Estimación de potenciales ahorros energéticos y beneficios medioambientales para España derivados del uso de control de radiación ("cool roofs") en los tejados de viviendas

Abstract

Cool roofs are an inexpensive method to save energy and to improve the comfort level in buildings in mild and hot climates. A high scale implementation in some regions of Spain may contribute to reduce contamination and to lower peak electricity demand, yielding significant economical savings for electrical companies and for consumers. A high scale implementation of cool roofs in Andalusia, one of the most southern regions in Spain, could potentially save 295,000 kWh per year (a 2% reduction in the electrical consumption for residential use), considering only residential buildings with flat roofs using electrical heating. At the current energy prices, consumers can save 59 million euros annually in electricity costs and the emission of 136,000 metric tons of CO2 can be directly avoided every year from the production of that electricity. If radiative forcings are considered, Andalucía can potentially offset between 9.44 and 12 Mt of CO2. A house in Cádiz with a flat dark roof will save 19% of the thermal energy with a cool roof if using electrical heating and 36% in the final energy cost when using gas heating. A house in Huelva would save between 10% and 15% and one in Sevilla between 7% and 10%. All the provinces in the rest of Spain are also studied in this dissertation. Cool roofs yield positive savings for all the regions studied (using gas heating) except Oviedo, Lugo and Coruña. The biggest savings are achieved in Gran Canaria (48%), Tenerife (48%), Cádiz (36%), Murcia (33%), Huelva (30%), Málaga (29%), Almería (29%) and Sevilla (28%), where savings are greater than 2 euros per square meter of flat roof for old buildings with dark roofs. For the biggest cities the range of savings obtained with gas heating are: between 7.4% and 11% in Madrid (0,2 to 0,76 €/m2), between 12% and 18% in Barcelona (0,25 to 1,1 €/m2) and between 14% and 20% in Valencia (0,36 to 1,4 €/m2). The marginal cost of a cool roof is very low during the construction or regular upgrade of the roof: less than 2 €/m2 for a high quality certified paint. In general, it is profitable to invest in cool roofs in most of the Spanish regions, but attention should be paid on when the house was built and where it is located: 􀁸 Very high profitability area (includes Sevilla, Málaga, Murcia, Palma de Mallorca and Las Palmas): it is recommended to focus efforts in old buildings (built before 2008); to promote employment by organizing cool roof training, as investments in cool roofs are profitable for citizens even contracting external workforce; to prioritize legal enforcement of cool roof materials in regular roof repairs and in new building construction. 􀁸 High profitability area (includes Barcelona and Valencia): focus actions in old buildings with dark roofs; promote “do it yourself” o volunteers programs to adapt old buildings with medium colored roofs (red, green, light grey, etc.); recommend always cool roof materials in roof repairs and new buildings. 􀁸 Medium profitability area (includes Madrid and Zaragoza): promote volunteers or “do it yourself” programs to adapt old buildings with dark roofs; recommend cool roof materials in roof repairs and new buildings. 􀁸 Not recommended for cool roofs area (includes Bilbao and all the northeastern regions): do a case by case analysis with local weather data and consider other options like green roofs.