Macroclimate microclimate

Lesson on the different climate situations. definitions and context of climate in built environment

1. CLIMATE What is climate?

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.  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

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

16. Factors Affecting Micro Climate

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