Assessment and Analysis of Thermal Comfort Courtyards of Shiraz Historical Houses in Qajar Era

The process of climate change in a long term can reduce the presence of men in the outdoors so that they resort to the indoors particularly in the hot and dry climates. The problem may decrease the rate of health among individuals as the effect of high temperature and increase the amount of consuming energy in the building due to the long-term use of indoor space. According to the need of proposing climate strategies to improve the outdoor climate quality and comparing with the native architecture, this research intends to assess the adaptation level of central courtyard of tradition houses in Qajar era with the climate condition in Shiraz, Iran. In other words, how can physical and environmental features such as outdoor percentage, direction, sky view factor, vegetation, water and certain materials affect the thermal comfort and extent of using space by men? seven Qajar houses in Shiraz were selected with the aim of prioritizing the effectiveness of above components, Using ENVI-met V.4 Basic for 3D simulation and assessment of microscale urban conditions, the assessment of thermal comfort level determined based on PMV index. The results demonstrate that more shading is seen for the courtyards with the least sky view factor and area so that it results in a better outdoor thermal comfort for the dwellers. Meanwhile, the direction of optimum rotation is about 27° SW. factors such as shading of trees and humidity effect of water pools cannot be forgotten in softening the microclimate air in the central courtyards. According to the coefficients of analyses, there is significant correlation between mean radiant temperature and PMV thermal comfort index in hot and dry climate in Shiraz.
Keywords: Houses of Shiraz, Qajar Era, Outdoor Thermal Comfort, Central Courtyard, ENVI-met.
 
Introduction
The elements such as central courtyard by utilizing appropriate shading, specific vegetation, and a pool influence the thermal and visual comfort of dwellers on one hand and providing a convenient climate conditions on the other. These open spaces (outdoors) provide a suitable situation in bringing human interactions among family members, entertainment and physical activities. Thus the main function can be known as the creation of adaptation with the climate conditions in the region that is less seen in today courtyards. The level of thermal comfort in the central courtyard is intensively under the influence of amount of receiving radiance that the studies have paid less attention. Thus, the present research resolves the shortcomings and focus on the gray points with the aim of maintaining and restoring historical textures and of finding appropriate pattern for new construction in line with the microclimate conditions in Shiraz traditional houses in Qajar era. The work also analyzes accurately the thermal comfort in central courtyard by measuring the effect of components such as dimensions and proportions, pool, tree, and green space. Covering two fundamental topics, the research answers the following questions:
- What is the effect of climate on the construction of courtyards in Qajar era?
- What is the role of geometric form and available elements in courtyards in the level of thermal comfort in Qajar houses in Shiraz?
- What is the optimum direction of courtyard rotation for supplying the thermal comfort?
The main hypothesis is that the traditional houses in historical texture of cities of Iran and specifically Shiraz possesses such potentials to supply thermal comfort so that studying and analyzing them flourish design strategies. In so doing, seven Qajar houses (Zinat Al-Molk, Nasir Al-Molk, Amoyi, Afsharian, Atroush, Ardakani and Sons) in historical district were selected. This paper generally presents in two parts the theoretical principles and data analysis by means of ENVI-met Software. The simulation process is as follows:
- Modeling and determining situation of each house in terms of direction, dimensional proportions of courtyard, sky view factor, vegetation and aquatic levels;
- Determining climatic conditions and extracting meteorological data of Shiraz;
-  Determining spatial point in the middle of central courtyard;
- Determining temporal range for analysis in 1st day of summer in 9 A.M. and 17 P.M.; and
- Extracting qualitative data and converting results to graphic diagrams on Leonardo1 Software
 
Findings
After executing the modeling, the outputs of climate model were calculated on ENVI-met for 2 time ranges of 9 A.M. and 17 P.M. on 22nd June (1st day of Summer). Amuyi House has the lowest rotation angle towards north; Afsharian House has the highest rotation angle; courtyard of Zinat Al-Molk House has the largest area (550 m2), and Amuyi House has the smallest area (61 m2). Accordingly, the sky view factor ranges from 0.19 in the walled courtyard to 0.56 in the widest courtyard. Proportion of height to width is another important parameter on radiance time Amuyi House has the largest proportion (H/W: 0.75) while Zinat Al-Molk House has the lowest proportion (H/W: 0.2). On the other hand, the data analysis shows that we observe a minimum 20° rotations in Amuyi House and 31° in Nasir Al-Molk House in southwest. About 27° rotations is seen among the houses selected. The extent of thermal comfort varies between 1.5 and 4.9 at 9 A.M. and 17 P.M. The best conditions for thermal comfort is for Amuyi House at 9 A.M. (PMV: 1.45) and the worst conditions is for Zinat Al-Molk House at 17 A.M. (PMV: 4.81). Other houses do not vary in terms of thermal comfort in both times because of close geometric situations of courtyards and same radiance time on their intended point.
In addition, increasing sky view factor in open spaces will increase the direct sun radiance and consequently increase the mean radiance temperature. There is also a significant relationship between “mean radiant temperature” and “PMV thermal comfort index” so that increasing mean radiant temperature increases the thermal stress of individuals and reduces the thermal comfort.
 
Conclusion
The geometric situation of courtyards brings about difference in time and angle of direct sun radiance to the courtyard. The radiance difference leads in different thermal comfort to the dwellers. On the other hand, paying attention to the effect of direction in residential areas to prevent radiance is one of the main factors. It is worth noting that appropriate direction is southwest in Shiraz. According to the results, about 27° rotations towards north is optimal in such a way that the direction does not clear appropriate effectiveness unless it is mixed with the factors such as proportions, vegetation and so forth. Therefore, ratio of height to width, angle of widespread areas of courtyards and using adaptation measures (watering, relocation in seasons, planting various deciduous plants, etc.) should be taken into consideration in designing the open spaces next to residential buildings. Finally, it should be noted while building houses with central courtyard may not make sense in today urbanization situation; the resultant strategies can be luminous.