**2.1.2 Methodology of the experimental measurements**

During the experimental study, the temperatures of a large number of materials that are usually used for the open spaces in Greek cities, as well as for the flat roofs of buildings, were measured. The experimental measurements were conducted on the flat roof of a building. The temperatures of all the materials were measured for a total period of two weeks. The first day measurements included the night-time readings. The measurements were taken with an Optex Thermo-Hunter PT-5LD Infrared (IR) thermometer from 8:00 to 20:00 at 1-hour intervals. Furthermore, for a one-day period, a contact thermometer (Technoterm 9500) was used simultaneously with the IR one, in order to confirm the accuracy of the IR readings and reveal possible discrepancies. Air temperatures, relative humidity and air velocity were also measured on the site.

In order to define the methodology of the experimental study, a small-scale preliminary study was conducted with samples of cement and ceramic products (slabs and tiles), in order to define the placing mode, which is closest to that of actual conditions (materials placed on a concrete substrate). This was as a result of the fact that the placement of the materials influences their surface temperatures. Three identical cement slabs and three identical ceramic tiles were used with the following placement details: fastened with sandcement mortar on a dense concrete slab, 30cm thick (base case), set directly on a flat roof constructed with light blue-grey ceramic tiles and laid on a 3cm slab of extruded polystyrene (XPS) painted white.

The results of the preliminary study showed that the samples which were placed on the insulating layer, tended to overheat and develop surface temperatures that were significantly higher than those of the base case. The surface temperatures of the samples, which were directly placed on the flat roof, were higher than those of the base case, but quite close to them. Based on these results, all the samples should have been set on a concrete substrate or placed on gravel or sand substrate. Nevertheless, for the large number (80) of examined materials that the study involved, this was not possible. Consequently, it was decided that the materials would simply be placed on the flat roof of the building, without the interference of another layer.

Fig. 1. Short-scale preliminary study. Different placing modes.

Fig. 2. Short-scale preliminary study. Mean daily temperature fluctuation.

#### **2.2 Results of the in-situ measurements of paving materials**

The results of the in-situ measurements, reported here constitute an overview of the overall study. For this reason, the analysis does not cover every urban space separately, but covers the different categories of materials, in general. The results of the measurements are presented in Table 1.

Klafthmonos Square Dikaiosinis Square Korai Street

significantly higher than those of the base case. The surface temperatures of the samples, which were directly placed on the flat roof, were higher than those of the base case, but quite close to them. Based on these results, all the samples should have been set on a concrete substrate or placed on gravel or sand substrate. Nevertheless, for the large number (80) of examined materials that the study involved, this was not possible. Consequently, it was decided that the materials would simply be placed on the flat roof of the building,

without the interference of another layer.

Fig. 1. Short-scale preliminary study. Different placing modes.

Temperature (\*C)

8:00

**2.2 Results of the in-situ measurements of paving materials** 

presented in Table 1.

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Tair

Fig. 2. Short-scale preliminary study. Mean daily temperature fluctuation.

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14:00

Hour of day

Cement slab on concrete substrate Cement slab on XPS substrate Cement slab on flat roof surface

The results of the in-situ measurements, reported here constitute an overview of the overall study. For this reason, the analysis does not cover every urban space separately, but covers the different categories of materials, in general. The results of the measurements are

16:00

18:00

20:00

Fig. 3. Pictures of the some of the urban open spaces, where the in situ measurements were conducted.
