Analysis of Building Regulations in a Changing Climate. Methodology and Case Study.

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1 CIB W107 Construction in Developing Countries International Symposium Construction in Developing Economies: New Issues and Challenges January 2006, Santiago, Chile. Analysis of Building Regulations in a Changing Climate. Methodology and Case Study. M. Casals, M. Gangolells, N. Forcada and X. Roca. Technical University of Catalonia. School of Industrial Engineering of Terrassa (ETSEIT). Department of Construction Engineering. Ed. TR Terrassa. (Barcelona) Spain. marta.gangolells@upc.edu Abstract One of the most cited adaptation measures to climate change in the literature is the revision of building regulations and voluntary building codes since current constructed buildings will be kept on when the most serious impacts of climate change begin to be evident. The main objective of this paper is to establish a methodology in order to assess the level of adjustment of those thermal building regulations to the new conditions imposed by the climate change. The methodology exposed in this paper will allow the analysis of thermal building regulations in any country taking into account the expected evolution of the temperature due to climate change. To verify the methodology, current Spanish thermal building regulation has been analysed and its level of adjustment to the future climatic context has been assessed. Keywords Climate change, adaptation strategies, building regulations, Spain. INTRODUCTION Recent observed trends in climate and recent observed extreme events are lending importance to climate change in the entire world. In addition, the envisaged climate changes due to global warm over the next 50 years. It suggests important changes in mean and extreme values of temperature, precipitation and wind. The full range of the impacts resulting from these changes is still uncertain; however, it is becoming increasingly clear that adaptation to climate change is necessary and inevitable within several sectors [Lisø et al., (2003)]. Adaptation to climate change can be described as adjustment in natural or human systems in response to actual or expected climatic stimuli or their effects, which moderates harm or exploits beneficial opportunities [McCarthy et al., (2001)]. The expected life span of many new and existing buildings (from 60 to more than 100 years) means that the building stock of the future consists of the today s building stock and of new construction. In the future, part of the present building stock will be adapted to changes in the environment, while the rest will be kept as they were designed. Bearing in mind this context, one of the most cited adaptation measures to climate change in the literature is the revision of building regulations and voluntary building codes. Lowe 2004 states that It is increasingly obvious that a range of different mechanisms will be required to address the problems of adapting to climate change. Options include regulation, financial instruments, market forces,

2 CIB W107 Construction in Developing Countries International Symposium Construction in Developing Economies: New Issues and Challenges January 2006, Santiago, Chile. provision of information and exhortation. According to Hasegawa, 2004, in general, building regulation is the instrument that makes building reach predetermined levels of performance in the most certain way if they are effectively enforced and should play a significant role in adaptation. Larsson 2003 adds that maintaining or improving operating energy performance requirements of new and existing buildings through regulation constitutes a measure that will serve both adaptation and mitigation efforts. The main research objective in this paper was establishing a simple but reliable methodology that would allow the assessment of the level of adjustment of those thermal building regulations to the new conditions imposed by the climate change. Despite climate change being a planetary phenomenon, the potential impacts, and subsequent human adaptative action, differ across countries and climatic zones. For this reason, a case study based on the Spanish thermal building regulation is exposed in this paper in order to validate the methodology. METHODOLOGY In order to assess the level of adjustment of thermal building regulations to the new conditions imposed by the climate change, a four-step methodology is proposed: Step 1: Analysis of temperature influence into thermal building regulations. Bearing in mind the particularities of construction regulations in each country, influence of temperature into thermal building regulations must be carefully studied. In most European countries, these regulations define several numbers of climatic zones depending on its degree days (parameter which is a measurement of the severity of the climate). Other countries limit themselves to one climatic zone in spite of the relatively large variation among the degree day figures in their territory. Minimum or maximum mean temperatures for a certain period of time can also be included in thermal regulations. Step 2: Analysis of recent observed trends in temperature during the 20th Century. Recent tendencies of temperature in a national scale during the 20th Century must be analysed. Data should be translated according to its processing in the thermal regulation. As stated, one of the most used indexes in thermal regulations is degree days figures. This parameter can be calculated as the addition, for every day of a certain period of time, of the difference between a fixed temperature (normally 15ºC or 20ºC) and the mean daily temperature, when this daily temperature is lower than the fixed temperature. In order to simplify, we can accept that the monthly mean temperature can represent daily mean temperature. As minimum or maximum mean temperatures for a certain period of time can be included in thermal regulations, its trend during the 20 th Century must be also analysed. Step 3: Establishment of climate change scenarios over the next 50 years in order to assess the likely changes in temperature values in a national scale. Envisaged climate conditions must be taken into account in order to assess the level of adjustment of thermal building regulations related with climatic variables. In order to make projections of the climate change, global climate models are currently used. Obviously, these models are forced with evolutions of the levels of greenhouse gasses and aerosols accumulated in the atmosphere. These predicted evolutions are synthesized under four scenarios (A1, A2, B1 and B2) in the Special Report on Emissions Scenarios, taking into account coherent hypotheses of the future evolution of world population growth, energy demand, efficient use, global economic growth among other considerations.

3 Step 4: Assessment of the level of adjustment of thermal building regulations to the new conditions imposed by the climate change This final step includes a comparison between on the one hand, recent observed trends in climate and the envisaged climate conditions and on the other hand, weather patterns included in thermal building regulations. CASE STUDY: ASSESSING THE LEVEL OF SPANISH BUILDING REGULATIONS ADJUSTMENT TO THE FUTURE CLIMATIC VARIABLES Step 1: Analysis of temperature influence into thermal building regulations. This case study will be focused in NBE-CT 79 Thermal Conditions in Buildings approved by Royal Decree 2429/1979 of 6 July. This Compulsory Basic Building Norm defines the thermal conditions that buildings envelope must satisfy in Spain, establishing two classifications based on climate factors. The first classification of the NBE-CT 79 divides Spain into five areas (from A to E), according to its annual degrees day. The second one establishes five areas (from V to Z), according to its mean minimum temperature in January. Fig. 1 Climatic zones established in NBE-CT-79, according to its annual degree days. La Coruña Pontevedra Orense Lugo Caceres Badajoz Santander Donosti Vitoria Burgos Pamplona Leon Palencia Logroño Huesca Zaragoza Lerida Zamora Gerona Valladolid Soria Barcelona Salamanca Tarragona Segovia Teruel Guadalajara Madrid Cuenca Toledo Castellón Ciudad Real Albacete Palma Area Annual degrees day based at 15ºC A 400 B C D E > 1800 Cordoba Jaen Murcia Huelva Sevilla Granada Almeria Cadiz Alicante Santa Cruz Las Palmas Fig. 2 Climatic zones established in NBE-CT-79, according to its mean Tmin in January. La Coruña Pontevedra Huelva Cadiz Oviedo Santander Donosti Lugo Vitoria Pamplona Leon Burgos Orense Palencia Logroño Huesca Lerida Zamora Gerona Valladolid Soria Zaragoza Barcelona Tarragona Guadalajara Salamanca Teruel Madrid Cuenca Castellón Toledo Valencia Ciudad Real Palma Badajoz Caceres Albacete Ceuta Cordoba Jaen Sevilla Granada Malaga Almeria Melilla Murcia Alicante Santa Cruz Las Palmas Area Min. temperature in January (ºC) V 10 W 5 X 3 Y 0 Z -2

4 Step 2: Analysis of recent observed trends in temperature during the 20th Century. There is no doubt about the generalised temperature rise during the last quarter of a century [Moreno, (2005)]. According to Hulme, 1999 during the 20th Century, annual mean temperatures in Spain showed a warming of 1.6ºC. Figures 3 and 4 show the warming underwent in Spain from 1901 to 2000 in degree days and the evolution of recorded minimum mean temperature in January. Step 3: Establishment of climate change scenarios over the next 50 years in order to assess the likely changes in temperature values in a national scale. Considering six global climatic models (CGM, CSIRO, HadCM3, NIES2, ECHAM4 and GFDL) included in DDC-IPPC database, Moreno, 2005 suggests that in Spain the temperature may increase from 2.1ºC to 3.5ºC during period. The lowest warming is shown under the B2 Emission Scenario Family during the winter. For the A2 Emission Scenario Family the warming will be maximum (3.5ºC during the summer in the period). In general, warming will be slightly greater in the summer season (June, July and August) than in winter. Fig. 3 Degree days based at 15ºC in Spain from 1901 to Source: Own elaboration with information from Tyndall Centre for Climate Change Research. Degree days in Spain ( ) Degree days based at 15 (ºC) Year

5 Fig. 4 Minimum mean temperature in January in Spain from 1901 to Source: Own elaboration with information from Tyndall Centre for Climate Change Research Minimum mean temperature in January in Spain ( ) Min. mean temperature (ºC) Year Table 1: Changes projected in surface mean temperature in the centre of Spain for the period in relation to the period. Source: Moreno, Season SRES-A2 SRES-B2 T (ºC) T (ºC) DEF MAM JJA SON Table 1 shows the changes projected by the six global climatic models in surface mean air temperature (ºC) in the grid of each one, which includes the centre of the Peninsula. The results are seasonal averages (DJF winter, MAM spring, JJA summer and SON autumn) and correspond to two emission scenarios (A2 and B2). Changes are projected for the period As there is no available information about the changes projected in monthly mean temperature we have to accept that seasonal mean temperature can represent monthly mean temperature. Degrees day based at 15ºC calculated taking into account the above projections are 664 in the A2 scenario and 683 in the B2 scenario. Step 4: Assessment of the level of adjustment of thermal building regulations to the new conditions imposed by the climate change Analysis of the classification based on degree days As stated above, Basic Building Norm NBE-CT-79 Thermal Conditions in Buildings divides Spain into five areas (from A to E) according to its annual degrees day (see fig. 1)

6 Analysing this classification with monthly mean temperatures from National Meteorological Institute recorded during the period [Instituto Nacional de Meteorología (2001)], we can conclude that the 24% of the seventy nine Spanish weather stations studied should be classified in a warmer category whereas only two of them should be classified in a cooler category. Degrees day based at 15ºC calculated taking into account climate projections are 664 in the A2 scenario and 683 in the B2 scenario, which corresponds in both cases to Area B in NBE-CT-79 classification. Considering that these projections concern to the centre of the Iberian Peninsula, weather stations such as Madrid, Guadalajara (initially considered in area D) or Toledo (initially considered in area C) should be classified in the next future in a warmer category. Table 2: Spanish areas revised according dates from National Meteorological Institute. Weather station Degrees day Classification Actual based at 15ºC in NBE CT 79 classification Bilbao-Aeropuerto De Sondica C B A Coruña C B Pontevedra-Mourente C B Madrid-Base Aérea de Torrejón de Ardoz D C Madrid-Retiro D C Madrid-Aeródromo de Cuatro Vientos D C Madrid-Base Aérea de Getafe D C Ciudad Real-Escuela de Magisterio D C Huelva-Ronda Este B A Córdoba-Aeropuerto B A Sevilla-Aeropuerto B A Sevilla-Tablada B A Cuenca E D Teruel E D Valencia B A Palma-Centro Meteorológico B A Ibiza-Aeropuerto San José B A Analysis of the classification based on mean minimum temperatures in January Basic Building Norm NBE-CT 79 Thermal Conditions in Buildings establishes five areas (from V to Z), according to its mean minimum temperature in January. (see fig. 2). Comparing this classification with mean minimum temperatures in January from National Meteorological Institute recorded during the period [Instituto Nacional de Meteorología (2001)], we can conclude the 19% of the seventy nine Spanish weather stations studied should be classified in a warmer category.

7 Table 3: Spanish areas revised according dates from National Meteorological Institute. Weather station Mean T minimum Jan Classification Real ( C) in NBE CT 79 classification Asturias-Aeropuerto Ranón 5.4 X W Asturias-Oviedo-El Cristo 4.2 X W A Coruña 7.6 W V Ponferrada 1.0 Z Y Segovia-Observatorio 0.3 Z Y León-Virgen del Camino -0.8 Z Y Salamanca-Matacán -0.7 Z Y Madrid-Retiro 2.6 Y X Melilla 9.9 W V Tarifa 11.4 W V Almería-Aeropuerto 8.2 W V Cuenca -0.8 Z Y Albacete 'Los Llanos Base Aérea' -0.4 Z Y Palma 'Centro Meteorológico' 8.3 W V Ibiza 'Aeropuerto San José' 8.1 W V Assuming that the change projected in temperature for the winter season can represent the increase in minimum temperature in January and considering that these projections concern to the centre of the Iberian Peninsula, weather stations such as Segovia, Leon and Salamanca (initially considered in area Z) or Ciudad Real (initially considered in area Y) should be classified in the next future in a warmer category. CONCLUSIONS The application of the methodology exposed in this paper has demonstrated that the Spanish Basic Building Norm NBE-CT 79 Thermal Conditions in Buildings must be updated taking into account the historical weather records from the last thirty years. Moreover, the current scientific consensus states that the growing tendency of mean temperatures will accelerate under the combined effects of historical and future emissions. Spain climate change scenarios for the 21st century agreed on a warming from 1.1 to 1.2ºC every 30 years in winter and from 1.8ºC to 2ºC in summer depending on the global climate model and the emission scenario family considered [Moreno, (2005)]. In this area, a major problem is the inevitable uncertainty in future climate predictions: although climate modelling will improve with time, the uncertainty that arises from future policy decisions on mitigation will not be reduced during the next years. At the purely conceptual level, taking this uncertainty about future climate into account should not be difficult. As building regulations at present are based on statistical analysis of data, climate change will add an extra element of uncertainty to this process but not introduce a new principle Although thermal building regulations can be updated taking into account the new climatic context, the flux of new construction will be small when compared with stock of existing buildings, due to its long lifetime. Therefore, one of the most important questions still to tackle in Spain is the potential adaptation of the existing built environment to these weather changes. It is necessary to emphasize that NBE-CT 79 only deals with winter situations. As recent observed trends in climate and Spain climate change scenarios for the 21st century agreed on a remarkable warming, it is foreseeable that the energy needs for heating in winter could

8 conceivably decrease whereas the energy required for cooling in summer is likely to rise. Since the use of air-conditioning will significantly increase energy consumption and greenhouse gas emissions from buildings, it is urgent to include hot situations in the scope of thermal regulations. In addition, Basic Building Norm NBE-CT 79 supposes that the unique form to save energy is to use insulations. In order to save energy and to prevent climate change impacts, this norm should include solar earnings, contributing to the development of passive thermal control in buildings. On 6 May, 2000, Act 38/1999, of 5 November, the Building Act (Ley de Ordenación de la Edificación, LOE) was enacted in Spain. The LOE establishes a set of basic requirements (mainly those relating to functionality, safety and habitability) which must be satisfied in order to guarantee the safety of people, the welfare of society, and the protection of the environment. In its Second Final Provision, the LOE authorises the government to approve a Technical Building Code (TBC) setting the mandatory standards required to ensure safety and habitability. Bearing in mind the importance of the climate change impacts on the built environment, Technical Building Code should include measures related to the adaptation to these changes of the building sector. IMPACT The exposed methodology, which constitutes the first step into the way of adoption of adaptation strategies to climate change in the building sector, can be easily applied to other countries in order to analyse other national building regulations. This methodology could also represent the basis for the development of further research in this field. Moreover, it could be the start point for future government initiatives addressing climate change adaptation, especially in case of revision of building regulations. REFERENCES Hasegawa, T (2004) Climate change, adaptation and government policy for the building sector. Building Research and Information, Vol. 32, No 1, pp Hulme, M, Sheard, N (1999) Climate Change Scenarios for the Iberian Peninsula. Climatic Research Unit, Norwich, UK, 6pp. Also available on-line at (accessed May 2005). Instituto Nacional de Meteorología (2001) Guía resumida del clima en España. Subdirección General de Programas Especiales e Investigación Climatológica. Servicio de Desarrollos climatológicos. Larsson, N (2003) Adapting to climate change in Canada. Building Research and Information, Vol. 31, No 3-4, pp Lisø, K R, Aandahl, G, Eriksen, S and Alfsen, K H (2003) Preparing for climate change impacts in Norway's built environment. Building Research and Information, Vol. 31, No 3-4, pp Lowe, R (2004) Lessons from climate change: a response to the commentaries. Building Research and Information, Vol. 32, No 1, pp McCarthy, J J, Canziani, O F, Leary, N A, Dokken, D J, White K S. (2001) Climate Change 2001: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge. Also available on-line at (accessed May 2005).

9 Mitchell, T D, Carter, T R, Jones, P D, Hulme, M, New, M (2003) A comprehensive set of highresolution grids of monthly climate for Europe and the globe: the observed record ( ) and 16 scenarios ( ). Journal of Climate: submitted (August 2003) Also available on-line at (accessed May 2005). Moreno, J M (2005) Evaluación preliminar de los impactos en España por efecto del cambio climático. Proyecto ECCE. Universidad de Castilla la Mancha. Also available on-line at (accessed May 2005). Spain (1979) Basic Building Norm NBE-CT 79 Thermal Conditions in Buildings (Norma Básica de la Edificación NEB-CT-79, sobre condiciones térmicas en los edificios). Also available on-line at (accessed May 2005).