habitat rupestre.pdf - Società Friulana di Archeologia

M. N. Assimakopoulos; A. Tsolaki; E. I. Petraki; S. Bekakos; D. Asimakopoulosaccurate one has to test the material so as to be sure of the concludingresults received. In most cases natural stone is usedas a building or landscaping material and in the case where ithas a high SRI it contributes in reducing the heat island effect.Stones and other products that exhibit a high SRI index areencountered as advantageous materials in regions that haveshort periods of cold weather like in the Mediterranean. Forexample in the energy savings factor, when a roof has a highSRI index, it can offer energy savings up to 10-30% for anaverage daily summer load. The major benefit of the naturalstone is that usually it maintains the same colour throughoutthe whole of the structure, thus meaning that the reflectanceindex remains the same and no extra cost is needed for eithermaintaining, or adding reflective paints. The SRI is directlyaffected by three factors: the material composition, the surfacetexture and finally the orientation of the material.Nonetheless it has to be taken under serious consideration thatvariables such as materials aging, weathering and discolorationcan affect the long term SRI index. 10It is obvious that materials with lighter surfaces have high reflectance,and thus smaller surface temperatures. The smalltemperature range measured is mainly due to the lack of directsolar daylight as well as the direct contact with the soil thathelps them keep a stable temperature. Specifically, the lowestdaily temperature values that were displayed for the whiteplastered walls, in the deep part of the Cave, are due to thefact that the sunlight doesn’t arrive directly inside. Whereasthe highest daily values of surface temperatures, appear at theentrance (front-facade) as well as on the “wells- surface” usedfor the natural ventilation and lighting. High surface temperaturesalso appear on surfaces where we have artificial lighting.In the framework of this study samples such as plaster, volcanicstone, volcanic beach sand and stone from the Santorini islandwere collected (figure 16) and brought back to the laboratoryfor testing. The optical properties of the samples were measured.More specifically the spectral reflectance of the sampleswas measured using UV/VIS/NIR spectrophotometer (VarianCarry 5000) fitted with a 150mm diameter, integrating sphere(Labsphere DRA 2500) that collects both specular and diffuseradiation. The reference standard reflectance material used forthe measurement was a PTFE plate (Labsphere). Figure 17 depictsthe spectrophotometric measurements of the samples. Inthe visible range the reflectance curves present practically thecolour of each sample. This means that the lighter the colourof a sample is, the more it reflects in the visible range. Morespecifically, plaster which is white has a very high reflectancewhile volcanic sand, which is darker, is strongly absorptive.However, in the NIR range it can be easily seen that the sampleswith the darker colour present high reflectance. The highquality database was related to the energy consumption of thedwellings and some other special characteristics (constructionmaterials, age, indoor materials, usage etc.), so that usefulconclusions were drawn. Energy is directly related to thearchitectural structure of the dwellings since the bioclimaticstructure may lead to less energy consumption in comparisonwith the conventional architecture. The location of a building,as well as the structural-building materials used is directly relatedto the energy used by the residents. In the case where an“eco friendly design” took place, the need of air conditioningduring the warmest periods can be significantly deducted.Fig. 15 Infrared camera readingsFig. 16; Sample 1: volcanic beach sand; Sample 2: volcanic stone; Sample 3:plaster; Sample 4: natural stone.103volumeRicerca_OK_2012-11-15.indd 103 16/11/2012 15:01:56