India is home to an extraordinary variety of climatic regions, ranging from tropical in the south to temperate and alpine in the Himalayan north, where elevated regions admit sustained downtime snowfall. Climate can influence the planning of towns, buildings, and settlement designs and may evoke strategies to market the efficiency of thermal comfort. The built environment affects local and regional global climate change and influences health and luxury.
Table of Contents
Nature of the Composite Climate
The composite climate is neither constantly hot and dry nor warm and sticky. Their characteristics are ever changing, interspersing between long, hot, and dry ages to shorter ages of downfall and high moisture. There’s a significant difference in air temperature, moisture, wind, sky, and ground conditions throughout the time.
Designs here are guided by a longer prevailing climate. The duration of ‘uncomfortable’ periods in each season has got to be compared to derive an order of priorities.
The objectives set for composite climate apply to the objectives of both warm-humid and hot-dry climates.
During the cold season, effective temperatures are much less than within the warmer seasons and therefore the physical comfort will depend on heat loss, especially through the night.
In the warmer season, cooling is insufficient and designers attempt to increase it, the other happens during the cold season. The dissipation is excessive, hence heat retention is important.
Solutions for one season might be unsuitable for another.
Thermal design criteria recommended for hot-dry climates apply to both the hot-dry season and cold season of composite climate. For the monsoon, buildings should be designed consistent with the standards of warm-humid climate, which might require an entirely special solution. This duality of the matter has got to be handled tactfully by the designer. An analysis of the location climate will help the designer prioritize the requirements.
Design Considerations for a Climate Zone
The building should be located preferably in the North-East and South-West direction. This helps in receiving less radiation and more natural light & ventilation.
Form and Planning
The building must be compact and low-rise. Buildings with a courtyard are more suitable. A moderately compact internal planning of the house is going to be of benefit for many of the year. Buildings should be grouped thanks to cash in of the prevailing breezes during the short period when air movement is important.
A moderately dense, low-rise development is suitable, which can ensure the protection of outside spaces, mutual shading of the external walls, and shelter from the wind during the cold season. Shelter from dust and reduction of surfaces exposed to radiation. Shading walls are desirable, provided the roof features a low transmittance and good thermal capacity.
The building form also determines the airflow pattern around the building, directly affecting its ventilation. The compactness of the building is measured using the ratio of area to volume (S/V). The depth of a building also determines the need for artificial lighting. The greater the depth, the higher the need for artificial lighting. The circular geometry has a rock bottom S/+ ratio thus the conduction gains from the building envelope also as solar gains from windows are the smallest amount, in circular geometry in comparison to other building geometries which is the most energy-efficient in composite climate.
Sheltering or self-shading
The built form must be designed such that it self-shades through massing or articulation, resulting in cutting off a large amount of direct solar radiation. In a composite climate, with the help of external walls, the envelope should be designed so that it shades for the greater part of the day.
Roof and walls
Roofs and external walls should be constructed of solid masonry or concrete to have a 9 to 12-hour time lag in heat transmission. The thermal capacity will be beneficial for the cold and hot dry seasons. The roof pond system can be used as an insulator. Resistance insulation should be placed on the outer surfaces of the external walls or roof. Low rise development is the greater contact of the walls with the ground; thus, the ground will also act as thermal storage.
Colour and Texture
The external surfaces should be painted in medium-tone colors. The prevention of warmth entering through the outer surfaces of the walls and roof may be a fundamental rule. A light-colored or shiny polished metal finish is preferred for surfaces exposed to the sun during the hot and warm seasons.
Fenestration and Ventilation
Large openings (preferable with solid shutters on opposite walls are suitable which helps in cross ventilation. Recessed windows help in reducing solar heat gain in the external facade.
Orientation of the openings is determined by two factors–first, towards the breeze prevailing during the warm-humid season, to utilize its cooling effects and second, towards the sun during the cold season, to utilize the heating effect of radiation entering through the windows; If the two factors lead to a contradiction, the analysis of comfort will aid in reaching a final decision.
Reasonably large opening within the opposite walls is suitable, preferably with solid shutters which may be opened when cross-ventilation is important, possibly during the recent and humid season or cool evenings in the hot-dry season. The area of the openings shouldn’t exceed the world of the solid walls at an equivalent elevation. On the adjacent walls, the windows should not occupy more than 25% of the total area. Shade is required for external openings during the hot and warm seasons.
Daylighting has a major effect on the appearance of space and can have considerable implications on energy efficiency if used properly. Its variability is subtly pleasing to the user in discrepancy to the fairly monotonous terrain produced by artificial light. It helps to make optimum working conditions by bringing out the natural contrast and color of objects.
The presence of natural light can bring a way of well-being and awareness of the broader environment. Daylighting is vital, particularly in commercial and other non-domestic buildings that function during the day. Integration of daylighting with artificial light brings about considerable savings in energy consumption. A good daylighting system features a number of elements, most of which must be incorporated into the building design at an early stage.
Optimum Window Wall Ratio (WWR)
Window Wall Ratio is the ratio of the vertical window opening area to gross exterior wall area. The gross exterior wall area is measured horizontally from the outside surface; it’s measured vertically from the highest of the ground to the rock bottom of the roof. The optimum Window Wall Ratio would achieve a balance between cooling energy demand and lighting energy demand due to the integration of natural daylight.
Brise-soleils, louvers, and other sun breaks used to protect openings during the hot-dry period also are advantageous within the season, serving as a protection against rain. During the cold season, when solar gain is important, all shading is undesirable. Vegetation is easier to maintain because of the high rainfall, consequently also reducing dust. Deciduous plants are advisable.
A courtyard is the most pleasant outdoor space for most of the year because it excludes the wind and raps the sun during the winter. Deciduous plants on a pergola can be used to cover the courtyard.
Landscaping is a crucial element in altering the micro-climate of an area. It prevents reflected light from carrying heat into a building from the ground or other surfaces. Additionally, the shade created by trees reduces the air temperature of the microclimate around the building through evapotranspiration. Properly designed roof gardens help to scale back heat loads during a building.
Planting deciduous trees on the southern side of a building is useful during a composite climate. Deciduous plants like mulberry or Champa stop direct sun during summer, and as these trees shed leaves in winter, they permit the sun to heat the building in winter, which is suitable in a composite climate.
Summer setting sun can be avoided by planting dense trees and shrub plantings on the west and northwest sides of a building. Natural cooling can be encouraged by locating trees to direct southeast summer breezes in composite climates. Cooling breezes are going to be ready to undergo the trunks of trees placed for shading.
Location of Water Bodies
Water is a good modifier of micro-climate. It takes up an outsized amount of warmth in evaporation and causes significant cooling. Water features a moderating effect on the air temperature of the microclimate. It possesses a very high thermal storage capacity, much higher than the building materials like brick, concrete, and stone.
Large bodies of water in the form of lakes, rivers, and fountains generally have a moderating effect on the temperature of the surrounding area. This is because of the variation in airflow caused by the higher thermal storage capacity of water in comparison to land.
During the day the air is hotter over the land and rises, drawing cooler air in from the water mass, resulting in inland breezes. During the night, as the landmass cools quicker, the airflow will be reversed. In humid climates, water should be avoided because it adds humidity.
The character of the homes during a composite climate depends upon the relative predominance of hot-dry or hot-humid conditions during a year. A typical solution is to surround the ground floor with massive earth walls or masonry walls with large fenestrations. The building is laid around a courtyard to encourage ventilation.
Earth walls or large fenestrations allow cool air to come inside the house. The first floor is made out of lightweight materials, which helps in reducing the heat gain due to built mass. This type of planning cools quickly in the dark, to permit fairly comfortable sleeping conditions during the most well-liked parts of the year. In such a hybrid structure, the family shifts its activities throughout the day with seasonal changes in the climate.
Advanced Passive Cooling Systems
Passive cooling systems believe in natural heat-sinks to get rid of heat from the building. These systems achieve cooling from either evaporation, convection, and radiation without using any mechanical device. All passive cooling strategies believe in daily changes in temperature and ratio. The applicability of every system depends on the climate. The relatively simple techniques that can be adapted to provide natural cooling in the building through solar passive design strategies have been explained earlier.
Efficient natural ventilation requires openings in opposite pressure zones. Natural ventilation can also be enhanced through tall spaces like stacks, chimneys, and so on in a building. With openings near the highest of stacks, warm air can escape whereas cooler air enters the building from openings near the bottom.
In a wind tower, the recent air entering the tower through the openings within the tower gets cooled, and this becomes heavier and sinks down. Cool air movement is induced as a result of the inlet and outlet of rooms.
After an entire day of air exchanges, the tower becomes warm in the evenings. During the night, cooler ambient air comes in touch with the rock bottom of the tower through the rooms. The tower wall absorbs heat during the daytime and releases it at night, warming the cool night air in the tower. Warm air moves up, creating an upward draft, and draws cool night air through the doors and windows into the structure. In thick civic areas, the wind palace has to be long enough to be suitable to catch enough air.
Due to the incident of radiation in a courtyard, the air gets warmer and rises. Cool air from the bottom level flows through the louvered openings of rooms surrounding a courtyard, thus producing air flows. At night, the nice and cozy roof surfaces get cooled by convection and radiation.
If this heat exchange reduces roof surface temperature to wet-bulb temperature of the air, condensation of atmospheric moisture occurs on the roof and the gain due to condensation limits further cooling.
If the roof surfaces are sloped towards the interior courtyard, the cooled air sinks into the court and enters the lebensraum through low-level openings, gets warmed up, and then leaves the room through high-level openings. However, care should be taken that the courtyard doesn’t receive intense radiation, which might cause conduction and radiation heat gains into the building.
Earth air tunnels
Daily and annual temperature fluctuation decreases with the increase in depth below the ground surface. The temperature inside the earth remains nearly constant at a depth of about 4m below ground and is almost adequate to the annual average temperature of the place.
A tunnel within the sort of pipe or otherwise embedded at a depth of about 4m below the bottom will acquire an equivalent temperature because the surrounding earth at its surface and thus the ambient air ventilated through this tunnel will get cooled in summer and warmed in winter and this air is often used for cooling in summer and heating in winter.
Passive downdraught cooling
In this system, wind catchers guide outside air over water-filled pots, inducing evaporation and causing a big drop in temperature before the air enters the inside. Similar wind catchers come as the primary rudiments of the architectural form as well.
The composite climates are a culmination of the characteristics of hot-dry and hot-humid climates. The dominant prevailing climatic condition analysis helps choose design solution priorities. The places which experience a composite climate are central India, central South America, and south-eastern North America.