Designing for tropical conditions – a case study

 

Talking with Gabo and Juan last week, we discussed the need to reference a case study on tropical building strategies – incorporating passive solar strategies to maximise energy efficiency and increase comfort. So for this week I thought it would be appropriate to discuss a building that is often talked about in Australia as an exemplar of tropical building strategies (and one of very few designed with Aboriginal communities in mind).

Glenn Murcutt – Marika Alderton House (1994)

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The building is located in the town of Marika, which is in the Northern Territory state of Australia. Being 12 degrees south of the equator it has similar solar conditions to that experienced in Calakmul (18 degrees north of the equator), thus the strategies discussed here are directly translatable. What this means is that in both locations the angle at which the sun hits the building will be high for most of the year. Similarly, in this part of the Northern Territory there is a clear distinction between the wet and dry seasons (average temperatures are comparable to Calakmul), with dry (winter) and wet (summer) winds also affecting the building.

Sunshading

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An important part of designing for tropical locations involves sunshading.

Here we can see how the extended roof structure (eaves) keep the sun away from the building both during the summer – when the sun is at its highest angle, and in the winter (at its lowest) it is still kept away from the interior of the building.

Direct sunlight is never allowed directly into the building throughout the year – this is unnecessary as temperatures never drop low enough that the interior needs to be heated.

*This is something you can see in the traditional Mayan buildings which also have an overhanging roof shape and minimise direct sunlight passing through to the interior of the building.

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Cross-Ventilation

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The ability to operate openings on all sides of the building is necessary to allow for breezes to pass through the building, which cool the interior space. This building also uses large panels which allow for light to enter the building but keep the direct sunlight (heat) out. So as the conditions change, occupants can respond by opening or closing the various sections – this adaptability is also important because it gives the occupants a sense of control over their living conditions.

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The speed of the cooling breezes can also be modified by the size of openings during the different seasons. In summer you can increase the speed of the breeze by having small openings in the facade (wall) which cools the interior more effectively (just like a fan) and also minimises the amount of direct sun exposure. This is maybe not as necessary in winter, when the building opens up completely to make use of the dry winds from the southeast.

– Again the adaptability of the building is important for responding to the complex nature of tropical climates. (The building may be closed up entirely for a cyclone / hurricane event).

Stack Effect 

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So what happens when there are no breezes available to cool the interior of the building? The stack-effect is useful in such conditions and basically means that by placing an exhaust (fan) at the highest point of the ceiling space, cooler air entering from the lower parts of the building will heat up and rise out of the building – this cools the interior space. Murcutt’s building has openings where the floor meets the wall to allow for air to enter at floor-level).

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Raised Floor (permeable)

The building is also raised above ground on a series of stilts to protect against floodwaters in the rainy season (and which also keeps the snakes / pests out of the building)*. Additionally, breezes are allowed to pass through the floor and this assists in cooling the interior space.

*This is an issue Rodolfo has previously mentioned exists in 20 de Noviembre.

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“Touch the earth lightly” – An Aboriginal proverb 

This building has no glass windows (*20deNov are paying a window-tax to govt. – meeting with Rodolfo 25.09)  and is constructed of light-weight and readily-available materials. It demonstrates strategies for using simple metal roofing (tin is used in 20 de Noviembre) and the adaptability of operable facades.

Additionally, the building was designed in co-operation with the indigenous occupants and responds to their patterns of use. (It is not over-planned, large open spaces allow for flexibility).

I think a lot of these strategies are already evident in Mayan traditional houses of the area – working with 20 de Noviembre is an opportunity to develop the existing housing strategies towards responsive and adaptable spaces which increase community resilience through addressing fundamental communal needs.

– Flynn

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