Designing a house in the tropics should always try to consider and respond to its region’s climate.
This design approach is becoming increasingly relevant as climate change is projecting warmer temperatures in the future. As a result, designing a house to be more responsive to the tropics and its climate is essential.
When designing and building a home in a tropical climate, they are vital principles that you should consider. These include orientation, solar shading, and passive ventilation and are all strategies associated with tropical architecture.
The type of windows and their placement is especially critical when building a house in the tropics. Carefully locating windows gives the ability to create an ideal thermal comfort level for you and your family. All this without the need for air conditioning.
It would help if you also gave special attention to the materials used to construct your roof and walls. These materials will dictate how heat transfers into your home.
Incorporating outdoor spaces that offer great functionality is also an asset.
When you sit with your design professional (architect, building/project designer, etc.), here are some fundamental principles you should consider when designing a house in the tropics.
1. Site Orientation
Your home’s orientation on the site determines how well it uses the prevailing winds and protects against sun exposure. These factors are dependent on your project’s location in the world.
For example, in the Caribbean, the prevailing winds generally come from the east, with the sun path passing primarily to the south for most of the year. The reason for this sun pattern is because the Caribbean islands are north of the equator.
However, the winds in northern Australia come from the northwest or southeast, depending on the time of the year. Since they are south of the equator, the sun passes to the north for most of the year.
For rectangular homes, where possible, consider orienting the length of your building east to west. This orientation minimises the exposure to the morning (east) and evening (west) sun.
The heat from the sun, especially during the evening, tend to be very hot and intense. Also, because of the sun’s low angle at those times, they are difficult to shade.
However, orienting a home on a site to minimise sun exposure needs to be weighed with capturing the wind.
It is best if you positioned your building to take full advantage of the prevailing winds. Having as much wind as tolerable, passing through your home, is ideal for designing a house in the tropics. Prioritise rooms that need the most ventilation and locate them towards prevailing winds.
Your architect/designer will guide you regarding these concerns. This knowledge will help you and your design professional decide on issues such as the locations of openings, roof overhangs and other shading devices. It can also assist with where best to locate trees and other vegetation.
2. Shading
Shading from the sun prevents walls and other surfaces from heating up and transferring that heat to interior spaces. Direct sunlight through openings can significantly increase the internal temperature. Shading to stop direct sunlight from entering your home is ideal.
Having a general understanding of sun angles helps implement shading strategies. For example, if you live north of the equator, the sun’s path will track to the south for most of the year, as mentioned previously. It will also be lower than the north. The reverse occurs if you live south of the equator.
Horizontal shading is ideal for both the north and south-facing walls and openings. As such, if you live north of the equator, a small roof overhang might be able to protect the north-facing wall of a single-storey home. However, you may require a much larger overhang to shade the entire southern wall. The depths of overhangs depend on how far north of the equator you are.
Verandas and patios are also great for shading northern and southern walls when the sun is at its highest during the middle of the day.
In the mornings and evenings, the sun angle is low and comes from the east and west. The evening sun generally appears hotter than the morning since mornings tend to be cooler.
Walls facing east and west require vertical shading, such as screens or vegetation, to protect them from solar heat gain.
Large trees can also provide general shading to your house and the external areas around your home, creating cooler air temperatures entering the house.
3. Ventilation
Having a constant flow of air moving through your house is critical for creating a comfortable indoor temperature. You can achieve this movement by allowing cool air to pass from one side of a room to the other. This action is called cross ventilation and occurs when air has an unobstructed path through a room or building.
Ideally, they should be at least two openings in each room. They should also be on two different sides of the room. You should also position them to encourage air movement throughout the entire room and not just one corner.
Photo: Peter Eve | Inside Out House | Sabi Design
Having large windows and doors are good, but also consider the type of window or door.
For example, casement and louvre or jalousie windows are great as they allow air to pass through almost 100% of their opening. However, sash or sliding windows permit less than 50% of its opening.
It will also be ideal if windows are protected to remain open when the rain is falling. In addition, they should be capable of staying open overnight without compromising security.
Hot air rises, so it is a good idea to provide vents at or near the roof level to allow that hot air to escape. These elements include roof vents and clerestories. Jalousies or louvre windows are also advantageous in these situations.
Another advantage of this is that the process of hot air escaping at the higher level draws in cool air through windows at the lower level. This process is called the stack effect.
4. Wall Materials and Construction
Lightweight materials are generally better for house designs in tropical climates for their thermal qualities. This idea will be unpopular in many regions, including the Caribbean, where I live.
In several tropical areas, concrete blocks, in-situ (cast-in-place) concrete, or masonry bricks are preferred.
Typically in the Caribbean, small, low-income houses use lightweight construction. As such, this type of construction is unpopular in other residential buildings.
Materials such as wood, metal and cement boards on a framed construction system cool down rapidly. This process creates a more comfortable environment at night.
However, framed walls do not store heat like their heavyweight counterparts.
In addition, you can engineer such wall systems to withstand tropical storms, hurricanes and cyclones.
Though commonly used, concrete walls are not ideal unless they have proper sun shading. The reason is that they can store heat absorbed during the day and release that heat into the room during the night.
However, concrete walls do offer many other benefits for tropical regions. We prefer them because of their natural resistance to hurricane-force winds and flooding. They are also resistant to mould and termites.
Therefore, if you use a mass wall system like concrete blocks, try shading them with roof overhangs, screens or shady trees.
5. Roof Design
The roof is the single most exposed area to the sun’s rays of any building and, as such, has the potential to radiate a lot of heat into a house.
Light-coloured, reflective roof covering materials reduce the amount of heat that passes through.
A double roof system also has benefits in reducing the heat that enters your home. Double roofs comprise two layers of roof. An air space typically separates the two layers. Hence, the upper roof layer protects the lower roof from direct sun exposure. This system significantly reduces the heat gain on a roof.
High roofs and steep pitches allow the heat gained at that level to be a safe distance away from people occupying the space below.
As mentioned before, creating a way for that heat to escape is also beneficial.
In addition, many tropical regions have rainy or monsoon seasons. Roofs with a steep pitch allow rainwater to run off quickly. Flat roofs or roofs with a low pitch take longer to get rainwater off of them. This condition could result in leaks.
Large roof overhangs also help protect open windows from rain entering inside. Hence, the windows can stay open when the rain is falling. However, this situation depends on the direction the window and roof overhang face.
6. Exterior Spaces
Incorporating exterior spaces such as patios, verandas, and courtyards is beneficial to have as part of your home. Our temperature range is such that these spaces are habitable throughout the year. They can also provide shade to the interior areas of the house. In addition, outdoor spaces are a great way to connect people with the natural environment.
You should partially or entirely cover exterior areas to provide shade and facilitate their use even when the rain falls.
Designing exterior spaces as functional rooms, such as a dining or sitting area, would also encourage their use. Patios that do not have a primary function can often go unused because of this. Hence, it is ideal to find ways to make your covered outdoor area more usable.
7. Water And Energy Efficiency
Climate change has heavily affected the world we live in, with experts forecasting that environmental conditions will worsen.
Issues such as depleting fossil fuels and the carbon emissions from burning them are a concern. Those issues and the changing rain patterns we are experiencing across tropical regions are serious concerns that will impact our future when designing a house for the tropics.
Over 20% of the world’s energy usage goes towards construction and maintaining houses, apartments and other residential buildings.
This statistic enforces the need for the industry to use more energy-efficient strategies and practices.
Consider using renewable energy sources like sunlight. You can use solar thermal panels for heating water. Also, solar/photovoltaic (PV) panels could generate electricity to run our lights and appliances.
Avoid the use of air conditioning systems. A well-designed home in most tropical regions will not require much use of any mechanical ventilation systems throughout the year.
Specify low-wattage lighting such as LED bulbs and energy-efficient appliances. Also, employ water-saving devices.
Collecting and storing rainwater from roofs for irrigation and other similar situations reduces the strain on our groundwater supply in water-scarce countries.
References:
Sustainable Tropical Building Design – Cairns Regional Council
Greenhouse Friendly Design for the Tropics – COOLmob
Related Topics In This Series:
Want to find out more about designing in the tropics? Explore more of the topics in this series.
Site Orientation: The orientation of your home on its site dictates how well it responds to passive design principles.
Shading Strategies: Reducing the solar heat gain in your home can create a better thermally comfortable home.
Passive Ventilation: Natural or passive ventilation is one of the primary concerns of a tropical home.
Wall Materials and Construction: In hot, humid climates, your wall materials need to perform various functions.
Roof Design: Choosing the right roof in hot tropical climates is essential to minimize heat gain.
Exterior Spaces: Making outdoor spaces and nature part of tropical homes is ideal.
Water and Energy Efficiency: With climate change, renewable energy and water resource management are crucial.