**3.1.2 Methodology of the experimental measurements**

The materials, which temperatures were measured during the experimental study, were mainly materials that are used for building facades with ventilated facade system. Fortyfour (44) samples were selected and mounted on two experimental arrangements, which aimed at simulating the ventilated facade system. Each experimental arrangement comprised a 30mm insulating board (extruded polystyrene - XPS), which was fixed on an 18mm chipboard. The samples for surfacing materials were mounted with the use of metal screws, which suspended the materials at a distance (air gap) of 20 to 30 mm from the insulation layer. The distance between the samples was to ensure that there was no contact between them, while each screw was individually "planted" into the insulating to avoid thermal bridges. In all the temperatures of seven (7) samples of marble slabs and five (5) samples of granite slabs were measured, making a total of 56 samples.

The measurements took two weeks: one week (7 days) for the western orientation (10- 17/07/2004) and the other week for the southern orientation (31/07-06/08/2004). The measurements were by an Optex Thermo-Hunter PT-5LD Infrared (IR) thermometer, from 8:00 to 20:00 at 1-hour intervals. One day of the measurements included night-time readings (from 20:00 to 08:00) in order to examine the cooling rate of the materials. 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 account for possible discrepancies. Air temperatures, relative humidity and air velocity measurements were also done at the site.
