Passive Strategies For Humid And Rainy Climate

Tropical regions, especially in the south-west and north-east regions of India have always received high amounts of rainfall. One huge threat is the flooding due to excess rains and overflowing rivers. The other is the discomfort within the buildings due to the humid climate.

The vernacular style of the structures in such regions have been developed over the long years taking into consideration all the above problems.

Methods To Improve Building Comfort Levels In Humid Climates

• Ensure Good Ventilation
• Large Openings With Deep Shading
• Avoid Flat Roofs
• Use Trees And Other Structures As Screens
• Building Orientation And Shape
• Thermal Comfort
• Materials Choice
• Plinth Level
• Enable Stack Ventilation
• Increase Height

A) Ensure Good Ventilation

One of the basic but effective passive techniques for humid climates is to enable as much natural ventilation as possible. The continuous airflow within the building interiors greatly reduces discomfort by reducing the feeling of stickiness due to sweat.

Design Strategies

• Orient building along the local wind direction.
• Have openings like doors and windows on the opposite sides to increase cross ventilation.

B) Large Openings With Deep Shading

Larger the openings, better the natural ventilation. But in rainy and humid climates, the water might seep in due to the heavy rains and the interiors heat up because of solar radiation.

Design Strategies

• Make sure that the windows and other openings are deeply recessed.
• Have window overhangs and sunshades.
• Other shading devices like awnings, canopies and projecting fins can be used to reduce heat gain.

C) Avoid Flat Roofs

If you observe the traditional architecture of humid regions, you might notice that they rarely have flat roofs. 

Design Strategies

• Make the roof sloped, preferably on both sides (pitched roof).
• This reduces stagnation of water, as well as increases the building height, letting the hot air rise and escape out.
• Extend the roof from the walls to act as a passive shading device for the building. This also makes sure that the rain water does not fall on the building itself.

D) Use Trees And Other Structures As Screens

Planting trees and other plants should always be a must in any of our designs regardless of climate. But they also provide additional advantages in this case.

• Trees can act as screens which reduces heat gain by the building.
• They also prevent flooding and soil erosion in the site.

Design Strategies

• Plant native trees.
• Go for green roofs and walls.

E) Building Orientation And Shape

Building orientation is the first passive strategy that should be implemented in all of your design. There are multiple factors which decide the ideal direction the building should face.

• The sun's path
• Solar radiation
• Wind direction
• Rain

Design Strategies

• Align the building in such a way that the longer side faces receive lesser heat and radiation. Lesser the surface area facing the sun, lesser the heat gained by the building.
• North side should have most of the openings.
• Southern part of the site should have gardens and courtyards.
• Avoid West-facing openings.

F) Thermal Comfort

One big disadvantage of designing in a humid and rainy climate is that the weather tends to be unpredictable. The design should ensure comfort to the users regardless of the climate.

Design Strategies

• Having a thermally regulating material as a core in between walls is a good strategy.
• The choice of materials for construction should also be done carefully. 

G) Materials Choice

Choosing proper materials for your designs is crucial. Humid climates mean high heat, radiation, excess rain, fluctuation in temperature and weather on a daily basis. The chosen material should be able to withstand all these factors.

Design Strategies

The following materials are suitable for humid climates.

Walls:

• Hardwood
• Concrete

Roofs:

• Asphalt shingles
• Metal roof
• Spanish tiles
• Metal roof

Coatings/Insulations:

• Fiberglass
• Cellular glass
• Spray foam insulation

H) Plinth Level

Excess rain may lead to floods. To prevent flooding of water into the interiors, plinth level should be raised up to a certain height depending on the local regulations and average flood levels of that area.

I) Enable Stack Ventilation

Stack ventilation is a passive ventilation method which takes advantage of the pressure, temperature and density difference between the interior and exterior airflow.

Design Strategies

• Placing sky windows allows hot air to rise and escape out of the building.
• Vents and gaps on roofs can also be used to achieve the same result.

J) Increase Height

If you observe architecture in flood-prone areas, you might notice that the structures are built at a certain height on stick-like structures- these are called stilts. Stilts not only reduce damage to life and property, they also double as storage and cattle sheds. 

Although it is extremely difficult to achieve comfort using passive techniques alone, these are certainly proven to reduce energy and power usage in the long run. A mix of active and passive techniques can be implemented to achieve best results.