WSUDs (Water Sensitive Urban Design Systems) Thermal Behavior

Abstract

The aim of this communication is showing briefly the results of a two-year research about the WSUDs thermal behavior.

WSUDs (Water Sensitive Urban Design Systems) try to integrate the urban water cycle in the urban design to improve the environmental behavior in the urbanization of the cities. When we urbanize we transform pervious surfaces into impervious surfaces.

With WSUDs pervious surfaces are implemented. Water presence should improve surfaces thermal behavior. This is the main hypothesis of the research. Thus the question is: are there thermal benefits in using WSUDs that improve outdoor spaces surfaces temperatures?

This question has been tried to be answered with this two year- research. The methodology has been mainly experimental. Some WSUDs Barcelona, built before and during the research, have been thermally measured during some of the warm and cold months of the year with a thermal camera. Some other parameters have also been measured such as environmental temperatures or surface humidity and wind speed. The tools used to do so have been a hygrometer and an anemometer.

During the first years the trend of these surface temperatures showed a “temperance effect” of some WSUDs during the warm months of the year. This “temperance” effect consists in the measurement, during the warm months of the year, of some WSUDs surface temperatures to verify they are lower than the environmental temperatures at the same place and moment.

These WSUDs are built with whether green or stone materials. The main difference though between them is the presence of water and how and where it is present in the WSUD. Therefore, depending on how and where water is present in WSUD it causes a strong thermal effect on its surface; stronger than the thermal effect of the material the WSUD is built.

This concept required to be verified; therefore, during the second year of the research a WSUD self-financed was built at the ETSAB experiments yard. There were also some pervious surfaces that helped as well to verify some aspects of the previous year trend registered.

At the end of the article, in the conclusions, the reason is explained. The cause-effect is based in the specific heat of the diatomic molecules due to their thermodynamics behavior. The internal energy of the diatomic molecules is so high that it is hard to increase their temperature. That is the cause of the “temperance effect” that supports this research. This preliminary communication tries to show, analyze and explain this effect, cause of the better thermal behavior of some WSUDs surfaces.