Passive strategies for thermal comfort is ideal in the tropics. Thermal comfort is a state we always want to be in. In homes in tropical climates, this can be achieved through passive strategies. However, they are many factors that go into determining your thermal comfort.
What Is Thermal Comfort?
Thermal comfort is essentially the level of thermal satisfaction you feel in your environment.
It can depend on several factors or the combination of different factors and is dependent on each individual. As such, thermal comfort is subjective and almost impossible to pinpoint down to a precise measurement for every individual in a room.
Factors That Influence Thermal Comfort
Many factors go into determining your thermal comfort and what is required to achieve it.
Your age, gender, clothing, activity, metabolic rate and even the amount of moisture on your skin help to determine your thermal comfort.
Depending on these factors, thermal comfort can be achieved in various ways. These include adjusting the temperature, the relative humidity and the speed of the air touching your skin.
However, satisfying every individual in a room can sometimes be a challenge because of various factors.
Passive Strategies To Promote Thermal Comfort
The two main passive strategies that are required to promote thermal comfort in the tropics are natural ventilation and solar shading.
Tropical climates are characterised by their warm temperatures compared to regions further away from the equator. As such, the most important thing you can do to create a thermally comfortable home is by reducing the indoor temperature. It is one of the fundamental aspects of tropical architecture.
Natural Or Passive Ventilation
The first way you can decrease the indoor temperature is by increasing the amount of air moving through your space.
Natural or passive ventilation is the process of naturally moving air through your building. This is achieved through the difference in indoor and outdoor air pressure.
Cross Ventilation
One of the most common methods of naturally moving air through a home is wind-driven strategies. This includes cross ventilation which is one of the most effective methods. Cross ventilation is when air enters one side of the building and exits through another.
Wind enters your home through an opening on the windward side. This is the side of your home that faces the direction of the wind. Wind flows through your home and out the other side.
This process alone can flush stale, warm air out of your home. However, it would be even more effective for thermal comfort if that wind can pass over your skin. Air moving across your body is better able to cool you than if it is just passing through a corner of your room.
Hence, it is ideal to locate windows where the path of the wind will pass across your body.
For example, in your bedroom, the height, size and location of the windows and doors should be positioned to allow the air to move across your bed. In your living room, it should be where you are likely to be sitting.
However, the differences in wind direction or even your movement and activity in the room may require the air movement to be redirected.
Your window and door selections may help offer flexibility by redirecting airflow. The type of window along with the difference in sizes and locations can also help increase or decrease the velocity of the air movement through your home.
Ceiling and other fans can also help increase the air velocity in the room.
Stack Effect
Another method of natural ventilation is the stack effect. This method is buoyancy-driven and uses the density of air to promote air movement.
The buoyancy of air changes due to its temperature or humidity. When the temperature of the air inside is warmer than the air outside, the air inside rises. You see this in a hot air balloon. If that air can escape through an opening near the roof or upper level of your room, then cooler air from outside is pulled in to replace it.
This method is perhaps not as effective in the tropics, where the difference in indoor and outdoor temperatures is not as significant. However, it can be used to help achieve thermal comfort when there is not a lot of wind.
The speed of the air moving through is not as great as cross-ventilation either, but it can reduce indoor temperature.
Passive Solar Shading Strategies
The next major method of reducing the heat in your home is by protecting it from solar heat gain.
When the sun comes into contact with the walls, windows or any interior surfaces of your home, that can increase the temperature in your room and reduces thermal comfort.
Direct sunlight entering your tropical home should be avoided as this increases the temperature.
The materials used in your home are also an important factor to consider. Lightweight materials such as wood and metal will heat up quickly but will lose their heat quickly as well. While thermal massing materials such as concrete will slowly heat up but retains that heat for longer periods. It then releases the heat back into your space at night. This is not ideal in tropical climates and hence, such materials should be shaded from direct contact with the sun.
Solar shading strategies use devices to reduce the impact of direct sunlight on your home. They prevent direct sunlight from entering through your windows and doors. It can also prevent sunlight from touching your walls. Walls that are heated up by the sun can transfer that heat into the home.
Roof Overhangs And Verandas
Large roof overhangs and verandas can help protect your home from the sun’s rays.
They are more effective on the north and south-facing walls because of the angle of the sun. However, depending on how deep your veranda is, it can also assist with east and west-facing walls.
Double Roofs
A double roof system is another strategy that reduces the heat gain in your home.
Your roof receives the most direct sunlight than any other part of your home. Having a double roof where one roof is directly over the other protects the one at the bottom from the sun. Hence, reducing the heat that transfers into your home via the roof.
Screens And Shutters
Shutters and screens are a good way to protect your home from direct sunlight. They can protect your windows, doors as well as your walls from solar heat gain.
Photo: Rungkit Charoenwat | U38 House | OFFICE AT Co., Ltd.
When sunlight passes through a glazed opening like a window or door, that heat enters your room and gets trapped inside. This increases your indoor temperature.
Having your windows protected with screens or shutters that block out the sun but allow natural ventilation is ideal.
The term brise soleil (which means sun breaker in French) is sometimes used in architectural jargon and refers to a feature in a building to reduce heat gain.
Breezeblocks, timber or metal screens and other materials can be used to create a thermal barrier. This helps reduce the heat in your home and improve your thermal comfort.
Vegetation
Trees, plants and other vegetation can help improve thermal comfort in two ways.
Vegetation around your home can provide shade to your walls, windows and doors. Large trees can provide shading to large portions of your home. Plants are also beautiful to look at and provide psychological benefits to you and your family.
Trees and plants can also create a cool microclimate around your home. They provide shade and add soft surfaces around your home that makes it cooler. This means that the wind blowing through your home will also be cooler and is a great strategy for improving thermal comfort.
Conclusion
Creating thermal comfort through passive strategies is a main consideration for designing a house in the tropics.
To do this you should ensure that your home receives ample natural ventilation through cross ventilation. Using stack effect strategies are also useful.
Your home should also be protected from direct sunlight by using large roof overhangs, verandas screens and vegetation to protect it.
These techniques can help improve the thermal comfort of your home for you and your family to enjoy in the tropical heat.