Keywords

1 Introduction

Nowadays, the awareness of excessive use of energy and its cost and environmental impact have been increased. However, achitects, engineers, and designers prefer providing building designs that suit the climatic condition and adapt to nature. Applying natural ventilation methods in buildings that suit the climate and environment is important to provide the cooling and heating required with environmentally friendly passive design features and less energy consumption.

Natural ventilation has different methods depends on the building’s design, location, and climatic conditions, such as, single- sided ventilation, cross ventilation, stack ventilation and courtyard ventilation. In this study the focus will be on the courtyard method and its effect on the building and energy use. The courtyards method has been recognized as an option to provide healthier and comfortable environment with minimal energy consumption.

This paper introduces the natural ventilation systems along with the different methods used to achieve it. The courtyards method will be discussed in detail to provide natural ventilation in the buildings and achieve the indoor environmental quality and thermal comfort. A case study of beauty centre building in Germany will be introduced to study the energy consumption of the building when the HVAC system is working all over the year. Following to this, a courtyard method will be implemented in the building in 3 different scenarios to study the natural ventilation system in it and compare the results of the energy consumption outcomes with and without courtyard. This study and analysis will be done using IES VE computer software.

2 Literature Review

Natural ventilation can be defined as a method of driving outdoor fresh air to the indoor environment of a building through building’s envelop using passive forces. The main driving natural forces that affect natural ventilation in buildings are thermal buoyancy and wind (Ventive n.d.). Courtyards are one of the methods that can be used as a passive design to achieve natural ventilation (Krarti, 2018).

2.1 Definition of Courtyard

Reference to Oxford’s Dictionary, it defines courtyards as an unroofed space that is surrounded entirely or partially by walls, houses or buildings (Oxford University n.d.). On the other hand, the definition of a courtyard in the Cambridge Dictionary is a flat ground outside place that is entirely or partially surrounded by a building’s walls (Cambridge University n.d.). Both definitions agree that the courtyards are an open area surrounded by buildings or wall and has no coverage.

2.2 Courtyard Forms and Elements

Courtyards are flexible with their design, they can be designed in any shape, but the usual design is square, rectangular, and circle. These forms have been designed to achieve environmental aspects like topography, site limitation, building orientation and function to provide different forms such as [U shape, L shape, T shape, V shape, H shape or Y shape]. Different design forms can be applied for the courtyard of one or two storey building as shown in Fig. 1. The main purposes of designing a courtyard are to provide natural light, fresh air through natural ventilation, play area for the children, and for rest and activities (Abass, Ismail & Solla, 2016).

Fig. 1
An illustration of courtyards. A. Fifteen different designs of courtyards with one and two-story buildings. B. Semi and fully enclosed L-shaped, U-shaped, square and inner courtyard shapes.

(Adapted from (Abass, Ismail & Solla, 2016))

A: Different applied design forms for courtyard of one or two storey building, B: Fully and semi enclosed design of courtyards

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2.3 Characteristics of Courtyard in Four Climates

The characteristics of courtyard design can vary in different climate conditions in order to function as a passive design strategy for optimum use of natural element such as daylight and wind. Table 1 shows the different characteristics of courtyard design in different climate condition. The courtyards are used as a source of daylighting, natural ventilation, and natural heating and cooling (Taleghani, Tenpierik & van den Dobbelsteen, 2012).

Table 1 The different characteristics of courtyard design in different climate condition
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3 Research Methodology

This research will start by providing a literature review about the natural ventilation system including definition, different types of natural ventilation and its impact on thermal comfort and energy consumption. The courtyard method as one of the natural ventilation types will be selected to explore more and discuss it in detail. Moreover, the courtyard method will be applied on a case study of beauty centre building in Germany to analyze and compare the natural ventilation effect in the building with and without the implementation different types of courtyards in 3 scenarios. IES VE software will be used for the computer simulation, analysis, and results.

3.1 Climate Analysis

Germany has variation in the climate analysis due to various mountains and hill areas over the country. However, the climate in Berlin characterized by a maritime temperate climate. In the summer, Berlin’s temperature gets high along with many warm sunshine hours between May and August. July is the peak of the summer in Berlin where the temperature reaches 25 C°, while the lowest amount of sunlight is in December. The temperatures range between 20 C° to 25 C°. July is the warmest month with average maximum temperature of 25 C°. While in the winter, the weather gets cold with maximum temperature of 3 C° in January (World Weather & Climate, 2021). For the wind, the month of January has the most wind average, and August has the least wind average. The most prevailing wind is from the south-west direction, and the annual average speed is 9.6 mph (IEM: Site Wind Roses, 2020).

3.2 Case Study and Project Detail

The case study is about a beauty centre building located in Berlin, Germany. The building consists of ground floor plan with one main entrance, operable windows on the external walls and different room functions inside it as shown in Fig. 2. The total floor area is 110 m2.

3.3 Modelling using IES VE software

Building Code and Specification Standards

Berlin has specific building energy efficiency standards and policies that are required in designing and constructing new buildings. The supporting policies covers different building aspects for the U-values of roof, wall, floor, and window. The U-values required for new buildings are: roof is 0.2 W/m2K, wall and floor is 0.28 W/m2K, and window is 1.3 W/m2K (Energy Conservation Regulations (EnEV) | Global Buildings Performance Network n.d.). The model set-up via IES VE software includes: setting out location and weather data, creating construction material for walls, floors, roof and windows, creating profile for cooling, heating and occupancy, setting out thermal template - Apache system, internal gains, and air exchanges.

The Base Case Model Design via IES VE Software

Figure 2 shows the ground floor plan and the three-dimensional base case model of the beauty centre building using the mentioned U-values.

Fig. 2
Three illustrations. A. an illustration of a ground floor plan of a building with a hall, kitchen, bedrooms, and other rooms. B and C are the front and rear views of the building with a main door and windows.

(Source (Taleb 2021, via IES software)), B: Front view of the beauty centre, C: Rear view of the beauty centre, Source (Eid 2021, via IES software)

A: Ground floor plan of beauty centre building in Berlin, Germany

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The Optimal Orientation

Selecting the optimal orientation was done through Sun cast simulation in the IES software. Table 2 shows the total energy consumption of each direction. Reference to Apache simulation results, the optimal orientation is 180 degrees from the north (south direction) is the optimal orientation as it has the lowest energy consumption.

Table 2 Total energy consumption of the base case in different directions
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3.4 Design Strategies

The focus will be on three design strategies for courtyards to study their effect on natural ventilation. The first strategy is the courtyard location, second is the percentage of openable windows area around the courtyard, and third is Courtyard proportions from x to 2x as width, where x is the courtyard height. The simulation was done on July 14 for all strategies as it is the hottest day.

Strategy 1: Courtyard Location

Fig. 3
Three illustrations of 3 types of building layout plans. a. Central courtyard with rooms on all sides and an open area at the center. b. U-shaped building with rooms on all three sides of the open area. c. Inner courtyard with rooms on either side of the open area.

Source (Eid 2021, via IES software)

Layout plan of scenario 1, 2 and 3,

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Summary of Strategy 1: Courtyard Location

Reference to Fig. 3 and Tables 3, 4 and 5, the best-case scenario in strategy one is scenario 1, as it is the lowest in total energy consumption, and it is better in terms of air temperature, relative humidity, solar gain and CO2 concentration.

Table 3 Summary of scenario 1
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Table 4 Summary of scenario 2
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Table 5 Summary of scenario 3
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Strategy 2: Percentage of the Openable Window Area Around the Courtyard

Fig. 4
An illustration of the layout plan of buildings with openable windows for the courtyard. a. Rooms and courtyard with 25% openable window. b. Rooms and courtyard with 50% openable window. c. Rooms and courtyard with 75% openable windows.

Source (Eid 2021, via IES software)

Layout plan of scenario 4, 5 and 6,

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Summary of Strategy 2: Percentage of the openable window area around the courtyard

Reference to Fig. 4 and Tables 6, 7 and 8, the best-case scenario in strategy two is scenario 4, as it is the lowest in total energy consumption, and it is better in terms of air temperature, relative humidity, solar gain, and CO2 concentration.

Table 6 Summary of scenario 4
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Table 7 Summary of scenario 5
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Table 8 Summary of scenario 6
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Strategy 3: Courtyard proportions from x to 2x as width, where x is the courtyard height

Fig. 5
An illustration of the layout plan of buildings with courtyards of different sizes. a. Rooms and courtyard of measurement x to 1 over 2 of x. b. Rooms and courtyard of measurement x to 1 of x. c. Rooms and courtyard of measurement x to 2 of x.

Source (Eid 2021, via IES software)

Layout plan of scenario 7, 8, and 9,

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Summary of Strategy 3: Courtyard proportions from x to 3x as width, where x is the courtyard height

Reference to Fig. 5 and Tables 9, 10 and 11, the best-case scenario in strategy three is scenario 8, as it is the lowest in total energy consumption, and it is better in terms of air temperature and solar gain.

Table 9 Summary of scenario 7
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Table 10 Summary of scenario 8
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Table 11 Summary of scenario 9
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3.5 IES VE Simulation Results

To summarize, it was clear that the predicted mean vote, external velocity, and external pressure almost did not change through the three strategies. The winning case scenario has total energy (MWh): 12.7, while the base case scenario has 15.0477 MWh. For the air temperature, there was a slight change, but however, the temperature can be dropped in Berlin during the summer, and there will be a need for heating elements. In cold climates the need of ventilation is less, that is why the size of courtyards for one or two storey buildings are smaller in order to reduce the heat losses caused by it. In contrast, during winter season the natural heating is required for the building along with natural day light all the year.

4 Conclusion

Courtyards as a natural ventilation method are very useful as they allow for air circulation to enhance the indoor air quality. In addition, they provide daylight as they do not have top roof. Ventilated courtyards can be designed and applied for wide buildings whether they are residential or commercial buildings. Different cooling elements can be added to the courtyard to provide and enhance the natural ventilation, indoor temperature and solar gain.

This paper has been used IES software for investigating the performance of courtyards as a natural ventilation method within a Beauty centre in Berlin, Germany. Different strategies and scenarios have been implemented to reach the optimum natural ventilation performances. The design factors include shape and location of courtyard, the percentage of window openings around the courtyard, and courtyard proportions from x to 2x as width, where x is the courtyard height. To conclude, implementing courtyards in the buildings will enhance the indoor environment like the air quality and daylight, and thus improve the building’s occupants’ thermal comfort. However, different factors should be considered prior implementing courtyard design in any building. Building type and location along with the climatic conditions have major effect on the courtyards design and function. Different climatic conditions require different characteristics of courtyards design for optimum function. All these factors should be studied and considered in the design phase of a building.