Influence of Iwans on the Thermal Comfort of Talar Rooms in the Traditional Houses: A Study in Shiraz, Iran

Abstract: In traditional buildings many climatic strategies have been used to provide indoor thermal comfort in south and central parts of Iran. A common element is called an iwan. This study investigates the indoor thermal comfort of a room adjoined to a talar in a traditional house which has an iwan, in Shiraz, Iran. The data related to the temperature and relative humidity of the room are used to calculate the thermal comfort index of PMV (Predicted Mean Vote) and PPD (Predicted Percentage of Dissatisfied) by considering the following two cases: a talar room with an iwan and one without an iwan, by means of DesignBuilder software. For the purpose of validation, the air temperature and relative humidity of the talar room with an iwan were measured over 10 days and compared to the results of the simulation. Having a valid simulation, computation was conducted for the selected house in various cases for an annual passive operation of calculating PMV and PPD. The numerical results revealed that the talar room adjoined to an iwan located in the south front of the courtyard had relatively good conditions during the hot months, including June and July. In addition, it could provide fully satisfactory comfort conditions during August and September. According to the results, it is found that the iwan makes a talar room 62% more desirable for the hot months in comparison with a talar room without an iwan.


Introduction
Today, a considerable amount of energy is spent on heating and cooling indoor environments to provide thermal comfort for the building's residents. The availability of modern heating and cooling systems has led to little attention being paid to passive systems in modern architecture [1,2]. Greenhouse gas emissions and global warming in recent years, in addition to high energy consumption in residential sectors, have caused the emergence of a greater interest in climatic strategies. Meanwhile, more effort is devoted to using such strategies in local and traditional architecture in modern buildings [3][4][5]. For a long period of time, buildings and climatic strategies have been constructed based on trial and error for local and traditional buildings; however, these experiences are going to be forgotten [6,7].
Most traditional buildings in hot and dry climates have been comfortable for residences thanks to their passive temperature control systems. Also, in comparison to modern buildings, they consume less energy for air conditioning [8]. Comparisons between traditional and contemporary houses have indicated that traditional houses, which employ building design strategies, are more compatible with the environment, resulting in better thermal comfort in indoor spaces. Although in contemporary houses many technologies are used to achieve indoor thermal comfort [9][10][11], several studies have Lighter colors on the outer surfaces and local materials with low thermal conductivity such as wood, bamboo or palm tree trunks, stone, mud, and lime are used in buildings to reduce the transformation of heat from outside to the inside [28]. The central courtyard in this region is small so as to receive less sunlight during the day. The heat is easily transferred to the surrounded environment during the nighttime through the external surfaces of the courtyard and roof. This in turn helps the building to act as a heat sink and remove the heat quickly [27]. Lighter colors on the outer surfaces and local materials with low thermal conductivity such as wood, bamboo or palm tree trunks, stone, mud, and lime are used in buildings to reduce the transformation of heat from outside to the inside [28]. The central courtyard in this region is small so as to receive less sunlight during the day. The heat is easily transferred to the surrounded environment during the nighttime through the external surfaces of the courtyard and roof. This in turn helps the building to act as a heat sink and remove the heat quickly [27]. Fernandes et al. [29] studied the climate strategies in vernacular architecture from the northern and southern parts of Portugal, specifically in the Beira Alta and Alentejo areas, respectively. They selected a case study and used experimental tests to obtain measurements of hygrothermal and surveyed thermal sensations on occupants. Their results indicated that the vernacular houses Fernandes et al. [29] studied the climate strategies in vernacular architecture from the northern and southern parts of Portugal, specifically in the Beira Alta and Alentejo areas, respectively. They selected a case study and used experimental tests to obtain measurements of hygrothermal and surveyed thermal sensations on occupants. Their results indicated that the vernacular houses showed good thermal performance by passive strategies and the occupants felt thermal comfort. However, the occupants needed to use simple heating systems during the winter. Glazed balconies which were used in Beira Alta played a good strategy role receiving solar gains; in Alentejo, the focus was on passive cooling strategies and courtyards represented a good strategy for shading to reduce temperature. Another study investigated the thermal conditions of a vernacular building in Evora, Portugal. The results revealed that the passive cooling techniques used in vernacular buildings can improve indoor thermal comfort during the summer season. The difference between the indoor temperature and the maximum outdoor temperature in the courtyard and in the city center was respectively 7 • C and 16 • C. Several passive strategies used in vernacular houses can be mentioned as follows: small exterior doors and windows, high thermal inertia walls, white washed walls, courtyards, and patios. These vernacular strategies have great potential for decreasing energy consumption in modern buildings [30]. In addition, Fernandes et al. [31] investigated the thermal performance and comfort of vernacular buildings in Egypt and Portugal. The results showed the correlation between the thermal performance of vernacular buildings and human comfort perception in two different case studies located in the Mediterranean climate. It was revealed that the common passive techniques in both cases were different, based on the site selection. However, overall, vernacular passive strategies can be used to achieve indoor thermal comfort and reduce loads of mechanical systems.
Kubota and Toe [32] investigated how passive cooling strategies in vernacular houses were used in modern houses to reduce energy consumption in Malaysia. They used experimental measurements in two traditional timber Malay houses and two traditional masonry Chinese shop houses, then they investigated indoor thermal environments and passive cooling techniques in the case studies. The results revealed that the indoor air temperature of rooms adjacent to courtyards was lower than the outdoor temperature by up to 5-6 • C during the day. In addition, the indoor air temperature of rooms was similar to the outdoor temperature at night. They determined an adaptive thermal comfort equation for hot-humid climates. The indoor operative temperature reached more than 80% comfort in the Malay houses and Chinese shop houses. Passive strategies in vernacular houses included night ventilation, roof and ceiling insulation, window and wall shading, and courtyards.
Alrashed et al. [33] investigated the roles of Mashrabiyah, courtyards, and adobe construction for Dhahran, Guriat, Riyadh, Jeddah, and Khamis Mushait in Saudi Arabia. They designed a base and then calculated the electricity value of the houses adjusted with these passive strategies and materials. Their results revealed that in terms of energy saving, courtyards are not useful. Using Mashrabiyah can reduce energy consumption by 4% and 3%, and adobe can reduce energy consumption by 6% and 19%. Also in Chinese houses in a hot and humid climate, courtyard, patio, and semi-open spaces are used to create indoor thermal comfort [34]. Different types of courtyards of Chinese vernacular houses in a hot and humid climate perform different functions in improving indoor thermal comfort [35]. Another study indicated that using Shavadan spaces in traditional houses in a hot and humid climate can create thermal comfort and help to reduce cooling and heating loads [36]. Studies of passive strategies in vernacular houses in India revealed the relation of vernacular architectural features to thermal comfort conditions [13,37]. In addition, replacing rubble stone masonry with burnt clay brick masonry and stabilized soil block masonry was found to increase the embodied energy of the dwelling by 9.7 times (870%) and 2.8 times (182%), respectively [13]. Applying traditional materials, such as adobe, could be the best option in hot and humid climates [38].
Different parameters influence the thermal comfort of the individuals in closed environments. For instance, the value of insufficiency of clothing influences the thermal transaction between the human body and environment. In addition, the speed of the flaw (the appropriate amount of which is variable) and the amount of individual labor (which specifies the rhythm of metabolism) should be determined [39].
Mean radiant temperature was calculated in assessment of thermal comfort, which is the relationship between the radiant and room surfaces (floor, ceiling and walls) [39]. The two factors of relative humidity and air temperature have a great effect on an individual's thermal comfort. A relative humidity less than 30% may result in dry skin, eye irritation, and breathing problems, while a relative humidity (RH) higher than 60% may result in an environment suitable for mold growth and allergic problems [40].
According to ISO 7730 [41], to assess thermal comfort the two indicators of PMV (Predicted Mean Vote) and PPD (Predicted Percentage of Dissatisfied) were determined and the dissatisfaction rate was expressed by percentage. PMV has different borders and each has a different meaning, as listed in Table 1.

PMV
Thermal Sensitivity In this index, the thermal sensitivity of the environment is divided across the range from hot to cold. The PMV value is determined using Equation In which M = metabolic free energy production (w/m 2 ), w = external work (w/m 2 ), Pw = the partial pressure of water, f cl = the ratio of clothed/nude surface area, T cl = clothing surface temperature ( • C), h cl = convective transfer coefficient (w/m 2 K), and T r = mean radiant temperature ( • C). Meanwhile, the PPD value is calculated according to the PMV, which is specified in Equation (2) [41]. PPD is predicted percentage dissatisfied. PPD indicated percentage of dissatisfy people of thermal comfort in indoor room.
Reviewing previous studies revealed that vernacular houses in hot and dry climates have used several strategies in order to create indoor thermal comfort. The performance of vernacular houses is better than that of modern houses. In vernacular houses materials with high thermal capacity, light colors, domed roofs, and wind catchers were used. Underground spaces and semi-open spaces are also used in vernacular houses in hot and dry climates. Courtyards create microclimates in vernacular houses and are very effective in creating indoor thermal comfort. Also, vegetation and water are used for increasing relative humidity. The iwan is a very important element in vernacular houses for the hot and dry climate in Iran. Previous studies have supported this idea and emphasized the effect of iwans on the indoor thermal comfort. However, previous studies on iwans with the approach of considering climate are either qualitative or descriptive.
Their effect has not yet been studied quantitatively by numerical simulation or the implementation of fieldwork. The purpose of this study is to investigate the role of the iwan on the thermal comfort of a talar room of a traditional house in Shiraz, Iran. The effect of an attached iwan on the thermal condition of the selected room is determined by field measurement and numerical simulation. The full-scale experiment is carried out using various sensors for the evaluation of the current condition of the building as well as the validation of the numerical simulation. Finally, the significant effect of the iwan on the summer passive condition of the adjacent talar is determined and presented for different periods of a year.

Case Study
Iwans, as shown in Figure 1, are widely used in Iran's traditional buildings for various climate conditions including hot and dry, cold, hot and humid, and mild and humid. Amongst all of the iwans constructed for traditional houses in Iran, iwans belonging to traditional houses in Shiraz were selected as the iwan is considered as an architectural element evident in traditional houses of this city. To make the function of the iwan in traditional buildings obvious, Figure 2 represents how the iwan schematically alleviates the thermal conditions in a traditional house in Shiraz.
Among the traditional houses in Shiraz, the Manteghi-Nezhad house was selected. The iwan of this house represents the most common type of iwan amongst all traditional houses of the city. The Manteghi-Nezhad house was a residential house built in Qajar era (1870-1890). The building includes a ground floor and an underground floor. The house has a flat-roof iwan with two pillars and it opens on a central courtyard, as shown Figure 3.

Case Study
Iwans, as shown in Figure 1, are widely used in Iran's traditional buildings for various climate conditions including hot and dry, cold, hot and humid, and mild and humid. Amongst all of the iwans constructed for traditional houses in Iran, iwans belonging to traditional houses in Shiraz were selected as the iwan is considered as an architectural element evident in traditional houses of this city. To make the function of the iwan in traditional buildings obvious, Figure 2 represents how the iwan schematically alleviates the thermal conditions in a traditional house in Shiraz.
Among the traditional houses in Shiraz, the Manteghi-Nezhad house was selected. The iwan of this house represents the most common type of iwan amongst all traditional houses of the city. The Manteghi-Nezhad house was a residential house built in Qajar era (1870-1890). The building includes a ground floor and an underground floor. The house has a flat-roof iwan with two pillars and it opens on a central courtyard, as shown Figure 3.    Table 2 shows typical traditional houses in Shiraz, which were selected randomly and the pattern of spaces and their interconnections are represented.  Table 2 shows typical traditional houses in Shiraz, which were selected randomly and the pattern of spaces and their interconnections are represented.              The talar room is placed at the back of the iwan, which is a considerable space in the building. The room has grille windows which are made of stone and glass, equipped with sashes capable of opening and closing the windows. It has doors that connect to rooms on both sides. The plan of the ground floor and underground sections of the house are shown in Figure 4, in which the place of the iwan and talar room in ground floor are marked by the hatched area. The talar room is placed at the back of the iwan, which is a considerable space in the building. The room has grille windows which are made of stone and glass, equipped with sashes capable of opening and closing the windows. It has doors that connect to rooms on both sides. The plan of the ground floor and underground sections of the house are shown in Figure 4, in which the place of the iwan and talar room in ground floor are marked by the hatched area.

Microclimate Study
Shiraz is located between 29.39° north latitude and 52.35° east longitude. According to Figure 5, the climate of Shiraz is hot and dry. Shiraz is situated 1486 m above sea level. The monthly normal climate of Shiraz is given in Table 3. Based on Table 3, June, July, August, and September are the warmest months of the year.

Microclimate Study
Shiraz is located between 29.39 • north latitude and 52.35 • east longitude. According to Figure 5, the climate of Shiraz is hot and dry. Shiraz is situated 1486 m above sea level. The monthly normal climate of Shiraz is given in Table 3. Based on Table 3, June, July, August, and September are the warmest months of the year. The talar room is placed at the back of the iwan, which is a considerable space in the building. The room has grille windows which are made of stone and glass, equipped with sashes capable of opening and closing the windows. It has doors that connect to rooms on both sides. The plan of the ground floor and underground sections of the house are shown in Figure 4, in which the place of the iwan and talar room in ground floor are marked by the hatched area.

Microclimate Study
Shiraz is located between 29.39° north latitude and 52.35° east longitude. According to Figure 5, the climate of Shiraz is hot and dry. Shiraz is situated 1486 m above sea level. The monthly normal climate of Shiraz is given in Table 3. Based on Table 3, June, July, August, and September are the warmest months of the year.

Numerical Simulation
DesignBuilder software [43] with the Energy Plus engine was used for the simulation of the Manteghi-Nezhad house. The thermal exchange between the spaces of the building, iwan, talar, and surrounding rooms were simulated. Also, the adjacent buildings which contribute to creating shade were considered as block components and some parts of the neighboring houses and underground spaces below the talar and surrounding rooms were assumed to be adiabatic. Two scenarios were simulated using this software. In the first case, the current situation was simulated according to Figure 6. In the second case, the talar was considered without the iwan, as shown in Figure 7.

Numerical Simulation
DesignBuilder software [43] with the Energy Plus engine was used for the simulation of the Manteghi-Nezhad house. The thermal exchange between the spaces of the building, iwan, talar, and surrounding rooms were simulated. Also, the adjacent buildings which contribute to creating shade were considered as block components and some parts of the neighboring houses and underground spaces below the talar and surrounding rooms were assumed to be adiabatic. Two scenarios were simulated using this software. In the first case, the current situation was simulated according to Figure 6. In the second case, the talar was considered without the iwan, as shown in Figure 7.  The exterior and interior walls and roof of the building, which were made of traditional materials, were simulated by the DesignBuilder software based on layers with the current status. In Table 4, forms of the layers, the thickness and density of their material, their specific heat, and their thermal conductivity are presented.
The doors and frames of the windows and sashes are made of wood and the windows above the doors are made of common glass with a thickness of 3 mm. To find the extent to which the iwan passively affects the environment of the talar room in a normal situation, no heating or cooling system was considered for the talar and surrounding rooms in the software. Ventilation was considered normally. The number of persons using the talar room was considered as the average number of members in an Iranian family, four people [44], and other rooms such as bedrooms were considered to have a one-person capacity. Detailed information is presented in Table 5.

Numerical Simulation
DesignBuilder software [43] with the Energy Plus engine was used for the simulation of the Manteghi-Nezhad house. The thermal exchange between the spaces of the building, iwan, talar, and surrounding rooms were simulated. Also, the adjacent buildings which contribute to creating shade were considered as block components and some parts of the neighboring houses and underground spaces below the talar and surrounding rooms were assumed to be adiabatic. Two scenarios were simulated using this software. In the first case, the current situation was simulated according to Figure 6. In the second case, the talar was considered without the iwan, as shown in Figure 7.  The exterior and interior walls and roof of the building, which were made of traditional materials, were simulated by the DesignBuilder software based on layers with the current status. In Table 4, forms of the layers, the thickness and density of their material, their specific heat, and their thermal conductivity are presented.
The doors and frames of the windows and sashes are made of wood and the windows above the doors are made of common glass with a thickness of 3 mm. To find the extent to which the iwan passively affects the environment of the talar room in a normal situation, no heating or cooling system was considered for the talar and surrounding rooms in the software. Ventilation was considered normally. The number of persons using the talar room was considered as the average number of members in an Iranian family, four people [44], and other rooms such as bedrooms were considered to have a one-person capacity. Detailed information is presented in Table 5. The exterior and interior walls and roof of the building, which were made of traditional materials, were simulated by the DesignBuilder software based on layers with the current status. In Table 4, forms of the layers, the thickness and density of their material, their specific heat, and their thermal conductivity are presented.
The doors and frames of the windows and sashes are made of wood and the windows above the doors are made of common glass with a thickness of 3 mm. To find the extent to which the iwan passively affects the environment of the talar room in a normal situation, no heating or cooling system was considered for the talar and surrounding rooms in the software. Ventilation was considered normally. The number of persons using the talar room was considered as the average number of members in an Iranian family, four people [44], and other rooms such as bedrooms were considered to have a one-person capacity. Detailed information is presented in Table 5.

Validation
For the validation of the DesignBuilder simulation software, information related to temperature and relative humidity were collected from 9:00 a.m. on 24 January 2017 to 9:00 a.m. on 2 February 2017 (10 days). This period included the coldest days during 2017 according the meteorological organization of Iran. The interval time for the data collection was 20 min. The location of the data logger is shown in Figure 8. The measurement was taken in the center of the talar room and the data logger's height was 0.8 m.

Validation
For the validation of the DesignBuilder simulation software, information related to temperature and relative humidity were collected from 9:00 a.m. on 24 January 2017 to 9:00 a.m. on 2 February 2017 (10 days). This period included the coldest days during 2017 according the meteorological organization of Iran. The interval time for the data collection was 20 min. The location of the data logger is shown in Figure 8. The measurement was taken in the center of the talar room and the data logger's height was 0.8 m. The accuracy of the data logger device in measuring the temperature was ±0.5 °C and its accuracy in measuring the relative humidity was 3% for temperatures between −30 and +70 °C. It had the capacity to connect to a computer and data could be transferred to a PC. This data logger connected to computer as PC and it do not connect to laptop. After collecting related field data, they The accuracy of the data logger device in measuring the temperature was ±0.5 • C and its accuracy in measuring the relative humidity was 3% for temperatures between −30 and +70 • C. It had the capacity to connect to a computer and data could be transferred to a PC. This data logger connected to computer as PC and it do not connect to laptop. After collecting related field data, they were compared to software data for the same period of time. Variation of temperature and relative humidity for the mentioned period is illustrated in Figure 9.
According to Figure 9, the difference between the field data and simulation for temperature was 1.7%, which was in an acceptable range. Also, the difference between the field data and simulation for relative humidity was 3.8%. Based on the agreements, the results of the thermal performance of the talar room using the software are calculated in the next section. were compared to software data for the same period of time. Variation of temperature and relative humidity for the mentioned period is illustrated in Figure 9. According to Figure 9, the difference between the field data and simulation for temperature was 1.7%, which was in an acceptable range. Also, the difference between the field data and simulation for relative humidity was 3.8%. Based on the agreements, the results of the thermal performance of the talar room using the software are calculated in the next section.

Discussion
In this section, data related to simulation scenarios of the talar room at the Manteghi-Nezhad house in the two cases of considering the talar with an iwan and without an iwan are represented. In Figure 10, the air temperature (Ta), radiant temperature (Tr), and relative humidity of the talar room with the iwan and without the iwan are illustrated over one year in order to distinguish the performance of the iwan during warm and cold months.
The indoor temperature and radiant temperature of both cases were less than the outdoor dry bulb temperature in the warm months (according Table 3, the warm months are June, July, August, and September). Furthermore, in the cold months Ta and Tr were higher than the outdoor dry bulb temperature. This was due to the materials of the house, which responded well in both warm and cold months. The figure shows that the indoor temperature and radiant temperature of both cases were less than the outdoor dry bulb temperature in the warm months. This was because of the talar room, which was located on the south side of the courtyard with the backside towards the sun and with sufficient shadow. In the warm months, the average air temperature of the talar room with the

Discussion
In this section, data related to simulation scenarios of the talar room at the Manteghi-Nezhad house in the two cases of considering the talar with an iwan and without an iwan are represented. In Figure 10, the air temperature (T a ), radiant temperature (T r ), and relative humidity of the talar room with the iwan and without the iwan are illustrated over one year in order to distinguish the performance of the iwan during warm and cold months.
The indoor temperature and radiant temperature of both cases were less than the outdoor dry bulb temperature in the warm months (according Table 3, the warm months are June, July, August, and September). Furthermore, in the cold months T a and T r were higher than the outdoor dry bulb temperature. This was due to the materials of the house, which responded well in both warm and cold months. The figure shows that the indoor temperature and radiant temperature of both cases were less than the outdoor dry bulb temperature in the warm months. This was because of the talar room, which was located on the south side of the courtyard with the backside towards the sun and with sufficient shadow. In the warm months, the average air temperature of the talar room with the iwan was 2.3 • C less than the outdoor temperature but the average T a of the talar room without the iwan was 1.2 • C.
Furthermore, the average difference of T r for the talar room with the iwan in comparison to the talar room without the iwan was 0.4 • C. This is because more shadows were provided by the iwan. However, in the cold months, the average of air temperature of the talar room without the iwan was 2.3 • C higher than the outdoor temperature, but average of T a of the talar room with the iwan was 1.7 • C higher than the outdoor temperature because the talar room without the iwan receives more sun radiation. Figure 10 illustrates that the talar room had the lowest relative humidity during the warm months, lower than 20%. The relative humidity in January, February, and December was higher compared to other months of the year as it was higher than 40%. iwan was 2.3 °C less than the outdoor temperature but the average Ta of the talar room without the iwan was 1.2 °C. Furthermore, the average difference of Tr for the talar room with the iwan in comparison to the talar room without the iwan was 0.4 °C. This is because more shadows were provided by the iwan. However, in the cold months, the average of air temperature of the talar room without the iwan was 2.3 °C higher than the outdoor temperature, but average of Ta of the talar room with the iwan was 1.7 °C higher than the outdoor temperature because the talar room without the iwan receives more sun radiation. Figure 10 illustrates that the talar room had the lowest relative humidity during the warm months, lower than 20%. The relative humidity in January, February, and December was higher compared to other months of the year as it was higher than 40%. After the analysis of air temperature, mean radiant temperature (MRT) wind speed, and relative humidity, the value of the PMV and PPD were calculated according Equations (1) and (2), as represented in Figure 11. The metabolic rate for calculated PMV and PPD was assumed to be 0.9. The metabolic rate is the average of light working, seating, relaxing, sleeping, and reclining according to After the analysis of air temperature, mean radiant temperature (MRT) wind speed, and relative humidity, the value of the PMV and PPD were calculated according Equations (1) and (2), as represented in Figure 11. The metabolic rate for calculated PMV and PPD was assumed to be 0.9.
The metabolic rate is the average of light working, seating, relaxing, sleeping, and reclining according to ISO 7730 [41]. Also, the clothing level was assumed to be 0.5 according to ISO 7730 [41] for typical summer indoor clothing.
According to previous studies, thermal comfort can be evaluated by the PMV index. Figure 11 shows the variation of the PMV of the talar room for the two cases-with an iwan and without an iwan. Based on Figure 11, the thermal sensitivity of the talar room in both cases in January, February, and December was cold. The PMV index in May, June, September, and October was nearly zero, which was very appropriate, and the thermal sensitivity of July and August was slightly warm. For case 1 in the warm months, the PMV index was less than that of case 2. Also, the PMV of case 2 was less than that of case 1 in the cold months. The difference of the PMV index between cases 1 and 2 was 2.8% because of the different air temperature and radiant temperature values, which are shown in Figure 10.
According to the PMV index, the PPD can be calculated. Figure 11 shows the percentage of dissatisfaction of the residents in the talar for both cases during various months. It can be seen that during warm months the PPD index was lower than that during cold months. The lowest value of the dissatisfaction index belongs to May, June, July, September, and October, being less than 25%. For the talar room with an iwan, this shows that in warm months the PPD was reduced.
It must be noted that, in reality, in Manteghi-Nezhad house, the talar room with a v form was used during the warm months. According to Figure 11, the iwan was an important element for achieving thermal comfort in the talar room during the warm months. According to previous studies, thermal comfort can be evaluated by the PMV index. Figure 11 shows the variation of the PMV of the talar room for the two cases-with an iwan and without an iwan. Based on Figure 11, the thermal sensitivity of the talar room in both cases in January, February, and December was cold. The PMV index in May, June, September, and October was nearly zero, which was very appropriate, and the thermal sensitivity of July and August was slightly warm. For case 1 in the warm months, the PMV index was less than that of case 2. Also, the PMV of case 2 was less than that of case 1 in the cold months. The difference of the PMV index between cases 1 and 2 was 2.8% because of the different air temperature and radiant temperature values, which are shown in Figure 10.
According to the PMV index, the PPD can be calculated. Figure 11 shows the percentage of dissatisfaction of the residents in the talar for both cases during various months. It can be seen that during warm months the PPD index was lower than that during cold months. The lowest value of the dissatisfaction index belongs to May, June, July, September, and October, being less than 25%. For the talar room with an iwan, this shows that in warm months the PPD was reduced.
It must be noted that, in reality, in Manteghi-Nezhad house, the talar room with a v form was used during the warm months. According to Figure 11, the iwan was an important element for achieving thermal comfort in the talar room during the warm months. The monthly averages of the PMV and PPD indexes in both cases during the warm months (June to September) are shown in Figure 12. As shown, the PMV of case 1 was 0.5 less than the PMV of case 2 in July, August, September, and October, whereas it provided comfortable conditions for the occupants. Based on Figure 12, the difference between the PMV index of the talar room with an iwan and that without an iwan was 62.5%. The monthly averages of the PMV and PPD indexes in both cases during the warm months (June to September) are shown in Figure 12. As shown, the PMV of case 1 was 0.5 less than the PMV of case 2 in July, August, September, and October, whereas it provided comfortable conditions for the occupants. Based on Figure 12, the difference between the PMV index of the talar room with an iwan and that without an iwan was 62.5%.
The average PPD index of the talar for the two cases during the warm months is presented in Figure 12. The results show that dissatisfaction rate of case 1 was less than that of case 2 during the warm months. The PPD of the talar room with an iwan decreased by 14% in comparison with the talar room without an iwan.
The relevant values of PMV and PPD of the talar room with an iwan ascertained that the good performance of the iwan could create more shadows. Thus, the iwan in the south orientation of the courtyard is an effective element in the Manteghi-Nezhad house to reduce heat, especially during the warm months. The average PPD index of the talar for the two cases during the warm months is presented in Figure 12. The results show that dissatisfaction rate of case 1 was less than that of case 2 during the warm months. The PPD of the talar room with an iwan decreased by 14% in comparison with the talar room without an iwan.
The relevant values of PMV and PPD of the talar room with an iwan ascertained that the good performance of the iwan could create more shadows. Thus, the iwan in the south orientation of the courtyard is an effective element in the Manteghi-Nezhad house to reduce heat, especially during the warm months. In order to analyze the indoor air temperature, relative humidity, and radiant air temperature in detail, a representative day during the hot months was selected. According to Figure 13, the selected variables were compared for case 1 and case 2 to find out the overall thermal conditions that the iwan can provide inside the talar room. The results of indoor air temperature and radiant air temperature showed that the iwan could significantly affect the overall indoor conditions in case 1. The difference between the indoor air temperature and the outdoor air temperature in the afternoon was measured as the highest value for the talar with the iwan. The indoor air temperature at 4:00 p.m. was 36 °C while the outdoor air temperature was more than 41 °C. The difference for radiant air temperature was higher than the indoor air temperature, where it rose up to 6 °C at 4:00 p.m. This was due to the shadow caused by the iwan projection at the southern direction of house. Comparison of the results during the nighttime and the early morning showed a small difference between the indoor and outdoor air temperatures in both cases. This was due to the absence of sun radiation. Even the difference of air temperature between cases 1 and 2 was less than 1 °C. This shows that the iwan could effectively reduce the air temperature as well as the radiant air temperature during the morning and the afternoon times.
According to Figure 13, the relative humidity in both cases was between 17% and 29% and the difference was trivial. Thus, it can be declared that the iwan could not affect relative humidity in the indoor environment. According to the results, the relative humidity in the evening was higher than that in early morning. This was due to the evaporation of water in the courtyard, especially in the afternoon when the solar radiation was intensive. Table 6 presents the comparison between different air temperatures, the PMV, and the PPD for both cases in a representative day. According to the results, the maximum difference between the air temperature and radiant air temperature of cases 1 and 2 occurred at 3:00 p.m. in the afternoon. The results show that iwan could decrease the indoor air temperature up to 3 °C where the same amount of solar radiation was received in the afternoon. The average indoor air temperature and radiant air temperature for 24 h indicates that the talar with the iwan could provide a better temperature in comparison with the talar without the iwan. The difference between air temperatures was more than 1 °C through the day. As a consequence, the PMV for case 1 was 1.1, which was better than case 2 with a PMV of 1.3. The Predicted Percentage of Dissatisfaction (PPD) for both cases showed that case 1 with the iwan had better thermal condition in 24 h. Based on the results, the PPD in case 1 was 9% less than that for case 2. In order to analyze the indoor air temperature, relative humidity, and radiant air temperature in detail, a representative day during the hot months was selected. According to Figure 13, the selected variables were compared for case 1 and case 2 to find out the overall thermal conditions that the iwan can provide inside the talar room. The results of indoor air temperature and radiant air temperature showed that the iwan could significantly affect the overall indoor conditions in case 1. The difference between the indoor air temperature and the outdoor air temperature in the afternoon was measured as the highest value for the talar with the iwan. The indoor air temperature at 4:00 p.m. was 36 • C while the outdoor air temperature was more than 41 • C. The difference for radiant air temperature was higher than the indoor air temperature, where it rose up to 6 • C at 4:00 p.m. This was due to the shadow caused by the iwan projection at the southern direction of house. Comparison of the results during the nighttime and the early morning showed a small difference between the indoor and outdoor air temperatures in both cases. This was due to the absence of sun radiation. Even the difference of air temperature between cases 1 and 2 was less than 1 • C. This shows that the iwan could effectively reduce the air temperature as well as the radiant air temperature during the morning and the afternoon times.
According to Figure 13, the relative humidity in both cases was between 17% and 29% and the difference was trivial. Thus, it can be declared that the iwan could not affect relative humidity in the indoor environment. According to the results, the relative humidity in the evening was higher than that in early morning. This was due to the evaporation of water in the courtyard, especially in the afternoon when the solar radiation was intensive. Table 6 presents the comparison between different air temperatures, the PMV, and the PPD for both cases in a representative day. According to the results, the maximum difference between the air temperature and radiant air temperature of cases 1 and 2 occurred at 3:00 p.m. in the afternoon. The results show that iwan could decrease the indoor air temperature up to 3 • C where the same amount of solar radiation was received in the afternoon. The average indoor air temperature and radiant air temperature for 24 h indicates that the talar with the iwan could provide a better temperature in comparison with the talar without the iwan. The difference between air temperatures was more than 1 • C through the day. As a consequence, the PMV for case 1 was 1.1, which was better than case 2 with a PMV of 1.3. The Predicted Percentage of Dissatisfaction (PPD) for both cases showed that case 1 with the iwan had better thermal condition in 24 h. Based on the results, the PPD in case 1 was 9% less than that for case 2.  Figure 13. Comparison of the air temperature, radiant temperature, and relative humidity of the talar room for cases 1 and 2 on 29 July, Shiraz, Iran.
Comparison of results for the selected scenarios ascertain that the iwan as an architectural element in traditional houses could significantly reduce indoor air temperature and radiant temperature, especially in the afternoon when a high amount of solar radiation penetrates the buildings. As a result, better thermal comfort can be achieved according to the results of PMV and PPD for the current study. Thus, this study recommends further studies on the implementation of iwans in the new development of housing in the same microclimate for the provision of better thermal conditions as well as for saving energy in residential buildings. Comparison of results for the selected scenarios ascertain that the iwan as an architectural element in traditional houses could significantly reduce indoor air temperature and radiant temperature, especially in the afternoon when a high amount of solar radiation penetrates the buildings. As a result, better thermal comfort can be achieved according to the results of PMV and PPD for the current study.
Thus, this study recommends further studies on the implementation of iwans in the new development of housing in the same microclimate for the provision of better thermal conditions as well as for saving energy in residential buildings.

Conclusions
The iwan has been used in hot and dry climates in many traditional houses in different forms and with various materials. The thermal comfort of a talar in a traditional house in Shiraz was studied for the two cases of the adjoined iwan with and without iwan. According to the results of field measurements and simulations, the following outcomes are specified.
(1) The average indoor temperature of the talar during the year was about 3.9 • C higher than the outdoor temperature in the case of the iwan with a ceiling. The indoor temperature of the talar room with an iwan without a ceiling was 1% higher than that of the talar room with the iwan having ceiling over the course of one year. The difference between radiant and operative temperature in the two cases was very low. (2) The relative humidity in the talar room in both cases was below 20% in June, July, August, and September, while it was between 20% and 40% in October, November, March, April, and May. The relative humidity of the talar room in January, February, and December was higher than 40%. (3) The talar in the case of the iwan with a ceiling was completely appropriate to fulfill the thermal comfort situation in June, July, September, and October. Furthermore, in August and September, it was in the range of warm and in December it was relatively cool. It was not under the comfort range in other months of the year, although a heating device was necessary. In the case of the iwan without a ceiling, the situation was not in the comfort range, especially in the summer months. However, the conditions improved slightly in the cold months. (4) Based on the calculated PMV index, the talar with the iwan without a ceiling was 8% better during the year, but for warm months the talar with the iwan with a ceiling was 42% better than the talar with the iwan without a ceiling. (5) In terms of the PPD index, the dissatisfaction rate in the case of the iwan with a ceiling was below 20% in June, July, September, and October, while the dissatisfaction index was about 40% in the two months of August and September. The dissatisfaction rate was poor for the cold months of the year. The PPD for the talar with an iwan with a ceiling was 18% better than that for the iwan without a ceiling during warm months. (6) The analyses of indoor thermal conditions for a representative day ascertained that the case with the iwan could significantly reduce the indoor air temperature. According to the results, the difference of indoor air temperature between the selected scenarios reached up to 3 • C in the afternoon, when high amount of solar intensity hit the building.
(7) According to the results, the iwan contributes to the thermal satisfaction inside traditional buildings. Thus, it is recommended that further studies be carried out in order to apply this architectural element to the development of new residential buildings for the same microclimate.