An Energy Self-Sufficient Alpine Hut: The Refurbishment of an Ex-Tobacco Farm Using Building Integrated Photovoltaics

Abstract

The abandonment and deterioration of historic rural buildings in Europe raise significant issues, including hydrogeological risks, the loss of productive land, and cultural heritage decline. Despite being underestimated, these structures hold significant potential for cultural and productive activities. Renovating these structures is crucial for local communities committed to preserving their heritage, and it is a more sustainable approach than constructing new buildings. This study explores activities undertaken in the Interreg IT/AT project “SHELTER” in Valbrenta (IT): through a participatory approach involving communities, stakeholders, designers, and researchers, an energy concept is developed for refurbishing an abandoned tobacco farm, chosen by the community, to be an alpine hut. Due to the inability to connect to the city electricity grid, the new energy concept focuses on minimizing consumption through envelope refurbishment, efficient heating, and domestic hot water systems. Additionally, the integration of renewable energy sources, particularly Building Integrated Photovoltaics (BIPV), is emphasized to preserve the building’s original appearance. This study demonstrates the feasibility of meeting seasonal energy needs entirely through renewables and explores the potential integration of biomass for meeting annual energy requirements.

1. Introduction

Traditional rural buildings in mountainous areas are often beautiful examples of historic architecture and valuable landmarks of the landscape. Preserving them means preserving the history, the cultural context, and the traditions of mountain places. Moreover, preserving and refurbishing historical buildings may serve as a significant draw for tourism, fostering economic growth and enhancing cultural identity within a community [1]. However, poor reachability and the common lack of electric grid connections make it even more difficult to plan the future use and refurbish these buildings, often condemning them to abandonment. The preservation of these historic buildings in Italy often relies on diverse financing methods that involve public investment and the private sector [2]. Thus, since a big public effort is always required, developing a participative approach with the local community for applying a sustainable energy retrofit, in combination with suitable technological innovations, can be the key to keeping them alive.

1.1. Participatory Planning and Building Integrated Photovoltaic Experiences

Public participation involves generating and disseminating a range of resources and activities aimed at equipping citizens and stakeholders with the capability to contribute to planning. This includes providing access to information, conducting consultations, and encouraging active participation [3]. Additionally, engaging in dialogues with stakeholders and citizens who have diverse needs can be advantageous for local authorities. It assists in defining priorities, identifying opportunities for innovation, and tapping into the local knowledge relevant to the design process [4], thereby gaining support. Indeed, designers and policymakers are increasingly recognizing the strategic value of participatory planning. There are today several works and case studies that include this approach, e.g., in some recent cases, the work of Bo Kyong Seo [5]; this study presents a collaborative urban planning activity in a case study of Hong Kong’s transitional social housing. Another interesting and recent study that presents a successful use of participatory planning is from Mu et al. [6], presenting a case study for an income-mixed community in An Kang, Taipei. The aim is to shape positive social interactions among diverse groups of residents, whose needs are to be fully integrated into the future housing management systems. The review presented by Neuhoff et al. [7] identified how existing research revolves around different forms of participatory processes, i.e., interdisciplinary expert-driven scenario-building, participatory planning for policy agendas, or public planning for social learning. However, it is important to mention that this approach is increasingly being contested due to the difficulty of making use of non-linear thinking, resulting in poor long-term visions; an alternative method was developed and used by Soria-Lara et al. [8]. Another study that is critical of the use of participatory planning was completed by McTague et al. [9], presenting the monitoring of the developments that have followed a comprehensive plan for Cincinnati’s Over-the-Rhine neighborhood, which was created in a participatory planning process.

Regarding the building integration of photovoltaics (BIPV), there are several positive experiences described in the literature; in fact, the number of interventions in this direction is increasing and is expected to grow in the near future [10]. As a general concept, photovoltaic systems can be integrated into the architectural finishing element to reduce their visibility and not alter the aesthetic value of the existing building [11]. Today, photovoltaic modules exist that can blend in the envelope, e.g., facades in the study of Saretta et al. [12] or roofs in the study of Jhumka et al. [13]. Moreover, several applicative studies demonstrated the positive impact on the building energy balance of BIPV, e.g., the study proposed by Abdalrahman et al. [14], which presents the impact on the energy balance of using ventilated BIPV windows, showing the potential impact. Also, the recent study by Pedersen et al. [15] presented the renovation of three listed traditional farmhouses in Trøndelag County (Norway), by the refurbishment of the envelope and integration of renewables through BIPV technologies. Still, BIPV can be found in several modern and refurbished buildings; the HiBERatlas (Historic Buildings Energy Retrofit Atlas) [16] is an up-to-date database to visualize the best practice, which includes BIPV examples with building images and key figures to inspire designers and researchers. Moreover, details regarding the context, retrofit solutions (improvements to walls, windows, roofs, airtightness, ventilation, and energy systems), energy efficiency, climate control, finances, and environmental impact are included.

The presented short review highlighted the potential of a participative planning approach in a lot of successful cases, while pointing out some criticalities in non-linear thinking for long-term planning and in mixing stakeholders from different social groups. Moreover, some uses of BIPV technologies are shown, which outline the possibility of integrating renewable sources without damaging the monumental image of the ancient building.

1.2. Aim of the Study

The paper presents the refurbishment concept developed for a former agricultural building of the tobacco farmers in the area around Valbrenta, Veneto (Italy). The ex-tobacco farm is part of a historic settlement built toward the end of the XVIII century on the terraced landscape high above the Valbrenta Valley and is thus part of a common building typology for the area. Although the simple stone wall building has been vacant since the mid-XX century, and hence is in poor condition like most of these buildings, it has a high identity value for the local population as a witness of history. The building faces considerable challenges: it is necessary to become energy self-sufficient as it cannot be reached by the city grid due to its location; energy measures should not alter the historic character, and it is important to consider the difficulties in conducting a construction site in an inaccessible location. However, this represents an opportunity to think about a sustainable use of the building. The development of an applicable energy concept would not only be beneficial for people in Valbrenta but be transferable to other detached and difficult-to-access historic buildings, which need an energy self-sufficiency solution; for this reason, the focus of the paper is the methodology employed for the revitalization of the building in three steps: After (i) a comprehensive assessment of the building’s history and typology and a (ii) participatory process with the local community that served to gather ideas for future use, (iii) an architectural refurbishment concept, with heritage-compatible measures, was developed. In this assessment, the energy demand was calculated and covered with renewable energy sources from on-site. Different scenarios, tailored to the use concept, were elaborated in order to achieve the building’s energy self-sufficiency for the proposed use.

2. Materials and Methods

Knowing the heritage significance and the construction method of the building in detail is a prerequisite for developing targeted renovation measures and energy concepts. From the study of the historical context and the activities with the local community for the engagement of future users (the relevant methodology is described in the present section), the new architectural concept was designed in order to include aesthetic preservation and energy self-sufficiency issues.

2.1. Historical, Landscape, and Architectural Values of the Case Study

In the first step, the building history, architecture, and design of the building typology, along with its characteristic elements, are surveyed using the following methods: (i) the historical and landscape building context, as well as the ancient agricultural context, which is particularly relevant to this building and the community, was analyzed by conducting a literature review and gathering information from the local museum “Museo Etnografico Canale di Brenta”; (ii) the architecture and design of the building typology were assessed through a literature review and several on-site visits conducted with local stakeholders, while (iii) the characteristic architectonical elements and the construction details of the building, relevant to this study, were determined and analyzed during on-site visits and with the help of previous studies of the building (within the project ALPTER [17]).

Building history and context: The Valbrenta area was characterized by tobacco cultivation from the seventeenth century until the mid-twentieth century. The steep, sunlit slopes of “Col Ventidue Ore” were transformed into flat levels through terracing to capitalize on favorable climatic conditions for the cultivation and processing of tobacco. The terrace system comprises impressive retaining walls, reaching up to six meters in height, constructed with dry stone; the drainage material consists of a mixture of earth and local pebbles. These terraces served the dual purpose of regulating water and featured gutters, wells, and cisterns for water collection. Following the decline of tobacco cultivation after the Second World War, the maintenance of these terraces gradually diminished. Within the terraced landscape, one can find a series of mostly vacant buildings situated halfway up or at the hill’s summit, strategically positioned to maximize exposure to sunlight. The Case Study is a part of the so-called “Casarette”, an agricultural settlement established by tobacco farmers toward the end of the eighteenth century and abandoned since the middle of the twentieth century. Today, it is situated along the “Alta Via del Tabacco,” a mountain path connecting settlements and terraces specifically built for tobacco cultivation.

Architecture and design of the building typology: The structure at Col Ventidue Ore aligns with the historical building typology of tobacco houses typical for the region. The building’s design is characterized by its tall and narrow structure, optimizing the limited land available on the terraces. Originally, the building served a dual purpose, combining agricultural and residential functions. As depicted in Figure 1, the lower section of the building, constructed directly on the ground, functioned as a stable and was partially submerged to shield the interior from temperature fluctuations during winter and summer. The stable and attic areas were dedicated to tobacco processing: the barn served as a space for soaking and fermenting tobacco leaves, while the attic was utilized for drying. The main façade’s orientation mirrors that of the terraces, predominantly facing south-east. Windows are strategically positioned to the south, maximizing exposure to sunlight [18].

Characteristic elements and construction method: Only the outer walls and portions of the floor slab of the building are present today. These elements are constructed directly on compacted soil and comprise masonry crafted from local stone materials of various sizes and shapes. The walls lack plaster both on the interior and exterior surfaces and are punctuated only by openings for doors and windows. These openings feature simple lintels made of robust wood. The floor slab consists of a layer of cement screed directly on the soil. Unfortunately, the roof is no longer intact. However, based on the adjacent building with the same typology, the existence of a wooden roof truss with wooden boarding and tile roofing is highly probable. Observable voids in the load-bearing masonry suggest that wooden beams for intermediate ceilings were originally integrated there.

2.2. Methodology for Community Engagement: Interviews and Focus Groups with Local Stakeholders

Public participation involves various activities aimed at equipping citizens and stakeholders with the capabilities to contribute to the planning of local interventions [3]. Additionally, engaging in active participation through dialogues among stakeholders and citizens with diverse needs can be advantageous for local authorities. It aids in defining priorities, identifying opportunities for innovation, and tapping into local knowledge relevant to the design [4]. However, based on our current knowledge, the scientific literature does not sufficiently emphasize participatory approaches in the design of renewable energy concepts for the refurbishment of historical buildings in mountain areas. Consequently, this study incorporates specific activities to gather the needs and aspirations of local stakeholders, aiming to inform the energy concept for refurbishment. The qualitative part of this study aims to identify the primary needs and aspirations of the local community regarding the future uses of the building, considering cultural and historical backgrounds. To address this part, we conducted interviews and engaged in focus groups with key stakeholders in the local community, including enterprises, associations, local administration, research, and school institutes.

A series of eight interviews and three focus groups (

Table 1. The demographic information of stakeholders.

Stakeholder	Interview	Focus Group	Gender	Age Group	Education	Job
A	Yes	No	Male	Over 60	Bachelor [19]	Retired [20]
B	Yes	No	Male	Over 60	Lower secondary education	Retired
C	Yes	No	Female			Clerical support workers
D	Yes	Yes	Female	46–60	Lower secondary education	Self-employed professional
E	Yes	No	Male	46–60	Bachelor	Professionals
F	Yes	No	Female	46–60	Bachelor	Clerical support workers
G	Yes	No	Female	31–45	Bachelor	Professionals
H	Yes	No	Male	Over 60	Bachelor	Retired
I	Yes	Yes	Male	46–60	Bachelor	Self-employed professional
L	No	Yes	Female	Over 60	Post-secondary non-tertiary education	Self-employed professional
M	Yes	Yes	Male			Craft and related trades workers
N	Yes	Yes	Male	46–60	Bachelor	Professionals
O	Yes	Yes	Male	Over 60	Bachelor	Professionals
P	Yes	Yes	Female	18–30	Bachelor	Professionals
Q	Yes	Yes	Male	46–60	Bachelor	Professionals
R	Yes	Yes	Female	31–45	Bachelor	Clerical support workers

) were conducted involving local stakeholders, including public authorities, enterprises, and associations. The purpose of these interactions was to gather ideas and opinions on various aspects, such as future uses, energy needs, utilization of renewable sources, local sustainable materials, and the significance or values attributed to the building by the community. The insights obtained from these engagements played a crucial role in shaping the renovation plans for the building. Our objective was to enhance its cultural, social, and historical heritage so that it can be cherished by future generations, thereby preventing the risk of abandonment and the loss of its historical, social, and cultural memory over time. During the process of identifying future uses for the renovated building, stakeholders also discussed the energy needs and the possibilities of integrating renewable energy sources.

2.3. Methodology and Tools Used for the Energy Assessments

In this study, different tools were used to conduct the building energy assessment, which are listed below, going over the complete workflow to build an energy scenario. Further details on the simulation set-ups for the specific assessments can be found in Section 3.3.

First, ProCasaClima 2018 [21], designed for energy calculation and building certification and developed according to the requirements of European Directives (EU) 2018/844/EU [22], 2010/31/EU [23], and 2012/27/EU [24], is used to calculate a building’s yearly energy demand related to heating and domestic hot water. The simulation setup considers as an external boundary condition the climate data incorporated in the software’s internal database (Cismon del Grappa-Vicenza), which was corrected through the specification of the altitude, due to the specific location of the case study. Afterward, the yearly energy demand for lighting home electric appliances is estimated.

Then, EDGE-HP (Electric Demand Generator for Heat Pumps), developed by Eurac Research within the Horizon 2020 project BIPVBOOST [25], uses the annual cumulative demand value calculated by the ProCasaClima 2018 software and a set of other inputs (i.e., outdoor temperature, setpoints, building features, and conditioned area) to include heat pumps. Afterward, EnergyMatching Tool, developed by Eurac Research within the Horizon 2020 project EnergyMatching [26], is applied: this software takes into account several techno-economic inputs, other than the building electricity demand (e.g., building geometry, weather conditions estimated using PVGIS tool [27], the morphology and materials of the surroundings, solar irradiation conditions calculated using the Radiance reverse ray-tracing engine [28], technologies’ and electricity costs, and technologies’ technical features) and provides a set of performance indicators (e.g., hourly time-step profiles of PV energy production and self-consumption, electric demand coverage, expected payback time, the Net Present Value after a specified time period, and the specific CO₂ emissions).

The above results are brought together in an Energy Balance Model implemented in an Excel spreadsheet, which balances the PV production, consumption, and storage for appliances on an hourly level, and integrates this with an overall energy balance, including the biomass as an energy source on a monthly level.

3. Results and Discussion

As mentioned, the refurbishment of the examined building aims to provide the new functionality proposed by the community, achieving energy self-sufficiency with minimal visual impact, in order to preserve its historical image. The subsequent sections describe the evolution of community engagement activities and their role in driving the energy assessment and the different scenarios developed.

3.1. Outcomes of the Interviews and Focus Groups

Considering the limited resources available for renovation, local stakeholders decided to propose a step-by-step retrofit approach. This approach allows for the flexibility to explore additional funding opportunities over time. In the initial phase of the renovation, the building is envisioned as a facility to support the activities of associations dedicated to the enhancement, protection, and maintenance of the local territory. For instance, activities like cultivating medicinal plants or ancient grains are already underway, and the building can serve as a valuable resource for these initiatives, providing storage space and shelter during inclement weather. During this phase, stakeholders interviewed perceive that the energy requirements are minimal and can be met by using a stove and a limited power supply. In the future, the aspiration is to enable a caretaker or a family to stay overnight in the building, particularly during the summertime, to ensure its ongoing management. Naturally, this would increase the energy demands, necessitating the installation of essential amenities such as toilets, running water, and a higher electrical and heating capacity. In the third phase, once the activities and the presence of a caretaker have been established, the site can serve as a platform for pilot sustainability projects involving Italian and foreign academia as well as tourists. To accommodate visitors, the energy requirements will further increase, necessitating the installation of a heating system that would allow for year-round overnight stays.

During discussions, local stakeholders also addressed the challenges associated with implementing these ideas. One such challenge is the difficulty of accessing the building, as it is only reachable via a mountain path. Additionally, providing running water without an existing infrastructure poses another obstacle. The solution proposed by participants during interviews and focus groups, which has been tested in the past, is to utilize a helicopter initially and potentially construct a cable car as part of a project conceptualized years ago but never realized. Furthermore, due to the cultural significance that the location holds for the local population, both local associations and the community expressed a desire to participate in the renovation and, more importantly, the management of the building. However, this desire clashes with Italian regulations, which do not allow unqualified individuals to be involved in works that require high safety standards and expertise. As a solution, participants suggested that the community could contribute to the renovation of the decorative and aesthetic elements of the surrounding area, such as creating a pathway or a stone wall.

The overarching idea is to strengthen the bond between Col Ventidue Ore and the entire community, fostering a sense of identification with a place considered both a cultural and natural heritage site. In line with utilizing local resources, interviewees and focus group participants proposed the installation of renewable energy technologies, such as solar panels, taking advantage of the excellent location of the building. It was discussed that the solar panels should not be installed directly on the building but on the surrounding land. Stakeholders believe it is vital to promote sustainable management of local resources, such as extracting biomass from forests, cleaning terraces, utilizing agricultural waste resulting from potential future cultivation, or utilizing wood from the Vaia storm for decorative purposes in the building. To process wood and stone, the involvement of local artisans was suggested to promote the preservation of local traditions. Moreover, the location between the two valleys creates a wind current that can be harnessed by wind turbines for energy production. However, a comprehensive study is required to determine the period of the year with higher wind circulation and evaluate its potential. Water-related issues were also discussed in the context of sustainability. Participants believed that the limited availability of water due to the isolated location could serve as an opportunity to educate people about the conscious use of this vital resource. In terms of the material renovation of the building, stakeholders expressed a preference for using local products in accordance with the traditional construction methods of the area. They also emphasized the importance of promoting sustainability by reusing waste materials such as tiles, stones, and rocks. Consequently, they requested the creation of a masonry base, while the interior and exterior finishes should be made of wood or “saldame”, a coarse-grained silica sand typical of the area that could provide the structure’s external color.

Thanks to the collaborative efforts during the interviews and focus groups, stakeholders have reached a consensus on the common goals for the project. Specifically, they agreed to renovate Col Ventidue Ore for use as a bivouac, refuge, or educational farm and establish regulations for the building’s usage by local associations. This section summarized the main aspirations of the local stakeholders engaged in the definition of future uses for the building that will be retrofitted. However, this acquired knowledge must be transformed into technical knowledge, which considers both the technical and economic feasibility of the interventions. This work is important to avoid the future abandonment of the building after its renovation. The building has already been abandoned once before. To prevent this from happening again, it is important for the local community to manage and take care of the resources they have on their land.

3.2. Energy Assessment of the Current Building’s State

Estimating the current building energy demand can help to give a general vision of the improvement that it is possible to achieve with a deep energy refurbishment. The current as-is state presents a collapsing building, missing some components. For the purpose of calculating the energy needs of the as-is building, it is necessary to hypothesize the presence of the roof, doors, and windows, reconstructing their original type. Regarding the currently conserved elements, the perimeter walls are described in the model by the state in which they are today, i.e., without external or internal plastering in stone masonry, while the basement is designed by considering only the existing cement screed. Regarding the roof, from the study of the historical types present on site, it is possible to hypothesize the presence of an external layer of tiles, supported by rows of wooden slats and beams. Doors and windows are also hypothesized in the historical type in wood, with single glass. The existing ground floor completes the construction elements. In order to estimate a more reliable scenario related to the architectural project, in which the residential use may be assumed only for the upper floors, the ground floor and attic were excluded from the thermal zone. For this reason, one slab to the ground floor and one to the attic will delimit the heated space. For this reason, an intermediate wooden floor is also assumed, as it probably existed in the past, to be made of a wooden structure and a wooden pavement. The assumed transmittances for all considered elements are shown in

Table 2. A summary of the building elements considered for the calculation of the as-is state energy demand with assumed thermal transmittance.

Building Element	Short Description	Assumed Transmittance [W/m2K]
Walls	Stone masonry	1.94
Basement	Cement screed	3.12
Slab towards the ground floor	Wooden structure, wooden pavement	1.49
Slab towards the attic	Wooden structure, wooden pavement	1.88
Roof (assumed)	Tiles, wooden slats, and beams	2.50
Windows (assumed)	Wood frame, single-glazed	3.00
Doors (assumed)	Wood	2.50

.

The calculated energy demand for the assumed as-is state building is 401 kWh/m²a. In this case, the thermal losses divided by the element, in percentage, amount to 48% for the walls, 32% for the slab toward the attic, 15% for the slab toward the ground floor, and 6% for the doors and windows.

Figure 2 summarizes the described results in terms of the distribution of the energy losses. In absolute numbers, the result is 16,076 kWh for the 40 m² if, as assumed, just one floor is used for a whole year of use. If only the months from May to October are used, the heating demand goes down to 10,050 kWh. Just keeping it frost-free (i.e., an indoor temperature of 5 °C) results in 1655 kWh. Heating it up just once per week would not reduce the demand proportionally, since each time, in addition to covering the losses, the heavy walls have to be warmed up again. Heating all three floors, instead, would result in a total of 45,128 kWh for 122 m².

3.3. Proposal for the Refurbishment of the Building

The refurbishment proposal involves the installation of a new steel structure inside the remaining perimeter masonry once they have been secured, according to the concept of “house-in-house” refurbishment, an approach that contrasts with maintaining the load-bearing walls inside the building. The “house-in-house” concept refers to a design approach where a new structure is created within an existing building, effectively forming a house within another house. This solution was widely applied in several cases, e.g., in the project of refurbishment of the Borgata Paraloup in Rittana (Cuneo, Italy) [29]. This solution allows for new living spaces to be integrated into a pre-existing structure without compromising its overall integrity or altering its original character. In fact, one of the key advantages of this concept is its ability to optimize the use of available space: although the loss of space due to the existence of a double structure (the old and the new one), the concept allows the limitation of load-bearing walls to be overcome, enabling the design of an open floor plan within the existing building. In this case, the architectural functional scheme involves constructing a self-contained unit within the existing building, with its own partitions, floors, and roof. This essential self-contained unit will accommodate bedrooms and bathrooms (upper floor) and a front office (ground floor).

From the aesthetic point of view, the “house-in-house” concept offers flexibility and adaptability, with respect to load-bearing walls whose openings cannot be changed. The new structure can be designed to complement the existing architectural style and to create in some parts an intentional contrast, allowing a harmonious coexistence between the old and the new. This approach at the same time gives the opportunity to incorporate innovative elements, i.e., modern technologies, into the new parts, while still preserving the historical or cultural significance and the recognizability of the original parts of the building.

3.3.1. A Building Envelope Refurbishment Solution with Wood Fiber Insulation

The described refurbishment concept chosen by the architects for this project has the characteristic of having a contained visual impact compared to the existing building, being able to show the existing building without being overlapped by the new construction; at the same time, the internal building can be designed as an efficient structure, working with the thinnest possible thicknesses, which is recognizable compared to the original material. The described refurbishment of the building envelope was developed element by element according to current Italian law D.M. 26 June 2015 [30], which implements EU legislation [23]. According to the mentioned norms, refurbished building elements were designed to meet the minimum regulatory limits and are described in detail afterward. The existing external walls are provided with an insulating layer of a 10 cm wood fiber panel, with a 3 cm fireproof layer of glass wool on the internal side and the vapor barrier. Finally, a wooden board is placed as internal finishing. In contrast, the roof’s outer surface will exhibit a contemporary feature, characterized by the presence of a sheet metal layer along its profile. This deliberate design choice ensures that the new intervention is easily distinguishable from the existing structure, aligning with the architectural principle of recognizability. The underneath insulating layer consists of 23 cm of wood fiber, with an internal finish made of wooden board. On the ground floor, a ventilated crawl space is created to reduce the rising damp risk, and an insulation layer of 12 cm of wood fiber is placed under screeds and flooring. Finally, the new windows and doors are chosen with wooden frames and triple glazing.

Table 3. A summary of the retrofit strategy for the envelope: insulation type, thickness (when applicable), final thermal transmittance per building element, and threshold from the current regulation.

Building Element	Insulation Description	Insulation Thickness [cm]	Thermal Transmittance [W/m2K]	Threshold for Thermal Transmittance [W/m2K]
Walls	Wood fiber panel	13	0.26	0.28
Ground floor	Wood fiber panel	12	0.26	0.29
Roof	Wood fiber panel	23	0.20	0.24
Windows	Wooden frames	-	1.40	1.40
Door	Wood	-	1.40	1.40

summarizes the retrofit strategy for the envelope, reporting a short description of the insulation layer and thickness with the final thermal transmittance per building element and the minimum threshold respected from the current cited regulation.

This refurbishment measure results in a calculated heating demand of 41 kWh/m²a. For the current total of 122 m², i.e., the three floors used, this results in an overall heating demand of 6068 kWh over a whole year and 1400 kWh, respectively, for the months from May to October. Keeping the building active over the winter would result in about 500 kWh. The scenario of using it only once per week is more interesting in this case, since the well-insulated building avoids the problem of the rooms cooling down significantly, and the thermal mass of the wood and insulation is heated up (which is designed as an interior layer) is lower.

3.3.2. Heating and the DHW System: Heat Pump and Biomass

The energy demand for domestic hot water (DHW) amounts to around 450 to 600 kWh/month. For the self-sufficiency scenarios, two different approaches for providing the heating and DHW were studied: First, a May-to-October scenario based on the electricity production from PV and a heat pump. Second, the integration of the PV system with heat from biomass, ideally through a combined stove for cooking, DHW (and heating), and/or a tiled stove. This is particularly interesting for a prolongation of the use of the building to the winter months, where the solar radiation becomes low and the energy demand is high.

3.3.3. Home Electric Appliances

Since the only available electricity will be self-produced by the photovoltaic system, the study specifically quantifies and minimizes the use of electricity in terms of home electric appliances.

Table 4. A probable abacus of the electric appliances, with the relative energy demands and their assumed hours of use, divided by rooms.

	Energy Demand [Wh]	Time of Probable Use
Kitchen
Oven and cooker (induction)	1800	12–13/19–20
Coffee Machine	550	07–08/13–14
Blender	750	12–13/19–20
Fridge	129	0–24
Bathroom
Hairdryer	1800	20–21
Rechargeables
Smartphones (recharge)	15	7–8/19–20
Laptop	160	06–07/12–13
Apartment Caretaker
Router (internet)	15	0–24
Printer (during copy or printing)	260	10–12

summarizes the considered appliances, with the relative energy demands and their assumed hours of use.

The occupancy scenarios considered were those of an alpine refuge for a maximum of 10 hikers, with a 24 h reception. Therefore, electrical appliances in a small kitchen (small refrigerator for food preservation), bathroom appliances (hair dryer), small rechargeable devices (smartphone and laptop), modem and printer for reception use, and evening lighting requirements were included in the electricity demand calculations.

3.3.4. Photovoltaic Integration Scenarios

A preliminary PV integration concept was developed starting from the outcome of the participative study presented in Section 3.1 and considering the Lombardy Regional Guidelines [31], which distinguishes between the following:

• A non-integrated PV system, detached from the building (e.g., pergolas, rows of panels resting on the ground);
• A partially integrated PV system, applied on the building surfaces, without replacing building components like the roof pitches;
• An integrated PV system (IPV), characterized by the replacement of the original building components (e.g., roof elements, window glass) with the PV modules.

With the purpose of protecting the landscape and the high-value terraces, and considering the absence of original roofing, a BIPV design alternative was selected. BIPV allows the visual impact of the technology on the volumetry of the building to be minimized, but at the same time, it requires a careful study of the final impact on the building. The cited Lombardy Regional Guidelines identify the following criteria to mitigate this impact:

• Study the conformation of the PV system in relation to the individual case;
• Avoid “patchy” insertions;
• Place the PV module arrays in harmony with the architectural lines of the building;
• Prefer integrating PV modules on a perimeter band along the eaves line.

Based on these criteria, two different integrated approaches are proposed for the PV:

-

Approach A: adopting lightweight flexible PV modules to be fixed on a new metal roof;

-

Approach B: integrating rigid glass PV modules with hidden cells, as the main components of the roof covering.

In both scenarios, the area of interest with respect to PV integration is the south-facing roof portion (tilt 24°), as shown in Figure 3.

Figure 4 (left) shows an example of lightweight flexible PV modules considered by Approach A. The modules are composed of two main polymer layers encapsulating photovoltaic cells. The integration of lightweight flexible PV modules was evaluated by considering different aspects. From the aesthetic point of view, anthracite-grey color modules were selected to match as much as possible (not completely, since a user-defined coloring based on RAL or RGB scales is not available for this product) the chromaticity of the metal roof chosen by the designers. Considering the technological solution adopted, the system is flexible, light, and easy to fix on the metal below. The integration could take place in the laboratory (at the company manufacturing the metal roofing system) or directly at the installation site. The modules are easily transportable, using the means of transport usually adopted for food. The site conditions are suitable for its installation, which requires a temperature range of 15–25 °C, typical for spring and summer seasons in Valbrenta. From an energy point of view, the PV modules considered have an efficiency of 16% and could provide an estimated annual amount of 185 kWh_el/m², if integrated in the selected roof portion. Figure 4 (right) instead shows an example of rigid glass PV modules considered by Approach B. The modules are composed of two main glass layers encapsulating photovoltaic cells that are not recognizable. The integration of rigid glass PV modules with hidden cells was also evaluated considering different aspects. From the aesthetic point of view, the selected color (anthracite-grey) exactly meets the project requirements. Considering the technological solution adopted, the modules replace the roofing element, assuming other functions in addition to producing energy, e.g., thermal and acoustic insulation, water tightness, and mechanical resistance. The system can be installed directly on-site, but it is a heavy solution that must be transported by helicopters. From an energy point of view, the PV modules considered have an efficiency of 13% and could provide an estimated annual amount of 150 kWh_el/m², if integrated in the selected roof portion.

3.4. Self-Sufficiency with on-Site Renewable Energy Sources

The energy assessment was performed as outlined in Section 2.3, aiming to estimate the potential PV contribution in covering the building’s electricity demand. As declared, using the ProCasaClima 2018 software and considering all the refurbishment measures previously described, the thermal energy demand for heating and domestic hot water (with possible electrical auxiliaries) was calculated, resulting in a value of 41 kWh_th/m²y. The EDGE-HP software was then applied to calculate the hourly time-step electric profiles that were later considered and summed to other profiles generated for home electric appliances as the input for the EnergyMatching Tool. Figure 5 shows the hourly consumption profiles generated for heating, domestic hot water, lighting, and home appliances, taking for example a day in the month of May.

The energy performance analysis performed assumes the use of the building in the time period between 1st May and 31st October. The EnergyMatching Tool was applied to run a set of optimizations, setting the target of reaching increasing thresholds of the consumption coverage percentage. For these evaluations, Approach A was adopted, i.e., to integrate 16% efficiency PV modules on the south-facing roof portion, 24° tilted (Figure 3). The considered PV module dimensions are 0.37 × 2.93 m. Figure 6 shows the optimizations’ results, i.e., the values of the PV capacity (kWp) and electric storage size (kWh) suggested to reach the set electric consumption percentage thresholds (variable from 20% to 90%).

Table 5. The electricity self-consumption percentage reached by the suggested PV system configurations.

Consumption coverage [%]	20	30	40	50	60	70	80	90
Self-consumption [%]	64	53	54	51	52	50	41	40

shows the resulting PV configurations’ performance in terms of the expected self-consumption percentage, observing how much of the produced electricity is used in the building (including the portion stored in the electric storage).

The results show that it is not possible to cover the whole building’s electric consumption, even if integrating large dimension PV systems, like with the 30.6 m² of PV plus the 53.1 kWh of electric storage; smaller and more reasonable PV configurations allow good results of consumption coverage percentages to be reached, and since users, in this case, do not necessarily expect maximum comfort, they might accept adapting.

Moreover, the suggested PV configurations allow from 40 % up to 64 % of energy self-consumption to be reached, meaning that a large portion of the produced electricity cannot be exploited. This is due to the non-correspondence between the PV production and building consumption curves, as highlighted in the following chart in Figure 7, which shows, for example, the average values expected during 10 days in the spring (1 to 10 May) and summer (1 to 10 August) seasons.

Both the production curves are related to the PV configuration that reaches 50 % of the consumption coverage (i.e., with 13.1 kWp of PV plus 3.1 kWh of electric storage), while the consumption curves represent the sum of the profiles generated for heating, domestic hot water, lighting, and appliances. As reported in Table 5, this solution reaches 51% of energy self-consumption, meaning that the storage support can partially solve the curves’ “non-correspondence” issue.

Using a heat pump in order to make most of the electricity produced on-site by solar energy and limit the use phase from May to October, as envisaged during the stakeholder meeting, was the first approach investigated.

3.5. Year-Round Use with the Integration of PV with Locally Available Biomass (Wood)

As an alternative, a second scenario integrating the use of biomass was studied. The biomass consists of locally available wood and is selected for its availability on-site, eliminating the need for transportation. The potential electricity production with the 30.6 m² scenario above (which covers the whole south-east facing roof and is, therefore, visually less impacting than a partial coverage option) would cover an energy-saving scenario of electrical appliances also during the winter months with limited solar radiation. This means that the whole year use of the building can be investigated, where PV would provide the energy for those appliances that strictly need electricity (light, fridge, hairdryer, etc.), and the heat for DHW and heating of the building is provided by an energy source other than solar. The stakeholder interviews clearly identified wood from the surrounding forests, the pruning of the cultivated terraces, and agricultural waste as possible energy sources. In this scenario, heating was considered only for the caretakers’ rooms, a common living and dining room for the guests, while the sleeping rooms for hikers and course participants would remain unheated. Moreover, a non-continued use is assumed, estimating that the building is used 50% of the wintertime overall, plus other holidays and weekends. Also, considering the rural character of the building, a wood-fired stove is proposed, which can be used for cooking but could also feed hot water storage to provide DHW and heating. The battery for the PV system must be dimensioned to mainly provide a balance over the production. A heat pump could of course be included also in this scenario to boost the efficiency, and to keep the system as simple as possible (reducing investment and maintenance), the electricity, when not used, is directly used for heating the storage tank. This reduces the consumption of wood from 5 m³ to 3 m³.

Figure 8 shows the monthly energy needs divided by type (left bar) and the production divided by energy source (right bar). The winter occupation (and consequently the load) in this scenario is reduced to about half. This way the photovoltaic systems cover nearly 60% of the energy needs, while the remaining 40% is covered by biomass (wood), as shown in

Table 6. The monthly energy balance for the scenario with 30.6 m² PV, 20 kWh battery, reduced winter use (50%), and energy-saving appliances (no electric cooking).

	PV Production	Electric Appliances	Electricity from PV Fed into Heat Storage	DHW	Heating	Cooking on Stove	Overall Heat Demand	Thereof Covered with Wood Stove	PV Used (for el. Appliances and Heat)	PV “Self-Consumption”	Not Covered, Must Be Saved (with Less appl.)	PV Consumption Coverage
	[kWh]	[kWh]	[kWh]	[kWh]	[kWh]	[kWh]	[kWh]	[kWh]	[kWh]	[%]	[kWh]	[%]
January	295	207	80	233	377	31	640	560	281	95%	7	97%
February	303	181	120	210	281	28	519	399	301	99%	0	100%
March	430	187	243	233	200	31	463	220	430	100%	0	100%
April	585	187	315	225	90	30	345	30	502	86%	0	100%
May	625	332	293	465	41	62	568	275	626	100%	0	100%
June	653	295	358	450	2	60	512	153	653	100%	0	100%
July	784	305	465	465	0	62	527	62	770	98%	0	100%
August	718	332	387	465	0	62	527	140	720	100%	0	100%
September	464	374	96	450	21	60	531	435	466	100%	5	99%
October	360	387	29	465	192	62	719	689	367	102%	49	87%
November	264	194	68	225	235	30	490	423	257	97%	5	98%
December	168	207	0	233	320	31	584	584	174	103%	33	84%
whole year	5649	3189	2454	4118	1758	549	6424	3970	5545	98%	99	97%
May-Oct.	3603	2026	1629	2760	255	368	3383	1754	3601	100%	54	97%

. Considering only the months from May to October, this relation is even more favorable: 2/3 of the energy comes from PV production and 1/3 from wood. The self-consumption rises this way to 98% (the remaining 2% is lost, since there is no grid to feed in, but compared to the summer-only and PV-only scenarios, much less is lost). Furthermore, also the consumption coverage of 97% is high enough to be considered acceptable.

The graph of the two 8-day periods in July and October, presented in Figure 9, shows how, during the evening and night in the summer, the basic electricity need is covered by the battery (compare the blue line and light green line), while in the morning, the solar gain exceeds the demand and is stored in the battery. As soon as the battery is full (before midday usually), the excess solar gains are used to heat the water storage. In October, due to more artificial lighting needed, but also due to more days with little sun, less excess PV electricity is fed into the heat storage, and less excess PV electricity can be stored in the battery. However, two sunny days are enough to bring the battery back to a fully charged status.

With a bigger battery, e.g., the 54 kWh as in the optimization scenario with only summer use and only PV as the energy source, the PV consumption coverage increases to 99%. At the same time, the wood needed increases slightly, since more electricity from PV can be stored in the battery and is thus not converted to heat. Decreasing the size of the battery to 10 kWh, on the other hand, would result in 181 kWh, with twice as much not covered of the electrical demand, and a demand of more than 105 kWh not covered even in the “summer use period” (26 kWh in September, 76 in October). With 5 kWh, the electrical demand not covered would increase drastically, and this would happen also in summer months like August. The fact that October showed itself to be a potentially critical month led to the idea to anticipate the summer use period from April to September: As expected, the amount of wood needed decreases slightly, the used electricity from PV increases, and the not covered demand goes down to half of its value for the May till October period. A total of 2% of the points of the not usable PV energy would disappear (self-consumption is now 100%) due to a considerable amount of solar energy in April that, under the reduced use scenario, could not be used.

The last variant investigated, presented in

Table 7. A comparison of the wood needed, PV used, and self-consumption as well as the not covered electricity need and PV consumption coverage for different variants of the scenario (marcked with “x”): a battery size from 5000 kWh to 54,000 kWh, the full use period from May to October and April to September, respectively, and a variant with an electric stove for cooking.

					Whole Year					Summer Use Period
May-October	April-September	Battery Size [kWh]	Cooking with Stove	Cooking Electrically	Wood Needed [kWh]	PV Used [kWh]	Self-Consumption [%]	Not Covered [kWh]	PV Consumption Coverage [%]	Wood Needed [kWh]	PV Used [kWh]	Self-Consumption [%]	Not Covered [kWh]	PV Consumption Coverage [%]
x		54	x		4045	5545	98%	23	99%	1762	3635	101%	13	99%
x		20	x		3970	5545	98%	99	97%	1754	3601	100%	54	97%
x		10	x		3884	5548	98%	181	94%	1712	3593	100%	105	95%
x		5	x		3548	5547	98%	518	84%	1486	3589	100%	334	84%
	x	54	x		3955	5627	100%	10	100%	1267	3589	100%	0	100%
	x	20	x		3916	5627	100%	49	98%	1263	3589	100%	5	100%
	x	10	x		3852	5631	100%	109	97%	1241	3589	100%	26	99%
	x	5	x		3494	5631	100%	469	85%	1077	3585	99%	195	89%
x		54		x	4030	5608	99%	167	96%	1792	3651	101%	96	96%
x		20		x	3952	5608	99%	246	94%	3952	5608	99%	246	94%

, was to consider a wooden boiler (without the possibility of cooking) and included the cooking as an electrical appliance: this resulted in considerably lower coverage (96% with the 54 kWh battery and 94% with the 20 kWh battery) and substantial gaps of 167 kWh and 246 kWh, respectively. Cooking with electrical devices should only be taken into consideration if other savings seem feasible.

4. Conclusions

The activities and studies on the restoration and refurbishment of the Col Ventidue Ore ex-Tobacco farm have highlighted its significant importance for the community and its potential use, alongside critical technical difficulties for the refurbishment (no grid connection, hard-to-reach location). The approach developed and used within the Interreg IT/AT project “SHELTER” has demonstrated itself to be an effective method for the inclusion of the community into the refurbishment process and can be extended to other cases. After an extensive analysis of the existing building and a participative process involving the local community and the architectural concept, an energy assessment was performed. The results showed the possibility of achieving a compatible architectural aesthetic with the chosen function of a hut, preserving the building’s historical value and energy self-sufficiency using renewable energy for seasonal use. In fact, in a seasonal use scenario, the heating, domestic hot water, lighting, and utility needs of the building’s demand are fulfilled through the installation of a BIPV system on the roof. Afterward, a year-round usage scenario was also assessed, proposing the addition of other thermal generation systems with biomass (wood, which is easily available on site). The results showed that in the winter, the energy generated by the BIPV systems can be used for powering lighting and appliances, while a biomass boiler can successfully cover the heating and DHW demand.

The successful development of a participative refurbishment study on the ex-tobacco farm in Valbrenta can serve for the future of this building, for which there is a strong interest from the local municipality, and as a case study applicable to similar communities, to save their most representative historic buildings. Moreover, this architectural energy concept can inspire designers regarding the refurbishment of similar off-grid and hard-to-reach buildings.