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Dbn163 # 04. macro micro climate
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  • 1. DBN163 – BUILDING SCIENCE (I) Site Climate / Macro-Micro ClimateSite Climate / Macro-Micro Climate 1 BALKHIZ ISMAILBALKHIZ ISMAIL JAB. BANGUNAN, FSPU, UiTM SARAWAKJAB. BANGUNAN, FSPU, UiTM SARAWAK
  • 2. General Introduction  In the built environment we are generally concerned with local climatic systems in particular: 1. Macro-climate the climate of a larger area such as a region or a country 2. Micro-climate the variations in localised climate around a building  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. 2
  • 3. Macro-Micro Climate 3
  • 4. Macro Climate  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.  The knowledge 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 4
  • 5. Macro Climate  General climatic data give an idea of the local climatic severity:  Seasonal accumulated temperature difference (degree day) - a measure of the outside air temperature, though do not account for available solar  Typical wind speeds and direction  Annual totals of Global Horizontal Solar Radiation  The Driving Rain Index (DRI) - the amount of moisture contained in exposed surfaces and will affect thermal conductivity of external surfaces. 5
  • 6. Site Climate  Assumption of climate for a large project that covering extensive area.  On small sites, where there is less scope for variations in siting and orientation, this exercise will be more limited, but some consideration of local climatic patterns will always be justified. 6
  • 7. Micro Climate 7
  • 8. Micro Climate  A local atmospheric where the climate differs from 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.  The term may refer to areas as small as a few square feet or as large as many square miles. 8
  • 9. Climate Deviation 9
  • 10. Factors Influencing Micro Climate 1. Solar Access  Minimising solar overheating in summer  while maximising solar access during the winter.  Buildings with a heating requirement should be orientated  north south with maximum glazing on the south face.  Trees offer an excellent means of site shading  The colour of surrounding surfaces will have an effect on  the solar radiation available to the building.   Grass planted outside a building will reduce the ground  reflected solar.  Use of courtyards and water can also moderate the  effects of high temperatures on summer. 10
  • 11. Factors Influencing Micro Climate 2. Wind Control  Avoidance of funnel-like gaps between buildings  Avoidance of flat roofed buildings and cubical forms  Avoid abrupt changes in building heights  Orientate long axis of the building parallel to the direction of  the wind  Use podium to limit down draught at ground level  Groups of buildings can be arranged inirregular patterns to  avoid wind tunneling.  Coniferous trees and fencing and other landscape features  (mounds of earth and hedges) - reduce the impact of wind  and driving rain on the building structure. 11
  • 12. Climate Deviation 12 Factors which may cause local deviation are:-
  • 13. Urban Climate The factors causing deviations of urban climate: 1.Changed surface qualities (pavements and buildings) – increased absorbance of solar radiation; reduced evaporation 2.Buildings – casting a shadow and acting as barriers to winds, channeling the wind by increase in velocity 13
  • 14. Urban Climate 3. Energy seepage – through wall and ventilation of heated buildings 4. Atmospheric pollution – waste products, smoke from motorcars, fumes and vapors 14
  • 15. Level of Deviation 1. Air temperature – a city will have a higher temperature than the surrounding countryside – 11°C has been reported 2. Relative humidity – reduced by 5-10% - quick run-off rainwater, absence of vegetation, higher temperature 3. Wind velocity – reduced to less than half of that in the adjoining open country 15
  • 16. REFLECTION What are the differences between MACRO & MICRO CLIMATE? 16