Macro and micro climate

Climatology

1. CLIMATOLOGY - I DEPARTMENT OF ARCHITECTURE NORTH-EASTERN HILL UNIVERSITY

2. 2 Micro & Macro Climate

3. 3 Macro and Micro Climate …… CLIMATE The climate of the Earth consists of a series of interlinked physical systems powered by the sun. In the built environment we are generally concerned with local climatic systems in particular. Macro – Climate the climate of a larger area such as a region or a country Micro – Climate the variations in localized climate around a building

4. 4 Macro and Micro Climate …… The macro and micro climate has a very important effect on both the energy performance and environmental performance of buildings – both in Summer and Winter season. 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, pollution levels, solar radiation that the building receives, temperatures and rain penetration.

5. 5 Site and Macro Climate …… The orientation of the building affects solar gains and exposure to the prevailing wind (ventilation). The location of neighboring trees and buildings affects the solar gains (shading) and wind patterns . Neighboring trees and buildings also protect the building from driving rain.

6. 6 Macro Climate …… The macro climate around a building cannot be affected by any design changes. 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 : Seasonal accumulated temperature difference (degree day) are a measure of the outside air temperature, though do not account for: Available solar radiation. Typical wind speeds and direction. Annual totals of Global Horizontal Solar Radiation. The driving rain index ( DRI )

7. 7 Macro Climate …… This Meteorological 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 .

8. 8 Macro Climate …… This Meteorological 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 .

9. 9 Micro Climate …… The site of a building may have its own micro climatic conditions caused by the presence of hills valleys, slopes, streams and other buildings. Micro Climate - Effect of Local Terrain Surrounding slopes have important effects on air movement, especially at the bottom of a hill. In the hills air warmed by the solar radiation rises upwards due to buoyancy effects ( Anabatic flow ), to be replaced by cooler air drifting down the slope ( Katabatic flow ). The result is that valley floors are significantly colder than locations part way up the slope.

10. 10 Micro Climate …… Micro Climate - Effect of Local Terrain Katabatic flows often result in frosts persisting for longer in low lying locations. The most favorable location in a valley is known as 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 . The crests of hills and ridges have unfavorable wind velocity profiles, the wind flow is compressed (as happens with an aero foil) leading to high wind velocities.

11. 11 Micro Climate …… Micro Climate - Effect of Buildings Buildings contribute to create micro-climatic conditions by shading the ground, changing wind flow patterns. One example of how buildings affect the local climate is the heat island effect in large cities where the average temperature is higher than the surrounding areas. 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.

12. 12 Micro Climate …… Micro Climate – Urban Heat Islands “An  urban heat island  (UHI) is a city or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities .” The phenomenon was first investigated and described by  Luke Howard  in the 1810s, although he was not the one to name the phenomenon . The main cause of the urban heat island (UHI) effect is from the modification of land surfaces, which use materials that effectively store short-wave radiation . The less-used term  heat island  refers to any area, populated or not, which is consistently hotter than the surrounding area.

13. 13 Micro Climate …… What is an Urban Heat Island ? As urban areas develop, changes occur in their landscape. Buildings, roads, and other infrastructure replace open land and vegetation. Surfaces that were once permeable and moist become impermeable and dry . These changes cause urban regions to become warmer than their rural surroundings, forming an "island" of higher temperatures in the landscape.

14. 14 Micro Climate …… Heat Island

15. 15 Micro Climate …… Heat Island

16. 16 Where does Heat Island occur ? Heat islands occur on the surface and in the atmosphere. On a hot, sunny summer day, the sun can heat dry, exposed urban surfaces, such as roofs and pavement, to temperatures 50–90°F (27–50°C) hotter than the air , while shaded or moist surfaces—often in more rural surroundings—remain close to air temperatures. Surface urban heat islands are typically present day and night, but tend to be strongest during the day when the sun is shining. Micro Climate ……

17. 17 Micro Climate …… Developed Environment Urban, suburban, and rural communities are the three main types of developed environments. All three of these environments have both common and unique land cover types. Each land cover may affect local air temperatures differently because of unique thermal properties. These areas have natural surfaces and impervious surfaces.

18. 18 Micro Climate …… Developed Environment Impervious surface : A hard surface area that either prevents or retards the entry of water into the soil as under natural conditions prior to development and/or a hard surface area that causes water to run off the surface in greater quantities or at an increased rate of flow from the flow present under natural conditions prior to development. Common impervious surfaces include, rooftops, walkways, patios, driveways, parking lots, storage areas, concrete or asphalt paving, gravel roads, packed earthen materials, and oiled, macadam, or other surfaces that similarly impede the natural infiltration of urban runoff.

19. 19 Micro Climate …… Why do we care about Heat Islands ? Heat islands can affect communities by increasing summertime peak energy demand, air conditioning costs, air pollution and greenhouse gas emissions, heat-related illness and mortality, and water quality.

20. 20 Micro Climate …… High energy demands Increased energy consumption: Higher temperatures in summer increase energy demand for cooling and add pressure to the electricity grid during peak periods of demand. One study estimates that the heat island effect is responsible for 5–10% of peak electricity demand for cooling buildings in cities .

21. 21 Micro Climate …… Increased Emissions Elevated emissions of air pollutants and greenhouse gases: Increasing energy demand generally results in greater emissions of air pollutants and greenhouse gas emissions from power plants. Higher air temperatures also promote the formation of ground-level ozone.

22. 22 Micro Climate …… Quality of life Compromised human health and comfort: Warmer days and nights, along with higher air pollution levels, can contribute to general discomfort, respiratory difficulties, heat cramps and exhaustion, non-fatal heat stroke, and heat-related mortality.

23. 23 Micro Climate …… Water Quality Impaired water quality: Hot pavement and rooftop surfaces transfer their excess heat to storm water, which then drains into storm sewers and raises water temperatures as it is released into streams, rivers, ponds, and lakes. Rapid temperature changes can be stressful to aquatic ecosystems.

24. 24 Micro Climate …… What can be done ? Communities can take a number of steps to reduce the heat island effect, using four main strategies: Increasing tree and vegetative cover Creating green roofs (also called "rooftop gardens" or "eco-roofs") Using cool or green pavements Installing cool or reflective roofs

25. 25 GREEN ROOF A GREEN ROOF is a roof of a building that is partially or completely covered with vegetation and soil, or a growing medium, planted over a waterproofing membrane. The term " GREEN ROOF " may also be used to indicate roofs that utilize some form of "green" technology, such as solar panels or a photovoltaic module. Green roofs are also referred to as eco-roofs, vegetated roofs, living roofs, and green roofs.

26. 26 GREEN ROOF

27. 27 GREEN ROOF RENZO PIANO

28. 28 CALIFORNIA ACADEMY OF SCIENCES WORLD’S GREENEST PLATINUM RATED BUILDING - LEEDS

29. 29 CALIFORNIA ACADEMY OF SCIENCES

30. 30 CALIFORNIA ACADEMY OF SCIENCES THE LIVING ROOF

31. 31 CALIFORNIA ACADEMY OF SCIENCES

32. 32 COOL PAVEMENTS – pervious pavements The term refers to materials chosen to reduce pavement temperature by increasing pavement reflectivity ( Albedo Effect ) or controlling temperature by other means through choice of materials and engineering design. Pervious pavements can be made of concrete , asphalt, open-celled stones, and gravel, that are mixed in a manner that creates an open cell structure allowing water and air to pass through.

33. 33 COOL PAVEMENTS – pervious pavements Advantage Pervious pavements allow rainwater to seep into the ground through the pavement: Vegetation is watered, reducing the need for irrigation Ground water is recharged Water resources are preserved Storm water runoff is reduced Storm water runoff quality is improved

34. 34 Micro Climate

35. 35 Micro Climate …… Improving Micro Climate through Design The aims of enhancing Micro-Climate around Buildings : Reduce costs of winter heating. Reduce summer overheating and the need for cooling. Maximize outdoor comfort in summers as well as winters. Improve durability of building material (reduced rain penetration). Encourage growth of plants. Facilitate open air drying of clothes.

36. 36 Micro Climate …… Means of enhancing the micro climate around a building include: Solar Access: Allow maximum daylight into space and buildings. Allow maximum solar radiation into space and buildings (For Cold areas ). Shade open spaces and windows from prolonged exposure to summer sun. Protect space and windows from glare.

37. 37 Micro Climate …… Means of enhancing the micro climate around a building include: Wind Protection: Protect space and buildings from prevailing winds and cold 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.

38. 38 Micro Climate …… Means of enhancing the micro climate around a building include: Features: Provide thermal mass to moderate extreme temperatures .

39. 39 Micro Climate …… Means of enhancing the micro climate around a building include: Features: Use vegetation for sun shading and wind protection ( transpiration helps moderate high temperatures).

40. 40 By altering wind movement, evaporation, moisture, and soil temperatures, vegetation influences the microclimate of an area, especially near the ground. Temperatures at ground level in the shade are lower than those in places exposed to sun and wind. Vegetation reduces the steepness of the temperature gradient above the ground surface and influences relative humidity and the height of the active surface, the surface of any object that receives or is impacted directly by solar radiation. Vegetative cover will also influence the extremes and daily maximum and minimum temperatures. Micro Climate …… The Importance of Vegetation

41. 41 Micro Climate …… Means of enhancing the micro climate around a building include: Features: Provide surfaces that drain readily .

42. 42 Micro Climate …… Means of enhancing the micro climate around a building include: Features: Provide water for cooling be evaporation (pools & fountains ).

43. 43 Factors Affecting Micro Climate WITHIN DESIGNER’S LIMIT BEYOND DESIGNER’S LIMIT Spacing and orientation of buildings Area and local climate Location of open spaces Site surroundings Form and height of buildings Site shape Fenestration Topographic features Tree cover , Ground profiling, wind breaks, surrounding surfaces (grass pavers etc.) Surrounding buildings

44. 44 Factors Affecting Micro Climate Two main possibilities for influencing Micro Climate are Solar Access and Wind Control. Solar Access: Solar access to a site is often a case of minimizing solar overheating in summer while maximizing solar access during the winter. Buildings with a heating requirement should be orientated north south with maximum glazing on the south face. Deciduous trees offer an excellent means of site shading, with shading being reduced in winter when the trees lose their leaves . The colour of surrounding surfaces will have a pronounced effect on the solar radiation available to the building – Albedo Effect

45. 45 Factors Affecting Micro Climate Two main possibilities for influencing Micro Climate are Solar Access and Wind Control. Solar Access: Light coloured paving will increase the radiation reflected from the ground into the building. Paving stones will also provide external thermal mass, moderating temperature swings immediately adjacent to the building . Grass planted outside a building will reduce the ground reflected solar radiation – thus trapping heat – Heat Island Effect Use of courtyards and water can also moderate the effects of high temperatures on summer.

46. 46 Factors Affecting Micro Climate Two main possibilities for influencing Micro Climate are Solar Access and Wind Control. Wind Control – The form of the building can have a great effect on the impact of wind. Avoiding of funnel-like gaps between buildings. Avoiding abrupt changes in building heights. Orientate long axis of the building parallel to the direction of the wind Use pitched rather than flat roofs and stepped forms for higher buildings Groups of buildings can be arranged in an irregular patterns to avoid wind tunneling. Coniferous trees and fencing and other landscape features such as mounds of earth and hedges can also reduce the impact of wind and driving rain on the building.

47. 47 Micro & Macro Climate