M. Soria, M. Costa, A. Oliva (Centre Tecnoldgic de Transferencia de Calor"),
D. Heineke, E. Antonicelli (University of Gottingen),

X. Farres, M. Vallds (Biosca & Botey),

J. Bordas, I. Hassanova (Jardineria Bordas),

M. Roa, J. L. Anguita (Arquitectura Produccions),

S. Juhling (Juhling),

M. Filippi, G. Marabini (Nature),

E. Martins (Percurso)

The central idea of the GREENFACADE project is to use decidous climbing plants to shade the facades of urban buildings. During winter, the vegetation loses its leaves and its effect is almost null, while during summer its effects tend to supress or reduce the overheating. However, the practical aplication of this simple idea is not straightfor­ward. With partial funding from European Comission, a multidisciplinar consortium has been gathered with the purpose of solving different problems associated with the use of vegetal elements as shadowing devices. In this presentation, an overview of the project after its first year will be given.

Introduction

Overheating during summer is a serious problem in Southern European climates, spe­cially in office buildings, mainly due to their bad passive behaviour. The use of air-conditioning relieves the problem, but at the expense of a great consumption of electricity.

Different solutions have been proposed to improve the passive behaviour of buildings with glazed facades. One of the better solutions is a combination of ventilated facades [5], [4], [6] with selective glazing. Such facades, if carefully designed, may have a thermal behaviour comparable to conventional (i. e., built with bricks) facades.

In our work, a well known traditional architecture solution is reconsidered. The central idea is to use decidous climbing plants to shade the facades. During winter, the vegetation loses its leaves and its effect is almost null, while during summer its effects are: (i) To reduce the solar radiation arriving to the facade. (ii) To decrease the ambient temperature due to evaporation and transpiration. (iii) To reduce the wind velocity at the facade surface. (iv) To reduce the heat lost by the facade due to thermal radiation. In general, solar radiation re­duction is the dominant phenomena, so the overheating during summer can be significantly reduced, if a part of the facade is covered by vegetation.

The goal of this presentation is to give a short summary of the GREENFACADE research project. The GREENFACADE consortium of SME companies and research institutions, with partial finantial support by the European Comission, has gathered a multidisciplinar team (engineers, biologists, architects, mathematicians and gardeners) with the purpose of solv­ing the problems associated to the use of vegetal elements as shadowing devices.

A good review of previous studies can be found in [3], where the effect of the vegetation is measured with an experimental set up and a conventional architecture simulation code (APACHE) is used to simulate different buildings. To do so, the vegetation is modelled as a set of passive materials. Other works, however, consider the situation mainly from an architectural point of view [7]. In our approach, architectural aspects are important, but other

*Centre Tecnologic de Transferencia de Calor (CTTC), Lab. de Termotecnia i Energetica,

Universitat Politecnica de Catalunya (UPC), labtie@labtie. mmt. upc. es, www. cttc. upc. edu

elements are also considered central, such as the optimization of the designs, considered from a heat transfer and solar energy engineering. This will allow us to quantify the amount of energy to be saved with this solution, and to compare the green facades with other bio­climatic architecture technologies.

The GREENFACADE project is oriented along two different lines:

• Find solutions to the architectural problems associated to the vegetation such as: acess for maintenance, aspect of the plants from the building indoor, lighting, outdoor design, identification of species of interest, etc.

• Develop a detailed (time dependant) numerical model of the vegetation, treating each of the previous phenomena separately, and using laboratory measurements of vegeta­tion properties. This model, integrated in the code AGLA [1], [2], will allow to determi­nate the amount of energy to be saved for different building types, facade orientation and vegetation density The model will be validated using experimental data from dif­ferent prototypes.