1

Reuse of Rural Buildings: the First Step Towards Sustainable Construction.

Martín Ocaña, Silvia; Cañas Guerrero, Ignacio

Departamento de Construcción y Vías Rurales. Escuela Técnica Superior de Ingenieros Agrónomos. Universidad Politécnica de Madrid. Avda. Complutense s/n. 28040. Madrid.

Tel: 913365767, Fax: 913365625, mail: smatin@cvr.etsia.upm.es icanas@cvr.etsia.upm.es

Abstract. The present article tries to establish the relationship between reusing rural buildings and sustainable construction. The advantages of reusing buildings opposite to new constructions are presented with regard to an environmental point of view. Some valuation criterions based on a bioclimatic approach for the reuse of rural buildings are added. The embodied energy in the construction process is about 10% of all energy consumed by buildings along their lifetime. The reuse of buildings can save an important amount of energy and then can reduce the greenhouse effect gas emissions. Furthermore the reuse of buildings presents an additional advantage that is the reduction of construction material wastes to the landscape. Keywords: reuse, rural buildings, sustainable construction

1. Introduction. In the present article the advantages of reusing rural buildings are studied from an environmental view point. First of all, we describe the meaning of sustainable construction as well as the impacts of the construction sector on the environment. The basic human need for shelter and protection against nature has defined the search for dwellings by the mankind through the ages. The main task of a building is to provide shelter and comfortable interior conditions for the development of human activities. This objective should be reached by means of the least use of resources as possible. In the early times man took advantage of natural resources like natural caves for shelter, these natural refuges did not produce alterations on the landscape, but a mere use of the existing natural resources in order to meet his basic needs. Later, man began to change the environment with the aim of improving his living conditions while the construction sector was inside a developing and technical processing. Nowadays the construction sector is responsible for most of the environmental impacts due to the improvement of human requirements. In developed nations, the construction sector consumes one third of all the generated energy. The guiding principle behind sustainable construction is the reduction of the environmental impacts from the construction, use and demolition of buildings (Lanting, 1996). The reduction of environmental impacts can be reached by means of: Reduce (energy and building materials), Reuse ( new use for the entire building or some parts) and Recycle ( recovery of elements or building materials from the old building for the construction of a new one).

2. Environmental impact from buildings. All the buildings need the use of energy in the different stages of the construction process, in addition, building materials are required and by-products are released causing some kind

2

of environmental impact. The environmental impacts from the buildings have three dimensions: local, global and internal. The last one is not studied in this article.

• Local effects: noise, dust …mainly from the extraction of building materials and from the construction and demolition of the building. In general, these effects are short in time and once the stage is finished they are eliminated. The exception is the visual impact that remains during the life cycle of the building. Man-made building forms may be considered undesirable on the landscape.

• Global effects: CO2 and green house effect gas emissions concerned in the global warming of Earth and in the destruction the ozone layer. The emissions are caused by the energy consumption, mostly from non renewable sources, and required during the construction process (embodied energy) as well as during the use of the building (heating and cooling). The energy consumed during the life cycle of the building can be calculated for each particular building (D.J. Harris, 1999). Conservation of fossil fuel energy for heating and cooling buildings will be increasingly important in the future.

The local and global effects mentioned above are caused in the different stages of the building process. The stages of the life cycle of a building are: Extraction of building materials, Construction, Useful Life, Loss of Use and End of Life. Each phase need the incorporation of energy and building materials and there is an output of the final product together with gas emissions (carbon dioxide, methane and others), noise and dust production and the disposal of wastes. Each stage is responsible for the consumption of energy and other inputs and for the elimination of outputs (Tiwari, P., 2001).

3. The bioclimatic architecture. The concept of bioclimatic architecture appeared in the 50´s thanks to the Olgyay´s attributions, it can be seen as the architecture that makes good use of the climatic conditions and natural resources from the environment by means of appropriate constructive solutions for the reduction of the energy use (Olgyay, 1998). The investigations carried out up to now show that the initial cost of a bioclimatic building could be 10% higher than a building constructed with usual techniques (Lloyd Jones, D., 2002), however important energy savings can be obtained along the life cycle of the building. The main problem related to energy use in the construction of contemporary housing is the need of maintaining an interior temperature inside the comfort limits. This problem is increased because the society has more and more demanding comfort standards. The passive design strategies could reduce the energy needs, although in most cases it is necessary to have a conventional source of energy for providing “extra” heat or cold according to the occupant´s requests. The passive design strategies are based on the study of the climatic conditions in the surroundings of the new building. In ancient times, when there was no technology for environmental control, man constructed buildings adapted to the prevailing climatic conditions. Some of the passive design strategies used today in bioclimatic architecture, can be observed on traditional buildings.

3.1. The thermal inertia. In Spain the passive design strategy of high thermal inertia or thermal mass has been employed since ancient times as can be seen from popular architecture. One of the first shelter of man was a natural cave, where the layer of soil surrounding the cave provide protection and stable interior conditions. The high thermal inertia in popular architecture

3

was achieved by the combination of two factors: the building material and the thickness of the envelope. The building materials usually found in popular architecture are natural materials like earth and stone depending on their availability in the local area. These are massive materials with high density so they have a high capacity of storing thermal energy. On the other hand, vernacular buildings were constructed with the technique of bearing walls. The exterior walls had to resist all the loads from the whole building so their thickness was high (thicker than 50 cm in most cases). The thickness of the walls together with the building materials employed gave high thermal inertia to the building. The thicker the wall, the longer the time lag. Therefore the temperature inside this type of buildings could be maintained almost stable for a longer part of the year, because solar gains could be absorbed into the mass during the day and released in the evening. The operation of the thermal mass in the building is showed in the next figure:

Figure 1: System of operation of the high thermal mass in the building. Some studies are being realized for determining the energy savings related to the increase of the thermal mass in the building envelope. Norem established that a building with high thermal inertia could be responsible for the reduction of the energy required during the operational phase of the building (heating and cooling loads) in 15% related to a standard building.

4. Reuse of buildings in Spain. In Spain there is a high amount of rural buildings that were abandoned during 60´s and 70´s due to the drift from the land. Today they are not in use. In the life cycle of a building the next stage to the loss of use is the end of the building life. All the buildings are constructed for a given purpose, when they are abandoned they get damaged until the destruction. Spanish rural areas are suffering this problem with the loss of lot of traditional buildings. Some people like “Local Action Groups” and Research Centers are studying the possibilities of reusing the abandoned rural buildings. The reuse of these buildings is a system for saving the loss of rural heritage that is causing the loss of regional identities. Today some activities like rural tourism are experiencing a boom; the abandoned rural

4

buildings could be reused for this purpose. The reuse of buildings have advantages in the frame of the economic and social context as well as the environmental context. The first step in the process of reusing buildings is the selection of the suitable building for the next use, it is carried out usually following aesthetically criterions. In this article we suggest the reuse of buildings looking at the energy savings it can mean. Most of the research realized in the field of sustainable construction are focused on the construction of new buildings. However, the most obvious way of reducing the environmental impact is the reuse of existing buildings. The reuse of buildings can be seen as a system of energy saving because two steps of the building life cycle are not necessary. The embodied energy of the building materials is not added because the building is constructed already. Furthermore, the demolition of the old building before the construction of the new one is not required, so the energy needed in this step is not added either. For the purpose of this study, we consider that the process of reusing buildings does not require important restoration works. Since this premise is accepted, only buildings whose physical condition is good can be reused. In other situations, there is another possibilities for reducing the energy use (see figure 2).

ENERGYSAVINGS PHYSICAL

CONDITION

Re-use of the

buildingRecovery of

construction elementsRecycle of building materials

Figure 2: Relationship between the physical condition and the energy savings in the different levels of reuse. Each superior level carries higher energy saving “a priori” because two steps of the construction cycle are removed. However, this can not be generalized to all cases, because the energy needed for reusing an existing building is related to its physical condition. If the building is in ruins, the energy required for its restoration before the new use could be higher than building a new one. The next figure shows the energy saving due to the use of recycled building materials. It can be seen that 36% of the embodied energy is saved in a building made of recycled materials as for a building made of standard building materials.

5

Figure 3: Comparison between the embodied energy from the construction materials in two buildings. On the left there is energy required for the construction of a building with new materials, on the right there is the energy required for the construction of a building with recycled materials. [7] A lot of abandoned rural buildings are vestiges of vernacular architecture, so they have construction elements for the adaptation to the prevailing climate of their surroundings. Some examples found in these buildings are:

• High thermal inertia. Most of the traditional rural buildings have thick walls made of stone or earth. They soften the high temperature fluctuations typical of the interior areas of Spain. Another example very common in some areas of Spain (Andalusia, Aragon and Castile) is the use of the underground space as dwellings.

• The “Gloria”, is a traditional system of heating usually found in some interior parts of Spain where there was no firewood or charcoal. It is a channel built under the floor in whose interior straw and other harvest wastes are burnt. It is believed that this element is originated in the Romans hypocaustum.

• The orientation of the building, looking for as much solar radiation as possible in winter.

By reusing buildings with some of these constructive elements the embodied energy of the building materials will be reduced as well as the energy needed during the building useful lifetime: heating, cooling and lighting. The following table shows summarily the energetic analysis carried out in four dwellings built in 1996 in Switzerland (Adalberth, 2000)

Energy required (Average of the 4 buildings analyzed) STAGES KWh/m2 %

Manufacture of building materials 900 12,5 Transport 40 0,5 Construction 80 1 Operation (50 years) 6150 84,5 Restoration 330 4 Demolition <10 0 Disposal of wastes 20 0 TOTAL 7295 100 Recovery of building materials -205 -3

6

The results showed above can be considered as valid, therefore, the reuse of existing buildings is able to reduce the energy needed during the life cycle of the building in 14%. Taking into account that the building to be reused could have high thermal inertia, the total amount of energy savings could reach as many as 30% of the total energy consumed during the total building life cycle. Besides the advantages related to energy savings, the reuse of buildings have another environmental advantage. During the demolition of the old building lot of wastes are generated, they have to be transported to some place far from the cities. In rural areas there is no control about these places so lot of wasteways appear throughout the landscape. In developed countries there is a real problem due to the lack of space for the disposal of wastes, the only way to avoid this problem is the reduction of wastes. By reusing the existing abandoned buildings the amount of wastes is minimized.

5. Conclusions. The present article discusses the advantages of the reuse of existing buildings, in particular, the case of Spanish abandoned rural buildings. In addition to the social and economic advantages, reusing buildings has environmental advantages as reduction of energy use and minimization of wastes. The existence of some passive design strategy in the building can be considered as a criterion for the selection of the buildings to be reused. So, the advantage of reusing buildings will be higher because the embodied energy as well as the operational energy will be reduced. The degree to which energy is conserved can vary depending on the individual design of the reused building and the climate, reaching as many as 30% of the energy used during all the building life cycle. Acknowledgements The authors wish to express their appreciation to the Ministry of Science and Technology of Spain within the Project of Investigation PB8-0720 “Aproximación a una metodología de reutilización de construcciones rurales” for their financial support. References 1. Adalberth, K. 2000. Energy use in four multi-family houses during their life cycle. International Journal of Low Energy and Sustainable Buildings, vol 1. http://bim.ce.kth.se/byte/leas/ 2. Harris, D.J. 1999. A quantitative approach to the assessment of the environmental impact of building materials. Building and Environment, 34: 751-758. 3. Lanting, R (1996) Sustainable Construction in The Netherlands -A perspective to the year 2010 (Working paper for CIB W82 Future Studies in Construction. TNO Bouw Publication number 96-BKR-) P007 (http://www.sustainable-design.ie/sustain/netherlands.pdf 4. Lloyd Jones, D. 2002. Arquitectura y entorno, El diseño de la construcción bioclimática. Blume. 5. Norém, A. Et altri. 1999. The Effect of Thermal Inertia on Energy Requirement in a Swedish Building - Results Obtained with Three Calculation Models. International Journal of Low Energy and Sustainable Buildings, vol 1. http://bim.ce.kth.se/byte/leas/

7

6. Olgyay, V. 1998. Arquitectura y clima. Manual de diseño bioclimático para arquitectos y urbanistas. Editorial Gustavo Gili, SA. Barcelona, España. 7. Thormark, C. 2000. Environmental analysis of a building with reused building materials. International Journal of Low Energy and Sustainable Buildings, vol 1. http://bim.ce.kth.se/byte/leas/ 8. Tiwari, P. 2001. Energy efficiency and building construction in India. Building and Environment, 36:1127-1135.