warm and humid climate

WARM AND HUMID CLIMATE

CLIMATOLOGY

hot and humid climateIn hot and humid climatic regions, high temperatures are accompained by very high humidity levels leading to immense discomfort. Cross ventilation is very essential here. Adequate shading measures are also necessary to protect the building from direct solar radiation.

The main design objectives should be(A) Resisting heat gain: Measures that are convenient to gain

unwanted heat gain are: (a)Decreasing surface area of the building

exposed to the outside. (b)Using materials that take a longer time to

heat. (c)Providing buffer spaces between the

outside and the inside. (d)Increase the shade of the building in

general. (e)Using materials that reflect heat.

(B) Promoting heat loss: To promote heat lost it is essential to

ensure: (a) Appliances used are well ventilated. (b) Proper ventilation occurs throughout the

day. (c) humidity levels are reduced as much as

possible.

General recommendations for building design in warm and humid climate

(1) Site: (a)Landform: For flat sites, design consideration for the

landform is immaterial. In case of slopes and depressions, the building

should be located on the wind ward side or crests to take advantage of cool breezes.

MAXIMUM AIR SPEED ON THE CREST

(b) Waterbodies: Waterbodies are not essential as they would

tend to further increase the humidity. (c) Street width and orientation: Major streets should be oriented parallel to

or within 30 of the prevailing wind direction during summer months to encourage ventilation in warm and humid regions. A north-south direction is ideal from the point of view of blocking solar radiation. The width of the streets should be such that the intense solar radiation during late mornings and early afternoon is avoided during the summers.

(C) Open spaces and built form: Buildings should be spread out with large

open spaces in between for unrestricted air movement.

In cities, buildings on stilts can promote ventilation and cause cooling at the ground level.

BUILDING SPACING SUCH THAT AIR FLOW IS PROMOTED

(2) Orientation and planform: As long as the temperatures are very high,

free plans and can be evolved as long as the house is under protective shade. An unobstructed air path through the interiors is important to ensure proper ventilation. The buildings could be long and narrow to allow cross ventilation. For example, a singly loaded corridor plan (i.e. one with rooms on one side only) is preferable over a doubly loaded one.

ELONGATED PLANS FOR MAXIMUM CROSS VENTILATION

(a)Heat and moisture producing areas like toilets and kitchens must be ventilated and separated from the rest of the structure.

VENTILATE KITCHENS AND BATHS TO EXHAUST HOT AIR

(b) Semi open spaces such as balconies, verandahs and porches can be used advantageously for day time activities as well as give protection from rainfall. In buildings a central courtyard can be provided with vents at higher levels to draw away the rising hot air.

WINDOWS AT HIGH LEVEL TO VENT HOT AIR

HIGH PITCHED ROOFS WITH LOUVERS FOR VENTILATION

(3) Building envelope:(a)Roof: In addition to providing shelter from rain

and heat, the form of the roof should be planned to promote airflow. Vents at the rooftop effectively induce ventilation and draw hot air out.

Insulation does not provide any additional benefits for a normal RCC roof in a non-conditioned building. However, very thin roofs having low thermal mass, such as AC sheet roofing, require insulation as they tend to rapidly radiate heat into the interiors during day time. A double roof with ventilated space in between can also be used to promote air flow. The space in between can also act as a heat buffer.

(b) Walls: The walls must also be

designed to promote air flow so as to counter the prevalent humidity. Baffle walls,both inside and outside the building can help to divert the flow of wind inside.

BAFFLE WALLS HELP TO DIVERT AIR FLOW

They should be protected from the heavy rainfall prevalent in such areas. If adequately sheltered, exposed brick walls and mud plastered wall work very well by absorbing the humidity and helping the building to breathe.

(c) Fenestration: Cross ventilation is of outmost importance in

warm and humid climatic regions. All doors and windows should preferably kept open for maximum ventilation for most of the year. These must be venetian blinds or louvers to shelter the rooms from the sun and rain, as well as for the control as air movement. Openings of a comparatively smaller size can be placed on the windward side, while the corresponding openings on the leeward side should be bigger for facilitating a plume effect for natural ventilation.

The openings should be shaded by external overhangs. Outlets at higher levels serve to vent hot air.

OUTLET LARGER THAN INLET INLET AT LOWER LEVEL AND OUTLET AT HIGHER LEVEL

Examples illustrating how the air movement within a room can be better distributed.

DISTRIBUTE AIR THROUGHOUT THE ROOM

(d) Colour and Texture: The walls should be pasted with light

pastel shades or white washed while the surface of the roof can be of broken glazed tile (china mosaic flooring) to reflect the sunlight back to the environment, and hence reduce heat gain of the building. The use of appropriate colours and surface finishes is a cheap and very effective technique to lower indoor temperatures. The surface finished should be protected from/resistant to the effects of moisture.

Remarks: Ceiling fans are effective in reducing

the level of discomfort in this type of climate. Desiccant cooling techniques can also be employed as they reduce the humidity level. Careful water proofing and drainage of water are essential considerations of building design due to heavy rainfall. In case of air conditioned buildings, dehumidification plays a significant role in the design of the plant.