Ancient Architects Set Example For Modern Eco-Efficiency

The scientific results gathered by the researchers could help save energy and money – which is also the objective of eco-efficient buildings. Their results have also verified what the people of Mediterranean regions have known for centuries, that during the summer their courtyards are cooler than the street. This simple fact, however, has serious ramifications for how houses are designed ‘Why then put air conditioning extractor units on rooftops or outer walls when we could save energy by taking the cooler air from inside the courtyard,’ suggests architect Juan Manuel Rojas. 

Researcher Rojas, together with two lecturers from the University of Seville, have developed a mathematical tool that for the first time is able to assess the complex thermodynamic behavior of the courtyard. ‘These spaces create a mixture of phenomena: stratification (hot air rises and cold air falls); convection (the walls heated throughout the day project air upwards); and flow patterns (whirlwind formation depending on the geometry of the space),’ explains Rojas. 

All of this information is brought together in a program using specific data on the local climate (average temperatures and wind speed) and that of the courtyard itself (height, width, the materials with which it was built) since not all absorb the same levels of radiation. The result is a ‘film’ showing air evolution throughout the day. 

‘The model allows for the thermal advantages of the courtyards to be assessed. In turn this provides new design possibilities for more efficient and sustainable buildings without going over budget,’ outlines the architect. This information, which has been used for over 4 000 years, he insists has no expiry date and could still be utilised in the construction of modern day buildings. 

The introduction of eco-efficient projects in recent decades tended to do away with courtyards or used glass covered atriums because of the belief that the greater surface area will lead to greater energy transmission. ‘But the energy rating used to calculate this assumes that the air inside and outside of the courtyard is the same temperature. This is not the case and must be considered,’ insists Rojas, who recognises that closed atriums can work well in central and northern Europe. 

Since its initial creation, the model has been successfully put to the test in a hotel in Malaga and follows the thermodynamic strategies of the courtyard for an overall improvement in their energy efficiency. By taking in air from the lower part of the courtyard, which can be up to 9 degrees Celsius cooler, the hotel air conditioner energy bill can be significantly reduced as the building consumes half the energy that surrounding buildings do. 

The study also offers a new thermodynamic interpretation of historical courtyards ranging from traditional examples in Cadiz and Seville to cloisters of Santiago de Compostela Cathedral and the Palazzo Farnese in Rome. By comparing different courtyards they are able to suggest which type of courtyards are better suited to specific climates. 

‘The deepest and narrowest courtyards work better in hotter regions, whereas more open ones work better in the North, as we can see by simply searching on Google Maps,’ says Rojas. 

The architect believes that the climate, and not culture or art, has conditioned the most appropriate courtyard type according to region, which has then been continued due to tradition: ‘In the same way that natural selection chooses the best organisms, the area itself has always determined the use of architectural options that have best exploited available resources.’

Contacts and sources:
CORDIS