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Sustainable Design FAQ/ guide Index:
An Introduction to Alternative Construction Methods.
Within these next few paragraphs are just a few different alternative construction methods utilized in sustainable design.
Alternative construction addresses a form of construction that utilizes methods not normally used in typical construction.
Typical construction in turn would imply the standard platform framing used in residential and light commercial buildings in North America.
Or precast concrete panels with reinforced columns and beams in many developing countries. Therefore "alternative" usually refers to a type of construction
that the majority of builders or contractors may not be familiar with or utilized in their normal operations. Typically it now refers to sustainable
forms of building. Alternative construction can minimize or reduce the use of diminishing natural resources like timber.
Below are just a handful of examples, note that there are vast resources on the web and in published formats that can provide you
with far better terminology or explanation of systems. What we provide within these pages is a simple description to help you grasps the basics.
Use what you find here as a spring board to research sustainable design and building.
Straw Bale Construction:
Probably one of the better known methods of alternative construction known to most lay people. There has been a lot of publicity for
the use of straw bales in construction. The latest for a transit facility design by HOK.
There are two approaches to using straw bales:
The first approach is to use straw bales as the main load bearing component within the walls of the building. This method tends to be used on single story buildings.
Cement plaster/ stucco tends to be used as the exterior and interior finish. Different methods are utilized to compress the bales which are typically stacked using
a running bond pattern (similar to what you would see in a brick wall, where they are staggered or offset over the course below).
Historically more difficult to obtain permits because of the lack of knowledge on the part of building officials, however that seems to be
changing, with more than 200 straw bale homes built just within the State of California.
The second approach initially started by utilizing straw bales within heavy timber or post and beam structures. Technically the load was carried by structural
members that are more common and readily acceptable to building officials. The acceptance of the insulating values of straw bale has resulted in more
methods being develop that allows straw bale to be used in more or less conventional methods of construction. Traditional stud framing, stress skin panels, concrete cast in place
or shotcrete walls have all be utilized.
Note that the type of rice species used in California has a high silica content, has little nutrient value in the straw and takes a long time to decompose when distributed over open fields.
The use of straw helps the environment in several ways by minimizing the disposal of straw through burning and technically to eliminate and use productively what is agricultural waste.
Do note that straw bale walls tend to be thicker than conventional walls. 22-24" thick walls as compared to a typical 6" or 12" wall. That's a lot of area taken up by a wall, yet its
insulating values (~ R30-42 for a two string straw bale vs R-19 in a typical 2x6 wall using fibreglass batts) provide for a better insulated building and its thicker walls impart a different aesthetique that appeals to many people and imparts a feeling of stability in soundness.
Typically used in traditional mission/ spanish style buildings, or adobe, it can be utilized succesfully within modern and contemporary designs.
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Rammed Earth:
Rammed earth or the use of compacted earth to build has been around for centuries. It's resurgent as an alternatvie method of construction.
Benefits include thicker walls, better acoustics, thermal mass, wide availability of raw earth, load bearing, uses no processing and reduces usage of timber.
Historically, a process of construction that involves hand ramming and compressing earth/ soil between wooden forms to build up a wall
(many of these buildings have been around for centuries). Considering their reputation and history as durable and long lasting structures,
it sort of negates the un-informed view that earthen based construction may not fare well in a rainstorm.
Newer technology is helping bring this process more mainstream. David Easton's method of pneumatically
shooting a mixture of earth and cementitious stabilizers against
a one sided form work, is a good example. Easton's process is referred to as PISE (Pneumatically Impacted Stabilized Earth).
Obviously the benefit of using earth is that it is a building material that is widely and fairly cheaply available. If your site requires grading and
removal of dirt or soil, it might be feasible to explore using rammed earth or other methods that utilize earth.
There are no design boundaries when it comes to aesthetiques. The old adage that alternative materials lend themselves to vernacular or traditional looking homes or buildings does not hold water.
It really depends on a client's foresight and the architects abilities. Properly designed, a rammed earth building can be utilized successfully in any climate.
Rammed earth in residential construction seems to be widely accepted in Australia.
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Cob:
As with rammed earth, Cob utilizes soil or earth as a base material. It has similar benefits of thermal mass, termite resistant, good acoustics and well suited
for passive solar technology and inversely, passive cooling. Lime based plaster should be utilized as the exterior finish for protection
as opposed to cement based plaster/ stucco. Recent research and findings have shown that earth based walls like Adobe tend to fail if covered with cement based plaster.
It doesn't allow the walls to breathe and release any built up moisture. Cob does not require formwork and is made from a combination of sand, clay, straw and water. It is normally formed by hand.
Cob structures have been known to have survived for centuries, as can be seen by Cob houses in England. Earthen based construction tends to be labor intensive and slower than the standard form of construction.
However you are using a material that is readily available under your feet and less timber (which is important when you consider deforestation and it's impact on the global climate).
Obviously you need to protect a cob structure from rain or water and factor in labor cost and building regulating agencies. Quite recently
an entire village in Thailand was rebuilt using the labor of volunteers and villagers of a village that was displaced by the construction of a dam.
The villagers were given a grant (as part of a settlement by the government) to procure land but with limited funds, they had to resort to natural
building techniques.
Cob lends itself well to developing countries where labor is more affordable and soil is readily available. These buildings have to be detailed well,
with proper foundations and weather protection. Note: Cob isn't an acronym, so the letters by themselves do not mean anything. It's just the name applied to
this method of building.
Other Earth/ Soil base methods:
Earth ships, modular contained earth, light clay and adobe are other alternative methods of construction using earth.
Earth ships have been written about extensively and recent projects have been built in England. It's a process involving using old tyres, stacking them and
ramming with earth.
Modular contained earth actually emcompasses earth ships and also earth filled bag construction.
Earth filled burlap and or polypropylene bags are stacked and sometimes finished with a plaster based coating. SuperAdobe is a variation designed by architect Nader Khalili,
which utilizes a long bag system that can be coiled and stacked in organic looking structures.
Adobe as a building material is probably a method many people are familiar with. It evokes visions of Spanish missions stretching across California. Basically a clay based earth brick,
stacked with mud based mortar and grout, with a mud based plaster finish. It's use is probably the most widespread throughout the globe.
All these systems share similar benefits and disadvantages as those listed above.
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Other materials:
Beyond the systems listed above, other alternative construction materials can be as simple as reverting back to vernacular or aboriginal forms of construction in certain regions.
These are normally ways of building that have evolved over time to compensate for a region's climate. Tropical climates like New Orleans, Florida, The Caribbean Island, and South East Asia
have similar themes in their vernacular architecture. Raised floors to allow the circulation of air for ventilation beneath the buildings. Steep roofs and ceilings to shed heavy rainfall
and to allow hot air to be released through a stacked effect. Louvered window shutters to keep out rain but to allow for ventilation and daylighting. All effective methods that evolved through
time.
Bamboo has been utilized as a building material over the centuries. In Asia, it's used as scafolding to aid in the erection of high rise steel framed buildings. In South America and some parts of Asia,
it is being utilized as the structural framing. Bamboo is fast growing, and a great renewable resource. For the most part, only recognized as a new flooring alternative within the United States.
Though this seems to be changing as more bamboo products come to market.
Other materials while not utilized as structural members are seeing in-roads in the building industry as finishes or cabinets.
Wheat has been utilized in panels for kitchen cabinets and wall finishes. Cork within linoleum or cork flooring and wall panels. Recycled rubber from tyres can be used in ecoflooring and wall coverings.
Recent research has shown great promise for recycled rubber and rice straw combined as rigid insulation panels.
There are new solid surface materials made from recycled paper and resins which are durable, cost effective and easy to work with.
Sustainability is no longer a trend but a method of construction that is responsible and cost effective.
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References:
Much of the material we present within these pages came from the following books. The others from our own education, experience and from the almighty internet.