The most prominent characteristics of this climate are the hot, sticky conditions and the continual presence of humidity. Air temperature remains moderately high. There is a slight variation between day and night temperature between 21 and 32°C.
Humidity is high all through the year. Heavy clouds and water vapour in the air act as a filter to direct solar radiation.
Moisture in the air combined with moderate heat and high rainfall is preferable for the growth of vegetation. The plant ground cover helps reduce reflected radiation, and the ground surface doesn’t heat much.
Winds are generally of low velocity but somewhat constant in one direction.
Physiological Objectives
Heat loss to the air by convection or conduction is inconsequential.
Comfort is achievable by encouraging out-door breezes to pass through the building.
As there is no significant cooling down at night, the walls and the roof surface temperatures tend to even out and settle at the same level as the air temperature.
Radiant heat loss from the body will be negligible, as the surface temperatures are near to the envelope temperature. Radiant heat gain from the sun and the sky needs prevention.
Form and Planning
The building needs to allow maximum airflow and oriented to catch and Increase whatever air available.
Open elongated plan with a single row of rooms to promote cross-ventilation. The access to the rooms is usually from a verandah.
Doors and window openings should allow maximum air movement, hence large sizes are advisable.
A group of buildings need to be in a way so that it increases the airflow, creating a venturi effect to increase the wind speed by narrow spaces.
Elevate the building on stilts, consequently avoiding the stagnant slow-moving air at the ground surface, capturing the air movement of a higher velocity.
Openness and shading will be a dominant feature of the building.
The designer has to prioritize orienting the building to avoid solar heat gain or increasing wind speed. It is subjective to a detailed analysis of the site. With low rise building, where the walls won’t get too much radiation, the orientation chosen is to increase wind. With a high-rise building, avoiding the sun holds more importance.
External Spaces
Shading and path for air movement are the basic requirements to achieve comfort.
Vegetation is a reliable source for shading and adding value to the outdoor space.
Pergolas and light framing structure promote creepers growth, thus provide shade.
The density of the development in these regions is mainly due to the following reasons- (1)To allow free movement of air through the building and its spaces.(2)To provide privacy by distance. (3)The open area allows many human activities without much effort. (4)Tall trees with clear trunks are preferable as they cast a shadow and allow penetration of the breeze.
Roofs and walls
The principle of thermal storage cannot be relied on in this particular climate because the temperature of the outside air is almost the same as the day and night, a building cannot be cooled off at night time to allow storage of heat during the day.
A reflective upper surface, a double roof with roof ventilation, a ceiling with its upper surface highly reflective and have good resistive insulation. The Roof and the Ceiling should have a low thermal capacity.
Rainfall is rather high in the climate all year round hence a pitched roof covered with corrugated iron, asbestos cement or bright aluminium is advised.
Walls should be shaded to reduce radiation, this can be achieved by subsequent overhang sizes of the roof.
Ventilation
Openings must be placed suitably following the prevailing breeze to promote natural airflow, large and openable windows.
The airflow should not pass over hot surfaces like asphalt before entering the building. A water body in the building’s surrounding is suggested.
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Without the exchange of air, both the temperature and humidity of the air will increase due to heat and moisture from occupants and their various actives like washing and cooking. Frequent air change is essential.
Vernacular observations
The traditional shelter is often elevated on stilts and is constructed from locally sourced timber or bamboo which is open-weave matting, timber or split bamboo walls, floors, doors and shutters.
Thatch or built-up layers of leaves cover a bamboo or timber roof-frame, which usually has broad overhanging eaves.
The lightweight timber construction holds little heat and cools adequately at the night. The elevated position provides better security and better air movement than a single storey shelter. The thatched roof is excellent thermal insulation. The broad leaves shade the walls and openings, protect from the rain and sky glare.
The thatch does create a serious fire hazard, it is different to employ in a densely built-up area like a town or a city.
Conclusion
A hot-humid climate is prevailing near the equator, in places like Goa, Mumbai, Singapore, Thailand, etc. The primary attribute a designer has to follow is to maximize the airflow, for occupant comfort.
