9 minute read
Built Precedents
4.2 Built Precedents
Borujerdis House, Kashan
Advertisement
Location: Kashan, Iran
Co-ordinates: 33.97° N, 51.44° E
Architect: Ustad Ali Maryam
Design Strategy: Courtyard effect, natural ventilation, and evaporative cooling
Located in the hot desert region (BWh) of Kashan, Iran, the Borujerdis house is a two-story traditional middle eastern residence museum built in 1857 (Figure 4.8 and 4.9).
It is rotated 10o from the north-south direction to align perpendicularly to the regional wind direction (Figure 4.10). This is to maximize the wind flow within the building for passive cooling and natural ventilation during the summer (Soflaei, Shokouhian, and Soflaei 2017). Additionally, this project utilizes courtyards with an extensive fountain pool to provide thermal comfort and privacy to the inhabitants. The main structure is made of dried bricks, while straw and mud are used for the insulation.
Figure 4.8 Borujerdis house courtyard, Kashan (Source: Soflaei, Shokouhian, and Soflaei 2017)
Figure 4.9 Borujerdis house floor plans and sections (Source: Haji Ghasemi 1996)
The courtyard has a rectangular form with an area of 645 square meters and a 0.67 height-to-width ratio, typical of other vernacular courtyard houses in Iran. The linear water feature along the primary axis of the courtyard (10o of North-South) has a shallow depth to increase the surface area of the water in order to absorb maximum incident solar radiation and increase evaporative cooling, creating convective breezes throughout the house. In addition, green covers, including indigenous and drought-tolerant trees and plants, are used along the periphery of the courtyard to maximize shade in the indoor spaces, thereby reducing the indoor temperature, as discussed in Section 4.1 (Soflaei, Shokouhian, and Soflaei 2017). The water and landscape area allocated in the Borujerdis house in Kashan, Iran is 110.4 m2 and 180 m2, respectively. The right proportion of soiled, landscaped, and water area in relation to the courtyard can significantly increase the thermal comfort in the courtyard through increased evaporative cooling and adequate shading during the different seasons.
A recent study conducted some fieldwork and computational simulations to understand the thermal performance of the Borujerdis house in Kashan. A thermometer (Testo610) and laser distance meter (Leica D2) were positioned 1.5 m above ground in the courtyard for field studies. In summer, when the outdoor temperature varied from 30oC to 40oC, the instruments recorded an almost constant temperature of 28oC in the indoor spaces on the first floor (Cho and Mohammadzadeh 2013). As far as the simulations are concerned, Figure 4.11 summarizes the temperatures of the various zones of the house along with the temperature differences from the outdoors. For instance, zone 7 shows a significant temperature difference of up to 5.6oC, while zones 6 and 8 show a reduction of 5.2oC on average due to the natural ventilation and evaporative cooling from the courtyard (Cho and Mohammadzadeh 2013).
This thermal variation is potentially a result of the courtyard effect, although other factors like openings, thermal mass, and materiality might have also assisted in achieving this reduced temperature. The passive cooling techniques employed in this house and the climate are very similar to that of Sharjah. Hence, the same principles can also be utilized in the courtyard housing in Sharjah.
Figure 4.10 Orientation and rotation angle of the house and the courtyard (Source: Soflaei, Shokouhian, and Soflaei) 2017
Figure 4.11 Simulated zones and comparison of maximum temperatures with and without natural ventilation (Cho and Mohammadzadeh 2013)
Pearl Academy of Fashion, Jaipur
Location:Jaipur, India
Co-ordinates: 26.91° N, 75.78° E
Architect: Morphogenesis
Design Strategy: Courtyard effect, evaporative cooling, solar shading through Jaali screens and high thermal Mass
Although this particular case study is an educational institution, some of the passive principles used in this project can also extend to residential buildings in Sharjah. Moreover, the climate zone in both cases (Jaipur and Sharjah) are very similar: hot desert climate (BWh).
This project is built 4m below the ground consisting of two large curvilinear courtyards, water features, and Jaali (Figure 4.12). One of the courtyards has an aspect ratio of H/W>1, while the central courtyard has a ratio of H/W<1 (Rastogi and Bansal 2012). This partial earth sheltering assists in lowering temperatures by drawing air into the courtyards, which is further cooled by the water features through evaporative cooling. This cooled air is further drawn into the indoor spaces before escaping outside (Figure 4.13).
Figure 4.12 Pearl Academy of Fashion, Jaipur (Source: ArchDaily)
Figure 4.13 Conceptual section of the Pearl Academy (Source: ArchDaily)
The building consists of high thermal mass in the form of local Kota stone floors, white rendered walls, and earthenware pots roof that creates a thermal lag, reducing the heat absorption through the envelope of the building and hence, cooling the internal environment (Bhargava 2018). The Jaali on the outer façade also acts as a thermal buffer, shielding the indoor spaces from direct solar radiation (Figure 4.15). According to specific studies measuring the thermal performance of this building, these passive strategies, including the courtyards and the water feature, have resulted in significant temperature variation, with indoor temperatures ranging from 29oC to 30oC for 45oC outdoor temperatures (Rastogi and Bansal 2012). This is further reduced by using mechanical fans and added classroom ventilation. Furthermore, as part of the fieldwork by Swati Bhargava, 2017, data loggers were placed throughout the building at four specific spots for a typical summer week between April 11 and April 16 (Figure 25). With the outdoor temperatures varying from 43oC in day to 19oC at night, the indoor temperature differed by 9-10oC during the day, while courtyards experienced an additional reduction of 4-5oC due to vegetation (21.9% surface area of the site) and water features covering 3.7% surface area of the site (Figures 4.16) (Bhargava 2018).
The passive strategies in this building, specifically the courtyards, water features, and thermal mass, are a testament to the effectiveness of vernacular cooling methods and how they can be adopted in contemporary architecture. Drawing from this project, many residents in Sharjah could reduce their cooling load while maintaining optimum comfort levels.
Figure 4.14 Pearl Academy courtyard with water feature and sunken belly (Source: ArchDaily)
Figure 4.15 Thermal analyis of Jali (Source: Bhargava 2017)
Figure 4.16 Graph showing results from data loggers for April and energy consumption comparison (Source: Bhargava 2017)
Children Village / Rosenbaum + Aleph Zero
Location: Formoso do Araguaia, Brazil
Co-ordinates: 11.80° S, 49.52° W
Architect: Rosenbaum + Aleph Zero
Design Strategy: Courtyard effect, natural ventilation, solar shading through extended roof (creating a transitional space, loggia) and high thermal mass.
This project deals with the redevelopment of the rural school at Formoso do Araguaia, Brazil, which accommodates 540 students in approximately 23,000 m2 of built area (Hein Hsiao et al. 2021). The architecture is strongly influenced by the local savanna climate (Aw) (characterized by the alteration of hot and dry and hot and humid periods), with high air temperatures throughout the year and significant diurnal swings, especially in dry periods exceeding 10oC.
Three courtyards segregate the new organization, side by side, along with dormitories on the ground floor and classrooms, libraries, and other social spaces on the upper level. They are further shaded by a large roof structure, opening to the internal courtyards, slightly inclined and disconnected from the envelope, almost acting as a second cover and a transitional space (Liwan) (Figures 4.17, 4.18, and 4.19).
The courtyards favor cross ventilation and natural lighting in the indoor spaces, while at the same time, the large wooden roof, which covers the entire building complex, shades slabs and walls throughout the year. Furthermore, the large roof plan also protects the open living and communal spaces from the direct impact of solar radiation. Low environmental impact materials, such as unbaked adobe bricks made from local soil, clay, sand, and raw materials, are used similarly to the traditional houses in the region. They add thermal inertia to the internal environments to deal with high temperatures and diurnal swings (Hein Hsiao et al. 2021).
Figure 4.17 Children village, Formoso do Araguaia, Brazil (Source: ArchDaily)
Figure 4.18 Children village ground floor plan (Source: ArchDaily)
Figure 4.19 Children village section highlighting the wooden roof that covers the dormitory blocks and other uses, leaving the courtyard uncovered (Source: ArchDaily)
The computational simulations by Hein Hsiao et al. (2021) also demonstrate the potential of comfortable thermal and lighting conditions in the dormitory and their respective balconies throughout the year. For example, for a typical week of hot and dry conditions, operating temperature values in the internal spaces of the bedrooms were around 10oC below the external temperature, evidencing the influence of the thermal mass of the adobe walls, combined with natural ventilation and shading. The large roof, in particular, played a role in reducing solar gains, resulting in a difference of 3oC to 5oC in the bedrooms between the scenarios with and without the roof (Table 4.1) (Hein Hsiao et al. 2021).
The most significant impact of the large roof was seen in controlling daylight (avoiding glare). The analytical studies have shown that the cover has the potential to eliminate the occurrence of glare in all orientations, predominantly south orientation, which showcased the most discomfort hours without the cover, as illustrated in Figure 4.20 (Hein Hsiao et al. 2021).
In conclusion, the project highlights that thermal comfort conditions and acceptable levels of natural light are possible, even in extreme heat conditions and exposure to high levels of solar radiation, such as that of Sharjah (with external temperature values exceeding 40oC). It can be achieved through vernacular passive solutions suited to the local climate that is already known to reduce the thermal load of buildings, including shading, thermal mass, natural ventilation, and the introduction of transition zones.
Table 4.1 Annual percentage of hours inside and outside the thermal comfort zone in simulated environments (Source: Hein Hsiao et al. 2021)
Without wooden roof
With wooden roof
Figure 4.20 Illuminances calculated at the height of the work plane in the bedrooms and balconies of the central unit in Block A, for summer and winter solstices and equinoxes at 3 pm (Source: Hein Hsiao et al. 2021)
- Simos Yannas (2011)
