1 - Urban orientation
The major problem that has to be faced in the hot and humid climates is the excessive heat and the high humidity levels. So in order to response in an urban scale, we must provide wind all day for natural cooling and shade. To achieve that, the orientation of the urban fabric is needed, along with with some basic strategies.
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The streets must be oriented from 20-30o oblique to predominant wind.
In that way the breezes can enter a settlement for cooling it, while the buildings are not blocking it.
In that way the breezes can enter a settlement for cooling it, while the buildings are not blocking it.
The streets must be wide for the movement of the air.
In hot and humid climates natural cooling comes most from the air flow so the wider the streets are the more air enters the urban fabric. Street spaces should be long and straight to facilitate air movement and lined by high, shade-providing trees.
In hot and humid climates natural cooling comes most from the air flow so the wider the streets are the more air enters the urban fabric. Street spaces should be long and straight to facilitate air movement and lined by high, shade-providing trees.
There must be a respond to secondary wind direction.
In such climates not only the main but also the secondary wind must be exploited for more all year efficient cooling.
In such climates not only the main but also the secondary wind must be exploited for more all year efficient cooling.
Elongate N-S blocks for natural shading.
Elongated North-South blocks create more shadow for the pedestrians during the day. Not only that but large faces to the south must be avoided from the solar radiation.
Elongated North-South blocks create more shadow for the pedestrians during the day. Not only that but large faces to the south must be avoided from the solar radiation.
Ventilation: open ends & dispersed form widely open streets to support wind movement and extensive shadow
In order to allow the air flow the urban fabric should not be dense while the shadow of separated buildings covers more space during the day.
In order to allow the air flow the urban fabric should not be dense while the shadow of separated buildings covers more space during the day.
Dispersion of high rise buildings to support ventilation
When high rise buildings are in dense formation the air is blocked while the heat effect from solar radiation becomes more intense.
When high rise buildings are in dense formation the air is blocked while the heat effect from solar radiation becomes more intense.
Shadowing, planned tree zones
Tree zones help for the cooling of the breezes as well for the protection of the pedestrians from the solar impact
Tree zones help for the cooling of the breezes as well for the protection of the pedestrians from the solar impact
2. Topography
TOPOGRAPHICAL LOCATION OF SETTLEMENTS
Orientation to minimize sun radiation impact.
Settlements should be placed preferably on southern or northern slopes, ideally facing away from the equator. The warm-humid climate zones are generally located near the equator. As a consequence, east and west slopes receive more radiation compared to north and south slopes and are, therefore, disadvantageous
Settlements should be placed preferably on southern or northern slopes, ideally facing away from the equator. The warm-humid climate zones are generally located near the equator. As a consequence, east and west slopes receive more radiation compared to north and south slopes and are, therefore, disadvantageous
Orientation to maximize natural ventilation by winds.
Ideal sites are windward slopes near the crest or near the beach, where regular winds exist. The ventilation effect of winds can be improved by effective arrangement of vegetation.Buildings inside the urban environment have to be separated with large free spaces in order to allow the air circulation. Ideal sites are windward slopes near the crest or near the beach, where regular winds exist. Sites that are located on a hill or rise above the ground, at a 20- 40 angle to the prevailing breezes use the wind in a more efficient way for cooling. The outdoor areas should be kept open to warmer season breezes, and if possible protected from storm and cool season winds. The ventilation effect of winds can be improved by effective arrangement of vegetation.
Ideal sites are windward slopes near the crest or near the beach, where regular winds exist. The ventilation effect of winds can be improved by effective arrangement of vegetation.Buildings inside the urban environment have to be separated with large free spaces in order to allow the air circulation. Ideal sites are windward slopes near the crest or near the beach, where regular winds exist. Sites that are located on a hill or rise above the ground, at a 20- 40 angle to the prevailing breezes use the wind in a more efficient way for cooling. The outdoor areas should be kept open to warmer season breezes, and if possible protected from storm and cool season winds. The ventilation effect of winds can be improved by effective arrangement of vegetation.
Scattered pattern of buildings
Groups of buildings should not be built in too compact a manner. Extended settlements, arranged in a line across the prevailing wind direction give low resistance to air movement and are, therefore, the ideal solution.
Groups of buildings should not be built in too compact a manner. Extended settlements, arranged in a line across the prevailing wind direction give low resistance to air movement and are, therefore, the ideal solution.
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Hazards, mainly floods and storms, to be considered.
Although the wind velocity is generally low, occasional storms (hurricanes) can occur. Therefore, a firm structure is required. Floods are common in lowland locations and have to be kept in mind.
Hazards, mainly floods and storms, to be considered.
Although the wind velocity is generally low, occasional storms (hurricanes) can occur. Therefore, a firm structure is required. Floods are common in lowland locations and have to be kept in mind.
3 - Daylighting
Urban pattern must insure that every building is reached by efficient daylight. This can be achieved by the open space proportions which are the key to daylight access. Daylight is associated with solar access and shading. Light has a behavior and a geometry, rhythm and logic and can be composed with built forms in order to achieve an acceptable designing outcome. The source of light is the sun but it also comes from the sky and areas or materials that reflect it.
In hot and humid climates we must combine daylight access with daylight-enhancing shading and reflection strategies.
4 - Passive cooling and heating of urban outdoor spaces.
Hot and humid climates
The main objectives in urban outdoor spaces are too:
- minimize thermal discomfort and provide cooling
- protect from tropical storms and floods
Hot and humid climates
The main objectives in urban outdoor spaces are too:
- minimize thermal discomfort and provide cooling
- protect from tropical storms and floods
Minimize of thermal discomfort and cooling.
In order to achieve thermal discomfort it is necessary to provide shade for pedestrians and for outdoor activities. It is also crucial to enable good natural ventilation by creating open spaces that allow the wind flow and to minimize the “heat island “effect in build environment.
Protection from tropical storms and floods.
It is crucial to provide protection for pedestrians because of the intensity of the storms. For that the creation of declined roofs is needed. There must be also a rapid disposal of rainwater and the open space structures have to be elevated from ground level
In order to achieve thermal discomfort it is necessary to provide shade for pedestrians and for outdoor activities. It is also crucial to enable good natural ventilation by creating open spaces that allow the wind flow and to minimize the “heat island “effect in build environment.
Protection from tropical storms and floods.
It is crucial to provide protection for pedestrians because of the intensity of the storms. For that the creation of declined roofs is needed. There must be also a rapid disposal of rainwater and the open space structures have to be elevated from ground level
4.1 Materials for hot and humid climates.
It is crucial to avoid using materials with great thermal mass because the surfaces of the mass tend to the average daily temperature, creating discomfort by re-radiate heat after the sun is gone. Therefore, when building to hot and humid climates, we use lightweight and low heat-storing materials. Cold materials can be used because they exhibit higher reflectance in the infrared range of the solar radiation and for that develop lower surface temperature up to 10 degrees, compared to conventional materials. At the same time these materials cool faster and therefore transmit less heat to the interior of the building or the ones nearby. Another advantage is that they have a good resistant level while they come in a wide range of colors and designs. These materials are called cold urban landscaping materials and are used extensively for the reduction of the phenomenon of the urban heat island.
In addition to that, traditional and local materials can be used like wood, bamboo, palm and grass. Nevertheless they must be used carefully because of the insects that damage them or the rot that may occur from the humidity. Earth walls from mud blocks or comb can be used in an outdoor urban space formation because they absorb humidity and are less dense compared to concrete.
4.1 Materials for hot and humid climates.
It is crucial to avoid using materials with great thermal mass because the surfaces of the mass tend to the average daily temperature, creating discomfort by re-radiate heat after the sun is gone. Therefore, when building to hot and humid climates, we use lightweight and low heat-storing materials. Cold materials can be used because they exhibit higher reflectance in the infrared range of the solar radiation and for that develop lower surface temperature up to 10 degrees, compared to conventional materials. At the same time these materials cool faster and therefore transmit less heat to the interior of the building or the ones nearby. Another advantage is that they have a good resistant level while they come in a wide range of colors and designs. These materials are called cold urban landscaping materials and are used extensively for the reduction of the phenomenon of the urban heat island.
In addition to that, traditional and local materials can be used like wood, bamboo, palm and grass. Nevertheless they must be used carefully because of the insects that damage them or the rot that may occur from the humidity. Earth walls from mud blocks or comb can be used in an outdoor urban space formation because they absorb humidity and are less dense compared to concrete.
Bamboo- The bamboo is an extremely light and elastic material. It is a plant that grows in this type of climate and therefore much better to be used as a low carbon material. Above all bamboo is renewable raw material resource from agro-forestry and if properly treated can last up to 40 years.
Teak – Teak timber is valued for durability as well as its water resistant and can be used for exterior construction. It grows in hot and humid climates and is therefore perfect for use.
Earth walls - Solid earth walls are quite good for use in hot and humid climates because are less dense and absorb more humidity compared to walls from concrete. It is crucial to be protected from rain by a roof. Earth walls are low emissive materials.
Stone - stones and lightweight rocks are usually used in hot and humid climates as the foundations in structures or as a top layer as they are not influenced by humidity and last
long.
4.2 Planting
4.2.1 Cooling from vegetation
Green squares and parks can lower the temperature in a significant way. Especially in the city where walls, asphalt and pavements heat up and release the heat back. Therefore plantation acts as a protective filter between the sun and the structures. It is important to plant trees from the direction of the prevailing hot winds in order to cool them and lower the temperature but not to prevent the air flow.High trees with wide, shading crowns provide significant protection from solar radiation and should be incorporated as much as possible into any landscape planning. High bushes, however, should be avoided near buildings because the space between the ground vegetation and the high crowns of the trees should remain open, providing free access for the wind at the level of the living spaces. Therefore it is impotant to use the local vegetation
with the characteristics given above.
Green squares and parks can lower the temperature in a significant way. Especially in the city where walls, asphalt and pavements heat up and release the heat back. Therefore plantation acts as a protective filter between the sun and the structures. It is important to plant trees from the direction of the prevailing hot winds in order to cool them and lower the temperature but not to prevent the air flow.High trees with wide, shading crowns provide significant protection from solar radiation and should be incorporated as much as possible into any landscape planning. High bushes, however, should be avoided near buildings because the space between the ground vegetation and the high crowns of the trees should remain open, providing free access for the wind at the level of the living spaces. Therefore it is impotant to use the local vegetation
with the characteristics given above.
4.2.2 Shading from vegetation and roofs
Shading of buildings as well as pedestrians should be considered when designing in hot and humid climates. The sun can be quite intense especially from midday to afternoon and light colored materials used in this climate are reflective. A way to deal with that is by creating large overhangs along walls or by planting high trees with wide shading crowns. High roofs that allow natural ventilation by openings can be used in pavilions for the rest and shading of the users in open spaces.
Shading of buildings as well as pedestrians should be considered when designing in hot and humid climates. The sun can be quite intense especially from midday to afternoon and light colored materials used in this climate are reflective. A way to deal with that is by creating large overhangs along walls or by planting high trees with wide shading crowns. High roofs that allow natural ventilation by openings can be used in pavilions for the rest and shading of the users in open spaces.
( T.M)