2.11 Climatic Urban Design Strategies
2.11.1 Solar Effect
85 Figure 2.44: The variation of wind speed in the canyon of the four studied H/W ratios and in four
orientations (Al Znafer, 2014)
For this type of weather, reducing the solar effect should be the major target for the architect or urban planner. This reduction in solar gain will be reflected positively on the built environment. It will help to mitigate the effect of the
on urban level. Reducing the solar effect on urban level can be obtained th
urban geometry variables. It has been proved that the best orientation for reducing solar effect in a hot climate is extending the le
Hoffman, 2003). Todhunter (1990) highlighted that this orientation will reduce the solar gain in summer months as less area is oriented towards the south direction. Figure 2.
the S-N direction is exposed to the highest amount of sun radiation, and the will protect the largest area of the
Figure 2.45:Sun path and best solar orientation for less solar gain in summer (Eco The amount of the solar radiation received by the surfaces
amount is significant in the latitudes between 20 significant than winter in this location of the earth (
very import in this location to form and control solar irradiation effect
For this type of weather, reducing the solar effect should be the major target for the architect or urban planner. This reduction in solar gain will be reflected positively on the built environment. It will help to mitigate the effect of the UHI and reduce the energy consumption on urban level. Reducing the solar effect on urban level can be obtained th
urban geometry variables. It has been proved that the best orientation for reducing solar effect hot climate is extending the length of the buildings along the E-W
2003). Todhunter (1990) highlighted that this orientation will reduce the solar gain in summer months as less area is oriented towards the south direction. Figure 2.
direction is exposed to the highest amount of sun radiation, and the will protect the largest area of the buildings from sun radiation.
Sun path and best solar orientation for less solar gain in summer (Eco
The amount of the solar radiation received by the surfaces depends on the latitude. This amount is significant in the latitudes between 20°-40°, and the impact in summer is more significant than winter in this location of the earth (Arnfield, 1990). The
very import in this location to form and control solar irradiation effects.
86 For this type of weather, reducing the solar effect should be the major target for the architect or urban planner. This reduction in solar gain will be reflected positively on the built nd reduce the energy consumption on urban level. Reducing the solar effect on urban level can be obtained through adopting urban geometry variables. It has been proved that the best orientation for reducing solar effect axis (Shashua and 2003). Todhunter (1990) highlighted that this orientation will reduce the solar gain in summer months as less area is oriented towards the south direction. Figure 2.45 shows that direction is exposed to the highest amount of sun radiation, and the E-W direction
Sun path and best solar orientation for less solar gain in summer (Eco-who,2015) on the latitude. This and the impact in summer is more . The urban geometry is
87 Arnfield (1990) investigated the effect of the H/W ratio and two orientations on the amount of the solar received by the canyon ground and building walls. The researcher conducted a numerical study for all earth latitudes, and six H/W ratios of 0.25. 0.5, 1.0, 2.0, 3.0 and 4.0 (Figure 2.46).
Figure 2.46: Canyon surfaces solar irradiation in two orientations and six H/W ratios (0.25+, 0.5x, 1*, 2□,3Δ and4○) (Arnfield, 1990)
The researcher found that the ground receives more solar radiation than the walls in a low H/W ratio. Furthermore, the orientation affects the amount of solar radiation received by walls more than the ground. In summer it is more efficient to orient the building wall along the E-W axis in order to protect the wall from the exposure (Figure 2.46).
However, Toudert and Mayer (2004) found that exact E-W orientation provides less shading for the canyon in a hot and arid climate.
88 This will affect the indoor thermal performance by increasing the absorbed solar energy. The
researchers stated that orienting the block of buildings with an angle along NW-SE or NE-SW is better for the desired shading for the buildings. The NE-SW orientation increases
the solar exposure during the morning, while the NW-SE orientation increases the exposure to the afternoon radiation (Toudert and Mayer 2004). Furthermore, the diversity in buildings height within an urban canyon plays an important role in increasing the shading effect.
The effect of diversity in buildings height for creating comfortable outdoor environments was proved by Edward (2010). The researcher explored the benefits of the height diversity in a dense and compact form. The author presented the 'Environmental Diversity Map'.
This map shows the effect of height diversity on three of the microclimate parameters:
temperature, shading and wind (Figure 2.47).
Figure 2.47: The 'Environmental Diversity Map', the effect of the three parameters: a) temperature, b) shading and c) wind (Edward 2010)
Furthermore, the dense or compact configuration of buildings pattern provides the desired protection from the solar radiation. Previous studies proved the effect of the organic and dense patterns on creating the desired outdoor thermal comfort in a hot climate. Andreou (2014) highlighted the effect of the traditional compacted form in creating the desired shading in a Mediterranean city.
89 The researcher compared two locations, traditional and contemporary areas, in Greece. The researcher found that the compacted traditional pattern provides more desired outdoor shading comparing with the contemporary area (Figure 2.48). Furthermore, the author illustrated that street pattern, buildings configuration and latitude are some of the factors that contribute to the canyon solar access.
Figure 2.48: The shading effect on traditional area (up) and contemporary (down) in summer and winter (Andreou, 2014)