Understanding the climatic conditions of a region is very beneficial to the designers and the occupants. Each region has its own list of elements and conditions which should be thought upon before effective designing. In this article, the measures to be taken for effective analysis and planning in hot and dry climates are covered.
The knowledge of climatic conditions will enable the Architect to select the wall thickness, roofing, materials, size of the openings, and other features to effectively control the amount of solar radiation coming through.
Table of Contents
Characteristics of Hot and Dry Region
- The temperature in these regions ranges from 27 and 49°C and 22 deg C at night
- Humidity is moderate to low, with clear-skied most of the time
- The low humidity means less rainfall and therefore less vegetation in the region
- The wind flow is minimal but when there it’s hot and dusty.
The factors that should be adopted to prevent solar radiation should be considered at all levels of planning, construction, and maintenance.
Orientation and Form
The planning should be compact, and under one roof to avoid a lot of movement, which can cause unnecessary thermal loading and discomfort to occupants. The orientation of the longer side facade should be North-South, as the solar radiations are less harsh than East or West. The sun moves from east to west, therefore the sun’s rays are at a maximum in this direction.
The concept of planning in context with climate is seen in traditional times. Jaipur comes under a hot and dry climate, the Havelis were designed close to each other with narrow lanes, for an effective flow of wind as hot air when passed through narrow lanes cools the flow.
The shading is an essential part of hot and dry climates, unlike warm and humid climatic zones.
Shading of roofs, openings, and open spaces should be effectively enclosed with low thermal capacity materials
Also, the shading of openings in Havelis of Jaipur, be it courtyards, doors, or windows, was done in a beautiful manner. Jharokha windows were effective to block the harsh sun rays but allow cool air to enter inside.
Another method that is popularly used is the double roof, in which two roofs are constructed. The material for both should be reflective to prevent infrared rays. Due to this double roof, the inner roof is prevented from the rays and a large number of harsh rays are absorbed by the outer roof.
Thick exterior walls are ideal choices for hot and dry regions as this decreases the transmittance of sun rays from outside to inside. Cavity walls or double walls can also help to reduce the transmittance time.
Dark color surfaces should be avoided as they store the absorbed heat for a time as compared to light coloured wall surfaces
According to the traditional construction techniques, mud, stone, or brick walls provide good thermal capacity and will prolong the time of heat entering the structure.
Openings and Ventilation
Diurnal temperature variation plays a crucial role in planning in dry and hot climate conditions. Diurnal temperature variation is the variation between a high air temperature and a low temperature that occurs during the same day.
This can be achieved by the difference between temperature and airflow during the night and day.
During the day, the windows are shut or shutters closed, or even small windows should be used for ventilation. At night when the temperature is less and wind flow is cool, large windows are open to keep the interiors cool.
Buildings oriented at 45 degrees towards the windward side with broader facades will receive more ventilation, the negative pressure will be increased and an increased indoor airflow will result. For dust-free and cool air ventilation sources should be ducted.
Other Techniques to Keep Interiors Cool
Solar chimneys are wide, and tall structures attached to the building and work on the principle of buoyancy. The chimney absorbs all the solar radiation falling on the building, thus making it hot and full of warm air. Then this chimney in turn exits out all the hot air inside the building through the principle of the stack effect. It is important that the chimney is insulated from the building itself so that heat gains do not transmit into occupied spaces.
Using High-Performance Doors and Windows
Low E glass windows have an invisible coating that reflects infrared rays. These glasses reflect most of what thus keeping the interiors cool. Low E glass or Low emissivity means the ability of a surface to absorb and emit energy in the form of radiation. These glass windows reflect solar radiation but at the same time allow light to pass through.
As hot and dry regions have low humidity, evaporative cooling techniques can be majorly used to keep the structure cool. Inspired by the traditional Indian system, a water body such as a pond or lake is designed in accordance with the wind flow.
Evaporative cooling reduces the indoor temperature and also the load on the air conditioner is reduced. A water body in the courtyard or in the way of wind flow can be beneficial in cooling the interiors.
AHU system or cooling tower is air is precooled and then entered. This process can be done with the help of water sprinklers or water bodies.
In today’s architectural world, where technology has advanced so much, vegetation is not just limited to the ground. Roof gardens, Vertical Gardens, or creating different flow patterns through trees to cool the environment are popular as well as effective.
Vegetation reduces the direct impact of the sunrays and heats up the surfaces by acting as a buffer. It can also be used as a shading device. Roof gardens add to the thickness of the roof, thus increasing the thermal capacity and increasing the time lag.
In the time of climate change, it is of utmost importance to adapt to these measures despite being totally dependent on mechanical systems for cooling or heating. As a responsible architect or designer, it is important that the first step before planning should be to understand the site and climatic context and then proceed.
These measures may seem small or costly, but in the long run, they will be profitable both for the individual and the Earth.