Macroclimate microclimate
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Lesson on the different climate situations. definitions and context of climate in built environment
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Macroclimate microclimate
- 2. Macro climate the climate of a larger area such as a region or a country the variations in localised climate around a building Micro climate
- 3. Macro climate • The building site affects exposure to the prevailing wind, the solar radiation the building receives, pollution levels, temperatures and rain penetration.
- 4. Site and macro climate The orientation of the building affects solar gains and exposure to the prevailing wind (ventilation). The location of neighbouring trees and buildings affects the solar gains (shading) and wind patterns. Neighbouring trees and buildings also protect the building from driving rain.
- 5. Why consider the macro climate • Seasonal accumulated temperature difference • Typical wind speeds and direction • Annual totals of Global Horizontal Solar Radiation • The driving rain index (DRI) relates to the amount of moisture contained in exposed surfaces and will affect thermal conductivity of external surfaces.
- 6. Micro climate The climate of a very small or restricted area, especially when this differs from the climate of the surrounding area The site of a building may have a many micro climates caused by the presence of hills valleys, slopes, streams and other buildings.
- 7. Effect of Local Terrain • In hollows air warmed by the rises upwards due to buoyancy effects (anabatic flow), to be replaced by cooler air drifting down the slope (katabatic flow). • valley floors are significantly colder than locations part way up the slope. 1. http://www.boeingconsult.com/Environment/MacroMicroClimate.htm a wind that carries high- density air from a higher elevation down a slope under the force of gravity. warm wind which blows up a steep slope or mountain side, driven by heating of the slope through insolation. Upslope Flow Fall Winds
- 8. Where do you place the buildings? The crests of hills and ridges have unfavourable wind velocity profiles, the wind flow is compressed leading to high wind velocities. The thermal belt, lying just above the level to which pools of cold air build up, but below the height at which exposure to wind increases.
- 9. Effects of Buildings Buildings themselves create further micro-climates changing wind flow patterns.
- 10. Effects of Buildings Buildings themselves create further micro-climates By shading the ground
- 11. Example of the building effecting the climate The heat island effect in large cities where the average temperature is higher than the surrounding area
- 12. Heat Island
- 13. Climate Deviation • Slope, orientation, exposure, elevation, hills or valleysTopography • Natural or Man made surface, ground coverGround Surface • Trees, fences, walls, buildings3 D Objects
- 14. Urban climate Ground Surface quality Increase in absorption of solar radiation Less evaporation Buildings Atmospheric pollution – waste products, smoke for vehicles, industries, fumes, vapours
- 15. Level of Deviation Air temperature • A city will have a higher temperature than the surrounding countryside – 11˚ C has been reported recording. Relative Humidity • Reduction by 5- 10% • Quick run-off rainwater, • Absence of vegetation Wind Velocity • Reduced to less than half of that in the adjoining open country.
- 16. Factors Affecting Micro Climate Outside Designers Control Area and local climate Site surroundings Site shape Topographic features Surrounding Buildings Within Designer’s Remit Spacing and orientation of buildings Location of open spaces Form and height of buildings Fenestration Tree cover Ground profiling Wind breaks Surrounding surfaces (paving grass etc)
- 17. Enhancing micro climate • Reduce costs of winter heating • Reduce summer overheating and the need for cooling • Maximise outdoor comfort in summer and winter • Improve durability of building material (reduced rain penetration) • Provide a better visual environment in spaces around buildings • Encourage growth of plants • Discourage growth of mosses and algae • Facilitate open air drying of clothes
- 18. Solar Access • Allow maximum daylight into space and buildings • Allow maximum solar radiation into space and buildings • Shade space and windows from prolonged exposure to summer sun • Protect space and windows from glare
- 19. Wind Protection • Protect space and buildings from prevailing winds and cold (e.g. North/East) winds. • Prevent buildings and terrain features from generating turbulence • Protect spaces and buildings from driving rain and snow • Protect space and buildings from katabatic flows, while retaining enough air • movement to disperse pollutants
Editor's Notes
- The macro and micro climate has a very important effect on both the energy performance and environmental performance of buildings, both in the heating season and in summer. The site and design of a building can have a profound effect upon the interaction between a building and its environment. The building site affects exposure to the prevailing wind, the solar radiation the building receives, pollution levels, temperatures and rain penetration.
- The macro climate around a building cannot be affected by any design changes, however the building design can be developed with a knowledge of the macro climate in which the building is located. General climatic data give an idea of the local climatic severity: This Metereological data gives a general impression of the climate at the site of a building and the building design can be planned accordingly. However, the building itself and surrounding geography will affect the local climate.
- Solar energy absorbed and re-emitted from building surfaces, pavements roads etc. creates a warming effect on the surrounding air. Also the large quantities of buildings break up the wind flow, reducing wind speeds and causing the warm air to remain stagnant in the city. This also causes increased pollution as well as temperatures. The presence of local high rise buildings can degrade the local climate as wind speed at ground level can be significantly increased, while extensive shadows block access to sunlight for long periods, increasing space heating costs in surrounding buildings.