Sustainable Design FAQ/ guide Index:
An introduction to sustainable design in tropical climates.
The practice of sustainable/ environmentally friendly design tends to have captured the imagination of most people living in developed nations. For the most part, countries with moderate climates or those that have four seasons. Most sustainable design methods and bioclimatic data have been developed, are mature and fairly easily accessible within these countries in general. However this does not mean that sustainable or green design is not applicable within developing nations or in the tropics. The purpose of this specific guide or FAQ being written is due to the interest we have experienced first hand in South East Asian countries like Malaysia and Singapore.
Sustainability in the tropics: Issues of comfort and climate
The issues that concern human comfort within buildings in a tropical or subtropical climate are those of heat and humidity. In other words to limit heat build up or remove it and to reduce humidity. Anyone who has ever had to walk through a tropical city beneath the afternoon sun will relate to this. Since this isn't meant to be a scientific paper on the environmental factors affecting human comfort within tropical or subtropical climates and the sustainable design solutions that respond to them, please bear with our attempt to simplify and to present things in a general way or in layman terms. (Obviously we would be happy to work with researchers on real world application of systems.)
If you simplify matters and look at bioclimatic charts, you will find that for the most part, temperatures tend to stay consistent throughout the day and in the evenings. Roughly temperatures in the high 80s to low 90s with humidity around the 80% range. Somebody coming from a moderate climate will feel hot and uncomfortable throughout the day and the night without the aid of mechanical systems to help them achieve comfort levels. However a person living within this climate will feel that while it is hot during the day, there is relief during the evenings and nights when the sun goes down and some would feel cold in the mornings. It is a matter of acclimatization and perception. For countries nearer the equator, the sun tends to be high in the sky, therefore most solar heat gain tends to be from the east and west orientations. The hottest part of the day being the afternoon.
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Sustainability in the tropics: Current Construction methodology -base model
We begin by looking at typical construction methods that are practised in general. While newer modern construction methods are obviously in place within developing countries (i.e Petronas Towers in Kuala Lumpur and the new Singapore National Library), a percentage of building construction methods still follow methods that tend to be labor intensive and utilize materials that lead to waste.
So as a case study, the typical construction method for housing developments and light commercial structures:
We can use this as a base model against which to compare sustainable design strategies or alternative construction methods.
A structural framework of reinforced concrete for both exterior and interior walls/ partitions. These are then in-filled with masonry/ bricks before a layer of stucco/ plaster is applied as a finish layer. No insulation is used within walls. The roofs tend to be simple wood trusses with roof sheathing, wood battens and a clay or concrete tile roof over. As we stated, a general description that has several variations throughout the South East Asian region.
This is a relatively inexpensive method of building construction in Asia and relies on cheap labor.
If we break it down, to the way most of these countries are living today, it becomes an energy inefficient and a resource wasteful method of construction.
The same could be said of the traditional 2x6 wood stud or metal stud construction methods utilized within the United States.
Ergo, the move for alternative construction methods to
limit or stop the waste.
But let's look at this system before we look at other approaches. Technically clay bricks are actually a rather decent "green" material because it's natural resource is clay, sand, straw etc. (depending on the methods used in each country to manufacture it). All from the earth and resources that are fairly plentiful. It requires some skill to lay a straight wall but labor for now is somewhat affordable. However without really going in depth on the socio economic factors, we should note that many of the developing nations in South East Asia use immigrant labor in construction. As countries develop and salaries increase, so does the cost of labor.
Now let's look at concrete. The concrete itself is not so much an issue (but like many products requires energy to be expanded in the creation of cement. The high use of fossil fuels in both manufacturing and transportation of cement/ concrete produces substantial pollution) but the way it is used or formed during construction. Formwork made from wood panels or plywood are used to hold concrete in place while it sets. Most of these panels are discarded after the concrete beams or columns have achieved sufficient strength. Considering that these panels are made from tropical hardwoods that can take hundreds of years to mature, it is obviously not a very good use for such a valuable resource. Tropical hardwoods cannot be compared to fast growing coniferous/ softwood trees like Douglas Fir. So it's not really feasible for reforestation programs to use tropical hardwoods to maintain new growth for the future. So you tend to see growths of coniferous trees in some tropical countries. Not a good sign for the natural ecosystem. It's doubly ironic that most tropical hardwoods are not priced higher than softwoods.
Obviously there are easy ways to remedy the waste by utilizing reusable formwork for column and beams. Standardizing the systems used for the structural framework without taking away from
the design. There is no such thing as an ultimate sustainable building system. Each project, each site, each building must be approached on an individual
basis. In other words, a holistic approach that looks at all the factors that impact a site, the occupants, it's region, climate, culture
and resources before a strategy is employed. Any design solution used to solve climatic concerns also needs to look at how each society has adjusted
life patterns to suit new technologies as they become easier to acquire.
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Sustainability in the tropics: Design methodology
Many different designers approach sustainability from many viewpoints. At GLA we tend to see at as solving the baseline model using passive energy design methods and progressing from there. That is to try to achieve a comfortable living environment before applying other methods. Notice we didn't say energy efficient.
Passive energy methods can be employed by using lessons learned from the past. Using indigenous or vernacular architecture as a basis is an often used "green' design method within the tropics and in other parts of the world. The traditional Malay house or the long houses by the Ibans are good examples of vernacular and indigenous architecture that have evolved with the climate of their regions over time. Both are wood structures set on post with steep roofs and high ceilings. These designs enabled good ventilation and cooling of the interior spaces. Being up on post allowed for good ventilation beneath the buildings, has the added bonus of keeping the living spaces above the flood line and limits the possibility of invasion by predators. The materials used tend to be lightweight and therefore do not retain heat for long periods of time (low thermal mass). These traditional designs have been reinterpreted in more contemporary designs that utilized passive energy methods/ strategies.
From what we can see above and learning from the past, simple design strategies that can be employed would be to minimize solar heat gain from the sun by having sufficient
shelter from the sun. That is decent roof overhangs, limiting the exposure of windows or glazing on the east and west side of a building, whenever possible and trying to orient the building
so that east and western wall or building exposure is limited. To allow for decent ventilation and to use wide verandahs to achieve more shading and to encourage ventilation
and cooling from prevailing winds.
Problem is these ideas are not unknown but other factors like the desire to just build multiple structures cheaply and easily tend to have a negative impact on these easily achieved design strategies. We haven't even addressed large scale grading of hills to build cookie cutter houses on flat lots. While these are often driven by developers, their architects could do better by educating clients on better ways of achieving what they want in a sustainable fashion. Building sustainable communities does not mean lower profits. On the contrary, time and time again, sustainable design actually tends to lead to communities that are more livable, healthier and comfortable. Pleasant environments that usually have the added cache of a unique or interesting architecture. These communities tend to sell well and above expectations. Freeing up a developer's capitol quickly to progress onto other sustainable communities.
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Non-Sustainable Design Flaws
As with most developing nations, as new technologies are introduced and people get progressively wealthier, the drive for mechanical methods to achieve human comfort increases. Therein lies the problem. Air conditioning is now a widely used and accepted way of life, however buildings built using the methods outlined above are not really designed to use air conditioning effectively. The few concessions being installing casement or sliding windows in replacement of the old style jalousie or louvered windows. Yet the buildings themselves are not insulated, windows and doors do not have proper seals to prevent the heat from the exterior penetrating the structure. You end up with a building or home that is bleeding money through wasted energy from an air conditioner struggling to keep a building cool against all odds. What happens in these buildings the moment you turn off the air conditioner? They get stifling hot within minutes. So you have buildings not designed to work with the climate and have technology that is inefficient. Since buildings use 50% of a country's energy, you can see why for a developing nation, sustainability should be a priority.
Using a single family residence and a terrace house or row house as case studies, let's look at the repercussions of
the present construction methods and design strategies as it affects energy consumption and you.
Terrace houses or row houses are prevalent throughout South East Asia. Many tend to be single storey though with rising prosperity, a drive for bigger homes and multiple storey's. Using the construction methods outlined above, consider the terrace home. Masonry or brick are not good conductors or heat. That is they do not transfer heat easily through the material itself. However energy will travel through a wall made from these materials as by themselves they are not good insulators, in other words heat is going to flow from one side of a brick wall to the other. Think of a thermos or your picnic cooler and the insulating materials that limit the loss of heat or cooling tends to be entrapped air. A solid brick wall has no entrapped air to stop the flow of heat, it slowly conducts it from one side to the other. In a brick terrace home, if one unit has their cooling system on, they are losing cooling to the walls facing the exterior, as well as to the unit besides them. So if the unit does not have their cooling system on, your unit is expanding energy cooling theirs and the great big world beyond. There's nothing to stop the loss or to slow it down.
In a single family home or bungalow as they are referred to in the tropics, you are continuously losing cooling to the exterior without any form of insulation installed in the building. You are losing even more through the glazing or glass in your windows or doors. You may feel cool and not think too much about it but you are wasting both valuable hard earned income and resources through your walls, roofs, windows and doors. In other words, your home or building is energy inefficient.
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Summary of Building Design Problems in Tropical Climates.
What we have here is a classic case of countries developing and implementing all the latest comforts of home. Unfortunately the construction or building industry is not evolving or developing fast enough to factor in these new must have technologies. Compound this with the need to follow architectural trends set by developing nations without really understanding why certain movements or "styles" are adopted, and you have a major aesthetique and environmental problem. A good example of this is the widespread implementation of the "modern" movement in commercial structures throughout these countries through the 70s and 80s. Bleak buildings with flush windows and little or no ornamentation. Bland flat facades with aluminum windows all looking like ice cube trays (except ice cube trays have more variety). Topped of with the application of suitcase size air conditioning units attached like pimples to the exterior skin of the buildings.
Now add both the tropical sun and rain on buildings with no protection and you get moss, lichen and larger saprophytes literally growing on the buildings. No, not the romantic image of ancient temples in sweltering jungles but dirty buildings becoming eyesores in these thriving cities. It's not the modern aesthetique that is the problem, but the poor implementation of its core values. The good news is that there are architects like Ken Yeang who design modern tropical buildings with "green" design strategies. These buildings tend to be innovative, interesting and good performers. (At GLA, we obviously would like to be your architect on sustainable tropical buildings.)
It is not difficult to imagine that implementing passive energy methods to a building can help a building perform better in any environment or climate.
We will look at some sustainable/ "green" strategies possible for tropical buildings in our next chapter. Suffice to say for now, that a building
that has adequate protection from the sun will have a lower level of heat gain. Before even implementing measures like insulation, it is logical to realize
that if such a building had an air conditioning system, at least it would not have to work as hard to cool the interior.
As we said before, sustainable design should be approached from a holistic standpoint, where after understanding the unique problems facing a particular site, we find the appropriate solution instead of tacking on systems just because they are called "green".
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