CLIMATIC-CHANGE AFTER REGENERATION IN THE OLDEST QUARTER OF HEIDELBERG

During the last 100 years, the urban cores have been gradually built up in increasing density, so that the sun does not reach the lower windows of the houses. In the small courtyards, the air stays cool in the morning and mild at night; the wind is light or calm, the climate is described as a basement climate here. Ten courtyards in the oldest part of Heidelberg were studied. Winter temperatures were milder than those measured near the roof; in the daytime the average difference was 2.5 K and in the night 4 K, even in abandoned, unheated houses. Summer afternoons were uncomfortably hot. Some of the courtyards were reinvestigated after the renewal programme. Most of the outhouses and sheds had been torn down in order to extend the court and to allow trees to be planted. Following the renewal programme, solar radiation penetrates to the ground, temperatures are higher, and night temperatures cooler; the time lag is shorter than before. The temperature of the court approaches that measured near the roof by 1-2 K. One of the goals, to increase ventilation, was achieved only to a certain degree, so that the average wind velocity in the courtyard increased from 45 to 55% of that measured at roof level. There could have been more success if the ring of structures had been opened at two or more gateways. In this case, not only the wind would have gained access to the court, but also the noise from the street. © 1990.