One of the greatest issues nowadays is that of the urban heat island effect on the thermal conditions inside cities. The air temperature inside the city core is warmer than that in suburbs, thus deteriorating the quality of life for citizens and making outdoor spaces uncomfortable in terms of thermal comfort. This phenomenon is usually assessed in large scale cities worldwide and less often in medium-sized towns. The current study aimed to investigate the urban heat island effect and, therefore, to assess the outdoor thermal comfort conditions in a medium-sized city. More specifically, the methodology of the current study includes: (i) the combination of different monitoring techniques to quantify the urban heat island effect in a medium-sized Mediterranean city. Both in situ measurements and remote sensing techniques were applied to assess the urban heat island effect in terms of both the canopy layer (CUHI) and the surface (SUHI); (ii) the identification of the parameters that affect thermal comfort and the identification of the most appropriate bioclimatic indices that determine outdoor thermal comfort in the city of interest. Both questionnaire survey and in situ measurements took place on a sidewalk in the city of Xanthi, Northern Greece, during the summer. The CUHI effect was obvious, especially in the morning and afternoon. Downscaled MODIS satellite images also showed that the intensity of SUHI was higher in the morning and afternoon. Apart from air temperature, important differences in the values of most microclimatic parameters were recorded between the meteorological station placed inside the urban area and those gathered from a nearby meteorological station. The narrow roads, the thermal properties of construction materials, and the absence of greenery characterized the area of interest and may be the key factors creating these differences in climate. Concerning the thermal comfort assessment, the most significant parameters were the air temperature and solar radiation, although, both empirical and direct indices were found to describe the comfort values well. According to the results, downscaling techniques are also important for the SUHI effect to be investigating in detail in medium-sized urban environments.

Over the last few decades, there is a clear target for reducingenergy needs in the building sector. The above objective can be achieved both by renovating the existing building stock and/or by constructing new buildings that will meet the characteristics of zero or nearly zero energy buildings. In order to construct or renovate a building into a zero or almost zero energy building, different passive, active and hybrid systems can be used. One such system is a solar air heater collector. The above system was installed in the south facade of the outdoor test cell (ZED-KIM (Zero Energy Demand – Kimmeria)), located at the Campus of the Environmental Engineering School, DUTH at Xanthi (Greece). In the present study, the monitoring results of the solar air heater collector and its contribution to cover the cooling load of a building will be presented. The system was monitored under real weather conditions for the period June 2017 to August 2017. This period was separated in two sub-periods. In the first one, the system operated as a solar air heater and with the appropriate modifications air from inside the test cell was passed through solar collector and hot air was rejected out. In the second sub-period, a ventilation inlet was added in the north facade of the test cell, and the system operated as a solar chimney. The heating load that rejected out in the first sub-period was 12 KWh and in the second sub-period was 58.5 KWh. In other terms the cooling load of the test cell was reduced by 70.5 KWh for the whole period of measurements. In addition the cooling load for the specific climate zone of Greece and for 20 m² cooling space was 488 KWh so there was a reduction of 15 percent. Furthermore, it was noticed that the thermal efficiency of the system increased above 50 percent between 1^st and 2^nd sub period, with values being 16% and 34% respectively. Based on the above results, it is concluded that even in hot weather conditions prevailing in northern Greece, the use of a solar air heater collector with the appropriate modifications can cover, in a significant degree, the cooling load of a building and in conjunction with other passive and active systems it can lead at a nearly zero energy building.

The built environment influences urban quality of life, particularly through material properties and design decisions that affect thermal comfort, energy consumption, and environmental performance. Among the physical parameters shaping urban microclimates, surface reflectivity—albedo plays a central role in regulating both surface and ambient temperatures. While high-albedo materials are widely recognized for mitigating the urban heat island (UHI) effect and lowering energy demand, limited attention has been given to how material aging alters albedo and, by extension, thermal performance over time. This study investigates that relationship through field measurements conducted at 18 outdoor locations in Xanthi, Greece, across four dates with varying environmental conditions. Variables such as material color, age, and temperature were analyzed through statistical methods and linear regression. Results confirmed a strong correlation between color and albedo and identified a statistically significant relationship between aging and albedo. Additionally, the expected inverse correlation between albedo and surface temperature was reaffirmed. These findings underscore the dynamic nature of material performance and highlight the need for incorporating aging behavior into sustainable urban design. The study contributes data to the field and supports the development of long-term strategies in urban planning and maintenance aimed at preserving the reflective efficiency of surface materials.