Passive heating and cooling

Buildings play a fundamental role in the energy budget of European countries. Accordingly, efforts addressed to optimize building’s thermal behaviour are key important. Numerical analysis of passive systems such as green façades, double skin façades and Trombe walls have been developed and tested in the CTTC for many years.

Large and transparent areas in façades are a common architectural practice. One of the  main problems of these designs in  Mediterranean climatic conditions is the overheating in hot weather periods.  Double skin façades are a good solution for avoiding building overheating. They consist of two layers of glass separated by an air channel, which collects or evacuates the solar energy absorbed by the façade in order to warm up in cold season or to cool down in warm season the inside of the building, respectively, reducing the heating and air conditioning demands. In the CTTC the thermal behaviour of advanced façades which include advanced technological elements, like phase change materials, transparent insulation and façade integrated collectors-accumulators have been numerically studied [1,2].

CTTC has worked in the thermal design of singular buildings such as Agbar Tower in Barcelona [3], central headquarters of Caixa de Terrassa [4] in Terrassa city and headquarters of Association of Technical Engineers in La Rioja [5].

Fig.1: Agbar Tower

Fig.2 Headquarters of the old "Caixa de Terrassa"
Overheating problems can be solved as well by means of green façades, where the façades of urban buildings are shaded by deciduous plants. During cold seasons, the vegetation loses its leaves and its effect is almost null, while during hot seasons its effect tends to suppress or reduce the overheating (solar protection).
Fig. 3-4: Diferent examples of green facades

In the numerical simulation of such façades various effects of the plants over the façade were taken into account: (i) Interaction with solar radiation; (ii) Evaporating cooling; (iii) Reduction of wind velocity (and thus, heat transfer coefficient) at the façade surface; (iv) Shielding of thermal radiation. A Monte Carlo ray tracing code (VICACO VIrtual CAnopy COde) was developed to evaluate the fraction of incident solar energy that reaches the façade after multiple reflections within the canopy of plants.

Fig. 5: Different leaves shapes and their discretization to be used in the computational analysis of shades

Trombe walls are passive solar designs able to reduce heating needs. They are thick sun-facing walls made of heat-absorbing material on the exterior surface and are separated with the outdoor by a glass. Absorbed solar energy during the day is released toward the interior during the night. CTTC has studied with its newest modular building code, NEST [6], the thermal and fluid-dynamic behaviour of this type of walls [7,8].

Fig. 6-7: Basic analysis of a Trombe wall and schematic representation of advanced modular simulation
Fig. 8: Unsteady analysis of the natural turbulent flow of air in a closed channel Trombe wall
Video 1: Numerical simulation of air flow inside air channel of a double skin façade
Video 2: Growing process, colour and leave density changes of a green façade. The day of the year can be seen at the right hand side, where the four seasons are marked with different colours as a reference.

Related publications

[1] Faggembauu, D., Costa, M., Soria, M. and Oliva, A., "Numerical analysis of the thermal behaviour of glazed ventilated facades in mediterranean climates. Part I: Development and validation of a numerical model", Solar Energy, Vol. 75, No. 3, p. 217-228, 2003.

[2] Faggembauu, D. and Costa, M. and Soria, M. and Oliva, A., "Numerical analysis of the thermal behaviour of glazed ventilated facades in mediterranean climates. Part II: Application and analysis of results", Solar Energy, Vol. 75, No. 3, p. 229-239, 2003.

[3] Faggembauu, D., Oliva, A., Costa, M. and  Soria, M. Numerical analysis of the fluid-dynamic and thermal behaviour of the double envelope of the Agbar tower, designed by the architectures Ateliers Jean Nouvel and B720 Arquitecturas S.L. Technical Report, 2002.

[4] Faggembauu, D.,  Soria, M. , Costa, M.  and Oliva, A. Simulation of the thermal and fluid-dynamic behaviour of ventilated facades ofr Caixa Terrassa-building by J. Baca architect. Technical report, 1999.

[5] Faggembauu, D. and Oliva, A., Numerical analysis of the thermal and fluid-dynamic behaviour of the facades for the new headquarters of the Association of Industrial Engineers in La Rioja. Architecture Portales, Ingenieria, S.A. Technical report, 2005.

[6] Damle, R., Lehmkuhl, O. and Colomer, G. Modular simulation of buildings with an object-oriented tool 23rd IIR International Congress of Refrigeration pages 1-8, 2011.

[7] Damle, R., Lehmkuhl, O. Rigola, J. and Oliva, A. Numerical simulation tools for energy efficiency in buildings. HAM transfer in façades coupled with CFD models for air distribution. Proceedings of the 8th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings, paper Num. 1120, pages 1-8, 2013.

[8] Damle, R., Lehmkuhl, O., Lopez, J., Rigola, J. and Oliva, A. Parallelization of the coupling between CFD models for airflow and building energy simulation with an object-oriented infrastructure. In Proceedings of the 2nd International High Performance Buildings Conference, pages 3379, 1- 8, 2012.

[9] R. Damle, O.l Lehmkuhl, I. Rodríguez, A. Oliva. Coupling CFD models of airflow with building simulation with an object-oriented and parallel infrastructure. In Proceedings of  ISES-Europe Solar Conference, Croatia, 2012.

[10] R. Damle, O. Lehmkuhl, G. Colomer, and I. Rodríguez. Energy simulation of buildings with a object-oriented tool, In Proceedings of ISES Solar  World Congress, Kassel, Germany, 2011.


Related projects

Research project  ENE2009-09496
Government Institutions: Spanish Government.
Title: Development of new algorithms applied to Large Eddy Simulation techniques for the numerical simulation of the thermal and fluid-dynamic behaviour of bioclimatic buildings.
Period: 2010 - 2012.

Research Project C05859
Enterprises: Asociación de Ingenieros Técnicos Industriales de La Rioja
Title: "Simulación numérica del comportamiento térmico de una fachada de doble piel en el edificio de la nueva sede del Ilustre Colegio Oficial de Ingenieros Técnicos Industriales de La Rioja. Optimización energética."
Period: 2005

Research Project E00755 ref. ENK6-CT-2002-30033, GREENFACADE-VER (CTTC was the Research Project Coordinator).
Government Institutions: European Commission
Enterprises: Biosca & Botey, Jardinería Bordas S.A., Percurso, Nature, Arquitectura Produccións, Juhling GBR
Other Research Centers: UNIGOE
Title: "Vegetation for cooling advanced glazed façades: architectural integration, gardening technology, numerical simulation"
Period: 2003 - 2004