**2.1.1 Methodology of the in-situ measurements**

420 Solar Radiation

which can help better in understanding the summer thermal behaviour of the most commonly used surfacing materials in Greece. This experimental data can be qualitatively incorporated as input to the total "image" of each material, in such a way as to be easily

The study is divided into two parts: the first part presents the results that concern paving materials and the second presents those involving the facade materials. In each, both the insitu and the experimental measurements are presented in a cumulative way, in order to draw conclusions on the thermal behaviour of the various building materials during the

For paving materials, in-situ measurements were conducted in a number of selected urban open spaces in Athens, while experimental measurements involved samples of building materials placed on a flat roof. The materials, which were measured during both the in-situ and the experimental study, were classified into the following general categories: Loose, earthen materials, Natural stone products (slabs of marble, granite), Cement products (gavel concrete, slabs and blocks,), Ceramic products (tiles and blocks), Wooden products (boards), Asphalt products (asphalt concrete), Vegetal surfaces (in-situ measurements) and Water

For façade materials, in-situ measurements were conducted on the facades of a number of selected buildings, while experimental measurements involved samples of building materials placed on an experimental setting facing, first towards the West and then towards the South. The materials of which temperatures were measured during both the in-situ and the experimental study, were classified into the following general categories: Natural stone products (slabs of marble, granite), Cement products (lime-cement mortar on selected building facades), Ceramic products (tiles and panels), Wooden products (composite panels), Metal products (metal sheets and composite panels), Vegetal surfaces (in-situ measurements of wall covered with climbing plants) and Photovoltaic (PV) panels (in-situ

The in-situ surface temperatures of paving, as well as of facade materials, are influenced by their contact with the substrate, which, in turn, influences thermal storage and time lag. As a result, the surface temperatures, which are measured on placed materials, can be different from those measured on samples of building materials (Cook, et al., 2003). On the other hand, conducting measurements on samples of building materials exposed to the same environmental conditions provides the ability to simultaneously measure the surface temperatures of a large number of materials. While the measurements on samples of building materials might not reflect their real thermal behaviour, they provide comparative information on the fluctuation of their surface temperatures. Either way, due to the large number of parameters, which influence the surface temperature of building materials in the urban context, it goes without saying that the experimental measurements presented in this

The results of the in-situ measurements are presented in Table 1 for paving materials and Table 3 for facade materials, while those of the experimental surface measurements are presented in Table 2 for paving materials and Tables 4 and 5 for facade materials with west

evaluated and understood by architects and planners.

surfaces (in-situ measurements).

measurements).

summer period and the parameters that affect and determine it.

chapter should be considered as indicative and not absolute.

and south orientations, respectively.

The choice of the urban open spaces, where the measurements were conducted, is based on a number of criteria, such as: use of commonly applied materials, construction details, reduced overshadowing by adjacent buildings and increased insolation during the day, presence in the same space, of both exposed and shaded areas of the materials and architectural issues, concerning design and patterns of use.

The measurements were conducted in 20 open spaces in Athens, Greece for a month, from June 11th to July 8th. The measurement for each space was carried out for one day. The surface temperature readings were taken with an Optex Thermo-Hunter PT-5LD Infrared (IR) thermometer every half an hour, from 8:00 in the morning until 19:30 or 20:00 in the evening. Only days, which were characterised by predominantly clear skies (0/8) and elevated air temperatures (29.6 oC to 34.5 oC), were chosen. Relative humidity values were rather low (28.5 % to 52 %), whereas air velocities ranged from 0.6 m/s to 3.2 m/s.
