*3.1. Characteristics of Zone A*

Zone A (Figure 1) was observed to have the worst environmental conditions since 53% of buildings were heated with coal. It is also the zone located at the lowest elevation on the valley floor, ranging between 296 m above sea level to 306 m above sea level, with an average 1% incline in the opposite direction to that of the area's natural ventilation. This zone is hemmed in from the southeast and the northwest by 35-metre hills. In this zone, only 6 streets were observed to run parallel to the direction of the area's dominant winds. The remaining roads, i.e., approx. 39, were oriented perpendicular to the dominant wind direction. The ventilation of this zone was observed to be the worst because it had the most physical barriers—most of the buildings were oriented parallel to the roads. In zone A, 44% of the buildings were thermally insulated, although the average was skewed upwards by the smallest, sometimes new residential buildings. The largest percentage of the buildings were not thermally insulated. In general, small buildings emit much less pollution than large multi-family buildings, which were reported to be heated by either several individual installations or central former coal installations.

It is also the oldest and the most intensively built-up zone. The development density (the floor area to plot area ration) of this zone ranges between 0.3 and 2.0. In order to improve the quality of the environment, it is necessary to increase expenditure on new building heating systems This can be done by introducing subsidies for gas heating or by taking advantage of existing potential in the form of connection to the heating grid that is linked to the Jerzy Zi ˛etek housing estate. The largest stone buildings, often under heritage protection, require special expenditures.

## *3.2. Characteristics of Zone B*

In zone B (Figure 1), 48% of buildings were insulated, with the average inflated by infill buildings after 1980. The closer to the historical layout of the town centre, the more buildings without insulation and that used coal for heating were observed. On the other hand, insulated buildings were observed to be in breach of the building code (Ordinance concerning the technical conditions to be met by buildings and their placement of 2014), specifying the maximum energy intensity parameter at 120 kWh/(m2annum). To meet these parameters, common traditional brick wall technology requires a layer of mineral wool or polystyrene sheets with a thickness of 15 cm and a lambda factor of 0.031 W/(mK) (Figure 12) [58]. Typically, the insulation thickness ranged between 5 and 10 cm. In zone B, 39% of the buildings were heated with coal, which significantly contributed the deterioration of the quality of the environment in this area but at the same time affected the deterioration of the environment in zone A, which is located on the valley floor. In area B, on the slopes of hills, streets perpendicular to the direction of ventilation become natural pollution funnels that direct it towards the valley floor. According to Office of the City of Radzionków, the average age of coal boilers in Radzionków area were boilers installed 17 years ago—it can be assumed that the average boiler age in this area is compliant with official data. Most of the buildings in this zone are dated to the post-war period and were built mostly between 1945 and 1990.

**Figure 12.** Change of standards related to thermo-modernisation in Polish legislation in accordance with the Ordinance concerning the technical conditions to be met by buildings and their placement of 2014—120 (kWh/m2 annum); after 2017, the maximum value decreased to 95 (kWh/m<sup>2</sup> annum), while after 2021, it is to decrease further down to 70 (kWh/m<sup>2</sup> annum) [58].
