**2. Object and Method of Research**

Radzionków is a city and municipality in south-western Poland, in Tarnowskie Góry County in the Silesian Voivodeship. It is located in the northern part of the Upper Silesian Industrial District (GOP), which is one of the most important cultural, academic and economic centres in Poland. The oldest mentions of Radzionków are dated to between 1326 and 1357. The subject of the study was the northern and central part of the municipality of Radzionków. In terms of morphology, the central part of its structure is a surviving oval system with a historical trail. Most of the buildings in the area are located along streets that are delineated along plot boundaries. The buildings located in the city's core form frontages and have a regional, classicist character, with stone featured in their facades. Their architecture is typical of the end of the nineteenth and the start of the twentieth centuries. Historical architecture is complemented by Modern and Functionalist buildings. Most residential buildings were built after the Second World War, either in a Modern or Postmodern style. In the eastern part of the town, there is a railway line that divides its area into separate zones, with circulation between them provided only by historical tunnels or viaducts above the railway tracks. The eastern part of the city also includes the Silesian Insurgents Park and the Silesian Botanical Garden.

Three types of city heating zones were determined after first outlining six characteristic zones. These areas were selected based on their location, similarities within their development structure in terms of age and architectural form, as well as similar topography. Building insulation and central heating systems were inspected on site. Within the six areas, 60 buildings were randomly selected, and their heating systems and insulation were analysed. In total, the analysis covered 360 buildings divided into 6 groups composed of 60 buildings each. Based on the findings of the analysis, the author delineated 3 major urban zones that displayed distinct heating and insulation systems (Figure 1).

**Figure 1.** Three zones (A, B and C) with different morphological and environmental conditions in the city of Radzionków, for which different spatial policies should be pursued in terms of protecting the quality of the living environment. Zone A: 53% of buildings were heated with coal; zone B: 39% of buildings were heated with coal; zone C: 35% of buildings were heated with coal.

To better explain and illustrate the problem, 4 terrain profiles were presented, showing the valley-like character of the development structure (Figures 2–5). Slightly smaller height differences between the valley floor and its edges are present in the northern tip of the valley (Figures 2 and 3). However, the most urbanised part shows the greatest terrain height differences, as here the valley floor is surrounded on both sides by hills with a height of 30 metres (Figures 4 and 5). This adversely affects the natural ventilation of the central zone. One of the presented terrain profiles shows the rise of the terrain opposite to the direction from which fresh air is supplied, along with the prevalent wind directions, i.e., from the south-west (Figures 6–8). The area primarily sees south-westerly winds, and this dominant wind direction was presented against the background of the existing urban fabric. The figure also presents streets that are aligned with the city's direction of ventilation and the streets that form barriers and obstacles to ventilation (Figures 7 and 8). Figure 1 presents the main zones that were delineated after the analysis, designated A, B and C, respectively. Detailed tests and observations of PM2.5 and PM10 levels were performed for zone A (Figure 9). The city has one official air pollution monitoring station. Measurements in each zone were conducted using a certified portable manual measuring device—Steinberg 10030389 SBS-PM2.5/EX10030389. Tests for individual zones were conducted during the winter period in 2018 and 2019. The inspection of the individual zones was performed by moving the particulate matter measuring device to each location and then comparing its readings with results from the official air quality measurement station. The measurements were carried out at 3 locations in each of the following zones: A1, A2, A3, B1, B2, C1, C2 and C3. A total of 25 measuring points were designated in the city. The measurements were performed on days when air pollution readings were high, medium and very low. The test was repeated to verify the results. Sample measurement results will be presented in Figures 10 and 11 The tests were verified and compared with official documents [56,57].

**Figure 2.** Cross-section through the northern section of Radzionków's urban zone—the difference in elevation between the central and valley part is around 32 m; the terrain has a northwest-facing slope with an incline of around 7%. (Original work based on data from https://mapy.geoportal.gov.pl).

**Figure 3.** Cross-section through the central part of Radzionków's urban area—the difference in elevation between the valley part and the south-eastern side is 45 m, with a 7% incline. (Original work based on data from https://mapy.geoportal.gov.pl).

**Figure 4.** Cross-section through the valley. There are differences in elevation of 30 m on the north-west side and of 35 on the south-west side. The valley has a width of 1400 m in this area. There is an incline of 3.3% in the north and 5% in the south. (Original work based on data from https://mapy.geoportal.gov.pl).

**Figure 5.** Cross-section of the urbanised area of Radzionków, the difference in elevation between the valley floor and the surrounding hills is up to 35 m; the lowest and highest points are less than 500 m apart, and the terrain has an incline of 7%. (Original work based on data from https://mapy.geoportal.gov.pl).

**Figure 6.** Longitudinal cross-section of Radzionków's urban zone—a difference in elevation of 14 m over a length of 1400 m has been observed. (Original work based on data from https://mapy.geoportal.gov.pl).

**Figure 7.** Dominant wind directions for the Silesian Voivodeship. The illustration shows the strength and direction of the wind at two altitudes: at 10 m and at 50 m. Differences in wind force are clearly noticeable, with significantly weaker wind forces at low altitudes. This leads to there being very little air movement inside the valley, as most of it moves at higher altitudes along with south-westerly winds. (source: https://globalwindatlas.info/area/Poland/%C5%9Al%C4%85skie).

**Figure 8.** Radzionków's urban development structure compared with the dominant wind direction. The figure presents the roads that are perpendicular to the direction of wind flow (coloured magenta) and form barriers that inhibit the city's ventilation, as well as the low number of roads aligned with the directions of the dominant number of winds (marked yellow).

**Figure 9.** Air pollution at the measurement station at Szymały Street. (https://airly.eu/map).

**Figure 10.** Results of average PM2.5 level measurements performed in zones A, B, C for 3 different days, one with very high (25 February 2019), high (15 February 2019) and low pollution, respectively (1 February 2019).

**Figure 11.** Results of average PM10 level measurements in zones A, B, C for 3 different days, one with very high (25 February 2019), high (15 February 2019) and low pollution, respectively (1 February 2019).

According to official documents, during the formulation of the environmental quality policy, surveys were conducted for 991 buildings/dwellings (780 detached buildings, 116 semi-detached buildings, 76 terraced houses and 19 apartments in housing blocks or tenement houses), 24 businesses and 14 public buildings. In housing, the average house/flat floor area was 129.7 m2 [56,57]. The oldest

residential building was dated to 1860, the newest was dated to 2014, while the average building completion date was 1961. Some citizens reported having modern boilers (the latest was from 2015), but a large group of respondents used outdated central heating systems (the oldest being from 1960). The average boiler production year was 2003, and the average power was 20.3 kW. On average, there were 4 people per household. In businesses (firms), the average heated area was reported as 247.9 m2, and the average year of building completion was 1951 (the oldest being from 1800 and the newest from 2011). On the other hand, for used boilers, the average power was 27.5 kW, and the average production year was 2005. For public buildings covered by the survey, the average heated area was 579.0 m2, and the year of building completion was 1960 (the oldest being from 1885 and the newest from 1986). The average boiler power was reported to be only 5 kW, as most public buildings were reported to be connected to the heating grid, and boilers were used only as an additional source of domestic hot water. The average production year reported for these boilers was 2003. The municipal authorities have a plan to replace existing heating installations and co-finance boiler replacement with RES heating media. However, as these changes are being introduced very slowly, they were not observed to have a significant impact on the environment of Radzionków. An additional survey regarding interest in replacing the heat sources conducted on a group of 701 people showed that 81.31% were interested in replacing their heat sources or in purchasing renewable energy sources or a more eco-friendly energy source [56,57]. Another survey showed that only 9.13% of the respondents planned to postpone the replacement of their heating systems to an unspecified point in the future.

### **3. Results and Discussion**

Radzionków's urban area cannot be treated as a morphologically homogeneous structure. As evidenced by the attached terrain profiles (Figures 2–6), Radzionków's entire urban area is located in a small river valley located in the Szarlejka river catchment, with an incline of 1% from the north-east to south-west is 1%. The attached 4 transverse terrain profiles (Figures 2–5) and one longitudinal terrain profile (Figure 6) show the valley-like character of the town's layout. In addition, the historical layers of the town's urban tissue development indicate its expansion from the valley floor to areas located at a higher elevation. In order to examine specific environmental zones, 6 areas were initially delineated, selected on the basis of their location, similar development structure, the age and type of local buildings and similar topography. In these areas, 60 buildings were randomly selected and analysed in terms of their heating and insulation systems. A total of 360 buildings were analysed, divided into 6 zones with 60 buildings each. The findings of the analysis enabled the delineated of 3 major urban zones that were distinct in terms of dwelling heating and insulation solutions (Figure 1). Considering the most important environmental conditions from the point of view of urban tissue ventilation, westerly and south-westerly winds were observed to encounter a natural barrier in the form of a 35-metre tall hill on the eastern side of the city (Figures 2–5 and Figure 7). Additional obstacles include groups of buildings placed parallel to the roads running along the northwest–southeast direction (Figure 8). In the entire spatial arrangement of the city, only 19% of roads were observed to be oriented along the southwest–northeast direction, the remaining 81% being roads that are mostly perpendicular and thus not intended to ventilate the city (Figure 8). The road layout outside the city centre was mostly created via delineating them along the original outline of fields—perpendicularly to the slopes of hills. Considering the topography of the city and the dominant south-westerly winds, the city's location can be considered highly unfavourable in terms of its ventilation across the entirety of its territory.

Against the background of existing development tissue, when the age of the buildings is considered, three zones, named A, B and C, respectively, can be clearly distinguished on the basis of their distinct environmental conditions (Figure 1). They provide a basis for formulating conclusions concerning necessary actions related to the high PM2.5 and PM10 levels observed in the city (Figure 9).

In zone A, 53% of buildings were heated with coal; in zone B, 39% of buildings were heated with coal; in zone C, 35% of buildings were heated with coal. Outside these zones, new housing estates were heated with gas and renewable energy sources, public buildings were heated using the heating grid. In zone A, there were 44% insulated buildings; in zone B, 48% of buildings were insulated; in zone C, 68% of buildings were insulated. Outside of these zones, contemporarily built buildings constructed today were either all insulated or met thermal insulation standards (Figure 1) [58].
