USER SCENARIOS IN BALANCED RETROFIT: THE CASE OF BASERRIS University of the Basque Country UPV/EHU Institute of Architectural Technology, The Royal Emanuele Naboni Danish Academy of Fine Arts, School of Architecture Institute of Architectural Technology, The Royal Ola Wedebrunn Danish Academy of Fine Arts, School of Architecture
Ugaitz Gaztelu
ugaitz.gaztelu@ehu.eus emanuele.naboni@kadk.dk owede@kadk.dk
Fig 1: An abandoned baserri
Research summary The energy efficient adaptation of a historic building to future user scenarios is discussed with the case of baserris, the typical Basque farm. Following the industrial revolution several baserris were abandoned (fig. 1) as the inhabitants moved to the cities. Today, there is a necessity in repopulating the baserris with a series of contemporary users’ scenarios. The few examples of retrofitted baserris is based on the simplistic approach proposed by regulations, or standards such as the EnerPHit. The paper describes the hypothesis of an energy and culture balanced retrofit that sustains the adaptation to contemporary uses based on the understanding of a baserri thermodynamic behavior. The baserris as conceived in the XVth century and onwards are an example of an energy self‐sufficient thermodynamic system that capitalize internal heat loads generated by agricultural production systems. Energy stored by the thermal mass is a critical aspect of their function which is undermined by according to code interventions. This paper explores a balanced retrofit that complements future user scenarios’ thermodynamic implications and fabric interventions. Keywords: Energy Retrofit, User Scenarios, Built Heritage
1. Introduction
The baserri is the traditional farm of the Basque Country. There are approximately 45.000 baserris spread across the north of the Basque territory. In the Biosphere Reserve of Urdaibai1 (fig. 2) there are more than 1,400 baserris almost all of them based on the same typology. The Basques feel that their ancient rural history is written on the walls of the baserris. Their architecture has proved to be adaptive to changing agricultural demands for more than five centuries (Santana, A. Et al, 2001, pp. 32). The first trace of baserris appeared already in the XVth century, but it was in the XIXth and XXth centuries, that the industrial revolution brought devaluation to rural production and the abandonment of the territory. Since then, baserris progressively have been abandoned. This has caused a functional obsolescence, making th 70% of the internal spaces inoperable. In a future vision for the rural development of Urdaibai (IHOBE, 2009) the adaptive reuse of baserris is suggested as key factor for the financial, environmental, and socio‐economical improvement of the area (Bullen, P., et al, 2010). This research focuses on the baserris’ adaptation to tourism, agricultural production, permanent/temporary living and work. The hypothesis for an energy and culture balanced retrofit of a baserri, that leverage the investigated thermal behavior of the case study. 1 Urdabaiis a UNESCO protected area due to its natural, scientific, educative, recreational, and socioeconomic interest (Basque Government, 1989). Urdaibai has a strong correlation with the primary sector that occupies the 9.3% of the population
Fig 2. Urdaibai Biosphere Reserve.
2. Research Questions
Culture and Energy. These are two aspects and resources for conservation (Wedebrunn, O., et al, 2015, pp. 32‐38). Baserris represent the local identity as they are the consequence of anthropological, socioeconomic and cultural processes. Is it possible to pursue retrofit strategies that sustain both culture and energy reduction in use? The research investigates the adaptation to new uses and reduction of operational energy needs. It also seeks retrofit strategies that are based on how the baserri have operated across centuries with high thermal comfort of its occupants without the
use of mechanical system. Another logical question is: should a baserri change its thermodynamic logic and cultural identity for the sake of a building code or a certification system? User scenarios and fabric. This paper is specifi‐ cally focused on the role of the users in baserris energy demand. It is questioned whether or not, depending on the users’ scenario, it is possible to link to the practice of capitalizing internal heat. It is investigated under what circumstances the existing structure, when exposed to specific uses (and related generated internal gains) can be thermally effective. The baserris were built for a self‐sufficient production and as independent thermody‐ namic systems. Its construction made of thick external stonewalls (60‐75cm), shows a sophisticated system of capitalization of internal loads and zoning to create comfort. The opportunity of the covering walls with internal insulation according to European codes and EnerPHit (by the Passivhaus Institute) for retrofit is therefore debated. Considering that previous research shown that “complying to code buildings” are not always the most efficient (Naboni, 2015) there are two logical questions. Are prescriptive criteria applicable to cultural heritage retrofit? And more specifically: are prescriptive criteria of intervention valuable when a building used to be energy self sufficient as in the case of baserris? 2. Understanding how original baserri opera‐ tes Torre baserri. To answer to the research question a case study was isolated. Torre baserri was built in 1907, it represents the typical shape and construction system.
Moreover, Torre baserri has an interwined system of construction and users’ program that leads to thermal comfort with no need on mechanical plants. Torre is located in a rural area of Ibarrangelu, Biscay. It is a 3‐storey building, rectangular shape and with an important stone wall dividing it in two units (fig.3). The livestock was situated in the main floor (western side) and the living space on the opposite side. External stonewalls are 60 cm thick (U‐value= 1,73W/m2K) and with high heat capacity = 189,5 KJ/m2K. There is an internal oak structure, which supports a tiled roof (U‐ value=2,31 W/m2K). Windows to walls ratios vary with limited opening on the north. The small windows (60x80cm) are single glazed. The envelope is permeable to air. Barn and straw loft are constantly ventilated in order to dry the crop and straw.
Fig 3. Torre Baserris’ floor plans
Energy model. An EnergyPlus’ thermal and energy model of the building was created and calibrated with a series of onsite measurements and weather data collection. The model helped to clarify the strict relation between weather and the building. The local annual average temperatures are of 10.6ºC in winter and 19.7ºC in summer. The Cantabric Sea reduces temperature oscillation between
day and night, and the hilly topography is a barrier for air; clear sky is rare (6,9% and 10,5%, winter and summer). Given such scenario it is clear why baserri thermal concept focuses on capitalizing internal gains rather than external solar gains. The simulation models reproduced the traditional operation and it was noticed how thermal comfort was
Fig 4. Matrix of users’ scenarios, fabric interventions and heating demand
achieved for the majority of the hours of occupation. The analysis of the original building performance reinforced the concerns about the quality of the interventions suggested by prescriptive norms and the proposal to isolate the envelope.
3. The Experiment: Weighting Users Scenarios and Fabric Interventions
Cultural values, new user scenarios that reactivate the building and the reduction of energy demand lead to the design of specific user programs (fig. 4). Each scenario is planned to relate construction systems thermal properties and users’ needs, experience and comfort needs. Most of the programs reproduce high internal thermal loads by the means of occupants, livestock, production, etc. The zoning is intended to store heat and release it to other zones by conductivity, radiation exchanges and convection. Various modifications of the building fabric, ranging from conservation to transformation were simulated. Heating and occupation schedules. One of the model reproduces the Ancient scenario (fig.4), with self‐production and livestock production2 (fig.5). The livestock is situated at the west side of the main floor, living spaces are located on the opposite side.
Fig 5. Thermography of a cow in a baserri
2 “Eusko label”, the local brand, considers the following products to be produced in baserris: vegetables (tomato, potato and green pepper), honey, animal meat production (chicken, rabbit, pigs, sheep and cows), other products from the milk of sheep and cows, cider and oil. Those productions create internal heat gain that can be reused within the building.
The building is adapted to seven other simulated scenarios (fig.4). The Eco‐agriculture scenario is centred on fruits and vegetables production. The pantry is replaced by a dining room. Other scenarios include a Rural house and an Agro‐tourism and. The first with livestock and the second with space for agricultural tools. A Restaurant scenario encompasses the transformation of the west side of the 1st floor to provide natural light for living areas. The authenticity and the cultural value of baserri suggest that it can also be transformed in a Museum. Agricultural school is another alternative as baserris and rural areas are suitable for the circulation of local products and the education of next generations. In such case, the ancient barn is converted in a classroom. A further possibility is to subdivide the building into residential units. As the building size does not fit with most of the families’ size and needs, stakeholders propose to divide the baserri in a double housing. Fabric retrofit variables. The eight simulation models, each of which corresponds to a specific building user scenario, are simulated assuming no alteration of the building fabric. It should be noticed how planning the adaptation that mixes uses leads to low energy demand to heat the building. Two types of prescriptive fabric upgrades were simulated (fig. 6). The first upgrade is named the “Optimized Insulation Strategy” (OIS) for baserris (Gaztelu, U., et al., 2013). The OIS was developed to balance fabric interventions (mainly by adding insulation) with economic investment, payback period and energy efficiency according to codes. The second fabric upgrade is fitting the EnerPHit standard requirements (Passive House Institute, 2012).
5. Discussion of Results
Fig 6. Existing and Retrofit solutions thermal and ventilation properties
The EnerPHit standard proposes stringent insulation level requirements. Both systems suggest internal insulation. EnerPHit prescribes 25 cm of insulation for flooring, roof and walls, OIS requires 12 cm of insulation for the roof ‐ semi exposed ceilings, 10 for the external walls ‐ semi exposed walls and 8 for flooring. Both interventions reduce the ability of the thermal mass of being activated by internal loads. EnerPHit standard, prescribes triple glazed windows ‐0,8 W/m2K‐ and a tight construction ‐1 ac/h (50 Pa). OIS prescribes low‐e double glazed ‐1,4 W/m2K‐ and 1,4 ac/h (50 Pa). A total of 24 energy simulations were carried factoring 8 user scenarios with the existing, OIS and EnerPHit fabric solutions (fig. 6).
The role of user scenarios. Heating demand varies depending on the user scenarios (from 14,2 to 32,2 MWh/year) and the type of intervention (fig. 4). Programs with extended functions generating internal loads require lower energy to maintain comfort conditions. Among such solutions, it is not a surprise that the Torre baserri has a low annual energy demand when the Ancient Scenario is reproduced (14,2 MWh/year). Here wall are exposed and able to collect, store and release heat to other zones or within the same spaces with well‐studied time lag. For instance, the influence of the livestock provides 52.54 kWh/day; 20 times bigger than the annual average solar gains 2.5 kWh/day. Within this scenario, the livestock can provide up to 3 times more energy than the annual heating demand. This demonstrates the importance of understanding baserris’ intrinsic thermal behaviour, where internal loads assume an essential role on their design. Internal loads should be stored accordingly. The scenarios with livestock productions demand less energy. This is shown by the comparison of Agro‐tourism and Rural house types. Their respective annual energy demands are of 17,2 and 30,2 MWh/year, and of 26,2 and 28,9 kWh/m2∙year depending on the fabric intervention. Therefore, adapting the building to more families requires 2.26 times the energy of the ancient scenarios. Mixes uses are therefore suggested. Requiring that an internal space is connected to production is a key factor that goes hand in hand with the symbolic link between the baserri and the land. Calibrating interventions space by space. Fig. 4 shows the potential of fabric interventions. OIS efficiency allows reducing heating loads, depending on the program from 51% to 70%,
while the EnerPHit standard achieves reduction of loads from 59% to 79%. EnerPHit requires an average of 15 additional centimetres of insulation, which leads to higher embodied energy for insulation, to an important reduction of internal space and to an architectural alteration. In addition the thermal storage potential of walls, when not exposed to internal gains is reduced. It is therefore needed, case by case, to evaluate the optimal fabric intervention and specifically relate to each of the spaces qualities and use: having exposed thermal mass could be beneficial for some of the zones, while other may be insulated. This approach differs for the one proposed by OIS and EnerPHit that wrap indistinctively the full building envelope in order to create a flat temperature across spaces. Differentiate the building into thermal zones with specific thermal conditions and “atmospheres” should also be taken into account. 6. Conclusions The experiment demonstrates the importance of the user scenario for the energy efficiency of cultural heritage. It is essential to understand existing buildings, context and system and to adapt them as resources for possible scenarios. An appropriate occupancy of the inner spaces can have a bigger influence than any intervention on the envelope. For this reason, the process for an appropriate adaption starts from the definition of the user scenario and follows with a sensitive constructive and architectural intervention and the insulation level is assigned. This must be calibrated space by space, coordinating the internal gains and the intrinsic thermodynamic behavior of the building with the cultural value of its constructive element. An understanding that is
missed in criteria prescribed by regulations and by the EnerPHit standard. The research also does an approach to link the production systems to new functions. A sustainable adaptation needs to balance the socio‐economic development of the territory with cultural values and the use of energy. The paper demonstrates that the conservation of the symbolic correlation of these farms with the agricultural and livestock production reduces energy demand. To finish, this research is yet another step in the way to a long‐lasting and high quality preservation of the baserri, while at the same time it presents some keys which can be extrapolated to the adaptation of other traditional buildings in rural areas. 7. Acknowledgments The main author would like to thank the Royal Danish Academy of Fine Arts and the School of Architecture giving the hospitality to develop this research within the Institute of Architecture and Technology. 8 . References Basque Government. 1989. Boletín Oficial del País Vasco, nº145, 2100. The Basque Government Bullen, P., and Love, P.E.D. 2010. The rhetoric of adaptive reuse or reality of demolition: Views from the field. Cities.27 (2010) 215‐224 Cañas, I., Ayuga, E., Ayuga, F. 2009. A contribution to the assessment of scenic quality of landscapes based on preferences expressed by the public. Land Use Policy. 26 (2009) 1173‐ 1181. Fuentes, J.M., Gallego, E., García, A.I., and Ayuga, F. 2010. New users for old traditional farm buildings: The case of the underground wine cellars in Spain. Land Use Policy. 27 (2010) 738‐ 748
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