Riyadh city is the fastest growing city in Saudi Arabia. The rapid urban growth that happened recently in Riyadh was not based on the traditional urban planning principles, which have been established and applied for the city development process. The imported building regulations have created a new urban structures and street patterns. The contemporary urban form in Riyadh city is based mainly on traffic and economic consideration with the neglect of environmental dimensions. This research aims to examine the impacts of building regulations on the thermal performance of residential buildings in Riyadh city, with the ultimate goal of establishing planning guidelines that consider the environmental conditions of the city. The methodology adopted for achieving the aim of this study consists of two phases. First, the literature related to building regulations development in Riyadh, as of 2018, was reviewed. Second, buildings energy simulation was conducted to examine the thermal performance of the typical current status of residential building blocks in Riyadh city, and then several changes to building regulations were made to investigate their impacts on the thermal performance of buildings. The results showed that the impacts of Riyadh building regulations on the thermal performance of residential buildings differ across the evaluated cases. The ratio of building height to street width, urban block street orientation, and building orientation are the main factors affecting thermal performance of buildings within urban block. The study also concludes that adjusting the ratio of building height to the distance between buildings could have a significant impact in reducing cooling loads. This study will help policy makers, planners and designers to investigate the shortcoming in the current building regulations.
Global warming and climate change anthropogenic greenhouse emission, made it mandatory to make immediate initiatives to avoid sever consequences for future generations. Buildings are responsible for releasing 50% of the atmosphere emissions and 70% of sulphur dioxide into the atmosphere. They are also accounting for consuming 40% of the world energy and 40% of the total GHG emissions [
In Saudi Arabia, electricity consumption has rabidly increased at a rate of 7% [
As a part of the Paris agreement of climate change [
established in 2010 to reduce energy demand for all sectors including buildings through regulations, education and audits [
Furthermore, there is a dramatic increase in the population of Riyadh in the last decades, it has increased from an estimated of 14,000 in 1902, to 666,480 in 1974, to reach more than 2.8 million in 1992, more than 4.8 million in 2004, 5.25 million in 2010 and to more than 6.5 million in 2016 [
Urban pattern, building orientation and shading are some of the traditional techniques used to reduce the impact of local climate and to improve the thermal comfort inside buildings in desert environments [
Riyadh is located in the eastern part of the Arabian Peninsula, between latitudes 24˚ and 28˚N and longitudes 44˚ and 48˚E, and approximately 600 metres above sea level. It has a hot arid climate with extreme difference in temperatures between summer and winter. The temperature ranges from (33 - 45)˚C in summer, and from (0 - 20)˚C in winter [
Riyadh was affected by the huge scale of building program in two ways. First, a new system of transportation was introduced, where motor vehicle became the only modern transportation system used in Riyadh. Secondly, the size of Riyadh was stretched rapidly and its physical growth was defined [
The development of zoning regulations in Saudi Arabia comprises three main phases. First, the development of regulations before 1930 when the first master plan of Riyadh was developed. Second, regulations and master plan of Riyadh developed by Doxiadis, which confirmed the setback requirement and the minimum lot size standards and accompanied by a documented guidelines and planning regulations. The third phase includes the development of zoning regulations which were modified by the new proposed master plan of Riyadh [
This study aims to evaluate the impacts of building regulation on the thermal performance of residential housing in Riyadh with the ultimate goal of reducing energy consumption. There are three types of residential buildings in Riyadh: Villa (detached single unit), attached unites (duplexes) and apartments. According to Alaidroos and Krarti [
The DesignBuilder software was developed by DesignBuilder Software Ltd, United Kingdom. It is a popular software tool used for modelling and simulating energy efficiency in buildings [
Residential building’s lands in Riyadh vary in depth and frontal elevation. In a study supported by Riyadh Development Authority (2006), the results showed that the average depth of a single residential land area is 30 m, land area is 30 m, the average frontal elevation is 20 m, and the average area in Riyadh is 600 m2. For this study, the typical base-case housing unit was developed with physical characteristics illustrated in
Physical characteristics of the prototype residential building is shown in
After assessing the thermal performance of the base-case building, the simulation results was compared to that of the performance of same building when being in the middle of several cases of urban block that have urban dimensions based on Riyadh building regulations as shown in
The study examined the impact of building regulations on the thermal performance and energy consumption of residential buildings. It investigated three main parametres which are:
· The ratio of building height to street width (H/W).
· Street orientation.
· The building orientation.
| Base Case Building | |
|---|---|
| Location | Riyadh (24˚N Latitude, 46˚E Longitude, and 600 m above sea level) |
| Number of floors | Two and the third recessed floor |
| Ceiling height | 3.5 m |
| Window to wall ratio | 12% |
| Type of window glass | Single glazing |
| Interior walls construction | Concrete block (200 mm). |
| Exterior walls construction | Concrete block (200 mm). |
| Interior walls finishes | Plaster (20 mm). |
| Roof construction | Concrete roof slab |
It should be noted that the ratio of building height to spacing between adjacent buildings (H/D) equals (1.87) in all simulation cases according to Riyadh building regulation which defined the minimum rear and side setback to not be less than 2 m, and building height to not be more than two floors and the third recessed floor. The impacts of the mentioned parametres on building energy behavior and annual cooling loads were investigated. Energy simulation was performed on stand alone base-case and while in the middle of urban block. The study included the following four main street widths which represent the most common street widths in Riyadh: 12 m, 15 m, 20 m, and 25 m. According to the current building regulation of Riyadh, the rear and side setbacks should not be less than 2 m, so it was assumed that the distance between adjacent buildings is 4 m. In terms of the frontal setback, the building regulation stated that it should not be less than fifth of the width of the main street, so it was assumed that the distances between buildings located in the parallel sides of the street including street width and frontal setback are 16.8, 21, 28 and 35 m, for the following values of street width 12, 15, 20 and 25 m respectively. The study included two basic street orientations, four building orientations and four different height to width ratios.
According to the above assumptions, simulation analysis consists of the following cases: urban blocks with their street main axis running north to south, and urban blocks with their street main axis running east to west.
For each of the above synarios, the following H/W ratios are tested: 0.44, 0.35, 0.26 and 0.2. Taking into account the four main building orientations, we come up with sixteen urban block alternatives which will be tested and compared with that of four synarios of reference building in case of being free standing and oriented to the four main orientations. Urban block configuration investigated in the study are shown in
The study examined annual cooling load, Incident solar radiation and hourly solar gain for the base-case building and the corresponding building within urban block. As a prelimnary simulation test, it was shown that the impact of the value 0.44 of (H/W) had the highest impact on the thermal performance of the building within urban block, with a slight difference in the impacts of the other values (0.35, 0.26. 0.2). So, the value of (H/W = 0.44) was taken as a representative value in the statistical analysis.
| (H/W) Ratio | Urban Block Section | North-South street | East-West street |
|---|---|---|---|
| 0.44 | |||
| 0.35 | |||
| 0.26 | |||
| 0.2 |
The thermal performance of the free-standing base case building was first assessed, then its predicted performance was compared to the thermal performance of the same building within sixteen cases of the urban block to investigate the impact of adjacent buildings on the performance of the building.
The thermal performance of the base-case of the free standing building was evaluated in case of facing the main four orientations: north, south, west and east by using the energy simulation tool. To evaluate the thermal performance of the building, an accurate hourly weather data is important to determine the solar heat gain received by the building. Therefore, an hourly weather file (epw) for Riyadh was imported from Energy Plus website and used as the weather data in the simulation. Because air conditioning is the main contributor for high energy consuming in residential buildings in Riyadh, the study mainly focuses on the evaluation of the cooling loads over the whole year. The simulation was run in the four main orientation: north, south, west and east, while the letters (B-N, B-W, B-S, B-E) was used to stand for the base-case stand alone building when being oriented to north, west, south and east respectively.
The simulation results showed that annual cooling load reached 64,267, 62,190, 64,240 and 62,187 kWh for (B-N), (B-W), (B-S) and (B-E) respectively. The results indicated that cooling load starts from 0 kWh in all base-case synarios during winter months (January) up to approximately 14,319, 13,902, 14,321 and 13,906 kWh during the middle of the summer (August) in (B-N), (B-W), (B-S) and (B-E) respectively. July and August are the hottest months in Riyadh, as a result, the cooling load has increased significantly due to the high temperature values. On the other hand, January and February are the coldest months in Riyadh, with temperature ranges between 0˚ to 20˚. It can be noted that in case of (B-N) and (B-S), the potential of solar radiation is very high because the long east and west facades are directly exposed to the sun, and this explains why there is a significant increase in cooling loads especially in summer months in compared to (B-W) and (B-E) where the long south and north facades are not exposed to the sun. Monthly cooling loads of (B-N), (B-W), (B-S) and (B-E) is shown in
The simulation results also indicated that the incident solar radiation for (B-N) and (B-S) reached 59,533 and 58,576 kWh respectively, which is comparatively higher than the amount of incident solar radiation received by (B-W) and (B-E) which reached 56,377 and 58,576 kWh respectively.
The same base-case building was evaluated by the same method of simulation within an urban block. About sixteen cases of urban block with four different street widths and two street direction (north-south, east-west) were modelled and simulated for cooling loads. A comparison of the annual cooling loads of the middle building and the corresponding base-case building was performed. The results of the simulation demonstrated that there is a significant impact of adjacent shadings on cooling loads as shown in
As mentioned before, the annual cooling load (B-N) when being free-standing without adjacent shading was 64,267 kWh, while when being in the middle of the (east-west) street urban block, with H/W ratio of 0.44 equals 57,072 kWh. The difference in the annual cooling load is 7195 kWh, which represents a reduction of (11.2%). It can be noted that there is a slight difference in the reduction when H/W ratio ranges between (0.44 - 0.2), because the reduction in cooling load is mainly caused by shading effects from the adjacent buildings located on the west and east side of the building which lead to a reduction of heat gain, thus, annual cooling load, while the effect of shading from buildings located on the opposite north side of the street is negligible, because the distance W is relatively longer than the distance D. Furthermore, the potential of incidence solar radiation on eastern and western facades is very high in comparison to the northern one. The results of the simulation showed that changing street orientation from east-west to north-south leads to a slight reduction in annual cooling load. The annual cooling load for (B-W) is 62,190 kWh, while that of the same building when being simulated in the middle of the north-south street urban block, with H/W ratio of 0.44 is 58,769 kWh. The difference in annual cooling load is 3420 kWh, which represents a reduction of 5.5% as shown in
The results also indicated that there is a significant impact of adjacent shadings on the incident solar radiation. The difference in the internal gain of the north facing building within urban block with east-west street direction when (H/W = 0.44) reached 32,212 kWh, which represents a percentage reduction of 54%. However, when changing street direction to north-south, the percentage reduction of incident solar radiation of the west-facing building reached 23,132 kWh, which represents a percentage reduction of 41% as shown in
Hourly solar heat gain was also investigated in the study. The difference in the amount of heat gain increases during the early and late hours of the day when the sun position has low latitude and the ability of adjacent buildings to block incident solar radiation become very high as shown in
In the previous simulation cases, urban dimensions were set according to Riyadh building regulation (As of 2018). This part of the study addresses the impacts of urban dimensions modification on the thermal performance of buildings. Two types of modification will be evaluated: height to adjacent building spacing ratio (H/D) and the height of west and north adjacent buildings.
According to 2018 Riyadh building regulations, the minimum side and rear setbacks should be 2 m, resulting a H/D ratio of 1.87. In this part of the study, the following H/D ratios was examined, 0, 0.93 and 3.75 which represents the following values of distance between adjacent buildings (D): 0 m, 8 m. and 2 m as shown in
The results of the simulation demonstrate that there is a significant impact on the building cooling load when the building is attached from two sides in a linear fabric (H/D = 0) as shown in
The results also indicated that the difference in annual cooling loads reached 17,699, 11,934, 16,828 and 11,466 kWh for north, west, south and east building respectively. In urban block with east-west street, the percentage of reduction in annual cooling load of the north-facing building was 27.5%, in comparison to the reduction percentage of 11.2% when H/D ratio equals 1.87. Buildings located adjacently to the east and west side of the north-facing building can offer a substantial reduction of solar heat gain and consequently a reduction of annual cooling load. However, in terms of urban block with north-south street, the results indicated that the reduction percentage in cooling loads of the west facing building was 19.1% in comparison to the reduction percentage of 5.5% when H/D ratio equals 1.87 as shown in
Under this situation, the incident solar radiation was affected significantly. The results indicated that the difference in incident solar radiation reached 48,761, 38,440, 42,162 and 37,566 kWh for north, west, south and east building respectively. The percentage of the reduction in incident solar radiation of the north facing building within urban block with east-west street, reached 81.9%, while the reduction percentage of that when H/D ratio equals 1.87 was only 54.1%. In case of urban block with north-south street, the percentage of reduction in incident solar radiation in the west facing building was 68.1% as shown in
The results also indicated that there is a significance difference in the hourly solar heat gain of the building during the day hours. In urban block with eastwest street, the hourly solar heat gain of the north faced building was significantly reduced during the early and late hours of the day, where the sun position has low latitude and the ability of east and west adjacent buildings to block incident solar radiation become very high as shown in
Changing height to distance between adjacent building ratio (H/D) to 3.75 results in considerable changes in annual cooling loads and incident solar radiation as shown in
The percentage of the reduction in annual cooling loads of the north facing building in the urban block with east-west street equal 15.4%, while the reduction percentage of that when H/D ratio equals 1.87 was only 11.2%. This is because buildings located to the east and west side of the building offer substantial shading of diffuse solar radiation leading to reduce the amount of heat gain. In terms of urban block with north-south street, the results indicated that the reduction percentage in cooling loads of the west facing building was 7.81% in comparison to the reduction percentage of 5.5% when H/D ratio equals 1.87 as shown in
In terms of incident solar radiation, the results indicated that the difference in incident solar radiation reached 42,576, 30,177, 32,930 and 30,757 kWh for north, west, south and east building respectively. In urban block with east-west street, the percentage of the reduction in incident solar radiation of the north facing building reached 71.5%, while the reduction percentage of that when H/D ratio equals 1.87 was only 54.1%. In case of urban block with north-south street, the percentage of reduction in incident solar radiation in the west facing building was 53.5%.
Heat gain during day hours was also rescued when (H/D) ratio equals 3.75. A comparison of the hourly solar heat gain of the north facing building in the urban block with east-west street when H/D ratio equals 3.75, to the hourly solar heat gain of (B-N) is plotted in
On the other hand, changing H/D ratio to 0.93 had a negative impact on annual cooling loads and incident solar radiation in comparison to the ratio of 1.87. The difference in annual cooling loads of the building within urban block reached 4112, 2016, 3884 and 1941 kWh for north, west, south and east building respectively in comparison to the corresponding base-case building. The percentage of the reduction in annual cooling loads of the north facing building in the urban block with east-west street reached only 6.3%, however, this value is less than the reduction percentage of (11.2%) when H/D ratio equals 1.87. This is due to the decreased amount of shadings casted by the buildings located to the east and west side of the building, and consequently the increased amount of heat gain. The pattern of reduction in annual cooling loads of the west facing building was similar to that of urban block with north-south street. The percentage of reduction in annual cooling loads of the west facing building in urban block with north-south street reached 3.2%, in comparison to the percentage reduction of 5.5% when H/D ratio equals 1.87 as shown in
The difference in incident solar radiation reached 19,433, 13,742, 15,718 and 13,877 kWh for north, west, south and east building respectively. The percentage of the reduction in incident solar radiation of the north facing building reached 32.6% in urban block with east-west street was, while the reduction percentage of that when H/D ratio equals 1.87 was 54.1%. However, changing the street direction of the urban block to north-south direction resulted in a percentage reduction of 24.3% for the west facing building.
The hourly solar heat gain of the building was also affected negatively during the early and late hours of the day when H/D ratio equal 0.93 in comparison to the impact of the ratio 1.87, as shown in
With the above in mind, a comparison of the percentage reduction of annual cooling loads in urban block with the following simulated H/D ratios: 0, 3.75 and 0.93 to the percentage reduction of the north building when H/D ratio equals 1.87 is plotted in
The number of building floors allowed by Riyadh building regulations is two floors and the third recessed floor which results in urban blocks with uniform buildings heights. In this part of the study, the thermal performance of the building was evaluated when changing the height and number of floors of adjacent buildings. Two cases was included in the study, the first case is changing the height of the western adjacent building to 4 floors in case of urban block with east-west street, while the second phase is changing the height of the southern adjacent building to 4 floors in case of urban block with north-south street. In urban block with east-west street and four-floor western adjacent building, the simulation results indicated that the reduction of annual cooling load of the north facing building reached 13.5%, while the reduction of that when the western adjacent building has two floors was only 11.2%. It is noted that the pattern of reduction in annual cooling load in urban block with north-south street, and four-floor northern adjacent building is similar to that of urban block with east-west street. The simulation results indicated that the percentage reduction of annual cooling load of the west facing building when the southern adjacent building has four floors reached 6.7% while the reduction of that when the southern adjacent building has two floors was 5.5%.
A comparison of the hourly solar heat gain of the north facing building in the urban block with east-west street when the western building has four floors, to the hourly solar heat gain of (B-N) is plotted in
This study was undertaken to gain better understanding of energy demand in residential buildings in hot and dry climates by addressing the influence of building regulations on the energy behaviour of buildings in Riyadh. Energy simulation of a base case building was performed under the climatic condition of Riyadh. The results showed that the impacts of the current building regulations (as of 2018) on the thermal performance of residential buildings differ across the evaluated cases. The ratio of building height to street width, urban block street orientation, and building orientation are the main factors affecting thermal performance of buildings within urban block. The results indicated that the ratio of building height to street width had a slight impact on the cooling loads due to the long distance between opposite buildings. For the aim of investigating the impacts of building regulations in improving thermal performance of buildings, the study further assessed the impacts of urban dimensions modification on the thermal performance of buildings. Adjusting the ratio of building height to the distance between buildings was the main factor that made a significant impact in reducing cooling loads. In comparison to the current building regulation of Riyadh, the adopted urban dimensions were able to significantly improve the indoor conditions, reduce the heat gain from solar radiation and consequently reduce cooling load. The simulation analysis offers the potential for major savings in energy consumption for cooling purposes of residential buildings in Saudi Arabia. The reduction of energy consumption is based on few planning principles that could have a significant impact on the energy behaviour of buildings. To improve thermal performance of residential buildings, it is vital to move towards taking consideration to environmental aspects in building regulations to come up with compatible building regulations with hot, dry climate of Riyadh. Further study could be done to test the impacts of the new building regulation which will be introduced in Saudi Arabia in 2020. The findings of this paper are not only limited to residential buildings in Riyadh, but they can be applied to any buildings in hot arid climate.
The authors of this paper would like to thank the Deanship of Scientific Research at King Saud University and the Research Center at the College of Architecture and Planning for supporting this research.
The authors declare no conflicts of interest regarding the publication of this paper.
Baharetha, S., Amer, E. and Kotbi, M. (2021) The Impacts of Building Regulations on the Thermal Per- formance and Energy Consumption of Resi- dential Buildings in Riyadh City-Saudi Arabia. Open Journal of Energy Efficiency, 10, 1-21. https://doi.org/10.4236/ojee.2021.101001