Urban planning – architectural report on thermal stress in the city of Warsaw

Summary This following study was prepared on behalf of the research project entitled "Embodying climate change. Trans-dyscyplinary research on urban overheating” (EmCliC). It is a three-year research project, that brings together social anthropology, sociology, climate science, epidemiology, atmospheric physics and innovative technology, in order to understand and demonstrate the ways in which people experience climate change on a daily basis. The project is focused on studying urban heat experiences among elderly populations of Warsaw and Madrid. This study concerns urban and architectural issues that affect the experience of high temperatures by people in urbanized areas, for the case study of Warsaw. The study is centered on multi-family housing development that creates an environment for the daily life of residents. The study is aimed at systematization of urban-related and architectural factors that affect the phenomenon of city overheating, developing a typology of housing development in Warsaw, with account to the issue of overheating, presentation of urban and architectural solutions applied in order to counteract the phenomenon, as well as adaptation of city spaces and buildings in order to improve their thermal comfort during heat periods, Five groups of multi-family buildings typical for Warsaw were distinguished according to the time of their construction, following the criteria of erection technology and thermal insulation parameters. These are buildings erected: prior to 1945 - historical architecture - historical technologies, massive brick walls, no thermal insulation requirements; 1946 - 1966 - reconstruction of war damages and new estates with the use of demolition bricks, cheap, economical construction; 1967 - 1989 – prefabricated, large-panel prefabricated construction; 1990 ~ 2002 – more diverse technologies similar to modern ones but less restrictive in terms of thermal insulation of walls; following 2002 – stronger than before emphasis on thermal insulation and energy efficiency, improvement in technology. The analysis of these groups prompt conclusions concerning the types of multi-family housing that are prone to overheating to a lesser and greater degree. Buildings most exposed to the above problem are the ones built by the 1990s that have not yet been subject to thermal modernization. Newer buildings, especially those erected after 2002, are marked with improved technological standards related to thermal comfort, but the spaces around them, due to the high density of building development and the low share of greenery, may be at risk of overheating. In conclusion, the group of factors that influence thermal conditions inside buildings and in their surroundings (including the issue of overheating) comprises numerous issues and is subject to various design decisions at all design stages. These can be divided into: urban planning solutions – spatial layout of building complexes and their orientation in relation to the surroundings, building development intensity, proportions between developed and open areas, distribution and selection of greenery, ratio of water-permeable areas, surface hardening materials; architectural solutions - the building form and its orientation in relation to the surroundings, the distribution of functions within the building, the layout of internal spaces, the ratio of glazing and its location on the facades, elements of the surroundings around the building (hardened surfaces, greenery, shading installations), colors; construction-related solutions - materials used in building the construction (e.g., their heat accumulation properties) and internal and external building finishing elements (color; properties in terms of solar radiation reflection and absorption), thermal insulation materials, glazing parameters. installation-related solutions – such solutions can support natural phenomena that take part in regulating the interior climate (e.g., hybrid ventilation) or can create the climate in an artificial way (e.g., mechanical ventilation, air conditioning). In order to apply the pro-ecological approach, it is required to compare the effectiveness of individual solutions, together with the assessment of their ecological footprint. According to this approach, the potential of passive, simple solutions (e.g., rational spatial design, materials and solutions with a low share of advanced technologies) should be used in the first place, and supplemented with more advanced systems (e.g., air-conditioning). Like many other large cities, Warsaw is affected by the urban heat island phenomenon. In 1981-2014 an increase in the average annual air temperature in the city area was noted; it amounted to 0.02-0.04°C per year. In 1976–2011, the urban heat island phenomenon occurred in Warsaw for almost 87% of the year. Due to natural and historical conditions, Warsaw displays a dense central layout. The greatest intensification of building development and technical infrastructure occurs in an almost geometric center of the city (closer to the west side). Implementing the construction investments planned for 2070 will significantly modify the spatial distribution of the urban heat island in Warsaw. Not only will it increase the areas where the highest intensity of the phenomenon occurs, but also areas where the UHI is not extremely intense will grow. Areas with no urban heat island will be limited. Protection of Warsaw against the effects of urban heat island requires the analyzed problem to be approached on various scales - the city as a whole, parts of the city, buildings and their immediate vicinity, individual apartments and the user habits. Therefore, problem of thermal stress affect the processes of city spatial planning, urban design of districts, housing estates, building development quarters, architectural design of buildings and their surroundings (including landscape design) and interior design. The scale of activities is rather wide. Moreover, it comprises various regulations, which are improperly arranged in the Polish law. A clear need is noticeable for long-term, comprehensive development concepts that should be consistently implemented regardless of political conditions. The most important elements of such strategies should primarily include efforts to: challenge the dominance of developer models for conducting housing investments, provide absolute protection of strategic areas in terms of nature, including the system of aeration corridors, exert control over building development intensity, increase the effectiveness of Local Spatial Development Plans as legal instruments with which to impose high environmental and social standards, increase design standards at the study and conceptual stage, increasing the rank of urban design. Short-term actions should mainly concern modernization of the existing housing development. The analysis conducted in the study above proved the necessity to analyze the building and its immediate surroundings as a whole. Undoubtedly, thermal modernization of buildings, successively performed in housing estates that fail to meet modern energy standards, yields a satisfactory effect. Such actions should be better supported by central or local authorities, but it is also necessary to: update technologies and change them to more ecological ones, extend the goals of thermal modernization - from the approach of protecting the building against heat loss to the approach of protecting it also against overheating the rooms during hot periods, develop and promote appropriate solutions for buildings of historical value, where the facades should remain uncovered, so as not to lose valuable architectural details. Among the solutions, described above, which affect temperature balance in summer, a group of solutions can be distinguished that are likely to yield satisfactory results, are simple and require little intervention. Their introduction is within the capabilities of cooperatives or apartment owners (it is also worth co-financing them under municipal programs). In general, these solutions also fulfill many environmentally and socially valuable goals. These include: external shading systems, biologically active surfaces, instead of hardened surfaces in the vicinity of the building, tall trees in vicinity of buildings, shaded places in the vicinity of buildings as places to spend time at (trees, seasonal roofs), seasonal shading of balconies, green roofs and balconies, water retention, water reservoirs in neighborhood recreational spaces, drinking water intakes, seasonal cooling water curtains. Installation of air conditioning units in individual apartments, although it seems an almost immediate solution and, in many respects, the simplest one, is unfavorable in terms of overall environmental and social assessment. Multiplied by the number of flats that require this sort of improvement, it may overall worsen the climatic situation of the city.The research leading to these results was funded by the EEA Financial Mechanism 2014 - 2021 (The Embodying Climate Change grant number: 2019/35/J/HS6/03992)