1.Urban orientation
In temperate climates with conflicting seasonal requirements a mixture of strategies should be applied. The advantages and disadvantages should be weighed together, considering not the extreme, but the prevailing climatic conditions. In the hot period shading and wind cooling is the priority, while during the cold season, the winter sun must be exploited for the heat but protection from the cool winds is obligatory. For that reasons the urban design should include semi-compact forms and functions in order to provide both results.
BASIC PRINCIPLES
The orientation should be +/- 30o from cardinal sun.
In order to benefit from the solar radiation during the cold months, the urban fabric has to be orientated to the south where the cardinal sun is. With the declination of +/- 30o the hot east or west sun are still benefiting the settlement.
In order to benefit from the solar radiation during the cold months, the urban fabric has to be orientated to the south where the cardinal sun is. With the declination of +/- 30o the hot east or west sun are still benefiting the settlement.
The East-West streets need to have the proper width for solar access.
Streets should be wide in order to allow the solar radiation to reach the east and west facades of the buildings for solar gain and natural lighting.
Streets should be wide in order to allow the solar radiation to reach the east and west facades of the buildings for solar gain and natural lighting.
Mix of building height to shadow the city.
Buildings can be arranged in order to protect open spaces or other buildings from solar radiation especially during the midday – afternoon sun.
Buildings can be arranged in order to protect open spaces or other buildings from solar radiation especially during the midday – afternoon sun.
Mixture of open & enclosure forms with structures or trees. Compact forms.
As the seasonal requirements are conflicting a more complicated urban design is required. Depending on the orientation and microclimate open forms can benefit from solar radiation and breezes while enclosure are protected from the intense sun and cold. Trees and structures can be a tool for protection.
As the seasonal requirements are conflicting a more complicated urban design is required. Depending on the orientation and microclimate open forms can benefit from solar radiation and breezes while enclosure are protected from the intense sun and cold. Trees and structures can be a tool for protection.
2. Topography
Topography, south sloping preferred.
In areas of intensive land, use buildings should be located on south slopes, where the sun exposure is adequate. Sites oriented south-southeast and located in the middle or the lower middle of a slope are preferred. Here solar gain is best. Excessive wind effects as well as cool air pools should be avoided. The layout of town structures should follow the same goal of sheltering against winds and utilizing the effects of the sun’s heat.
In areas of intensive land, use buildings should be located on south slopes, where the sun exposure is adequate. Sites oriented south-southeast and located in the middle or the lower middle of a slope are preferred. Here solar gain is best. Excessive wind effects as well as cool air pools should be avoided. The layout of town structures should follow the same goal of sheltering against winds and utilizing the effects of the sun’s heat.
Orientation, so as to benefit from the winter sun.
In lowland regions settlements should be exposed to the wind and protected from the sun. In winter the opposite is required: Exposure to the sun and protection from the wind.
In lowland regions settlements should be exposed to the wind and protected from the sun. In winter the opposite is required: Exposure to the sun and protection from the wind.
Protection from winter winds.
In upland regions, shelter against the wind and orientation for maximum solar radiation gain are required all the year round Houses should be located behind a wind shield, but be assured of exposure to the sun. This shield can be formed by existing or newly planted vegetation, by other structures or by topography.
In upland regions, shelter against the wind and orientation for maximum solar radiation gain are required all the year round Houses should be located behind a wind shield, but be assured of exposure to the sun. This shield can be formed by existing or newly planted vegetation, by other structures or by topography.
Form, semi-compact.
The layout of town structures should follow the same goal of sheltering against winds and utilizing the effects of the sun’s heat.
The layout of town structures should follow the same goal of sheltering against winds and utilizing the effects of the sun’s heat.
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 temperate climates during the cold season we must combine daylight access with solar access while in the summer we must combine daylight access with daylight-enhancing shading and reflection strategies.
The propper natural lighting of a building is affected by street width and the form of a building.Depending on the solar elevation of every place a building can block tha sun rays to another and thus deprive natural light and thermal gain. The mass of a building can be formed to allow sun rays while the width of a road provides the correct distance for the same reason.
A building can be lighted from indirect light as well from glare. This kind of lighting cannot be controled and it is unwanted during the warm months.Materials such as glass reflect sun light and create thermal discomfort in the summer.
4. Passive cooling/heating of outdoor urban spaces
Temperate climates
The main objectives in urban outdoor spaces are to:
- Seek solar radiation gain in winter and provide shading in summer
- Provide wind protection in winter and proper ventilation in summer
In temperate climates there must be a combination of strategies in order to achieve both results in summer and winter. It is important to benefit from the solar heat in winter through the proper orientation but also to provide shading in summer to avoid intense solar radiation. The same applies for the air movement as in the cold months the wind must be blocked while during the summer it is needed for natural cooling.
The main objectives in urban outdoor spaces are to:
- Seek solar radiation gain in winter and provide shading in summer
- Provide wind protection in winter and proper ventilation in summer
In temperate climates there must be a combination of strategies in order to achieve both results in summer and winter. It is important to benefit from the solar heat in winter through the proper orientation but also to provide shading in summer to avoid intense solar radiation. The same applies for the air movement as in the cold months the wind must be blocked while during the summer it is needed for natural cooling.
4.1 Materials for temperate climates. Materials can be categorized in cold and warm and depending on environmental strategy. In temperate climates there is a need for protection from the heat during the warm months..
Cold materials are those that 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.
Cold materials can be classified into two categories .One concerns the development of materials related to the building envelope , which is either cold coatings on the outside of buildings, tiles , paints or materials relating to the exterior surfaces like cement tiles , marble , terrazzo , stone , asphalt roads .
Some other materials that are often used in temperate climates with similar qualities.
Stone is a durable material that is frequently used in open spaces. It is water resistant and maintains the aesthetic features it has through a quite long period of time. It is a low carbon natural material that is used since ancient times.
Gravel has the same properties as the stone but is much more quick
and cheap to construct as it adjusts to the landscape. It is a reused
material and can protect surfaces from water and solar radiation.
and cheap to construct as it adjusts to the landscape. It is a reused
material and can protect surfaces from water and solar radiation.
Brick is a material that comes in many types of surface texture, density, weight, absorption and pore structure, thermal characteristics, thermal and moisture movement, and fire resistance. In open spaces bricks are used for block paving and pavements.
Ceramic tiles have good resistance to solar radiation, water and freezing and are therefore used for outdoor flooring. It is also a material that do not have a harmful impact on the environment and health.
Concrete is highly used in open spaces because it can be formed easily
and it is durable. Nevertheless it is better to be protected by the intense
summer sun because it releases back the heat.
and it is durable. Nevertheless it is better to be protected by the intense
summer sun because it releases back the heat.
Synthetic wood (deck) . Composite materials usually cost more than natural timber, but their long life and low-maintenance requirements make them more economical in the long run. Many composites are often made partially out of recycled plastics and waste wood, ,which makes them an environmentally friendly, efficient use of resources.
4.2 Planting
Planting in a city has many benefits in both environmental and aesthetic matters. There are many strategies that can be applied through vegetation in temperate climates.
4.2.1 Wind blocking
In temperate climates the strategies must be combined. To counteract the winter wind direction, evergreen windbreakers are desirable. Trees and bushes can block the cold winds whereas in the hot period should not block the prevailing summer breezes. Evergreen trees are best for wind protection, whereas deciduous trees are suitable for shading purposes because during winter they allow the solar rays to pass while in the summer protect from the sun.
Planting in a city has many benefits in both environmental and aesthetic matters. There are many strategies that can be applied through vegetation in temperate climates.
4.2.1 Wind blocking
In temperate climates the strategies must be combined. To counteract the winter wind direction, evergreen windbreakers are desirable. Trees and bushes can block the cold winds whereas in the hot period should not block the prevailing summer breezes. Evergreen trees are best for wind protection, whereas deciduous trees are suitable for shading purposes because during winter they allow the solar rays to pass while in the summer protect from the sun.
4.2.2 Wind cooling
Natural ventilation can be applied from the proper orientation to the cooler breezes during the hot months. This can be amplified with proper planting for the cooling of the air.
Natural ventilation can be applied from the proper orientation to the cooler breezes during the hot months. This can be amplified with proper planting for the cooling of the air.
4.2.3 Shading
In the hot period, open spaces used from people must be protected from solar radiation and glare. In the cold season, however, solar heat gain is desired. Hence, shading devices should be movable, which involves a somewhat complicated mechanism and also the attendance users. Deciduous trees can be used in the same way, for shading in the summer and solar gain in winter.
In the hot period, open spaces used from people must be protected from solar radiation and glare. In the cold season, however, solar heat gain is desired. Hence, shading devices should be movable, which involves a somewhat complicated mechanism and also the attendance users. Deciduous trees can be used in the same way, for shading in the summer and solar gain in winter.
4.2.4 Green roofs
Green roofs and vertical planting can reduce the urban heat island phenomenon. This can be achieved because the light is absorved by vegetetion and it is not converted into heat energy.Another benefit from green roofs and planting is that they reduce gas emmisions and therefore create a cooler and healthier urban environment. The aeshetic improvement when applying green roofs in a city is also notable.
Green roofs and vertical planting can reduce the urban heat island phenomenon. This can be achieved because the light is absorved by vegetetion and it is not converted into heat energy.Another benefit from green roofs and planting is that they reduce gas emmisions and therefore create a cooler and healthier urban environment. The aeshetic improvement when applying green roofs in a city is also notable.
4.3 Water element
The water element can be used during the hot period for natural cooling. Combined with summer breezes and by evaporating it creates a cooler microclimate providing thermal comfort. Fountains can be used in the urban environment in order to achieve this natural cooling method.
The water element can be used during the hot period for natural cooling. Combined with summer breezes and by evaporating it creates a cooler microclimate providing thermal comfort. Fountains can be used in the urban environment in order to achieve this natural cooling method.
(T.M.)