Thesis document - Jana Milosovicova - Urban Design English

• Urban geometry: Tall buildings within urban areas provide multiplesurfaces for the reflection and absorption of sunlight, increasing theefficiency with which urban areas are heated – called the urbancanyon effect. Another effect of buildings is the blocking of wind,which also inhibits cooling by heat transport (Wiki UHI, online);• Anthropogenic heat waste coming from vehicular traffic, air-conditioning,electric devices such as computers, refrigerators etc.;• Urban “greenhouse” effect: Long-wave radiation emitted frompolluted urban atmosphere.Matzarakis (2001) stated that it is the thermal characteristics of constructionmaterials (particularly the level of surface sealing) and theeffects of urban geometry that influence the UHI extent in the mostsignificant way (Matzarakis 2001, p. 50-51). Interestingly, the immissions-relatedgreenhouse effect is “relatively unconsiderable” (Matzarakis2001, p. 51), compared to the two above mentioned factors. 9Fig. 7 Causes for UHI (Emmanuel 2005, p.25)Emmanuel (2005) summarized approaches explaining the nature of urbanheat islands, and stated that it is the energy-based approach thatnot only explains the causes, but also points to urban design solutions.According to this summary, the primary energetic effect of urbanization,causing the UHI is “(…) partitioning of more heat into sensible (=thermal heat) rather that latent form (= thermal energy withdrawn inthe process of vaporization of water, not connected with increasing oftemperatures)” (Emmanuel 2005, p. 25). The imperative message thusis to bring more evapotranspirative surfaces back into cities. 10The evapotranspiration of water affects the air humidity, which influencesthe intensity of the UHI. The higher the air humidity, the lowerthe temperature differences between the city and its surrounding naturalenvironment. In the cities with higher air humidity in coastal regionsof mid-latitudes (Park 1987 in Marzluff 2008, p. 241) and in tropicalhumid climates, the intensity of the UHI is much lower (Matzarakis2001, p. 111). The increase in air humidity to tackle high urbantemperatures with the help of evapotranspiration is thereforeessential.A fundamental argument of this Thesis however is that it is both surface/landscapedesign and urban form that have a significant effect oneither increasing the UHI or in reducing it. The way in which we designcities might thus contribute to the alleviation of UHI, maybe even withpositive effects on regional and global climate. Interestingly, even theIPCC Report 2007 only mentions the relevance of the reduction of GHGemissions to mitigate the climate change, but not the direct effect ofland use modification – and thus the changed surface characteristicsand temperatures and options for their mitigation.Fig. 8 Values of solar radiation on a clear day(above) and on a cloudy day (below). Recordedon 18 July 2006 and 3 August 2006, in Třeboň,Czech Republic (Kravčík et al. 2007, p. 24).9 And, since urban design does not offer ways to deal with the emission of pollutantsitself, only on their trapping (with providing ventilation exchange betweenthe pollution sources, such as highways, and compensation areas, such as urbanparks; and with enhancing greenery – all discussed in the next chapters), nodetailed attention will be given to the pollution issue in this Thesis.10 Key terms are highlighted in bold typeface as takeaway for the reader who isinterested in applying the CSUD guidelines to his/her projects.14Climate Sensitive Urban Design in Moderate Climate Zone: Responding to Future Heat Waves. Case Study Berlin Heidestrasse/Europacity