Potential Regenerative Impact of Implementation of Cultural Vernacular Elements (Rowshan) in Jeddah, Saudi Arabia

Abstract

The present study aims to explore rowshans as essential vernacular architectural elements in designing houses in very hot-dry climates such as Jeddah, Saudi Arabia, to determine their most significant effects on air movement, ventilation, and mitigating cooling loads. A comprehensive combination of building performance simulation and computational fluid dynamics (CFD) analysis was used to model a room with six different sizes of rectangular openings and quantify rowshans’ potential as passive elements in providing occupants with comfort and reducing energy use. Analysis of the passive element revealed the thermal performance and natural ventilation in single-family homes for the Jeddah climate, created by outdoor and indoor temperature, airspeed, and pressure differences in the room model, were improved, lowering sensation temperature for inhabitants’ comfort. The results highlight the beneficial effects of rowshans in lowering a house’s temperature during the daytime: from November to April, at noon, indoor air temperature (IAT) could reach a 15% to 22% reduction in the north orientation. The findings also show that rowshans with 5 × 5 cm opening grids can keep the air volume flow rate within an acceptable range and keep the room in the comfort zone range for 42.3% of hours annually, equal to 3704 h. An implication of these results is the possibility of establishing housing design criteria that can enhance efficiency and thermal comfort conditions, lower the cost of operations, provide occupants with satisfaction, and reduce emissions to regenerate the environment, leading to affordability and sustainability in the Jeddah region.

1. Introduction

Understanding the complexity of implementing natural ventilation efficiently is vitally important to minimize energy consumption in new houses. In recent years, there has been a dramatic increase in the sustainable development of high-performance buildings, the provision of thermal comfort using passive architectural elements, and cooling buildings through natural ventilation, which minimizes energy consumption, especially in countries with hot climates. A considerable body of literature has recently grown around minimizing energy use by improving natural ventilation in building performance for commercial-scale projects or improving the technology efficiency of the mechanical systems for buildings. On the other hand, residential buildings in developing countries have been increasing remarkably, and this is becoming challenging to ignore because it will substantially intensify the growth in energy use. In addition, over centuries, people in hot-dry climates have invented many strategies for passive cooling systems through natural ventilation, such as courtyards, wind towers, and domed roofs [1]. This paper’s central thesis concentrates on a traditional Middle Eastern vernacular passive element, the rowshan, a protruding window surrounded by carved wood latticework. In particular, rowshans are an important architectural element in houses in the city of Jeddah, where they play an essential role in enhancing natural ventilation. Using strategies employing architectural elements such as rowshans in designing new houses in Jeddah has significant potential to reduce indoor air temperature, as reflected in lower cooling loads. Implementing sustainable practices can help to reduce energy consumption and emissions, while also promoting the regeneration of the environment. The following academic studies have highlighted multiple factors and forces that must be considered to enhance Jeddah houses; specifically, natural ventilation potential during the cooler months.

1.1. Household Electricity Consumption

Data from several global sources, such as the IEA, have identified the increasing demand for electricity in buildings. According to the IEA’s semi-annual Electricity Market Report (2021), global electricity demand was set to rise by close to 5% in 2021 and 4% in 2022, pushed by the global economic recovery [2,3]. For example, cooling electricity consumption in the Middle East alone has been estimated at 65%, and the number of air conditioning units in the Middle East is estimated to increase from 1.1 billion to 3.1 billion by 2050, growing from three units to five units per capita [4]. The extremely hot climate pushes building occupants to use air conditioners to ensure their thermal comfort [5]. Additionally, most developing countries are experiencing economic growth, which results in an immediate increase in energy demand over the following years; the challenge here is that most of the energy resources in these countries are generated from finite sources [6]. Therefore, reducing the effects of energy consumption on the environment is essential for the future of society, and reducing cost and energy demand will minimize impacts on environmental sustainability. This is evident when electricity uses non-renewable resources; for example, 57% of electricity in the Kingdom of Saudi Arabia (KSA) is derived from oil and 43% is derived from natural gas [7]. KSA was one of the top ten countries for CO₂ emissions generation in the world in 2015 at 2% with 17.04 metric tons of CO₂ emissions per capita [8,9]. Electricity and heat production generate approximately 42% of global CO₂ emissions [10]. Also, the energy produced by fossil fuels increases greenhouse gas (GHG) emissions globally, leading to many environmental and health problems [11]. However, KSA supports climate action, sharing global environmental considerations, and the country has committed to reducing its carbon emissions to zero by 2060 [12].

However, the residential sector uses 80% of the electricity generated in KSA, 70% of which is exclusively used for air conditioning [13,14]. The average KSA household consumes 177 kWh/m² of electricity annually, which is higher than U.S. housing units and the global average in similar hot climates, respectively amounting to 130 kWh/m² and 120 kWh/m² [7,9]. The total population in KSA at the end of 2017 was around 33 million, with an annual average population growth rate of 2.52%.

1.2. Jeddah’s Climate

The Köppen climate classification has been used for numerous research areas, and it depends on air temperature and rainfall [13]. However, most countries develop their classification zoning maps for building energy conservation standards by using heating and cooling degree days to relate to the operation of HVAC systems, which are based on the air temperature variations in different areas [13]. Jeddah’s climate zone belongs to the category “1B” Very Hot-Dry based on International Climate Zone Definitions [14]. The primary concern for this climate is dealing with harsh climate conditions, with annual cooling degree days (CDDs) of 6853 °C. That large amount of CDDs leads to more energy consumption; therefore, more solutions to decrease energy consumption are required. It is interesting to note that Jeddah is situated on the Red Sea and has a climate characterized by high humidity throughout the year [15]. However, despite this, Jeddah’s climate is classified as hot and dry due to the lack of precipitation. Jeddah’s outdoor relative humidity (RH) is generally very high, with sunny skies and prevalent wind coming from the northwest (seaside); wind speed ranges from 6 to 15 km per hour for most of the year. The RH average is 55%, and the summer temperature ranges from 19 °C to 47 °C, with an average of 30 °C, and in the winter months, the temperature ranges between 9 °C and 33 °C, with an average of 24 °C [9,14]. The Adaptive Comfort Model in ASHRAE Standard 55 (2017) states that temperatures ranging from 23 °C to 31 °C in a hot climate represent a comfort zone for naturally conditioned spaces. The range of Jeddah’s ambient temperature in winter allows those buildings, as in most of the cities in KSA [16], to not need heating/cooling from November to March.

1.3. Architectural Identity of Jeddah as a Historic Town and Rowshan Design

Jeddah is a coastal city situated on the west coast of KSA, known as an essential port for trade routes on the Red Sea since the seventh century [15]. Jeddah is also the gateway for Muslim pilgrims heading for the holy city of Mecca’s to perform Hajj. These two city functions mean that the city is influenced by many cultures worldwide, contributing to its unique architectural character [17]. Scholars have reported that the historical building characteristics in Jeddah’s old houses are a mix between those of the older, southern Arabian tower houses found in Yemen and traditional courtyard houses in the Middle East (see Figure 1, Figure 2 and Figure 3) [15]. A rowshan is a distinguishable element of those historical buildings, and recent works have concluded that the rowshan is a building façade strategy to provide privacy, daylight, and ventilation. Hence, the large screened windows in the façade catch all possible breezes that may enter the house, especially from the seaside (north, northwest, or west) [14,17,18,19,20].

In a different study, the rowshan is characterized by Di Turi and Ruggiero (2017) as an ancient traditional element used in Islamic countries or the Middle East for environmental and cultural benefits. The authors described the rowshan as a window with carved wooden latticework that controls light and natural ventilation, regulates airflow, decreases temperatures, and increases humidity in the interior space to make it more comfortable and provide privacy [20,21]. Additionally, Babsail and Al-Qawasmi (2015) and Alothman and Akçay (2017) agree that rowshans provide privacy because they block pedestrians from seeing through the tiny holes at eye level and allow users to see out to the street. That function of the rowshan in Islamic regions came from the privacy requirement, an essential value of the Islamic culture. Furthermore, the tiny holes allow the rowshan to let light pass through to the interior and prevent direct sunlight; thus, the glare does not increase the interior space temperature [19,22]. The rowshan’s design differs from place to place; they are different in size, pattern, construction material, and openings, but mostly they assume the human body’s relative size and are constructed of wood, such as teak, ebony, oak, and mahogany. While the opening size of the rowshan depends on the local climate, it is typically 2.7 to 3.5 m in height, 2.4 to 2.8 m in width, and about 0.4 to 0.6 m in depth into the street; it is wide enough for a person to comfortably lie down for a sleep [18,23,24]. The structure of the rowshan typically consists of panels and grilles. Each rowshan structure has certain components, including the bottom part, which is a different base; the central part, which is a movable part that can rise and extend outside; and the exterior, consisting of horizontal wooden panels to allow fresh air to enter the room. The upper part has a wide mesh to allow air and light to enter [18]. Another recent study by Bagasi et al. (2021) describes a different type of rowshan that uses small jars of water to cool the air through the apertures via the influence of evaporation, which could minimize the cooling load in indoor spaces, especially at night. Unfortunately, due to countless factors, the usage of rowshans began to decline in the 20th century. Some of these factors include modernity, the growth of globalization and the economy, and decisions to ignore vernacular traditions and the craft industry by relying on mechanical industries [22].

1.4. Modern Rowshan Design and the Challenge of Creating Thermal Comfort through Natural Ventilation

The primary global concerns have recently been related to energy conservation; however, the fundamental concern for environmental design is human thermal comfort [25]. Enhancements to thermal comfort can be achieved through architectural design, which is one of the most practical methods [26]. However, connecting modern and architectural heritage in the region has been considered by academicians. Alothman and Akçay’s (2017) study claims there are misconceptions about designing rowshans because the proper standards for designing the rowshan have been ignored. Therefore, the researchers evaluated four projects including the modern versions of the rowshan in three notable forms: primitive, sustainable, and advanced technology. As a result, Alothman and Akçay’s work presented several findings. First, any modern rowshan is acceptable, as long as the design achieves some of the primary functions of the vernacular architectural element. Second, some recent projects have restored the concept of the rowshan but ignored some of the primary standards to create that element, which changed the main goal of the element. Third, the glass layer has been placed behind the façade, creating what is known as double-skin façades that detract from the relationship between the modern and traditional rowshan because the traditional one has a space that has functions as a stand for water jars or as seats for women to look outside. However, the modern one uses a double-skin façade system and creates a small space with no function. Additionally, the double-skin façade system blocks airflow and does not provide stable thermal zones, so the building requires cooling devices. Fourth, high humidity in the region is a big issue, and using steel or any metal materials to create the modern rowshan structure makes it difficult to achieve the humidity adjustments provided by a wooden rowshan. Metal or glass does not have the same properties as wood; for these reasons, the new alternative materials must be addressed and must have similar or better properties as wood because the wood properties are related to absorption and evaporative phenomena. For example, during times with sunlight, the rowshan releases moisture into the air that passes through, increasing the humidity within a home and reducing its temperature [22]. Additionally, the rowshan absorbs moisture that is carried by the wind at night and passes through the rowshan holes. Also, using metal for rowshan construction is unreasonable because such a detailed metal structure could cause heat gain, leading to more energy use and greater costs [22].

Recently, Elnaklah et al. (2021) published a paper that compares different international and local standards in the Middle East for green building codes because the thermal comfort range differs between recommended standards and occupants’ comfort and sensations. The study provides large-scale thermal comfort surveys of people in 31 air-conditioned buildings. These included five types of buildings with mixed-mode ventilation or full HVAC systems in four countries in the Middle East, such as mosques in Dubai, UAE; office buildings in Amman, Jordan, and Doha, Qatar; and a hospital in Jeddah, KSA. In addition, all buildings in this study followed the standard recommended range for indoor conditions to design these buildings. However, Elnaklah et al. found differences, suggesting that only 40% of occupants found these conditions acceptable. In some cases, 39% of people felt cold, in contrast with the PMV predicted model, which suggested that 40% would feel hot. Furthermore, the study claimed that the PMV model failed to predict the thermal sensation for 94% of occupants in the five types of buildings 58% of the time. In contrast, the authors concluded that increasing the indoor temperature by 2.3 °C and 4.1 °C in some office buildings in Amman and Doha would reduce the annual building energy demand for space cooling by 20% and 13%, respectively. Overall, this study highlighted the gap between observed and predicted thermal comfort, and one standard is not suitable for all the Middle East. Therefore, the study recommends the development of a new thermal comfort model that is more localized to mitigate energy demand for space cooling to suit occupants in each country [4].

1.5. CFD Analysis of Residential Airflow through Natural Ventilation

As far back as 2001, Maghrabi investigated airflow behaviors through louvers and compared multiple cases of full-scale room models and laboratory results (CFD predicted results) to study louvers’ airflow characteristics. The multiple cases included different louver blade sizes, depths, blade gap dimensions, and wind speeds ranging from 0.6 to 2.05 m/s to examine the louvers’ effects in the room regarding the different wind speeds. The authors identified that the louvers’ performance depends on the distance between louver blades and the distance from the louvers to the room, and there is no critical effect on airflow velocities from small changes in the louvers’ blade depth [27]. However, the study did not consider other environmental variables, such as air temperature and humidity. Such variables should be considered when designing modulated louvered windows or rowshans because they play a significant role in changing the air characteristics inside the room.

In 2021, Bagasi et al. conducted an experimental analysis of fieldwork on the ventilation strategy for buildings in hot climates based on integrating the traditional rowshan in Jeddah. The measurement points of the environmental factors included air temperature, globe temperature, relative humidity, air velocity, and surface temperature. The measurements considered summer days from August to September. The study found that an open rowshan provides daytime airflow, enhances air circulation in the room, and reduces the indoor temperature by 2.4 °C, which has a positive effect on the building. However, during warm weather, a rowshan alone is not enough to provide a cooling effect; therefore, other passive cooling methods are required for thermal comfort [24]. Unfortunately, Bagasi et al.’s study did not measure the environmental factors inside the rooms, did not analyze air volume and flow, and did not study the rowshan’s effects within different climate conditions to improve thermal performance.

Many of the functions of rowshans have been evaluated; e.g., comparing the use of glass windows and rowshan, allowing proper daylight for indoor spaces, and delivering evaporative cooling and fresh air. Nevertheless, few studies have examined the rowshan’s effects within airflow in new house designs in the Jeddah climate. In addition, there is a lack of CFD simulation analysis studies to prove the benefits of integrating local architectural elements into modern house designs in Jeddah. Architects and designers could benefit from CFD analyses studying airflow to enhance building performance and reduce energy consumption. There is a clear gap between architectural science and fluid dynamics science regarding the engineering knowledge of natural ventilation techniques functionalized by architects into design strategies [28]. Therefore, the lack of studies prevents the potential regenerative impact from enhancements in building performance and reductions in energy consumption through airflow analysis. Well-designed buildings employing natural ventilation can provide comfort better than mixed-mode buildings [29].

In this study, an analytical investigation was conducted to explore the natural ventilation potential for cooling new houses in Jeddah, KSA; the study focused on the analysis of the typical single-family home in Jeddah, not all the multifamily housing types. In addition, the house model for this research concentrated on a particular architectural element; namely, the rowshan. Therefore, this study’s findings may help explore the potential of natural ventilation and evaluate the effectiveness of rowshans within new houses in Jeddah. In addition, further investigation including experimental validation is needed to evaluate the effectiveness of rowshans and other local architectural elements within new houses in hot-dry climates like Jeddah and compare the impacts of these elements in providing fresh air and cool spaces through the year.

2. Materials and Methods

To date, various methods have been developed to measure buildings’ thermal comfort. For example, a weather data analysis method is a proper technique for assessing simulation studies of natural ventilation potential. However, the weather analysis method alone is not sufficient to determine a viable solution for natural ventilation in hot-dry climates because it needs to be corroborated by responsible house designs to be applicable for occupants. Four phases were applied in this study to gain detailed insights into the impacts of passive architectural elements, thermal comfort, and a viable solution for naturally ventilated spaces. These phases included measuring the outdoor and indoor viability hours for natural ventilation, identifying a room’s comfort level through the room’s operative temperature (T_op) and air volumetric flow rate and speed, predicting a mean vote (measurement process), and investigating rowshan performance through a CFD analysis.

2.1. Data Processing Tools

Various tools trusted by academia and industry were employed to evaluate the simulation and verification results in this paper, such as using the Typical Meteorological Year (TMY3–2004–2018) weather data file derived from the U.S. NOAA’s Integrated Surface Database (ISD) and identifying design recommendations to understand the climate data for this study; namely, ASHRAE Standards, Climate Consultant 6.0, and Integrated Environmental Solutions Virtual Environment (IES-VE 2021). In addition, the simulation results analysis was accomplished by using IES-VE 2021 software to gather different data based on multiple scenarios and conditions for the simulated models to obtain further in-depth information on the effects of rowshans on new houses in Jeddah (see Figure 4).

2.2. Investigation Models (Model/Geometry Description)

To establish the thermal comfort investigation, six room models were analyzed to investigate the effects of passive architectural elements on the single-family home, as shown in Figure 5, starting with a full-size window and reducing the size by 50% each time for the smaller opening grids. This research focused on a single room under the most significant weather conditions for simplification purposes. All the models had the exact room dimensions, with 20 m² for room area and 78 m³ for room volume. However, they differed in the inlet areas/opening sizes, which ranged from 7 m² for the largest and 2 m² for the smallest inlet. To mimic the rowshan’s operation and analyze its performance, six models were considered with the following opening grids: (a) full-size window opening, (b) 100 × 100 cm, (c) 50 × 50, (d) 20 × 20 cm, (e) 10 × 10 cm, and (f) 5 × 5 cm. Based on a background study of the software limitations, these numbers could not be made smaller than 5 × 5 cm. Also, each rowshan was 0.6 m above the room floor; the room door was assumed to be open and represented the models’ outlet area. Furthermore, it was assumed the rooms were empty, and the ventilation strategy assumed a naturally ventilated, cross-ventilation strategy. Finally, the building envelope materials for those rooms were assigned based on the minimum requirements for climate zone “1B” Very Hot-Dry, as presented in the Saudi Building Code-201, 2018 and Saudi Energy Conservation Code for Low-Rise (Residential) Buildings-602, 2018 [14,30].

This study included three different groups based on building orientations for the six models demonstrating different results. The first group faced north to represent the best scenario, the second group faced south to represent the worst scenario, and the third group faced northwest, representing a moderate/average case. On completion of all models, the processes for different models, the conditions, and the scenarios were simulated using the extreme condition day (8 July), which had the daily annual maximum dry-bulb temperature (DBT) and maximum dewpoint (DPT) temperature; the daily annual average condition (16 May); and the daily annual minimum (2 February). Based on TMY3 weather data, these simulation days were chosen for Jeddah to identify representative days instead of selecting the whole year for the simulation (see

Table 1. Based on TMY3 weather data, three representative days were chosen for Jeddah to simulate three different groups of building orientations for six models, each of which demonstrated different results (a total of 54 simulations were conducted).

Groups	Model Position/Opening Position	Six Simulated Room Models/Code	The Daily Annual Maximum Condition (8 July)		The Daily Annual Average Condition (16 May)		The Daily Annual Minimum Condition (2 February)
			DBT	DPT	DBT	DPT	DBT	DPT
1	Faced north to represent the best scenario	(a) Full-size window opening/RM-FullSize-OG	39 °C	16 °C	36 °C	19 °C	30 °C	11 °C
		(b) 100 × 100 cm opening grids/RM-100 cm-OG
		(c) 50 × 50 cm opening grids/RM-50 cm-OG
		(d) 20 × 20 cm opening grids/RM-20 cm-OG
		(e) 10 × 10 cm opening grids/RM-10 cm-OG
		(f) 5 × 5 cm opening grids/RM-5 cm-OG
2	Faced south to represent the worst scenario	(a) Full-size window opening/RM-FullSize-OG
		(b) 100 × 100 cm opening grids/RM-100 cm-OG
		(c) 50 × 50 cm opening grids/RM-50 cm-OG
		(d) 20 × 20 cm opening grids/RM-20 cm-OG
		(e) 10 × 10 cm opening grids/RM-10 cm-OG
		(f) 5 × 5 cm opening grids//RM-5 cm-OG
3	Faced northwest, representing a moderate/average case	(a) Full-size window opening/RM-FullSize-OG
		(b) 100 × 100 cm opening grids/RM-100 cm-OG
		(c) 50 × 50 cm opening grids/RM-50 cm-OG
		(d) 20 × 20 cm opening grids/RM-20 cm-OG
		(e) 10 × 10 cm opening grids/RM-10 cm-OG
		(f) 5 × 5 cm opening grids//RM-5 cm-OG

).

2.3. Measuring the Outdoor and Indoor Viability Hours for Natural Ventilation through the Air Temperature and Relative Humidity

Air temperature and RH should be involved in evaluating the natural ventilation potential. However, the comfort zone for Jeddah’s climate in terms of the air temperature ranges from 23 °C to 31 °C, as previously mentioned. The ideal RH should range from 30% to 70% based on the Adaptive Comfort Model in ASHRAE Standard 55, as well as the Method for Determining Acceptable Thermal Environment in Occupied Spaces in ASHRAE Standard 55 [31]. Therefore, the first step in this process was finding out how many hours per year of natural ventilation would represent a viable solution in light of the outdoor air dry-bulb temperature and the ideal RH; then, the process was repeated to compare the outdoor and indoor conditions. The study determined the potential hours of natural ventilation by utilizing the following formulas, which were related to the comfort zone range in terms of air temperature and the ideal RH for Jeddah’s climate.

The formula used for calculating monthly outdoor air temperature and RH-% hours in the range for the potential hours of natural ventilation:

= (≥23 °C to ≤31 °C) (30–70% RH)

The formula used to calculate the annual air temperature and RH-% hours in the range:

= (>23 °C to ≤31 °C) (30–70% RH)

Once the processes were completed and the expression formula used was inputted to create the relationship between DBT and RH, the number of potential hours for natural ventilation was determined. These processes are essential to such an investigation and verify that natural ventilation has potential in a specific location.

2.4. Identifying Rooms’ Thermal Comfort Level

The second method used to identify the room comfort involved the operative temperature, T_op, and air volumetric flow rate. The T_op combines air temperature and mean radiant temperature, making it a single value, depending on air velocity and radiation. The calculated values of T_op were used to find acceptable thermal comfort ranges for naturally conditioned spaces within 80% acceptability limits. The second part of identifying the thermal comfort was better understanding how the air volumetric flow rate affected the room’s comfort level; this required the measurement of the ventilation flow rate or air changes per hour. This study used the ventilation flow rate to evaluate the air flows entering the room from the external environment. According to Atkinson et al., four primary conditions help achieve building ventilation: ventilation rate, air direction, air distribution, and pattern [32]. It is essential to remember that all room models in this study used a cross-ventilation strategy, which means the inlet and outlet were positioned on opposite walls in the space, making a clear flow path between them. However, investigating the impacts of natural ventilation in buildings for a specific location requires looking at the wind resource, as it drives natural ventilation due to indoor/outdoor air force and density differences. Wind speed and direction are crucial factors for natural ventilation because they drive the air to flow from the windward building façade to the leeward façade, from high-pressure to low-pressure openings, which can change the thermal comfort level in any space. Based on Jeddah weather data, February has the highest average wind speed at 4.3 m/s, December records the lowest average wind speed at 2.5 m/s, and both months have an average air temperature of 25 °C. The annual average wind speed in Jeddah is 3.6 m/s from the north and west (sea side).

2.5. Predicted Mean Vote (PMV) Measurement Process

To determine the breadth of possible comfort measurements in occupied spaces, the predicted mean vote (PMV) was used to evaluate the predicted percentage dissatisfied (PPD). The PMV model combines six factors to determine thermal comfort in terms of the average response of people and uses heat balance principles. The factors include metabolic rates (Met), clothing insulation (Clo), air temperature (T), mean radiant temperature (MRT), relative air velocity (V), and relative humidity (RH) [31]:

PMV = f (T, RH, V, MRT, Met, Clo)

Based on the comfort sensation scale, a metabolic rate assumed to be 1.0 for seated/quiet activity, and a clothing level assumed to be 0.5 Clo or 1.0 Clo for typical summer/winter indoor clothing, within an air speed range considered comfortably pleasant to acceptable, air movement less than 1.0 m/s ranged from 0.25 m/s to 1.0 m/s. The measurement positions used in the room model were taken from the center of the room. This area was assumed to be an occupied area near both the rowshan and the room door within 1.2 m of the floor, which is the level of the occupants. According to the ASHRAE Standard 55 (2017)—Thermal Environmental Conditions for Human Occupancy, the operative temperature is calculated per the following formula:

T_op = A Ta + (1 − A) T_r

where T_op = operative temperature, Ta = average air temperature, and Tr = mean radiant temperature. A is a function of the average airspeed and may be selected from the following values: Va.

Va = <0.2 m/s → A = 0.5, Va = 0.2 to 0.6 → A = 0.6, Va = 0.6 to 1.0 m/s → A = 0.7

The PMV scale ranges between −3 and +3 and consists of seven points of thermal sensation; i.e., −3 cold, −2 cool, −1 slightly cold, 0 neutral (perfect condition), +1 slightly warm, +2 warm, and +3 hot. The general acceptable thermal environment ranges from −0.5 to +0.5 [25,31]. PMV calculations require knowing the metabolic rate and clothing insulation values. In residential models, the average metabolic rate is assumed to be 1 met, with 0.5 Clo thermal insulation provided by clothing. Additionally, thermal environment satisfaction for spaces may be determined using the PMV and PPD because they are based on an 80% occupant satisfaction rate. The PPD index predicts the percentage of occupants expressing dissatisfaction with a room’s thermal environment, and the 10% represents the percentage of people who feel dissatisfaction based on whole-body discomfort [25,31,33]. A PMV investigation was carried out on six models to assess the potential for natural ventilation in winter, compared the PMV ranges for all models with opened and closed doors for the minimum day (2 February) and a north orientation. The PMV investigation here was a brief study aimed at confirming the findings on natural ventilation during cooler months in Jeddah.

2.6. Computational Methods for Simulation Process

Once the data were identified using all methods previously described, a CFD analysis for different scenarios and conditions was developed to analyze the natural ventilation potential for each rowshan model; each model used 100 × 100 cm, 20 × 20 cm, and 5 × 5 cm opening grids. Table 1 presents different room scenarios, and

Table 2. Summary of input data for boundary condition settings used in the CFD simulation.

Simulation Setups	Input Data
Turbulence model	k-e model
Grid settings	Grid spacing (m): 0.08 Grid line merge tolerance (m): 0.01
Surface heat transfer	MicroFlo in IES-VE 2021 calculates the heat transfer coefficient using local temperature and velocity data around the surface
Discretization scheme	“Upwind” scheme

shows input data for the boundary conditions used in the CFD simulation. The analysis presented the relationship between rooms’ air temperatures and air velocity in section views. To examine the performance model in different seasons and assess natural ventilation potential through airflow and air temperature, different scenarios and conditions were divided into three groups based on orientation: north, south, and northwest. Each group also included three representative days (8 July, 16 May, and 2 February). By segregating the TMY3 weather information for Jeddah, it was possible to identify specific weather conditions for various days of the year. For instance, 8 July experienced the highest daily maximum dry-bulb temperature (DBT) and maximum dew point (DPT) temperature, which represent extreme conditions. On the other hand, 16 May represented the daily annual average condition, while 2 February was the day with the daily annual minimum temperature.

3. Results and Discussion

3.1. Natural Ventilation Viability for Indoor Conditions Improvement: Driven Airflow Effects

The purpose of evaluating indoor natural ventilation viability hours was to determine the improvement in natural ventilation achieved by driving airflow effects. According to the weather data, the first set of analyses detected that 2765 of 8760 h per year might have viable natural ventilation potential in Jeddah, which equal 32% annually. As can be seen in

Table 3. The potential hours of high natural ventilation were from November to April in Jeddah.

Monthly Outdoor Air Temperature and RH (% Hours in the Range 1)
Month	Percentage (%)	Hours (h)
January	56	416
February	47	312
March	41	307
April	57	410
May	29	217
June	17	120
July	11	79
August	0	2
September	6	45
October	15	114
November	64	459
December	38	284
Annual	32	2765

¹ The formula was used for calculating monthly outdoor air temperature and RH-% hours in the range for the potential hours of natural ventilation (≥23 °C to ≤31 °C) (30–70% RH).

, the month of November showed significantly more potential hours than the remaining months throughout the year, with the highest acceptable range of natural ventilation potential hours at 459 of 744 h per month (64%), followed by January, with 416 h (56%). In contrast, August had approximately 0% of the acceptable range of potential hours, as expected. These figures were based on outdoor air temperatures ranging from 23 °C to 31 °C and an RH range from 30% to 70%. The table compares six potentially high natural ventilation months in which approximately 50% of the hours in the entire month are considered possibly suitable for natural ventilation.

Data from

Table 4. Comparison of all the six room models’ performance with the outdoor condition.

Room Model	Latticework Grid (Opening Sizes)	Annual Air Temperature and RH (% Hours in Range 1)
		Indoor		Outdoor
A	One large opening	35.1%	3079 h	32%	2765 h
B	100 cm	35.3%	3090 h
C	50 cm	35.4%	3101 h
D	20 cm	35.9%	3143 h
E	10 cm	36.1%	3165 h
F	5 cm	42.3%	3704 h

¹ The formula was used to calculate the annual air temperature and RH-% hours in the range (>23 °C to ≤31 °C) (30–70% RH).

can be compared with Table 3, which demonstrates the annual natural ventilation potential for outdoor versus indoor conditions in the six room models. The table reveals that only the model with the minor opening grids (smallest inlet size: RM-5 cm-OG) exceeded 10%, with 939 more hours of difference than the outdoor condition for natural ventilation potential hours through the year. RM-5 cm-OG created a potential range for natural ventilation hours up to 42.3%, equal to 3704 of 8760 h per year.

The discussion of the results begins with the first set of questions, which were aimed at determining the number of hours that allow a viable solution for natural ventilation through the outdoor air temperature and RH in Jeddah. The most interesting aspect of the results indicates that a healthy house design can minimize air conditioning usage for several months in Jeddah, positively reflecting decreases in electricity consumption for a household. This study found that Jeddah’s weather has 32% (2765 h) hours per year of natural ventilation that could provide a viable solution. These results are consistent with Indraganti and Boussaa’s (2017) study, which found that buildings in most KSA cities do not need heating/cooling from November to March [16].

The next question investigated the impacts of rowshans in cooling new house designs by improving natural indoor ventilation. The findings also revealed that RM-5 cm-OG yielded remarkable results because it could increase the potential annual natural ventilation hours by up to 10%. Interestingly, integrating only one vernacular architectural element in the model design, the rowshan, raised the potential hours of annual natural ventilation by 10%. The more interesting question is what can a mix of other vernacular architectural elements do to enhance the model design? The results obtained from this data analysis back up the arguments in support of reducing electricity by minimizing the usage of air conditioners in Jeddah, but a responsible building design would be required to achieve that goal. Well-designed buildings for natural ventilation can more effectively provide comfort and satisfaction for users [29].

3.2. Addressing the Effect of Rowshans’ Size on Indoor Operative Temperature, Air Volumetric Flow Rate, and PMV

This section discusses the impact of the size of rowshans on indoor operative temperature, air volumetric flow rate, and PMV. It focuses on three main parts—the possibility of analyzing the energy efficiency of natural ventilation based on weather data, the effect of rowshans’ size, and the effect of rowshans’ orientation.

3.2.1. Analysis of Rooms’ Operative Temperature

An important in-depth component of this research related to thermal comfort demonstrated an exciting correlation between inlet size and the room operative temperature (T_op) and airflow. The analysis of rooms’ operative temperature included three different conditions based on three selected simulation days representing the extreme daily annual maximum (8 July), daily annual average (16 May), and daily annual minimum (2 February) in terms of DBT and DPT. Figure 6a compares the intercorrelations between the T_op in the six models and the outdoor temperature during the daily annual maximum (8 July). The plots indicate that the model with 5 × 5 cm opening grids on the extreme day reduces the peak air temperature during the daytime by almost 3 °C, but the T_op increases at nighttime by 3 °C. Moreover, Figure 6b compares the intercorrelations between the T_op in the six models and the outdoor temperature during the daily annual average (16 May). As illustrated in Figure 6b, the model with 5 cm perforations can reduce the peak air temperature in the daytime by almost 4 °C, but the T_op increases at nighttime by almost 4 °C. Figure 6c compares the intercorrelations between the six models’ T_op and the outdoor temperature during the daily annual minimum (2 February). As plotted in Figure 6c, the model with 5 cm perforations demonstrated that the peak air temperature in the daytime could be reduced by almost 5 °C, while the T_op during the nighttime was higher by almost 2 °C.

A possible explanation for the daily annual maximum (8 July) results might be that the rowshan solution is not very effective in the summer months, which have low natural ventilation potential because the comfort zone for Jeddah’s climate ranges between 23 °C to 31 °C. As seen in Figure 6a, the range is higher than 31 °C, which is the maximum limit of the comfort zone. However, Figure 6b indicates the rowshan solution can still achieve some effective design levels during the daytime for the daily annual average (16 May) because it reduces the air temperature by 2 °C to 4 °C, and during the nighttime, the air temperature is under 31 °C, which is the maximum temperature of the comfort zone. It is difficult to explain this result, but it might be related to a moderate natural ventilation potential for the rowshan solution during the average time (median period) through the year because it has some potential during the nighttime.

As seen from the data in Figure 6c, the rowshan solution is remarkably effective during the daily annual minimum (2 February) (cool months) because it keeps the air temperature under 28 °C during the daytime and higher than 22.5 °C during the nighttime. What stands out in this figure is the high natural ventilation potential during the cool months in Jeddah from November to March, which may help reduce high electricity consumption due to the use of AC systems to cool houses. That is a significant result, because it supports this study’s primary objective: determining how rowshans can help natural ventilation keep the air temperature in a room with the comfort zone range of 23 °C to 31 °C for that specific climate. These findings are consistent with those obtained by Babsail and Al-Qawasmi (2015), Alothman and Akçay (2017), and Di Turi and Ruggiero (2017): rowshan not only provides privacy but also allows natural ventilation, regulates airflow, decreases temperatures, and minimizes the cooling load in indoor spaces, making them more comfortable [19,20,22].

3.2.2. Analysis of Rooms’ Air Volumetric Flow Rate

This section evaluates air volume/volume flow rate/air changes per hour (ACH). It is important to note that all room models in this study had a cross-ventilation strategy, which means the inlet and outlet were positioned on opposite walls, creating a clear flow path between them. The following three charts show the volume flow rate in Figure 7a–c. The daily annual maximum (8 July), average (16 May), and minimum (2 February), comparing all model performances with wind speed, demonstrate that the model with 5 cm perforations could keep the airflow inside the room in an acceptable range in terms of air volume regarding natural ventilation, under 20 ACH as a maximum, with air velocity below 1.0 m/s. Based on the comfort sensation scale, air velocity that ranges between 0.25 m/s and 1.0 m/s is considered comfortably pleasant to acceptable air movement.

The volume flow rate from the simulation results yielded enormous numbers, which were attributable to the levels of the natural ventilation factors compared to the ventilation air requirements provided by active systems. The ventilation air requirements for one room with a floor area between 139 and 279 m² should be 21 L/s or 45 cfm [34]. According to the ASHRAE Standard 62.2—Ventilation and Acceptable Indoor Air Quality in Residential Buildings (2016), the ventilation air requirements for one room with floor area less than 47 m² should be 14 L/s [35]. A possible explanation for this may be the rule of thumb regarding wind velocity and the inlet/outlet opening; inlet and outlet windows should be the same size in most cases.

However, if the windows cannot be the same size, the inlet window should be smaller than the outlet window and face the prevailing wind direction to maximize the air velocity movement and the differential pressure across the room [28]. It is crucial to understand pressure differences through building openings. Positive to negative differences create wind-driven airflow, especially for a cross-ventilation strategy. The wind pressure on a building relies on three main factors: the wind direction, the wind speed, and the form of the building [28]. Another explanation for this is that air change rate or volume flow rate may increase with increasing inlet area. The data presented in the above charts reflect a relationship between the inlet size and volume flow rate; by increasing the inlet area, the volume flow rate increases. This result may be explained by the fact that the total opening size of the inlet area for a rowshan with 5 cm perforations is 2.0 m², which is equal to the outlet area (opening door). Therefore, this places the volume flow rate in an acceptable range. In contrast, the other models had larger inlet areas ranging between 3.8 m² and 7.5 m², which explains the high ACH/volume flow rate related to the other models.

3.2.3. Predicted Mean Vote (PMV) Investigation Focused on the Daily Annual Minimum (2 February) Due to the Higher Potential for Natural Ventilation in Jeddah

Further distinguishing between these six models’ possibilities for natural ventilation potential in winter, a PMV investigation was employed. Figure 8a,b compare the PMV ranges for all models with opened/closed doors through the minimum day (2 February) and with a north orientation. This study found that comparison models were effective in maintaining comfortable room temperatures during the coldest months of the year in Jeddah, reducing the need for excessive AC use. The PMV investigation focused on this period. The line charts indicate that both rooms with opened/closed doors could provide PMVs ranging from −0.4 to +1.5, which, based on 80% occupant satisfaction rates, can be considered neutral to slightly warm according to ASHRAE Standard-55, 2017. However, the PMV finding provides clear evidence that RM-5 cm-OG has greater potential than the remaining models to achieve indoor thermal comfort for that location. RM-5 cm-OG with an open door had a PMV range from −0.4 to +0.8 and a closed-door range from +0.1 to +0.3, and this result demonstrates an acceptable thermal environment for general comfort based on the PMV scale. On the PMV scale, 0 symbolizes the ideal thermal comfort, and the acceptable thermal environment for general comfort includes a PMV between −0.5 and +0.5.

What is curious about this PMV result in this study is the observed correlation between the findings of the different phases measuring the viability of natural ventilation potential. However, the current study’s findings do not support a portion of the previous research by Elnaklah et al. (2021), which claimed that the PMV model failed to predict the thermal sensation for 94% of occupants in the Middle East. A possible explanation for this might be that, at the outset, spaces need to be designed for natural ventilation not only using the international and local standards for green building codes. Green building codes help mitigate energy demand for space cooling, and well-designed buildings for natural ventilation can provide greater comfort than mixed-mode buildings. These findings are consistent with Passe and Battaglia (2015) and Rasheed and Byrd (2018). Therefore, green building codes and well-designed buildings for natural ventilation should be integral to any building’s performance design process.

3.3. Rowshan CFD Performance Analysis

In the follow-up phase of this study, the results for potential hours related to these processes were investigated. As previously mentioned, different climate conditions were used in this study, including three different representative days and three different room orientations.

3.3.1. Rowshan Performance with North Orientation

Data from

Table 5. Outdoor and indoor conditions with a north orientation for the daily annual maximum (8 July) at noon in vertical section view.

Outdoor Conditions with North Orientation for Daily Annual Maximum (8 July) at Noon
DBT: 39 °C		DPT: 16 °C			RH: 27%		Wind Speed (WS): 5.10 m/s			Wind Direction (WD): NW
Indoor Conditions with North Orientation for Daily Annual Maximum (8 July) at Noon
100 × 100 cm Opening Grids				20 × 20 cm Opening Grids					5 × 5 cm Opening Grids
DBT: 38 °C DPT: 17 °C RH: 28%	Top: 38 °C ACH: 126		MRT: 36.6 °C PMV: +3 (hot)	DBT: 38 °C DPT: 17 °C RH: 28%		Top: 37 °C ACH: 99		MRT: 36.4 °C PMV: +3 (hot)	DBT: 36 °C DPT: 16 °C RH: 31%		Top: 36 °C ACH: 11	MRT: 35.3 °C PMV: +3 (hot)
Temperature Contour and Velocity Vector Field in Section View

,

Table 6. Outdoor and indoor conditions with north orientation for daily annual average (16 May) at noon in vertical section view.

Outdoor Conditions with North Orientation for Daily Annual Average (16 May) at Noon
DBT: 36 °C		DPT: 19 °C			RH: 37%			Wind Speed: 5.10 m/s			Wind Direction: WNW
Indoor Conditions with North Orientation for Daily Annual Average (16 May) at Noon
100 × 100 cm Opening Grids				20 × 20 cm Opening Grids					5 × 5 cm Opening Grids
DBT: 36 °C DPT: 19 °C RH: 38%	Top: 35 °C ACH: 101		MRT: 33.5 °C PMV: +3 (hot)	DBT: 35 °C DPT: 19 °C RH: 38%		Top: 35 °C ACH: 81	MRT: 33.2 °C PMV: +2.98 (~hot)		DBT: 33 °C DPT: 19 °C RH: 43%	Top: 33 °C ACH: 10		MRT: 31.6 °C PMV: +2.58 (~hot)
Temperature Contour and Velocity Vector Field in Section View

and

Table 7. Outdoor and indoor conditions with north orientation for daily annual minimum (2 February) at noon in vertical section view.

Outdoor Conditions with North Orientation for Daily Annual Minimum (2 February) at Noon
DBT: 30 °C		DPT: 11 °C			RH: 33%			Wind speed: 2.10 m/s			Wind Direction: N
Indoor Conditions with North Orientation for Daily Annual Minimum (2 February) at Noon
100 × 100 cm Opening Grids				20 × 20 cm Opening Grids					5 × 5 cm Opening Grids
DBT: 28 °C DPT: 11 °C RH: 33%	Top: 27 °C ACH: 39		MRT: 26 °C PMV: +1.29 (~slightly warm)	DBT: 28 °C DPT: 11 °C RH: 34%		Top: 27 °C ACH: 31	MRT: 25.8 °C PMV: +1.24 (~slightly warm)		DBT: 26 °C DPT: 11 °C RH: 38%	Top: 25 °C ACH: 8		MRT: 24.7 °C PMV: +0.94 (~slightly warm)
Temperature Contour and Velocity Vector Field in Section View

regarding the north orientation can be compared with

Table 8. Outdoor and indoor (RM-5 cm-OG) conditions with south orientation for the three representative days in vertical section view.

Outdoor Conditions with South Orientation
Daily annual maximum (8 July) at noon			Daily annual average (16 May) at noon				Daily annual minimum (2 February) at noon
DBT: 38 °C DPT: 16 °C RH: 27%	WD: NW WS: 5.10 m/s		DBT: 36 °C DPT: 19 °C RH: 37%		WD: WNW WS: 5.10 m/s		DBT: 29 °C DPT: 11 °C RH: 33%	WD: N WS: 2.10 m/s
Indoor Conditions—Section of the 5 × 5 cm Opening Grid Model (RM-5 cm-OG)
DBT: 36 °C DPT: 16 °C RH: 31%	Top: 36 °C ACH: 11	MRT: 35.4 °C PMV: +3 (hot)	DBT: 33 °C DPT: 19 °C RH: 43%	Top: 33 °C ACH: 11		MRT: 31.6 °C PMV: +2.58 (~hot)	DBT: 26 °C DPT: 11 °C RH: 38%		Top: 25 °C ACH: 9	MRT: 24.5 °C PMV: +0.90 (~slightly warm)
Temperature Contour and Velocity Vector Field in Section View

and

Table 9. Outdoor and indoor (RM-5 cm-OG) conditions with northwest orientation for the three representative days in vertical section view.

Outdoor Conditions with Northwest Orientation
Daily annual maximum (8 July) at noon			Daily annual average (16 May) at noon			Daily annual minimum (2 February) at noon
DBT: 39 °C DPT: 16 °C RH: 27%	WD: NW WS: 5.10 m/s		DBT: 36 °C DPT: 19 °C RH: 37%	WD: WNW WS: 5.10 m/s		DBT: 29 °C DPT: 11 °C RH: 33%	WD: N WS: 2.10 m/s
Indoor Conditions—Section of the 5 × 5 cm Opening Grid Model (RM-5 cm-OG)
DBT: 37 °C DPT: 16 °C RH: 31%	Top: 36 °C ACH: 11	MRT: 35.4 °C PMV: +3 (hot)	DBT: 33 °C DPT: 19 °C RH:43%	Top: 33 °C ACH: 11	MRT: 31.7 °C PMV: +2.60 (~hot)	DBT: 26 °C DPT: 11 °C RH:38%	Top: 25 °C ACH: 8	MRT: 24.7 °C PMV: +0.94 (~slightly warm)
Temperature Contour and Velocity Vector Field in Section View

regarding the south and northwest orientations, demonstrating that the situation changed in the cooler months and the room temperature remained in comfortable ranges. The tables below compare the results obtained from the preliminary analysis of the CFD simulations. They summarize the potential for the 5 × 5 cm opening sizes to reduce air through natural ventilation and provide thermal comfort to indoor spaces. The discussion of the results begins with all of the parameters in the three models, which showed typical or minor differences in air temperature degrees depending on the representative days. Table 5 highlights the slight differences between the outdoor and indoor conditions for the models with 100 × 100 cm, 20 × 20 cm, and 5 × 5 cm opening grids on the daily annual maximum (8 July) at noon. For example, IAT was lower than outdoor DBT for all three opening-grid models; the differences were 1 °C, 1 °C, and 3 °C, respectively. Accordingly, rowshans with 100 × 100 cm, 20 × 20 cm, and 5 × 5 cm opening grids alone would not be a solution to improve natural ventilation through design for the daily annual maximum (8 July) at noon.

Again, as indicated in Table 6, most parameters yielded slight differences in temperature for the daily annual average (16 May) at noon, depending on the opening grid sizes. From these data, it can see that RM-5 cm-OG had an IAT 3 °C lower than outdoors. Furthermore, no significant differences between the outdoor and indoor conditions for the other parameters were found. Therefore, rowshans with 100 × 100 cm, 20 × 20 cm, or 5 × 5 cm opening grids alone are not an adequate solution for improving natural ventilation through design for the daily annual average (16 May) at noon. As shown in Table 7, most of the parameters had essential differences in temperature degrees for the daily annual minimum (2 February) at noon. The differences between all of the parameter results were significant. For example, the IAT reductions for rowshans with 100 × 100 cm, 20 × 20 cm, and 5 × 5 cm opening grids were 2 °C, 2 °C, and 4 °C, respectively. Surprisingly, RM-5 cm-OG recorded the best reduction for most parameters, such as IAT, T_op, and PMV. Additionally, the ACH in RM-5 cm-OG had an acceptable air volume flow rate when compared with the other models.

Another crucial finding regarding airflow movement was a correlation between high temperature and high air volume. In other words, in relation to the rule of thumb, the air holds heat, and we are dealing with a hot-dry climate where more air is coming into the internal space related to a high temperature and vice versa. These results of the CFD analysis further support the idea that a rowshan with 5 × 5 cm opening grids alone might be an effective solution to improve natural ventilation through design and reduce energy consumption for the daily annual minimum (2 February). However, the diagrams and simulation data indicate that the north side had the most positive reduction in temperature degrees in term of RM-5 cm-OG. Table 5, Table 6 and Table 7 demonstrate the impacts of a north orientation on the internal space for the three rowshan models (100 × 100 cm, 20 × 20 cm, and 5 × 5 cm opening grids). In addition, they reveal the IAT and air movement differences for the representative days.

3.3.2. Performance of Rowshan with Minor Perforations with South Orientation

Table 8 shows the impacts of a south orientation on the internal space for RM-5 cm-OG for all representative days, and it presents the differences in air temperature and air movement. The RM-5 cm-OG was selected due to the high potential for natural ventilation, as presented in Table 5, Table 6 and Table 7.

3.3.3. Performance of Rowshan with Minor Perforations with Northwest Orientation

Table 9 shows the northwest orientation’s impacts on the internal space for RM-5 cm-OG for all representative days, and it presents variations in both air temperature and air movement. It appears from the results that the northwest orientation created no differences between the two conditions (outdoor and indoor).

The questions raised about CFD analysis related to airflow within rowshans are discussed in this section. The CFD analysis data are summarized in Table 5, Table 6, Table 7, Table 8 and Table 9. The results provide more explanations about the thermal comfort inside the room with the high-volume flow rate. The most interesting aspect of these tables and graphs is that a large inlet area leads to greater air volume and air velocity plus more heat. Additionally, large inlet areas increase the air change rate, and small inlet areas decrease the air change rate due to lower air volume and air velocity, which causes less heat. As the CFD simulation results show, the smaller inlets cause less air to come into a room with a lower temperature and vice versa. The larger inlet allows for more air with a high temperature and more air movement (air velocity). As previously noted, this study deals with a hot climate, and the air carries heat, so when there is a large amount of outdoor air coming into a space, it holds more heat. Therefore, allowing more air to enter a room means allowing more heat to enter the room, while less air entering the room allows less heat to enter.

Thus, reducing inlet areas generally allows for decreasing air change and volume flow rates. The smallest grid model was the only model that could keep the volume flow rate in an acceptable range from 8 to 11 ACH, including a PMV range below +0.95 in the afternoon of the daily annual minimum (2 February). Large inlet areas allow for greater air volume and air velocity in the room, and greater air volume is generally accompanied by more heat, depending on the outdoor weather conditions. In contrast, small inlet areas allow less air volume and less air velocity, leading to less heat entering the room. Therefore, the rowshan model with minor perforations shows better results for the thermal comfort range for naturally ventilated spaces in a hot-dry climate such as Jeddah, and the CFD analysis’s current findings support this.

4. Conclusions

This investigation sought to address the impacts of the rowshan, a cultural vernacular element, on new house designs in hot-dry climates like that of Jeddah. We combined four different methods to reduce active cooling systems’ usage through natural ventilation potential and, as a result, improve thermal comfort conditions. The aim of these methods was to analyze the feasibility of assessing the energy efficiency of natural ventilation based on weather data. This involved examining the impact of rowshans’ size and orientation on indoor operative temperature, air volumetric flow rate, PMV, and the performance of rowshans. The focus was on how the size of the rowshans affects the indoor environment and the effectiveness of rowshans in terms of both size and orientation. This study examined the impacts of six types of rowshan in empty rooms through detailed analysis to increase the thermal comfort level and reduce energy consumption throughout the year when rowshans are incorporated into single-family home designs in Jeddah, Saudi Arabia. Each rowshan model had differently sizeed holes/openings, including opening grids such as full-size window openings, 100 × 100 cm, 50 × 50 cm, 20 × 20 cm, 10 × 10 cm, and 5 × 5 cm.

The following contributions emerged from the present study. First, the natural ventilation potential hours in Jeddah were estimated at 2765 h, amounting to 32% per year through the cooler months from November to April. The second significant finding was that the rowshans with smaller opening grids could keep the room temperature in the comfort zone range from 23 °C to 31 °C through the cooler months for this hot-dry climate based on the Adaptive Comfort Model in the ASHRAE Standard 55 (2017). It was also shown that the model with the smallest grid (RM-5 cm-OG) resulted in 939 more potential viable solution hours per year for natural ventilation, equal to a 10% increase compared to the rest of the models. Thus, this study identified the capability of the model with the smallest grid to improve thermal comfort in a space and lower the daytime air temperature at noon from 2 °C to 5 °C, depending on the seasons and rowshan orientations. Another significant finding to emerge from this study was that in order to keep indoor airflow and air volume within an acceptable range for indoor thermal comfort through natural ventilation, the rowshan perforation sizes are recommended to be equal to or around 5 × 5 cm for the specific location under consideration.

Furthermore, the rowshan, as an essential vernacular architectural element, might be an effective solution for Jeddah’s new houses, helping households minimize the usage of AC systems to cool their houses and aiding the city in reducing energy consumption and emissions and regenerating the environment. That is the vital strength of the present work, which addressed the potential hours of natural ventilation in Jeddah, as well as how those hours could be increased by integrating only one local architectural element in house designs.

However, in terms of limitations, this study’s scope was focused on location, climate, and cultural design and it dealt with the essential validation parameters for ventilation strategies: temperature, humidity, and air change rates. Dealing with natural ventilation and CFD analysis presents limitations because the weather cannot be predicted accurately. It is possible that these methods and results are only valid for Jeddah’s new houses and specific conditions, such as the cultural design, may not be necessary for all the hot-dry climate regions. Further studies need to be carried out in order to validate the simulation model’s credibility and compare the results with experimental measurements of real systems to determine whether the model does/does not reflect reality. The authors collected real weather data from multiple existing houses in Jeddah by utilizing data-logger devices for a period of two to three years. The authors’ plan to present a comparison between actual weather data and simulated data in their future work. This research has thrown up many questions in need of further investigation and shown the benefit of CFD analysis for integrating other vernacular architectural elements to cool houses, which is strongly recommended. It would be interesting to assess the effects of airflow through different essential vernacular architectural elements and then compare it or integrate it with the rowshan findings.