Climatic Design of Buildings - An Overview

3. CLIMATE ANALYSIS

3.1 Use of Climatic Data

Climate analysis carried out at initial design stage may be used for:

• develop design strategies
• check condensation problems in some cases
• optimisation of insulation

• calculation of cooling and heating requirements
• design of heating, ventilating and air-conditioning (HVAC) systems
• energy estimation of buildings

EXAMPLE OF SUNSHADE ANALYSIS
1. Solar paths requiring shade Studying the sunpath diagram for each climatic zone, the shaded areas represent the periods of overheating, related to undesirable solar gain. In the lower latitudes there is total overheating, whereas in the higher latitudes overheating only occurs during the summer months.	3. Insolation The sunpath becomes more southerly as we move north, changing from a 'bow-tie' pattern near the equator to a heart-shape pattern in the temperate zones.
2. Sunshade analysis (vertical and horizontal) The diagrams show the optimum location of vertical sun shading, shielding the building from low sun angles in the morning and evening, and horizontal sun shading blocking the high midday sun. Tropical regions need both vertical and horizontal shading throughout the year. In higher latitudes, horizontal and vertical shading is only needed during the summer on the south-facing sides of buildings.	4. Sun requirements during winter There are obviously seasonal variations near the equator. Solar heating becomes more important than in the upper latitutdes. Beginning at the equator and moving north, the need for solar heating increases while the need for solar shading dimishes.

3.3 Wind Analysis
 

Wind direction Desirable and undesirable winds in each the climatic zones depend largely on local conditions. Any breeze in the lower latitude (tropical and arid climates) is beneficial for most of the year whereas in higher latitudes most wind is determental and has to be screened. There is also a small percentage of the time in a year (spring and/or autumn) when comfortable conditions can be achieved naturally, without any need for wind screening or additional breezes. Cross ventilation Cross ventilation is far more important in the tropics than in temperate zones. The theoretical strategy for blocking or inducing wind flow into a building is based on local prevailing wind conditions. Genrally, for the tropical zones as much ventilation as possible is desired. For the arid zone cross ventilation is required, but care has to be taken to filter out high-velocity winds. In the temperate zone, cross ventilation and shielding are both necessary (for summer and winter, respectively). In the cool region, the building should be protected from cold, high-veolcity winds, although cross ventilation is still required.

3.4 Humidity, Rainfall and Seasonal Variations
 

Annual Average Relative Humidity The curve on the left represents the annual average relative humidty in the four climatic zones. In the arid zone, the low level of humidity can be beneficial for evaporative cooling. In the tropical zone the high level of humidity can be very uncomfortable. Annual Average Rainfall The middle curve represents the annual average rainfall in the four climatic zones. Rainfall level can be seen to have a direct relationship with humidity levels. Annual Seasonal Variations The distance of the angled line from the vertical represents the annual seasonal variations in the four climatic zones. Higher latitudes, the cold and temperate zones, have pronounced seasonal variations. The lower latitudes have constant climates throughout the year.

3.5 Influences on Built Form

1. Zoning for trasitional spaces The black areas represent the traditional spaces used for lobbies, stairs, utility spaces, circulation, balconies and any othe areas where movement take place. These areas do not require total climatic control and natural ventilation is sufficient. For the tropical and arid zones, the transitional spaces are located on the north and south sides of the building where the sun's penetration is not as great. An atrium can also be used a transitional space. In temperate and cool zones the transitional spaces should be located on the south side of the building to maximize solar gain.	3. Use of atrium The diagram show the optimum position for atrium spaces in each building form in each of the climatic zones. in the tropical zone the atrium should be located so as to provide ventilation within the built form. In the arid zone the atrium should be located at the centre of the building for cooling and shading purposes. For the cool and temperate zones the atrium should be at the centre of the building form for heat and light.
2. Zoning for solar gain The black areas are spaces that can be used for solar heat gain. They follow the varying path of the sun in each of the climatic zones: in the tropical and arid zones the east and west sides; in the temperate and cool zones the south side.	4. Potential of roof/ground floor as useable exterior space The distance of the angled line from the vertical represents the potential of each zone's roof and ground planes to be used a exterior spaces. In tropical and arid climates there is a high potential to make use of all external spaces, whereas moving towards the northern latitutdes the external spaces have to be covered to be used.

1. Form The diagrams show the optimum building form for each climatic zone. Research has shown that the preferred length of the sides of the building, where the sides are of length x:y, are: tropical zone  -  1:3 arid zone  -  1:2 temperate zone  -  1: 1.6 cool zone  -  1:1 Analysis of these ratios shows that an elongated form to minimize east and west exposure is needed at the lower latitudes. This form slowly transforms to a ratio of 1:1 (cylindrical) at the higher latitudes. This is a direct response to the varying solar angles in the various latitudes. 2. Orientation Orientation as well as directional emphasis changes with latitude in response to solar angles.   Zone Building's main orientations Directional emphasis Tropical On an axis 5o north of east north-south Arid On an axis 25o north of east south-east Temperate On an axis 18o north of east south-south-east Cool On an axis facing south facing south

3. Vertical cores and structure The arrangement of primary mass can be used as a fator in climatic design as its position can help to shade or retain heat within the building form. For the tropical zone, the cores are located on the east and west sides of the building form, so as to help shade the building from the low angles of the sun during the major part of the day. In arid zone, the cores should also be located on the east and west sides, but with major shading only needed during the summer. Therefore, the cores are located on the east and west sides,but primarily on the south side. The arrangement of the primary mass in the temperate zone is on the north face, so as to leave the south face available for solar heat gain during the winter. The cool zone requires the maximum perimeter of the building to be open to the sun for heat penetration. Therefore the primary mass is placed in the centre of the building so as not to block out the sun'r rays and to retain heat within the building.

• Climatic Design