Arjun Basnet

Student no: 725563

.

AAR4907 - Sustainable Building Materials and Components

COURTAYRDS: Their roles in houses as climatic moderator in hot-arid climates

Sustainable Architecture

Faculty of Architecture and Fine Arts

Norwegian University of Science and Technology (NTNU)

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Student no: 725563

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‘They provide a place to bask in the sun or a shady and airy place to be cool, while the

houses are stuffy and either too cool from the night before or overheated by the

afternoon sun’. (Hyde, 2000, p.221)

The description above by Lisa Heschong exactly tells the usefulness of having

courtyards in buildings.

Abstract:

Design responding climate issues is an important environmental approach to building

design in today’s context of enhancing comfort condition with considerations of

sustainability and reducing energy consumption. A number of passive strategies can be

explored depending on the geography of a place and the nature of the climate. Use of

courtyards in building designs is one such efficient strategy whose usage can be

explored for both hot and cold climates. Courtyard is an internal climate modifier

(Majumdar, 2001, p.139), the existence of which will definitely change the surrounding

environment and the air temperature. As climate seems to have a major impact on the

building, there must be relationship between the architectural characteristics and

environmental / climatic conditions in order to achieve a good passive design.

Introduction:

Courtyard in general is an area wholly or partly surrounded by walls or buildings.

Conceptually, courtyard is considered as an open space that is open to the sky and

penetrates the mass of the building. Courtyards (Reynolds, 2002, p.ix) not only serve as

a connecting space to the surrounding rooms as traditionally thought of but also

mediates in filtering daylight, wind, rain and noise. In addition to bringing nature into the

building, they assist in moderating nature’s extremes, i.e., hot and cold. These spaces

are normally not as hot as summer’s afternoon sun and as cold as just before dawn or

late night. Courtyards when planned suitably protect outdoor spaces against winds,

maximise solar access and minimise shading in winter whilst opening to breezes in

summer, maximising shading vegetation and minimising solar access to vertical and

horizontal surfaces in summer. In cooler climates buildings can be arranged to trap

warm air or protect it from cold air in courtyards while in hot places, cooling through

courtyards can be further enhanced with the use of fountains, ponds and growing plants

by evaporative cooling.

In denser settlements especially in urban areas where natural light and ventilation

becomes important and is difficult to achieve, courtyard is necessary (Hyde, 2000,

pp.221-24). In the absence of courtyards, it is usually difficult to achieve passive way of

ventilating and some form of active system is required to provide the physical comfort of

building occupants. From the climatic design perspective, the size and degree of

enclosure have a significant impact on the performance of a courtyard and the building

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around it. If a courtyard starts becoming large, then it loses its identity as a normal

courtyard and instead becomes a square or a park. When it becomes too small, it may

look like a corridor; transferring it into a breezeway or to have the more selective

function of an air and light shaft. The usual function of a courtyard is to bring light and

ventilation into a building. However, it can create a useful micro-climate when combined

with different functions, wall types, building forms, materials and landscaping. The

position, orientation, shape and size of courtyards are important factors for the design of

courtyards. Their relation with other building elements open and semi open spaces must

be considered as well. The concept of space in a courtyard house and a western style

house is different as it is closed and more private in the former while it is open in the

latter (Figure 1: Courtyard & Western-style house..

Courtyards (Reynolds, 2002) are special areas that allow the inside and outside to

mingle; where rain, wind, daylight, night darkness, and sound can be somehow

controlled. Since at least 3000 B.C., courtyards have been incorporated into the

architecture of the day as a significant part of the physical and cultural landscape.

Ozkan has also stated that the concept of courtyard dates back to the Neolithic times

(Ozkan, 2006).

Greek houses, (Anon., n.d.) in the 6th and 5th century B.C., were built of stone, wood,

or clay bricks consisting of two or three rooms, arranged around an open air courtyard.

Larger homes had a kitchen, a room for bathing, a men's dining room, and perhaps a

woman's sitting area. Since the Greek women were allowed to leave their homes only

for short periods of time, they could enjoy the open air, in the privacy of their courtyard.

In Islamic culture (Ozkan, 2006), courtyard is an exclusively private part of a house and

is used only by members of the family. The courtyard is a multipurpose space where

Figure 1: Courtyard & Western-style house.

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most of the activities of the family take place. It also provides a climatically controlled

space from many of nature’s unwanted forces, like winds and storms.

The compact nature of planning around a courtyard offers efficient use of the

streetscape, as it is primarily used for accessibility and circulation. Therefore, by its

nature in the historical districts of hot, arid regions, very high densities are achieved by

low-rise architecture and an urban pattern that is humane. Courtyard housing is widely

considered to be a responsive typology to low rise high-density urban housing and is an

appropriate form of housing within contemporary mixed use sustainable urban

developments.

Courtyards are an interesting space in a building that have numerous and significance

importance. Their usages vary from place to place and culture to culture. In some

places, a courtyard serves only as a physical outdoor space or an extra space that

connects the outside street to the building. While in other places, according to their

placement, the function is different. If it serves as the entrance to the house, then it is

placed to the corner or to the side with one side adjacent to the street, separated by a

boundary wall. Some courtyards like the colonial Latin America (Venezuela) (Reynolds,

2002, p.4) have courtyards to the rear side of the building connected by a covered

entranceway from the street (see figure2). Typical courtyards have a direct entrance to

the courtyard like the one prominent in the north side of the Mediterranean as in figure2.

Many courtyards found in Kathmandu Nepal are also of this type. In case of ‘four in one’

Figure 2: Different courtyards (Reynolds, 2002, p.4)

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courtyard house in Beijing, public access is allowed to the first smaller courtyard but a

‘hanging flower gate’ screens the second, large and private courtyard. In some other

courtyards like that of the ancient Greece (figure2), the covered entranceway is placed

such that it leads directly to one arcade along the courtyard rather than the centre.

Scope:

Courtyards serve buildings with numerous functions. These are from providing privacy,

access to nature, serving various household and commercial activities to moderating

the climate. In the essay, I basically will focus on the climatic aspect of courtyards. Even

the climatic aspect of courtyards if researched, would produce books. Hence, the scope

of the essay is mainly to explore the moderating qualities of courtyards with climate

extremes in dwellings in hot-dry and hot-arid climates.

Context: hot-arid climate

Hot-arid climates (Mier & Roaf, 2002) are usually observed in hot dry deserts that

almost see no rain throughout the year with the air and soil being very dry. Summer

days are usually very hot and dry while nights are comparatively cooler. Winter days are

generally sunny with clear skies whereas nights are cold. Dust and sand storms are

common usually during the transition season. Drought is a common phenomenon in this

type of climate. The case of Marrakesh, Morocco is taken as the context.

Figure 3: Courtyard, Trondheim Norway; in cold countries large courtyards are sun collecting spaces. The spaces around the courtyard are also protected from the cold wind (picture to the right; http://kart.gulesider.no)

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Method:

It is a good idea to exploit the advantages of courtyard as a passive means in places

where it suits best. To write this essay, I basically collected information from books,

electronic sources and from supervisors. I have taken two cases as illustrations:

i) Turkey case: description to support the theme of the essay (Bekleyen &

Dalkilic, 2011)

ii) Morocco case: quantitative analysis of the thermal behaviour of courtyards in

hot-arid climatic context. (Raydan et al., 2003, 2006)

Research question and objective:

As mentioned above, courtyards serve as an important means for thermal comfort. In

cold areas like Norway, the courtyards are wider/larger to admit more of the winter sun.

They are usually protected from cold winds by the buildings surrounding it. In the

warmer countries, they are smaller to exclude the sun and its tremendous heat. So, we

see that the shape and proportion of the courtyard has a major role to play in thermal

comfort of a building which incorporates it. Courtyard usually assists in the natural

ventilation thereby creating a comfortable indoor environment. So, on the basis of these

facts, this research essay shall be based on the following research question:

What is the influence of a courtyard to thermal comfort in a building incorporating it in

hot-dry/arid climates?

The following objective can be drawn to reach a conclusion to the above question:

‘To study courtyards and their role in moderating the extreme climatic conditions in hot-

dry/arid climatic context’

Social Aspect of Courtyards

In Islamic cultures, privacy is one of the most important factors in a house. As per the

tradition, the male guests are to be entertained, (Zako, 2006, p.65) while at the same

time avoiding their access and contact with the female members of the house. This has

given rise to additional features to Islamic architecture and the courtyards have been

used in some form or the other. The entrance to courtyard is bent to create more visual

privacy from the street.

In Kathmandu Nepal, the old royal palace called the ‘Hanuman Dhoka’ has ten

courtyards. Until the existence of a king in Nepal, the main courtyard called the Nassal

Chowk just next to the entrance was very important for royal ceremonies like the

coronation. The other courtyard ‘Mul Chowk’ has a temple and so is used for religious

activities. The Mohan chowk has a sunken bath which on earlier days was used by the

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royals for bathing.

Similarly the

traditional settlements

around the palace

and other places in

the valley like Patan,

Bhaktapur, Kirtipur,

the buildings are

arranged around

courtyards. These

courtyards are very

important and are

used as community

spaces. Activities like

bathing, religious

activities in case a

temple exists, drying

grains, basking in the sun, various other social gatherings like marriages, parties and so

on. Even at present, when the houses have changed appearance, the courtyards have

remained unaltered posing themselves even more important as the few remaining open

spaces in the crowed city.

Activities in and around the courtyard

Although temporary, any activity can be carried out in a courtyard. Usually the

extensions of a living, dining and kitchen activities are carried out. Activities like sitting,

eating, gathering, celebrating, playing and even sleeping during hot summer nights is

carried out in the courtyard (Bahammam, 2006, pp.78-79). It is designed to be a

multifunctional family space in the house, drawing the family members out into the

courtyard holding them together while providing favourable atmosphere for social

interaction. The courtyard’s floor could have suitable materials for children to play out in

the nature without being threatened from traffic and other extrusions.

Courtyards function successfully as dwellings for older people. They combine the

advantages of compact, easily maintained living quarters with the provision of

communal outdoor places for public contact. The emphasis on the ground plane

minimizes stairs and permits an unusual degree of interaction among people with

limited mobility (Reynolds, 2002, pp.57-58).

Figure 4: Courtyards in Hanuman Dhoka Royal Palace, Kathmandu Nepal (John Sanday)

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Climate control

Courtyards, as per Reynolds (2000, p.79), represent an attempt to bring the forces of

nature under partial control. They intensify some aspects of the climate such as daylight

and dilute others such as wind. Use of Courtyards (Raydan et al., 2006) in hot-arid

regions fulfil several functions such as the creation of an open sheltered zone, the

adoption of ingenious natural cooling strategies, the protection against wind-blown dust

or sand and the mitigation of the effects of solar excess. However, in cold countries like

Norway, these are designed to create ‘pockets of solar gain’, thus balancing the

harshness of cold northern climates. So, a courtyard is either a sun protector or sun

collector depending on their proportions. A deeper courtyard will stay cooler in summer

but exclude sun for warmth in winter and hence are preferred in hot climates. In cold

weather, (Reynolds 2000, p.79) a common design strategy is to ‘huddle’ that is,

minimize exposure to cold air. Courtyard buildings expose only the street façade, the

four walls facing the courtyard, and the roof. Compared to the building surrounded by

open space, this design strategy works well to conserve heat.

During the day, (Medi, n.d.) solar radiation falling on the surface of courtyard warms up

the air which then rises up. In replacement, there is a flow of cool air from the openings

of surrounding ground level room; thus, creating an air flow. At night, the process is

reversed with cool air dropping to the courtyard from the roof and then flowing into the

living spaces through the lower level openings and then leaving through higher level

openings creating a ventilation pattern. This works best in hot-dry climates where day

time ventilation is undesirable, as it brings heat inside and at night the air temperature

becomes cooler and it can ventilate the building. However, when the courtyard receives

intense solar radiation, much heat will be conducted and radiated into the rooms as

against the induced air draft of air which is often problematic. The intense solar radiation

can also produce glare to the inside spaces.

Strategies

Creating suitable environment to avoid heat gain by using shading is one of the best

options for thermal comfort in hot-climate courtyard buildings. Green plants usually

vines or trellis filters sun and diminishes both daylight and wind. Cooling strategies

include evaporation, radiation and convection. Evaporation cools both building and

human skin surfaces quickly and the drier the air, the faster the evaporation. Dry

climates have much less water vapour in the air, so radiant losses to the cold sky are

much greater. And dry climates enjoy much cooler air by night providing a diurnal

convection ‘heat sink’ that humid climates lack (Reynolds, 2002, p.84).

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Wind

Wind (Reynolds, 2002, pp.88-90)

is sometimes helpful in hot dry

and temperate climates for

cooling, especially for night

ventilation when outdoor

temperatures are lower. Wind

moves primarily horizontally and

thus easily skips over the

horizontal opening to a courtyard.

If wind is to be encouraged,

several strategies are available. A

wind-catching strategy is to raise the height of the courtyard wall downwind (assuming

that a site has a prevalent wind direction). As wind moves across the lower roofs and

the courtyard opening, it then strikes

this higher wall. Most of the wind will

move up and over, but a down draft at

the wall can be enhanced if there is

an outlet at the bottom, that is, if some

wind can continue below the roof as

well as over it. Day ventilation

(comfort ventilation) (Mier & Roaf,

2002) will raise indoor temperatures,

while night ventilation will lower them.

In a building, (Wadah, 2006, p.157)

there are differences in temperature

between solid and void elements;

those open to the sun and those

shaded lead to differences in air

density which causes the following air

circulation: one is between the interior

courtyard and the exterior space at

day and night in summer and winter

conditions. The other is between the interior courtyard and the interior space of the

building (see figure 6). As a result, the wind acts as a positive agent in reducing ambient

temperatures simply because of the nature of the use of courtyard architecture.

However, besides moderating temperatures by the gradients created, wind-cooling can

reduce day-time surface temperatures which then benefits night-time conditions.

Figure 5: Wind strategy in courtyard

Figure 6: Air circulation between courtyard and adjoining rooms (Wadah, 2006, p.156)

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Hassan Fathy (Reynolds, 2002, p.91) describes how two courtyards of unequal size,

separated by a loggia, might induce rather weak air motion. More sun penetrates the

larger courtyard’s opening, creating a hot air space. As this hot air rises out the opening,

cooler air must flow into the smaller courtyard. This air is likely drawn either into the

smaller courtyard’s roof opening, or into rooms through open windows at the street. In

either case, this ‘new’ air is cooled as it passes through the shaded smaller courtyard or

cool room, and for those seated in the loggia between courtyards, a perceptible breeze

of cooled air is available for increased comfort.

Humidity to aid evaporative Cooling

Humidity (Wadah, 2006, pp.157-58) is important in reducing the dryness of interior air.

Excessive dry air can give a perception of excessive temperature while in reality; the

same temperature with slightly more humidity may feel more comfortable. Adding

moisture to the air via fountain or a pond can reduce temperature by evaporation as well

as adding a welcome increase in general air humidity. So a balance is often struck in

courtyard buildings between the shape for maximum temperature control from solar

radiation and that which facilitates wind and that which provides optimum levels of

humidity. Since, the water will need the sun to aid evaporation and hence humidify the

air, fountains and ponds are normally placed in the centre of the courtyards because of

the vertical midday sun in summer. For the air movement to the back of the rooms, the

wind towers and vents are usually at the perimeter of the building. This has resulted in

the distinctive design of courtyard houses with their centrally-placed courts and

peripherally-placed wind towers (Figure 7).

Figure 7: Courtyard house in Saudi Arabia illustrating humidification and ventilation strategy (Al-Saud & Al-Hemiddi, 2006)

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Thermal Mass

Thermal mass is a means to improve the diurnal temperature swings in hot-dry

climates. High thermal mass is the most obvious characteristic of traditional courtyard

buildings, and its primary cooling effect delaying the arrival of the afternoon heat, also

aided by shading. In hot-dry climates, high thermal mass can be cooled by radiation to

the night sky, by evaporation and by ventilation at night. The courtyard floor plays an

important cooling role, because it looks straight up to the cold night sky. The shallower

the courtyards, the more the floor exposed to the sky rather than the walls, and so the

more radiant heat loss by night. Use of thermal mass in a shaded and insulated building

can help lower indoor temperature by 35-45% of the outdoor ones when the building is

unventilated (Mier & Roaf, 2002).

Case1: Diyarbakir, Turkey

Courtyard houses (Bekleyen & Dalkilic, 2011) are common in hot and dry climates.

Environmental and cultural differences inform the diverse characteristics of courtyard

houses because they are used by a variety of cultural groups in a large number of cities.

Courtyard houses which are common in regions with hot and dry climates demonstrate

strict territoriality and attempts to create private space for introversion. This life style is

not only to reflect the culture but also is the result to moderate the effect of harsh

climate.

Diyarbakir is a city located in the South eastern Anatolia Region of Turkey and has a hot

and dry climate. The courtyard houses were surrounded by high walls within the

compact urban texture and were built to protect the inhabitants from both the extreme

heat in summer and unwanted interference from outsiders. In all of the houses

examined within the scope of the present study, a central courtyard exists, providing air

and light for the other spaces surrounding it. The windows of all rooms on the ground

floor have a view of the courtyard and they do not have a direct connection to the outer

part of the building. Planning in this way is suitable for hot climates; the space is

designed for users in a way that blocks sunlight in summer and allows sunlight in the

winter. Consequently, the spaces around the courtyard are designed appropriately for

seasonal usage (Bekleyen & Dalkilic, 2011).

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In the summer, according to Bekleyen and Dalkilic (2011), the spaces in the southern

part of the courtyard are used. These spaces are cooler because they face north and

are not exposed to direct sunlight. The ceilings of the rooms are high, and there are

wide windows that are always kept open in summer. They also have additional upper

windows close to the ceiling. The cool air comes into the room through the windows,

and after it gets warmer, it flows into the courtyard through the upper windows. This

creates a kind of ventilation. Even if the lower windows are closed, the upper windows

are always kept open. In some cases, these windows do not contain glass; instead, they

have ornamented wire fences. Thus the warm air in the room is continuously exchanged

through these openings. The semi open space faces the courtyard for summer comfort.

There is a special room specially designed for very hot days placed underground (one-

third or one-half of its space height is placed under the level of courtyard). The room

gets air and light from the upper windows facing the courtyard, and a small pool is

present to decrease the heat (Bekleyen & Dalkilic, 2011).

Figure 8: Seasonal horizontal movement (left); seasonal and daily vertical movement (right) in traditional Arabian courtyard houses (Bekleyen & Dalkilic, 2011)

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Case 2: Studies with reference to Marrakesh, Morocco

This quantitative analysis of the climatic aspect of courtyard in hot arid climate, is the

results from studies by Raydan, Ratti and Steemers (2006, p.135-145).

Contrary to what most people think,

courtyards fulfil several functions in

hot-arid regions (Raydan et al.,

2006, p.135). These include

creating open sheltered zone,

adopting natural cooling strategies,

the protection against wind-blown

dust or sand and moderation of the

effects of solar excess. Climate is

one strongest element that

determines architectural form and

this applies to shape of courtyards

as well. While in hot-arid climatic

regions, courtyards are created to

gain protection from the harsh sun; in countries like Norway, they are used as sun

collector. It is actually the proportions of the courtyard space that varies its climatic

properties.

Raydan, Ratti and Steemers (2006) tired to find out the suitability of courtyards

compared to alternative urban forms such as

high or low-rise box shaped buildings in terms

of response to climate. They calculated a

number of well-established environmental

variables on simplified vernacular courtyards

and two other architectural forms as mentioned

above. Raydan, Ratti and Steemers (2006,

Figure 9: Courtyard-based urban fabric, Marrakesh Morocco (Raydan et al., 2006)

Figure 10: Representation of a traditional Arabic courtyard and two pavilion type urban forms. Top: section of courtyard house (Raydan et al., 2003)

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p.136), while analyzing the climatic aspect of courtyards; have extended Martin1 and

March’s1 approach to examine different urban forms in the context of the hot-arid

climate. This has helped them to identify the environmental variables like surface to

volume ratios, shadow densities, daylight accessibility and view factors from the city to

the sky. These variables provide key measures related to solar radiation, thermal

comfort and urban temperatures, which can be tested against the environmental

pressure produced by hot-arid climates. For analysis three different urban forms; one

with a courtyard and two others high and low rise rectangular box shaped buildings

were considered. These box shaped buildings are referred to as the pavilions.

Following Martin and March’s (1972) analysis, the governing principle taken by Raydan,

Ratti and Steemers (2006, p.136-137) for simulation was that the chosen urban forms

have the same built volume, the shape being according to different forms. The main

case study selected for investigation was taken from a real prototype courtyard house.

The specific configuration and dimensions of the courtyard house were adapted from a

diagrammatic section of a courtyard urban dwelling as shown in the figure11. For the

courtyard type, three floors each 9m high were assumed. Although in real context the

street network are generally irregular, this urban texture seems representative of an

Arabic city, as in the figure10, that of Marrakesh, Morocco. The plot area covered by all

these three forms was also similar.

The second and the third forms were hypothetical yet fairly realistic pavilion types,

imitating potential modern urban transformations that might take place in a vernacular

courtyard context. The first type, pavilion 1, replaced each courtyard with an urban block

centrally located in the initial lot, preserving the height of 9m and built volume. It was

also assumed that this option would be a pedestrianised modern urban neighbourhood

with no vehicular traffic through the streets as in fig. This alternative seemed bulkier as

compared to the courtyard as there was a large surface area lost on the periphery of the

pavilion. (Raydan et al., 2006, p.138)

The second, pavilion 2, represented an urban

composition integrating four courtyards into one urban

block that could represent a mixed-use development

as in figure11. The street width was fixed to

accommodate two-way traffic, parking on the sides

and a small sidewalk. Building height was a result of

the condition that the built volume needed to be the

same as in the previous cases and resulted in a

realistic height of six storeys, double of the initial case

which is 18m (figure10) (Raydan et al., 2006, p.139).

Figure 11: Plan representation of the three cases of overlaid (Raydan et al., 2003)

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15797

10931

7168

27030 27030 27030

0

5000

10000

15000

20000

25000

30000

Courtyards Pavilion 1 Pavilion 2

Total surface m2 Total volume m3

0.584

0.404

0.265

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Courtyards Pavilion 1 Pavilion 2

Surface to volume

Surface to volume

The analysis addressed the

following parameters.

i. Surface to volume ratio:

This ratio is obtained by

dividing the total surface of

buildings by their volume. This

result gives a clear idea of the

building envelope surface that

is exposed to the outside

environment and ultimately is

a fundamental indicator for

implementing environmental

strategies (Raydan et al.,

2006, p.141).

There is more potential for

natural ventilation and daylight

and the values for surface to

volume ratios are higher.

Higher value is also an

indication for heat loss during

the winter and heat gain in the

summer. Considering the

above hypothesis, the

courtyard type with the highest

surface to volume ratio,

(0.584) (see figure12) would not seem to be performing thermally well. However, when

the potential heat loss/gain during respectively cold and warm seasons is analysed

within the complexity of hot-arid climatic context, results indicate quite favourable

conclusions (Raydan et al., 2006, p.141).

In hot-arid climates (Raydan et al., 2003) night-time temperatures are usually lower than

daytime temperatures throughout the year, with a diurnal temperature difference

between the average daily maximum and minimum ranging between 15 to 19°C for the

city of Marrakesh in Morocco. The winter which lasts for around three month, are

relatively mild and sunny. The diurnal swing is approximately 3°C. Therefore the critical

months of the year are the hot months, and moderating the temperature extremes of

this season is a must. The smart solution of the courtyard house type in hot-arid

Figure 12: Surface to volume ratio

Figure 13: surface area and volume

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10.989.78

6.1

0

2

4

6

8

10

12

Courtyards Pavilion 1 Pavilion 2

Mean Shadow Density (latitude 31°N)

Mean Shadow Density

12.4

9.9

2.80

2

4

6

8

10

12

14

Courtyards Pavilion 1 Pavilion 2

Mean Shadow Density (latitude 60°N)

Mean Shadow Density

climates is to use high thermal mass to store heat throughout the day in order to benefit

from it during the cooler night. By maximizing the surface to volume ratio, the courtyard

acts as heat sink and therefore alleviates the extreme temperature stress. The heat is

re-radiated indoors as well as to the surrounding and to the sky during the cooler nights

due to the time lag of the large thermal mass and the cooler air temperature. Hence, in

combination with the thermal mass, the large surface to volume ratio of courtyard is a

plus factor in the thermal performance of the building.

In cold climates very high degrees of thermal insulation is used in buildings to minimize

radiation heat from the interior to the exterior. Because of this the fabric heat losses are

relatively small. The geometry of the building whether court or pavilion is less critical in

terms of heat loss, whereas improvements through a more sheltered microclimate can

provide additional benefits. Increased average temperatures and protection from cold

winds, i.e., reducing ventilation losses may offset small disadvantage of the larger

surface area (Raydan et al., 2006, pp.141-42).

ii. Shadow density and daylight distribution:

Shadow density (Raydan et

al., 2003) is a climate related

measurement based on

detecting shadows on the

ground at hourly intervals on a

piece of city for a given day of

the year. The average number

of hours of shadows is

calculated at each point.

Figure14 shows the value for

shadowing simulation for

summer day (21st June) at two

different latitudes, 31°N

(Marrakesh in Morocco) and

60°N (average northern

latitudes of Oslo and

Stockholm. The comparison in

the result shows that

courtyard could prove useful

in cold climates as well.

The availability of daylight is

measured as illuminance

values falling on a plane; in Figure 14: Mean Shadow Density from simulation for Marrakesh (top) and Oslo (bottom)

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0.099

0.296

0.53

0.188

Courtyards Pavilion 1 Pavilion 2

Daylight Distribution

Daylight distribution at ground level

Daylight distribution in the courtyard

this case, the streets. The selected model of the sky used for simulation was the

standard overcast sky, which represents ‘ideal’ overcast conditions. Usually in hot-arid

climates, the sky conditions are usually clear and not overcast; the nature of the

simulation consists of investigating illuminance distribution only. Value 1 represents

illuminance falling on an unobstructed surface and 0 represents no illuminance

(figure15).

According to Steemers,

Ratti and Raydan (2003),

high values of mean

shadow density recorded in

the streets are beneficial in

hot-arid regions as they

provide protection to

pedestrians and to the

horizontal street surface

from solar radiation. In this

regards, courtyard type

which has the highest value

(10.98) seems to be an

advantaged configuration

(figure14). On the contrary,

high overshadowing also

means low illumination and the courtyard ranks dramatically lowest (figure15). However,

this observation seems to contradict the daylight benefits suggested through high

surface to volume ratios. It should be clarified that the shadow density reading in this

case is taken in the streets and that the illuminance values are an average of all ground

surfaces (street and courtyard floors). Taken in the courtyard itself, an average

illuminance of 0.188 (compared with the low value of 0.099 in the street) proves that

daylight is actually benefitted from through the courtyard and not through the external

facades of the courtyard type. This observation corresponds well with the reality that the

courtyard house type interacts well with the climate through the courtyard which is

reinforced by the shallower plan depth that can protect and enhance the courtyard

environment from the noisier and usually more polluted street environment. However,

the simulation here simply takes into account light falling directly from the sky and not

that reflected from the ground and buildings, which in some cases can give a significant

daylight contribution. Use of white paint in buildings’ external surfaces increases overall

illuminance values. The use of light colours in the external surfaces of courtyard houses

can be seen in countries like Morocco and in the Middle East.

Figure 15: Daylight distribution from simulation

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Student no: 725563

17

0.127

0.227

0.482

0

0.1

0.2

0.3

0.4

0.5

0.6

Courtyards Pavilion 1 Pavilion 2

Average sky view factor at ground level

Average sky view factor at gorund level

iii. Sky view factor,Ψ (SVF):

It measures the openness of the urban texture to the sky and has been associated,

among other indicators, to the increase in temperature in the urban context compared

with the surrounding rural context; called the urban heat island phenomenon (Raydan et

al., 2006). The relation between SVF and the urban heat island consists of the

observation that the smaller the SVF, the higher the temperature of cities.

Formula by Oke:

∆T(urban-rural)=15.27-13.88Ψsky,

is verified in a number of real

cities relates to the

maximum heat island

temperature between urban

and rural sites, where ∆T is

the maximum temperature

difference and Ψsky is the sky

view factor. The results in

figure17 show that courtyard

is a case of an inappropriate

response to climate. Again,

as per the results in the figure16, pavilion 2 seems to be the best urban form and the

traditional courtyard type as the worst (Raydan et al., 2006). So, one might think what

sense these simulations make.

Actually, extensive

scientific literature shows

that a low sky view factor in

reality is beneficial in hot-

arid climates (Raydan et

al., 2003). In hot-arid

climates, night-time

temperatures are usually

lower than the daytime

temperatures, and an

increase in temperature

would probably be

welcomed at night if the

extreme conditions of the

day were alleviated. The

existence of this

13.51

12.12

8.58

0

2

4

6

8

10

12

14

16

Courtyards Pavilion 1 Pavilion 2

∆T(max urban-rural) = 15.27-13.88Ψsky

Figure 18:

Figure 17: Formula by Oke to relate the maximum heat island intensity between urban and rural sites. Difference in temperature for different types

Figure 16: Sky view factor from simulation

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Student no: 725563

18

phenomenon can be discerned through a social habit in hot-arid countries like Morocco

where people sleep on building roofs at night, to maximise their radiative losses and

also to avoid higher indoor temperature partly due to time lag re-radiated heat caused

by large building thermal mass. As comfort is not only based on temperature, but also

on radiative exchange, this is where the benefit of low SVFs comes into play again,

especially during day-time hours when people are outdoors in the streets and urban

pedestrian comfort is a priority. During day time hours, low SVFs insure an increase in

direct shading and a reduction in reflected radiation.

There was a study made on the city of Fez, Morocco; based on field measurements to

find out the way courtyard dwellings worked. Temperatures were monitored in two

districts of the city associated with different housing types: a traditional one, based on

the compact clustering of buildings using the courtyard structure and a more recent one

based on modern two to three storey houses arranged along wide streets. In the

traditional courtyard district temperatures are higher during the night but during the day

a favourable cool island appeared. Overall conditions are more stable in the traditional

district than in the modernist development, with the tendency for moderating maximum

and minimum outdoor air temperatures.

Conclusions:

Hence, the courtyard configuration type shows better response through the calculated

environmental variables than the pavilion types in the context of hot-arid climates. The

potential to improve the environmental performance by adopting court forms in cold

climates also exists, although this is largely determined by a lower height-width ratio

than in hot-arid regions. However, courtyard typology would not be suggested for hot

humid climates where there is a narrow daytime temperature variation (Raydan et al.,

2003). The climate moderating qualities of courtyard is not efficient in isolation. In hot-

arid climate context, houses with large surface area in combination with high thermal

mass are desired. It is more beneficial to have a shallow plan form and daylight via the

courtyard into the house.

Limitations:

The study does not show that all courtyards behave better than all pavilions; the

influencing factor is the built proportions. (Raydan et al., 2003). Simulation results

always need to be carefully analysed and interpreted within the particularities of the

context in order to overcome misleading broad statements.

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Bibliography Anon., n.d. Greek Culture. [Online] Available at: http://www.crystalinks.com/greekculture.html

[Accessed 28 April 2011].

Bahammam, O.S., 2006. The role of privacy in the design of the Saudi Arabian courtyard house.

In B. Edwards, M. Sibley, M. Hakmi & P. Land, eds. Courtyard Housing: Past, Present & Future.

New York: Taylor & Francis. pp.77-82.

Bekleyen, A. & Dalkilic, N., 2011. The infuence of climate and privacy on indigenous courtyard

houses in Diyarbakir, Turkey. [Online] Available at:

http://www.academicjournals.org/sre/PDF/pdf2011/18Feb/Bekleyen%20and%20Dalkilic.pdf

[Accessed 2 April 2011].

Hyde, R., 2000. Climate Responsive Design: A Study of buildings in moderate and hot humid

climates. [Online] Available at:

http://books.google.com/books?id=BviH0WdDsR0C&printsec=frontcover&dq=books+by+Richar

d+Hyde&hl=en&ei=CrvSTYu0HYSUOpzJnIML&sa=X&oi=book_result&ct=result&re

snum=3&ved=0CEQQ6AEwAg#v=onepage&q=books%20by%20Richard%20Hyde&f=false

[Accessed 9 May 2011].

Majumdar, M., 2001. Energy-efficient buildings in India. Tata Energy Research Institute, Ministry

of Non-Conventional Energy Sources, India. [Online] Available at:

http://books.google.com/books?id=8i4auFjpkB8C&pg=PA139&dq=climate+and+courtyards&hl=

no&ei=oX7GTcueOY_HswaLlfX6Dg&sa=X&oi=book_result&ct=result&resnum=9&ved=0CE4Q6

AEwCDgU#v=onepage&q=climate%20and%20courtyards&f=false [Accessed 8 May 2011].

Medi, H., n.d. Design with Climate. [Online] Available at:

http://ikiu.academia.edu/artandarchitecture/Teaching/20425/Design_with_Climate [Accessed 2

May 2011].

Mier, I. & Roaf, S., 2002. Thermal comfort-Thermal mass: Housing in hot dry climates. [Online]

Available at: http://www.irbdirekt.de/daten/iconda/CIB6494.pdf [Accessed 2 May 2011].

Ozkan, S., 2006. Courtyard: a typology that symbolises a culture. In B. Edwards, M. Sibley, M.

Hakmi & P. Land, eds. Courtyard Housing: Past, Present and Future. New York: Taylor &

Francis. pp.xv-xix.

Raydan, D., Ratti, C. & Steemers, K., 2003. Building form and environmental performance:

archtypes, analysis and an arid climate. [Online] Available at:

http://www.sciencedirect.com/science/article/pii/S0378778802000798 [Accessed 16 May 2011].

Raydan, D., Ratti, C. & Steemers, K., 2006. Courtyards: a bioclimatic form? In B. Edwards, M.

Sibley, M. Hakmi & P. Land, eds. Courtyard Housing: Past, Present & Future. New York: Taylor

& Francis. pp.135-45.

Reynolds, J.S., 2002. Courtyards: Aesthetics, Social, and Thermal Delight. New York: John

Wiley & Sons.

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Wadah, H., 2006. Climatic aspects and their effect on the dimensions of courtyards in Arab

buildings. In B. Edwards, M. Sibley, M. Hakmi & P. Land, eds. Courtyard Housing: Past, Present

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courtyard houses. In B. Edwards, M. Sibley, M. Hakmi & P. Land, eds. Courtyard Housing: Past,

Present & Future. New York: Taylor & Francis. pp.65-75.

List of Figures:

Figure 1: Courtyard & Western-style house.

Figure 2: Different courtyards (Reynolds, 2002, p.4)

Figure 3: Courtyard, Trondheim Norway; in cold countries large courtyards are sun collecting

spaces. The spaces around the courtyard are also protected from the cold wind (picture to the

right; http://kart.gulesider.no)

Figure 4: Hanuman Dhoka Royal Palace, Kathmandu Nepal (John Sanday)

Figure 5: Wind strategy in courtyard

Figure 6: Air circulation between courtyard and adjoining rooms (Wadah, 2006, p.156)

Figure 7: Courtyard house in Saudi Arabia illustrating humidification and ventilation strategy (Al-

Saud & Al-Hemiddi, 2006)

Figure 8: Seasonal horizontal movement (left); seasonal and daily vertical movement (right) in

traditional Arabian courtyard houses (Bekleyen & Dalkilic, 2011)

Figure 9: Courtyard-based urban fabric, Marrakesh Morocco (Raydan et al., 2006)

Figure 10: Representation of a traditional Arabic courtyard and two pavilion type urban forms.

Figure 11: Plan representation of the three cases of overlaid (Raydan et al., 2003)

Figure 12: Surface to volume ratio

Figure 13: surface area and volume

Figure 14: Mean Shadow Density from simulation for Marrakesh (top) and Oslo (bottom)

Figure 15: Daylight distribution from simulation

Figure 16: Sky view factor from simulation

Figure 17: Formula by Oke to relate the maximum heat island intensity between urban and rural

sites. Difference in temperature for different types

Note:

1. Leslie Martin and Lionel March carried out an extensive study of the environmental

performance of courtyards at Cambridge University in the late 1960s. In a number of influential

papers like ‘Architect’s approach to architecture’, 1967 and ‘Urban Space and Structures’, 1972;

they addressed the question: ‘What building forms make the best use of land?’ The question of

course implies a definition of ‘best use’. They bound themselves to quantifiable parameters,

such as ‘built potential’ (the ratio of the floor area of the built form to the site area) and ‘daylight

availability’. They analyzed different archetypal built forms, such as pavilions, streets and

courtyards. According to them, the court form is seen to place the same amount of floor space

on the same site area with the same condition of the building depth and in approximately one-

third the height required by the pavilion form. (Raydan et al., 2006, p.136)