMV acceptability thresholds of +1 and −1, with winter dropping below a PMV of −1.5 and summer surpassing +1.

In the critical winter week, despite PPD reaching almost 80%, the hourly simulation shows that even on the coldest day of the year, acceptable levels of comfort above a PMV of −1 are achieved starting at 12:00 p.m., lasting until late afternoon.

During the summer period, the situation becomes more critical, with comfort levels exceeding acceptable thresholds starting at 10:00 a.m. Peaks of PMV nearing +3 are observed at 4:00 p.m., with acceptable levels not being restored until after 10:00 p.m.

A detailed daily PMV analysis reveals that while thermal comfort decreases slightly compared to Scenario 2, PMV levels stabilize over the year. The critical PMV peaks occur outside the Celler’s operating hours.

The percentages are similar: ideal comfort hours with PMV values between +0.5 and −0.5 amount to 2023 h, slightly more than the 2016 h in Scenario 2. However, total admissible comfort hours decrease slightly, with PMV values within the +1 to −1 range totaling 3343 h compared to 3489 h in Scenario 2 (

Table 7. Hours of comfort at the building level; passive improvement average values.

	PMV	Scenario 3: Architectural Rehabilitiation
Total hours of use		4015
Hours of use with 90% compliance	−0.5 < X > 0.5	2023
Hours of use with 80% compliance	−1 < X > 1	3343
Hours of use that exceed admissible comfort	>−1+1	672
90% compliance, PMV +0.5 and −0.5	%	50.39%
80% compliance, PMV +1 and −1	%	83.26%
Percentage out of admissible comfort	%	16.74%

).

The impact of the glazing is both logical and mitigable, but it remains detrimental in both summer and winter.

The study of translucent surfaces is a topic of its own. For this analysis, considering the building and the regional climate, the consequences are not counterproductive and remain within acceptable limits.

The Predicted Percentage of Dissatisfied (PPD) for annual hours in this scenario is 16%, compared to 37% in Scenario 1 and 13% in Scenario 2, with the discomfort in this case primarily concentrated during the critical summer weeks. The source of this discomfort is the large roof, which is exposed to intense solar radiation throughout the summer.

3.4. Scenario 4: Passive Improvement and Architectural Rehabilitation

The IPCC AR4 A2 refers to the Fourth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC), which examines scientific, technical, and socioeconomic perspectives on climate change, its impacts, and mitigation and adaptation options.

The A2 scenario envisions a heterogeneous world prioritizing self-sufficiency and the preservation of local entities. It is characterized by continuous population growth due to the slow convergence of fertility rates across regions. Economic and technological development occurs at a slower and more fragmented pace compared to more dynamic scenarios.

The solid lines in the graph (Figure 15) depict the mean global warming trends modeled for scenarios A2, A1B, and B1 relative to the 1980–1999 period. The shaded areas indicate the standard deviation of these means. The orange line represents an experiment where gas concentrations remained constant since 2000. The gray bars on the right display the best estimates and probable ranges for six IE-EE scenarios, considering multiple models and observational limitations.

Using the theoretical framework of the IPCC’s A2 scenario, an EPW climate file was generated to evaluate the future thermal comfort of the Celler Rocafort de Queralt and analyze how this historic building might respond to climatic variations under this model (Figure 16).

This analysis introduces a new scenario to this study. Beyond quantifying annual comfort hours, it aims to serve as a comparative tool for decision making on adaptation strategies.

In addition to thermal comfort, this scenario incorporates heating and cooling consumption into the comparison with the previously presented scenarios. These parameters are crucial for evaluating future climatic demands and ensuring a comprehensive approach to the challenges posed by climate change.

The simulation was based on the foundation established in Scenario 3, using the same material properties (Table 4) for passive solutions and the expanded volume introduced by the architectural intervention.

The theoretical consumption shown in the figure (Figure 17) is calculated with reference to a Fanger PMV level of +0.5 to −0.5.

The consumptions in the table are reduced based on a Fanger PMV range of +1 to −1. In the current state, the consumption would be 73.17 kWh/m²; for Scenario 2, it would drop to 16.27 kWh/m²; and for Scenario 3, it would be 20.26 kWh/m², with the latter still pending evaluation of the impact of solar gain reduction due to the biophilic pergola.

4. Discussion

At the beginning of this study, the potential for repurposing industrial buildings with cultural and historical value was highlighted. Despite this potential, energy efficiency regulations often exempt heritage buildings from meeting certain requirements, prioritizing the preservation of their historical values, which is frequently incompatible with the implementation of passive or active improvement strategies, since these interventions can alter the aesthetic and spatial perception of the building, especially active ones such as HVAC systems, which often significantly affect the interior space. Consequently, heritage buildings are often perceived as uncomfortable and highly energy-inefficient, which may lead to their progressive abandonment.

Climate change exacerbates this issue, particularly during warmer seasons, where the growing demand for cooling will lead to the inevitable use of facilities, which will increase energy consumption and environmental impact. This trend is difficult to mitigate solely through renewable energies due to the visual and structural impact these solutions have on the building and its surroundings.

On the other hand, previous research has shown that users of such buildings tend to accept adaptive comfort, expanding the usual thermal comfort range (22–24 °C and 40–60% RH). This behavior is attributed to the positive value users associate with the historical environment surrounding them.

This research analyzed, through dynamic simulation, the thermal comfort of users in the Celler de Rocafort de Queralt, an industrial heritage building known as one of the “Wine Cathedrals” in Spain. Located in a rural area surrounded by vineyards, this building currently has a non-permanent cultural use, including guided tours and workshops related to wine culture.

The analysis was structured into four scenarios: (1) the current state of the building; (2) after passive improvements, including 10 cm of thermal insulation on the roof, enhanced carpentry and glazing, and night-time ventilation in summer; (3) after passive improvements combined with architectural expansion derived from a contemporary project; (4) subject to the future climate projection for 2050 based on Scenario 3 and data from IPCC AR4 A2.

The simulation, conducted with DesignBuilder, incorporated real climatological data obtained from monitoring and adjusted the thermal comfort range to a PMV between −1 and +1, allowing up to 20% of users to experience discomfort during the most extreme periods of the year.

The research methodology outlined enables the assessment of thermal comfort in historical buildings—a task that is particularly complex for several reasons: (1) Climate data used in simulation and energy certification programs typically originate from weather stations located in airports, communication towers, or building rooftops. These sources fail to account for localized phenomena such as urban heat islands, shadowing effects, or solar radiation reflections from nearby surfaces. Additionally, the increasing impact of climate change in recent years is often overlooked. (2) Most simulation programs do not adequately consider certain passive systems inherent to historical buildings, such as the thermal inertia of walls or the presence of large indoor air volumes. (3) Accurately quantifying heating and cooling energy demands becomes challenging when using a more flexible interpretation of Fanger’s comfort parameters.

For the first challenge, an approximation to the actual climatic conditions can be achieved through on-site monitoring, which should ideally span at least one full year. Regarding the second point, parameters like thermal inertia and indoor air volume can be incorporated using the EnergyPlus engine within the DesignBuilder software. Lastly, for the third issue, the NECADA software provides a way to translate Fanger’s comfort metrics into the kilowatts required for each scenario.

The results indicated that the implemented passive strategies can ensure 86.9% annual thermal comfort, significantly improving the building’s energy performance and minimizing visual impact on its heritage values, since these strategies eliminate the need for active systems in the historical halls. The energy validation was carried out using the NECADA software, which confirmed the reliability of the obtained results.

Achieving 100% thermal comfort is possible by relocating cultural activities based on the schedule and building orientation. In winter, workshops could be held in the east wing in the morning (warmed by the sun) and in the west wing in the afternoon. In summer, the distribution would be reversed: workshops in the west wing in the morning (shaded from the sun) and in the east wing in the afternoon.

These recommendations are feasible due to the region’s temperate climate, characterized by low rainfall and high solar radiation, which facilitates the implementation of strategies based on the passive management of solar resources.

This analysis demonstrates that heritage buildings can achieve high levels of thermal comfort and energy efficiency while preserving their cultural values through tailored and sustainable solutions.

5. Conclusions

This is a significant finding, as the environmental impact associated with the materials used to construct HVAC equipment and ductwork, combined with the energy consumption and CO₂ emissions, is reduced to zero. Therefore, it can also be described as an nZEIB building. Furthermore, the impact on the building’s heritage values is also nullified.

This analysis can be extrapolated to other historic buildings of the same typology, such as churches, other temples, markets, and factories, which feature large interior air volumes. Factories, in particular, have enormous reuse potential due to their open-plan interior spaces and façade designs that enhance natural light penetration. However, there is no universal method for applying energy-efficient rehabilitation strategies to heritage buildings [50,51,52,53]. These strategies must be tailored to each specific case [52]. Although integrating energy efficiency standards into these buildings is challenging, case-by-case studies and dynamic simulations allow for approaches that align with nZEB behavior [44].

This approach also considers the critical role that the perception of thermal comfort plays in energy efficiency and heritage conservation [30]. Importantly, this perception differs from that in new construction, as it is influenced by the historical and cultural values of the building [31].

However, the question remains whether an annual comfort level of 86.9% is adequate for public cultural use. The answer is not straightforward, as it depends on several factors. First, it is essential to determine whether the intended use involves short stays (less than 1 h), intermediate stays (1–3 h), or long stays (more than 3 h). In the case of short stays, no additional measures would be necessary, relying instead on adaptive comfort—wearing a jacket in winter or using a fan in summer. For intermediate stays, minimal air conditioning would be needed on extreme days in the specific areas of use. For long stays, it would be crucial to analyze when periods of discomfort occur to propose complementary heating or cooling strategies.

In the case of the Rocafort de Queralt Cellar, after improving passive systems, discomfort primarily occurs on the hottest summer days. However, the activities carried out—cultural visits and wine-tasting workshops—are typically of short or intermediate duration. In this case, the building consists of three wings with different orientations and it is possible to relocate the activity to the coolest wing. For single space buildings, it would be advisable to air condition only the specific areas used during these activities, but never with air-based systems, as they cause stratification in these tall historic spaces. Instead, radiant systems should be employed directly where activities take place. Moreover, the energy supply should come from renewable sources, carefully studied to minimize impacts on the building’s historical and cultural values.

It is important to highlight a limitation of this study that should be addressed in future research. This pertains to the scarcity of real thermal transmittance values for historic building envelopes, such as the stone masonry walls of the façade in this case. Monitoring and obtaining accurate data could significantly impact the findings. If thermal transmittance values were higher, increased heat losses in winter and heat gains in summer would lower the percentage of hours of thermal comfort. Conversely, if thermal transmittance values were lower, as is often the case, the comfort percentage would likely exceed the estimates presented in this study.

Finally, while the historical value of a heritage building can also be regarded as a non-renewable resource [7], it is undeniable that its conservation must be compatible with tailored strategies to enhance sustainability. Many times, efficient HVAC systems do not guarantee user comfort, in fact, the way a space is used is often a determining factor for comfort [9]. Flexible use, therefore, becomes another key strategy.

Future research should also explore how to incorporate legal sustainability requirements into heritage buildings. While it is understood that European directives cannot impose obligations on heritage buildings due to the heterogeneity of Europe’s built environment and the lack of specialized technical and professional knowledge about historical construction, it would be beneficial to develop a procedural guide based on research conducted for different climates, building typologies, and construction systems.

Undoubtedly, the impact on historical and cultural values arises when attempting to apply strategies designed for new buildings to historic ones, rather than seeking to understand the thermal potential of their elements. Additionally, in the current context, it is crucial to simulate mid-term climate scenarios, as the environmental impact of an intervention that ceases to be efficient within a few years is the most detrimental.