Roofing

After investigating bamboo construction, anther aspect that I want to consider is roofing materials.

Traditional East Timor architecture that is non-colonial relies on banana leave thatching for waterproofing roofs. This is in no doubt sustainable as these materials are readily available and would otherwise be discarded.

Lightweight bamboo framing to support the thatched roofing

This type of roof weathers beautifully and has strong textures. It is difficult to know what it's thermal properties are like though, and what maintenance is like. However, this type of roofing is also used in rural England and has a long tradition of use in European countries.

Example of a thatched roof in Devon.

Although this type of roofing is readily available in East Timor, is actually what is the best materials for a building that is representative of an emerging nation? Yes, and no. I do not think that there is anything wrong with using this system, however, it must also fit into the notion of the entire building. How will the building look from a distance? Will maintanence and access be an issue. It would be a shame to have an overall form dictated by the roof material.

I wanted to look further afield at what is also on offer here in Australia. I looked at transportability, weight, texture and overall performance with respect to thermal and maintenance issue for a tropical climate.

Tensile Fabrics

Other lightwieght materials include tensile fabrics. A manufacturer, Ferrari Textiles has some excellent examples of what can be done:

http://www.ferrari-textiles.com/

The site is from a manufacturer of the products and includes numerous examples of its applications in architecture, both external and interior. There is also mechanical performance data.

Textile PVC fabrics are very light, flexible and perform very well in tension (due to weaving). It can either be opaque and flexible.

You can consider it a skin stretched tight over a frame in order to span large distances or create an enclosure. As can be seen from the picture above, you can also put the material through a printer to create patterned textures. This could be a good way of incldung iconic East Timorese patterns.

Tensile PVC fabric as a small scale umbrella. The frame maintains the shape. The fabric only performs in tension.

As the material is very light per square metre, the roofing structure could reduce its complexity by using less material, and thereby improving adaptability, sustainability and construction time.

However, on its own, it does not thermally insulate very well. As it is only a very thin membrane no thicker than 5 mm, moisture can also form on the interior if there is very high humidity. As humidity would be a common occurrance in East Timor, the material would need additional accompaniments to perform and keep people comfortable.

ETFE

Eden Project, England
Beijing Water Cube

Ethylene tetrafluoroethylene, ETFE, a kind of plastic , was designed to have high corrosion resistance and strength over a wide temperature range. technically ETFE is a polymer, and its systematic name is poly(ethylene-co-tetrafluoroethylene). ETFE has a very high melting temperature, excellent chemical, electrical and high energy radiation resistance properties. (http://www.iaso.es/iaso/es/arquitecturatextil/cubiertasyfachadasefte/cubiertasyfachadasefte.php)

This is quite a remarkable material not only due to its strength to weight ratio, but because it can be used to insulate a building, allowing the designer to permit only favourable qualities.

The above scan is from Verb Natures book by Actar Publishers. It is a diagram of how the material works on the water cube swimming complex in Beijing. Essentially, a pillow of the material is cut and welded to shape. Additional filaments to allow a certain percentage of light through can be intergrated. The pillow is maintained at a certain pressure between frames to maintain structural integrity. Additionally, pumps are used to maintain the pressure due to changes in temperature and wind loading.

Amazingly, ETFE is 98% lighter than glass! That is amazing, and also relevant to my project. Bamboo is lightwieght and accordingly, loading the frame up with additional volumes in weight from the roof would defeat the purpose of creating a lightweight structure.

I will investigate further into how to integrate this type of technology into East Timor and the amount of energy required to maintain this type of structure. perhaps the solar glass or panels could be used in the design?