Concept and Evaluation of Porosity in Façades of Tabriz Historical Houses

Façades are one of the architectural physical elements that play a significant role in the aesthetic preferences on their observer. The façade creates the first and perhaps the most important impact. Aesthetic is identifying and understanding factors that contribute to perception of an object or beautiful/pleasant process. In order to assess the beauty of a phenomenon, its factors and visual qualities should be studied, so finding a measure or a way to evaluate them are one of aesthetics’ priorities. Therefore, not only recognition of visual qualities, but also their quantitative evaluation is also important in aesthetics. Different visual qualities participate in the formation of façades, one of which is porosity. If these visual qualities studied, interpreted and measured, their factors, rules, and attributes can be extracted and using them as variables, the aesthetics of façades can be evaluated. This research is based on the question of how porosity can be measured and evaluated as one of the visual quality of façade and what is the relation between the quantitative measures of these buildings' façade's porosity? The purpose of this research is to investigate the concept of porosity as a visual quality and to decode the art of designing and constructing façades in Iranian-Islamic architecture by quantitatively measuring the porosity. The study in theoretical part, using the analytical-descriptive method, has presented a theoretical framework. In the first stage a comparative method will be used. Collecting information in this research, in addition to documentary and library studies, will also include field studies that are used to compile the subject literature review to find the thematic framework. At this stage, by expressing the perceptual concept, the architectural porosity elements as well as the study of its theories, criteria, rules and components are explained. In the second stage, a quantitative method for measuring porosity will be presented using the criteria and components obtained in the previous stage, the classification of porosity elements, factors and effective variables of façade's porosity. Structured questionnaires will be used to find the relationship between these variables and their impact on each other and facade's porosity. In the third stage which is the case study section, the theoretical framework and the porosity quantitative measuring method are carried out in 30 main facades of historical houses of Tabriz city and gathered data are analyzed with descriptive statistics. Based on the findings of the research, façades have a special feature called porosity number that is unique to them. The structure of the forming elements and the porosity changes of the façades also follow a particular pattern. The research also shows that the main trait of porosity is openness. Air circulation, light and the connection of internal and external spaces are major physical achievements of porosity and its spiritual achievement is space and raised meaning in architecture. Empty, despite the lack of material has an equal value, and sometimes more, than full, and how it is created and placed not only increases the physical and spatial quality but also can have an impact in facades’ evaluations. Porosity is one of the basic visual qualities, which over time has found a more significant role in façade. Porosity has a hidden and mysterious pattern that can be the result of aesthetic feedback from architects, observers/residents, and environmental conditions of the region. A certain evident percentage of porosity and a specific pattern and alignment of porous space arrangement found in this study indicate that, at least in Tabriz environmental conditions, a specific pattern of porosity is a part of the aesthetic preferences of the architects and the residential-historical architectural users of Tabriz city. This optimal and aesthetic level of porosity in the historical houses of Tabriz façades is close to 0.4 (40%).This pattern and alignment can be considered by contemporary architects in this cultural-climatic area as an aesthetic factor. Of course, the generalization of these features to other cities in Iran and beyond requires more and wider researches. This study showed that porosity as a visual quality and its quantitative measurement method can also be used as criteria of aesthetic evaluation of architectural façades.