Summer overheating mitigation in urban areas of rich cultural heritage: The Smart and Urban Tree Approach : Artificial structures as performance-optimizing supplement for historic cities.

Abstract

This contribution illustrates the idea, the methodological approach and prelminary results of a recent research and developement project adressing overheating and climate change mitigation in historic city centers. Such city structures represent regularly highly-densified agglomerations, and thus can be per se considered as fortunate in view of ecological footprint of its dwellers. Instances of the performance advantages of urban structures encompass the reduced necessity of individual motorization as well as the low carbon footprint of buildings due to their long existance (100 years and more). However, such city structures are potentially prone to overheating risk and strenous impacts of climate change. This is due to the high specific heat capacity of used materials (brick buildings), the competition for different usages of the interstitial public spaces, such as roads, and the lack of greenary. Moreover, large scale heat sources, such as A/C-split units lead to uncomfortable conditions during the hot season. Trees and greenary are considered to be the logical choice in reducing the negative impact of urban heat islands. Sadly, trees can not be applied everywhere, as not only above surface there is limited space, but also below terrain very often sub-soil lines for water, gas, and energy supply, as well as sewerage can be found. Moreover, sub-terrain public transport requires also space below the street surfaces. These obstacles often hinder the implementation of natural trees into the cityscape. Moreover, given the urgency of city cooling in the recent climate change scenarios, trees would require very often too long to have a strong impact on the local microclimate. This is where the idea of smart and urban trees would allow to supplement greenary and shading whereever natural trees are not applicable or not feasible to grow. In this paper, we discuss the relation of such artificial super structures (that we name smart and urban trees) in contrast to the cultural heritage cityscape via a demonstration project conducted together with graduate students of architecture at the TU Wien, Vienna Austria.