‘Passive cooling is a matter of smart design’

Constructing energy neutral in warm areas is near impossible without the application of passive cooling. Use Chinese rural architecture as a best practice example, proposes PhD researcher Xiaoyu Du. This type of architecture does not need energy slurping airconditioning through the smart space lay-out.

A typical house in Central China consists of several connecting rooms built around a patio or courtyard. A slightly lower-lying garden with shrubs and trees is often found next to the house. “If you open your doors and windows on a warm summer's day, this type of house enjoys a natural flow of air,” explains Xiaoyu Du, referring to a drawing to show how it works. “Cool air flows from the garden towards the courtyard, creating a pleasant indoor climate.”
In his research, he identifies a 'building microclimate' that presides in the inner courtyard or patio and the rooms around it. What are the factors that determine a building microclimate, Du wonders? The arrangement of the rooms is the most important factor. Patios and gardens provide relief in Central China’s warm, humid continental climate. Semi-outdoor areas also make a valuable contribution. Verandas, galleries and covered balconies all allow people to sit outside in the shade. Most partitioning walls are made from lightweight materials (wood) and feature doors and windows that can be opened and closed, thus enabling ‘cross-ventilation’ or ‘stack ventilation’. There is no mechanical ventilation; humans adapt their activity levels to the weather. Fans are only switched on if it is so hot that people can no longer sit under the veranda.

Simulation
According to Chinese architectural tradition, the varied arrangement of the rooms ensures a constant airflow, says Du. This creates thermal comfort. Measurements show that in a traditionally arranged house, the average airflow is 0.74 metres per second throughout the day. This is much better than in the modern, uniform mass housing that has been built in the last few decades. It’s hardly surprising that residents complain about the unpleasant indoor climate and that people are experiencing problems sleeping.
Du would like to see designers using lessons from the past in their new building designs. He has also taken measurements showing that even in modern concrete buildings, arranging rooms around patios with semi-outdoor areas and lower-lying gardens improves thermal comfort. “This also applies to the passive or zero-energy houses in the Netherlands,” continues Du.
However, a traditional layout is not the solution for mass housing in the Chinese metropolises. Urban buildings are much too close together and there is no room for creating natural ventilation. But varied architecture can definitely help to reduce demand for air conditioning in rural areas. “Between 2.9 and 6.7% of the energy consumed in houses and commercial buildings is used for cooling,” says Du. “Smarter house designs could substantially reduce energy consumption.”

More information

• PhD thesis ‘Space design for thermal comfort and energy efficiency in summer. Passive cooling strategies for hot humid climates, inspired by Chinese vernacular architecture'
• PhD Defence Xiaoyu Du