Sustainable Design FAQ/ guide Index:
In the last chapter of our FAQ, we outlined the climatic factors and building methodologies that affect human comfort,
energy efficiency and resources within tropical climates. Our guide/ article however focuses on sustainability within not only
tropical climates but also developing countries within the tropics.
We will try to present in a concise and hopefully readable presentation, strategies for implementing environmentally friendly and sustainable design within these communities.
Sustainability in the tropics: Design Theories
LEED has developed a tropical climate building model by which they form their basis and approach towards sustainability in tropical countries. The model was developed in Jamaica and has applicability within most tropical countries. This LEED model has the same basic approaches outlined in our last chapter outlining passive energy design methods. That being said, the model does not look at it's applicability within developing countries like Malaysia, Singapore or Thailand and how cultural or social mores may affect the effectiveness of their case study or model.
It calls for the use of lightweight building materials for construction as opposed to materials that have a lot of thermal mass like concrete or masonry. The theory being that lightweight materials tend to cool down faster than heavy mass materials that retain the heat for long periods of time. As we have stated before it doesn't help to just point to a design solution and state that this is the best approach. Everything needs to be considered and researched very carefully before making judgments as to the best applicability of a design approach. What are these lightweight materials called for in the report?
Assuming it means wood, what types of wood or species are they specifying? Tropical hardwoods as we have noted before tend to be very slow maturing trees. Deforestation is definitely an ongoing problem within the countries of South East Asia. Therefore it's important to use timber harvested using ISO 14000 standards or Forest Stewardship Council (FSC) certified wood timber. That being said, there are other materials available to satisfy the criteria for lightweight low thermal mass. Composition boards or panels have been developed from rubber wood and cement, and insulation panels from old rubber tyres combined with rice straw. These represent new construction technologies that recycle waste materials and are able to be installed using relatively simple methods. Sustainable design is not just the application of "green" design strategies to a building but an overall holistic approach to how the building impacts the environment before and after construction. In other words to limit any negative impact and to promote positive overall results to the environment. Properly executed, a good sustainable building can actually give back to the environment.
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Sustainability in the tropics: Thermal mass and evaporative cooling concepts.
From the basic climatic data listed previously and using text book approaches, you would assume that since there are no large variations between the high (80-90F)and low temperatures and with a humidity level hovering in the high 80 or 90 percentiles that using passive systems like evaporative cooling or thermal mass would be ineffective.
Evaporative cooling working on the concept of using differences in humidity levels to cause water to evaporate. The process of evaporating water then tends to have a cooling effect. (Again we apologize for over simplifying the process). Anyone who has ever splashed water on their faces on a hot day knows the effect of evaporative cooling. Evaporative cooling tends to work really well in hot dry climates. It is relatively less efficient in humid climates because the air tends to be saturated with water thereby making it less likely for more water to evaporate. The process by which water evaporates requires energy and the ability of the air to accommodate the moisture. This in turn means that in high humidity climates the air is saturated with moisture and has limited capacity to absorb anymore moisture, but if you have ever walked down a street in Kuala Lumpur or Singapore on a balmy sunny afternoon and just happen to pass beneath one of those big fans that are blowing a mist of water, you'll understand that while not exactly cold, it adds a degree of cooling and comfort.
Thermal mass for cooling works on the principle that a large mass tends to take a long time to heat up or cool down. Materials like stone or concrete which are slow conductors of heat,
tend to be really good materials for the application of thermal mass in both heating or cooling circumstances. Again if you have ever laid flat on a concrete floor on a hot day and felt
the coolness of the floor,
you'll grasp the concept really well. These systems tend to rely on significant differences in temperature or humidity to work.
But as we have pointed out above, it's a matter of perception. Passive solar homes in moderate or cold climates utilized thick walls of masonry or concrete or floors behind windows
that have good sun exposure
(south in the northern hemisphere and north in the southern hemisphere). During the day, the sun heats up the mass very slowly. But when night falls, the mass which has been storing all that
thermal energy now slowly releases it to the space it is in.
These properties are what help masonry/ stone or concrete feel cool to the touch during a hot day. A good example of using thermal mass for cooling is to visit an old colonial building in the tropics
with those thick stone walls. The strategy here is to shade the thermal mass from the sun, let it absorb the heat from your space and then use the cool of the night to expel that heat build up.
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Sustainability in the tropics: Sustainable Design Implementation
Let us stress again that the design strategies espoused within these pages are meant as starting points from which an overall holistic approach towards design begins. They are not perfect nor do they claim to be perfect. Most ideas have flaws but what's important is to gain the most out of it's implementation.
We touch on thermal mass above because recent housing trends in Asia tend to be vertically oriented. In other words, the high rise residential or condominium building. While these are starting to gain in popularity within major urban centers in Malaysia, Indonesia and Thailand, no where else in South East Asia are they as dominant a housing form as in the island republic of Singapore. The limited amount of available land tends to be the driving force that makes high rise residential construction a necessity within this country.
In Malaysia, Indonesia and Thailand which have more land, housing units tend to have more variety.
Regardless of the number of stories, the residential units tend to be row/ terrace houses, semi detach (duplexes),
bungalows (single family residence) or as is becoming more prevalent, high rise condominiums. Construction of these building types, tend to be similar to the high rise
residential towers and as outlined in the last chapter.
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High Rise Residential Towers-Sustainable concepts.
Therefore let's start by looking at Singapore. Most housing is government sponsored and erected by the Housing Development Board. All these buildings tend to be vertically oriented residential units or "HDB flats" as they are commonly referred to. Concrete structures with masonry infill or precast concrete panels for the walls and no insulation. Many of these buildings are clumped together and for the most part seem to have very little variety in form or heights.
A general solution, would be to ensure that proper site analysis/ studies are carried out before designs for any building is started. Understanding how wind and sun works on a particular site, can be the driving force of how these high rise buildings are formed and oriented. The unit plans of the flats could be arranged in a way to block solar heat gain from the western sun and to maximize cooling from prevailing winds. Buildings could be oriented to funnel winds through them and not block it. Additionally, instead of trying to maximize units within these buildings it may help to change the heights of the buildings to create daylight and wind corridors. While it is efficient to have all the units the same size because it easier to construct, sometimes having variations can provide variety to a buildings facade and help with passive energy design. Taking a page from commercial office towers like the Kommertzbank or Menara Mesiniaga, roof top gardens or mid level gardens that step through a building or open up atriums within the core of the building, can help create a "green" belt within the buildings themselves. Imagine if you would, buildings that have natural daylight, ventilation biodiversity through landscaping and evaporative cooling available through waterscapes in these roof gardens. These high rise residential buildings could use their building forms and orientation to take advantage of the sun to generate enough power to sustain themselves from an energy standpoint. The trick of course is to design the photo voltaic panels into the form of the buildings in a way that is both innovative and visually pleasant. It's not just about sticking panels to the roof or walls of a building.
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Residential Tower alternative construction.
Many sustainable advocates will point out that both concrete and steel have high embodied energy in their manufacturing process. This includes the direct and indirect energy used for their production but also for their extraction, transportation and installation. All that burning of fossil fuels tends to result in pollution. Therefore for some, these materials are not seen as being environmentally friendly, however until new technologies for building high rise buildings come about, concrete and steel will still remain the structural framework for these buildings. It should also be noted that some forms of waste materials from manufacturing and industry like fly ash can be incorporated into concrete as admixtures. A great way to recycle environmental waste. In addition much of the steel used in construction tends to be recycled steel. If construction methods were approached from a sustainable viewpoint, with long term planning taken into consideration, it would make sense that using light weight panels or materials would lessen the loads on the structure of these buildings. A lighter load in turn requires less structure to support it. Less structure in turn means less materials, resources, labor and pollution for its construction.
There's a reason why the mantra for LEED is, "Build green. Everybody profits."
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Lightweight Construction Methods.
While the focus has been on high rise buildings, these construction methodologies can be applied to most housing types within the developing countries of South East Asia.
Option 1: Insulated prefabricated panels. Prefabricated panels assembled in a factory, then installed in the field. Nothing new here and it has been done before. Exterior sheathing materials assembled against a frame work of wood or steel. The cavity between panels is filled with some form of insulation. Using new systems like these have certain advantages and disadvantages. Prefab panels will be lighter than brick or masonry infill, resulting in the lighter structure we have talked about. Beams and columns maybe smaller. We have simplified things overly much but you get the idea.
Option 2: Utilization of insulated masonry units. Terracotta/ Concrete masonry units with insulated cores. This enables the present workforce to build as they are used to but with energy efficient materials.
Option 3: Rain screen with steel stud construction with insulated wall cavities. Using systems similar to those in the United States. This requires the construction work force to adapt to a new way of building. However the overall structural framework remains the same.
Option 4: Researching and discovering alternative construction methods for a particular region's needs.
Option 5: Use the present construction method but apply insulation to the exterior and party walls. I.e. EPS rigid insulation panels applied on the interior face with sheathing panels over. Note that this is a retrofit of existing methods.
Insulation materials can be in the form of:
There are many different types of insulation materials available to the building industry. Fiberglass batt insulation being the most widely used. Fiberglass batts tend to lose efficiency when saturated with moisture, so it may not be a good option for tropical climates. Additionally, they are not a "green" product. Insulation that does not entrap moisture will tend to perform better. Utilizing waste products from agriculture would be a good option, however tropical climates are known for the myriad flora and fauna that thrive within their ecosystems. Before wholesale application of any organic material, it needs to be carefully researched to ensure mold or insects or other pest do not infest it. That is one of the reasons cellulose was not listed as an insulating material. Rice straw used for straw bale construction tends to come from species developed in California. They are not cultivated in paddy fields as in Asia and have high silica content, low moisture and very little nutritional value within the straw itself. The bales are compacted and because of the construction methods used have been proven to last for many years (over a hundred years in some notable instances). While some of these represent new and different ways of construction from the present, there are potentially many advantages beyond the sustainability of the buildings. New industries can be created resulting in new jobs. Construction costs can be lowered and reliance on unskilled imported labor can be reduced.
Things to consider:
Cradle to grave. A movement that looks at how all materials selected for a building impacts the environment. From it's creation to the end of it's useful life span. In other words, a lifecycle process and implementation. Just because an end product is labeled "green" when installed does not necessarily mean that the process used to create it was green or environmentally friendly. This can be weight against the idea that anything green is good and better than taking no action whatsoever and the good needs to be balanced with the bad.
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While the focus seems to have been on high rise residential towers, the sustainable and passive energy design strategies apply to all the housing types described previously. Proper orientation for day lighting, ventilation and cooling should always be the baseline approach to design. Alternative construction methods should be a process that is developed specifically for each region/ country using the available resources. Architects with good knowledge of sustainable design and awareness of socioeconomic, cultural and climatic factors can serve as the engine for building construction innovation. Gerard Lee Architects believes in sustainable design and would be willing to participate with developers, builders, research facilities, universities and governments in these regions to help formulate new sustainable building systems, materials and construction methods.
Sustainability in design can create new industries, save resources and energy while creating better communities.
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