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Kerpic08 - Learning from earthen architecture in climate change

International Conference

Cyprus International University, Lefkoşa / Northern Cyprus 4-5 September 2008

 

A Straw Bale Building in Güneşköy Ecovillage-

An Experiment in Ecological and Inclusive Design Process

Evren Yılmaz Tekin1

Ali Gökmen2

 

1Şeker Mahallesi 25. Sokak No:15 Etimesgut 06790

Ankara

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2Middle East Technical University, Department of Chemistry, 06531 Ankara

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ABSTRACT

Güneşköy ecovillage is to be an experimental human settlement       which aims to find ways of life in harmony with nature. Our straw bale building, built as part of UNDP- GEF supported Project:

‘Using Vegetable Oils as Tractor Fuel’, now houses the oil press. A range of natural materials were tested for use at every stage. Except for waterproofing, all our targets were fulfilled. The building has a reciprocal timber frame load bearing structure, with strawbales as wall infill, sealed with a covering of earth plaster. Members and volunteers of Güneşköy participated during the whole design and construction process. This anonymous product of around 30 people from different fields was led by Prof. Dr. Ali Gökmen. This paper explains the design and construction process of the building.

KEY WORDS :

Straw bale, ecological design, reciprocal frame, inclusive design process, ecovillage,Güneşköy

 

1 INTRODUCTION

Over the past decades, people around the world have experimented with alternatives to a society, which they consider destructive. The ecovillage vision was born out of these experiments, providing solutions both urban and rural, in both northern and southern hemispheres, and on every scale, from the family nucleus to local communities and global organizations. Ecovillages are basically a matter of living on the Earth with respect for all beings and natural systems. They embody a mindful lifestyle, which can be continued indefinitely in the future. As such, they are shaping nothing less than a new culture, designed to restore the Earth and her people.’ [1]

Güneşköy was founded in Ankara, in 2000. It is located near Hisarköy, a village of Kırıkkale province that is 65 km east of Ankara. Its goals are to design an example of sustainable living, search for ways of alternative energy, organic farming, environmental architecture, waste management and water conservation. Güneşköy started with poor uncultivated land that it intends to enrich using natural ecological means into a quality arable land. It hopes to show how cooperation between long-term residents of the area and others can benefit everyone: by reducing migration from villages, by using resources more effectively, by sharing information, by mutually supporting each other, by bridging between official sources and those who work the land.

The main activities of the organisation at present:

Organic Farming: 10000 m2 of our land (74000 m2) is cultivated (for the first time so there are no chemicals in the soil) to grow vegetables in a natural way, without chemicals. In 2008, 100 families receive a weekly box of fresh produce as a part of this project..

Energy project:  ‘Using Vegetable Oil as Tractor Fuel’. This is an UNDP-GEF supported poject. Türk Traktör company has donated a tractor that it adapted for effectiveness trials.

Our straw bale building, built as part of this project, now houses the oil seed press.

 

2 DESIGN PROCESS

‘Process is a fundamental aspect of ecological or sustainable design. The idea that average

users or participants, such as students, can have a direct hands on the design and construction of a new facility that they will use is at the core of the organic design process.’[2] This process is meant to be inclusive, and strives to involve all the stakeholders as a means of insuring a buy-in and some level of ownership of the project by all those who will be impacted by it.

Regular weekly meetings of Güneşköy members and volunteers allow all decisions to be made at these meetings after long discussions; meeting notes were published on the mail group.

When the need for a building to house the oil seed press was understood, a smaller group which was going to be responsible for the design and construction of the building was formed. The Group was composed of 2 architects, 1 civil engineer, 1 chemical engineer, 1 electric electronic engineer and 3 carpenters. This group made all technical research and drawings of the building and coordinated the construction process.

Alternatives for the structural systems and materials were presented to the larger group. 3D drawings were made to help everybody visualize the designs and the end product. It was made sure that everybody’s voice was heard and everybody was happy with the design.

The building’s possible future functions were also a main discussion topic, because at the end of the UNDP Project the press will be handed over to local Hisarköy villagers.

The location of the building was decided on the site. A group of around 7 people who visit the site regularly came together and considering the function and needs of the building they picked a position. However this position was changed 3 times according to comments by others (volunteers and specialists)

The design process was really challenging: hard, complicated and long. But it was also a real community glue: the product is now owned by everybody who was involved in the process. Having shared the labour, members and volunteers know each other much better.

An architect needs to be very careful when conveying her/ his ideas to the other people and giving guidence. Communication with people who would like to understand but do not have the professional background requires skills so that all are able to appreciate the variety of choices, and their consequences.

 

3 THE BUILDING

3.1 RECIPROCAL FRAME

Main focus was to design a structure which was as strong as possible using as little material as possible. In other words doing more with less [3].

At the beginning icosahedron models were made and studied in terms of strength, details and ease of construction. But the roof, openings and joints details did not satisfy the group.

Besides nobody liked the appearance of the building.

We then saw pictures of a reciprocal frame structure built at ZEGG (an ecovillage in Germany). ‘The reciprocal frame is a roof structure where each beam both supports and is supported by other beams in the roof structure. A minimum of 3 beams are required to create a reciprocal frame roof. As each beam supports the next in a reciprocal manner, no internal support structure is required.  Only the outer end of each beam requires a support, that is a post carrying the load of building.  The roof loads are transferred to these posts and in turn to the supporting foundation. The beams can be fabricated from timbers, laminated wood, steel or reinforced concrete. A very inexpensive roof structure can be made from logs. The reciprocal frame roof results in a very strong self-supporting structure with very unique features [4].

Figure 1. Reciprocal frame of Mandala building

The structure of roof is shown in  Figure  1. The radius of the circle that 12 poles are mounted is 3.80 m.

The interconnection of the beams was very impressive. To us, it symbolized the interconnection of beings in nature. Though there were difficulties with some roof details (roof cladding and the central hole) we decided to give it a try.

The building was called Mandala. ‘The word "mandala" is from the classical Indian language of Sanskrit. Loosely translated to mean "circle," a mandala is far more than a simple shape. It represents wholeness, and can be seen as a model for the organizational structure of life itself--a cosmic diagram that reminds us of our relation to the infinite, the world that extends both beyond and within our bodies and minds.’[5]

The ZEGG Mandala structure was 8 posted, but we chose 12 posts because of the larger size of our building. Once the bales were plastered on the outside, the 12-sided building looked round.


3.1.1 PRESERVING THE TIMBER

Timber was used for the 12 vertical posts, and for the roof structure. The diameter of posts was about 12 and 8 cm at the ends. Wood being an organic material, precautions should be taken to protect from climatic conditions decay, fungi and insect attack.

Contemporary timber preservation methods use chemicals dangerous both for human health and the environment. Especially timbers impregnated with CCA (chromated copper arsenate) releases chromium and arsenic. We thought of recyling old electric/telephone posts but as they were impregnated with CCA we did not want to use them.

There are more environmentally friendly ways of preserving wood. A waterborne product based on copper triazole technology is avaliable where the copper is derived from recyled sources and triazoles are organic biodegradable biocides. Other preservatives are based on water-soluble borate. Another option is heat treatment, in which thermawood is process of intensive heat treatment. Our timber frame was designed to be inside of the building. But 1m of the posts was going to be buried in the ground and in constant contact with earth and humidity. The bottom part of each post was burned to form a carbon layer which will not feed insects. Burned engine oil was applied on top of this layer to stop water penetration and insects as shown in Figure 2. To stop insects fuel oil was sprayed too.

Timber parts other than the structural frame, a door and five window frames were preserved by using synthetic linseed oil or pinotex and varnish.

 


 

 

 

 

 

 

 

 

 

 

 

Figure 2. Treatment of the parts of posts which were going to be buried in the ground.

3.2 STRAW BALE WALLS

We had 2 alternatives for the walls: mud brick and straw bales. Both materials were available locally. Mud brick, used in the area for millenia, is now seen as old fashioned by villagers who, fancying the houses of city people, think that concrete is modern. They all prefer concrete houses. Concrete is cheap and easy to use. Only a few old people remember how to make the traditional bricks.

Mud brick is a good material for thermal mass, an important quality in Ankara’s hot arid climate with great temperature differences between day and night.

While straw bale walls do not give thermal mass, they have high insulation value. Bales being light and flexible, the walls can be built easily and quickly. Furthermore they are earthquake- resistant.

‘The straw bales/ mortar structure wall has proven to be exceptionally resistant to fire. The straw bales hold enough air to provide good insulation value but because they are compacted firmly they don’t hold enough air to permit combustion.’ (Report to the Canada Mortgage and Housing Corporation) [6]

We neither had time to make mud bricks by ourselves nor money to pay someone to make them. As we had already built a small building with mud bricks, we wanted to experience another material so decided to use straw bales.

As far as we know there are 3 more straw bale buildings in Turkey. One is in Kırıkkale, Hasandede built by Demet Irklı Eryıldız and her team [7], another one was built by Buğday Derneği in İstanbul [8], the last one was built by Ismail Yenigün in Imeceevi, Küçükkuyu.[9]

Construction details of a straw bale building [10] and application to a round building with wood load bearing reciprocal frame was described online [11].


3.2.1 FOUNDATION

A foundation wall was built to keep the straw bale wall off the ground. The 50 cm wide wall was about 50 cm high at the north face and 100 cm high at the southern side, according to the slope of the land along a north-south direction. The stones were laid in a mud mixture, made of local soil, straw and water, as used traditionally in local buildings.

3.2.2 BALE RAISING

The straw bale wall was raised from ground level by stone wall to protect the straw from rain water and humidity in the soil. Besides, the first course of bales was raised further off the wall to prevent any water condensation on the stones or absorption through the mud mixture with a timber frame. First, 200 cm long (5x10 cm section) timbers were nailed around the 12 vertical posts, level with the top of the stone wall. The flat mud plaster surface on the top of the stone wall was aligned with the wooden frame. A breathing plastic membrane (impermeable

Figure 3. Strawbales were raised and ventilation was provided underneath to keep them dry.

 

to water, but permeable to humidity) was placed on the smoothed wall surface. Rectangular 80 cm long wood beams (5x10 cm section), were secured radially (protruding 30 cm into the inside of the building) between the vertical posts, with 5 such beams between the posts. The parts of the beams extending in the building will be used to built a round sitting place. Two rows of wood (2x5 cm section) were placed on the beams to make a base, lifting the first course of straw bales 12 cm above the foundation wall. The insulating wall memrane was folded up at the exterior and flat at the interior side of building to prevent exterior water coming into contact with the straw bale but still permitting ventilation of the straw bale wall As shown in Figure 3.

 

3.2.3 WINDOW AND DOOR FRAMES

Five timber window frames (cross section 5x10 cm) were fixed to the horizontal posts of the reciprocal frame at the top and the base frame at the bottom. The 180 cm wide door frame extends from roof to ground level of the building. The door was located in the west facing wall. Of the five window frames, one is on the north face, one is to the east and three are in the southerly direction. The wall length between south facing [x1] window frame is 90 cm on the outside and 80 cm on the inside due to round curvature of the building.

[x1] : Because they are the closest.

 

3.2.4 STAKE PINS

Round wooden stake pins (50 cm long, 2 cm diameter, sharpened to a point at both ends) were placed in the holes of radial beams located above the wall. Pins, vertical beams and the base plates are illustrated in Figure 4. Holes (2 cm diameter, 4 cm deep) in the radial beams held the first pins vertical while the straw bales were gently pressed onto the pins and slide down to the base. Each bale was fixed with two pins. In later rows, stake pins were inserted half way into the finished row, and the next level of bales were spiked onto the pins, so preventing lateral movement of bales.

 

 

 

 

 

 

 

 

Figure 4. Illustration of radial beams, base plate and stake pins for fixing straw bales. Timber sticks were used rather than metal, which could have caused condensation.

 

3.2.5 STRAW BALE TEMPLATE

A template was built from two pieces of wood to bend the straw bales to the round shape of building. The template is 100 cm long, with 30 cm between the two sides of the template (see Figure 5). Each straw bale was shaped by two people applying force on the length of the bale.

Figure 5. Illustration of template for bending straw bales to a round shape

 

 

 

 

 

 

3.2.6 PLACEMENT OF STRAW BALES

Bale’s sides differ, one face having straw fibers perpendicular to the surface and the other with fibers parallel to the surface. As the bale making machine sorts the straw fibers and cuts them along one side, the fibers are sorted perpendicularly to the cut side. In building the wall, these different faces were placed alternatively, to make plastering easier on the fibers located perpendicular to the surface.

Straw bale construction started from the wooden door frame. The last straw bale placed before the window frame had to be cut to the correct length. This was done by a conventional method: A straw bale needle was prepared from an iron strip (80x2x0.2 cm). The tip of pin was flattened with a hammer and two holes with diameter 0.5 cm were drilled as illustrated in Figure 6. Two  pieces of string were threaded through the holes and the needle was then inserted in the bale where it is cut into two pieces. Once the straw bale is bounded on the opposite sides, the original string is cut and bale is cut outside the new ties.


Figure 6. Needle used for retying straw bale before cutting to a smaller size

 

 

 

 

3.2.7 STABILIZING THE STRAW BALE WALL

Although the straw bale rows are bounded to each other by stake pins as illustrated in Figure 4, this was not enough for the stability of the whole wall. Before being fixed with straps, the straw bale wall was compressed to eliminate any void space. A strap binding tool (utilized for tightening truck loads) was used manually to compact the bales at every meter of the wall. Figure 7 illustrates this compacting process. Then, each section of straw bale wall was stabilized by vertical and horizontal wooden straps anchored to the load bearing posts. The vertical straps were fixed at the horizontal poles of reciprocal frame at the ceiling and the wooden base of the wall inside and outside of the building. The horizontal straps were only placed on the outside face, passed under the vertical straps. The wooden straps are shown in Figure 8. Metal wires were passed through the wall, from one side to the other using straw bale needle shown in Figure 6 to fasten vertical bars inside and outside of the wall and horizontal bars to the vertical posts of the reciprocal frame. Hence, the straw bale wall was integrated with the wooden frame firmly.

 

 

 

 

 

Figure 7. Compressing the bales

 

 

 

 

 

 

 

Figure 8. Fixing the wall by wooden straps

 

 

 

 

 

 

 

 

 

3.3 EARTH PLASTER

Plastering of inner and outer surfaces of the straw bales is essential to protect from weather, animal, and other damage. Plastering (with a mix of local soil, straw and water) was done by a local mason. We researched correct proportions of sand, clay and water. As we could not transport the ideal clay rich soil to the construction site, the soil on our land was used after experimentation to find the right consistancy. Lime added to the mix for some sections resulted in a brittle surface that cracked.

The hard, spiky side of the bales was easier to plaster than the soft smooth side, where the plaster was difficult to stick. When building the walls it is good to get a nearly

Figure 9- Exchange students from METU joined us for plastering. 30 students plastered 1/3 of the total wall area in one day.

equal mix of slippy and pointed sides of the straw bales on inner and outer sides of the building.

Chicken wire was used on both inside and outside walls to help hold the plaster and prevents cracks (Figure 9). It also increases earthquake resistance.

 

 

3.4 ROOF

A light and flexible material was needed for the roof materials considered were asphalt shingles and metal sheeting. Asphalt shingles are petrol based products. Metal sheeting was aesthetically satisfaying solution and it is more environment friendly because its long lifetime and ease of recycling. However, due to cost, installation difficulties and high energy use in its production of metal sheeting, we decided install shingles on the roof. (see Figure 10)

We would have liked to have had an earth roof but it would have been too heavy for our elegant timber frame. And again petrol based waterproofing materials would be needed underneath the earth.

Figure 10. Roof layers are from inside to outside; timber cladding, tar paper, industrial felt, 10mm OSB, asphalt shingle

 

For heat insulation we compared many materials. Cellulose (obtained from used paper) mixed with borax as a fire retardant was one of the best choices but it was expensive. It would have been sprayed under the roof inside the building. We could not be sure of how it would change the appearance of beatiful pattern of wood on the ceiling. The atmosphere in the building depends on the ceiling pattern.

In the end industrial felt was used for heat insulation as it was cheap, easy to install and light.

 

3.5 VENTILATION

On the Northen facade of the building ventilation holes were provided at the bottom of the wall so that cooler air enters the building from these walls. Warmer air is released through the roof window. Roof window has a simple design. Polycarbonate was fixed to the window frame from above. The angle of roof window is adjusted to allow maximum winter sun. Channels (on left and right) allow water drainage. This was cheaper than conventional roof windows but has not yet been tested under winter conditions.

 

 

 

 

 

 

 

 

Figure 12. Roof window

Figure 11.Ventilation holes at the bottom of straw bale wall and roof window.

 

4 CONCLUSION

There are places we love to be and feel alive. What is the quality these places have? What makes them so pleasing? Old towns and vernacular architecture can teach us a lot about that. They are at human scale, use local materials and techniques, with suitable dimensions for the materials. Many are self built or involve users-owners in the processes of design and construction, to create shelters, modest but effective, these places have organic development patterns and are much more alive than our modern concrete boxes with hygenic finishes.[12,13]

This strawbale building is the outcome of an experiment in an inclusive, ecological design process. We hope that people experiencing this place will love to be there. It was produced by many generous and sincere hands.

 

We are simply telling this story to celebrate our labour, and to inspire others who know deep inside that there is something terribly wrong with our contemporary culture.

A step by step guide for construction stages can be seen at:

http://www.flickr.com/photos/evreny/sets/72157603730681533/ or www.guneskoy.org.tr

 

5 ACKNOWLEDGEMENTS

It is impossible to count everybody who gave their precious time for us but some special thanks go to: Our carpenters who work for free Kıvırcık Usta, Ahmet Usta, Kamil Usta, and Duran Usta who did the plastering. Nihal Temürcü and Ceyhan Temürcü for the drawings and ideas and helping the coordination of construction, being with us. Aklan Mühendislik for the structural analysis of the reciprocal frame. Özer Tayiz and Aylin Tuncer for the ideas and support in the site, Filiz Telek helping to find straw bales, Claire Özel for correcting the manuscript, and all Güneşköy members who finance and made possible this project. UNDP SGP for funding of the project without their support it would be impossible to build the straw bale building.

 

6 REFERENCES

[1] Hildur Jackson, Karen Svensson, eds., Ecovillage Living Restoring the Earth and Her People, GaiaTrust Green Books, 2002.

[2] Alexander, 1975, www.patternlanguage.com

[3] Buckminster Fuller, http://www.bfi.org/

[4] http://www.mts.net/~sabanski/pavilion/pavilion_design.htm

[5] http://www.mandalaproject.org/What/Index.html

[6] Athena Swentzell Steen, Bill Steen, David Bainbridge with David Eisenberg, The Straw Bale House, Chelsea Gren Publishing Company, 1994

[7] http://www.mmf.gazi.edu.tr/journal/2000/87_104.pdf

[8] www.bugday.org

[9] www.imeceevi.com, http://www.ekolojikev.com/

[10] Clarke Snell and Tim Callahan, Building Green, Lark Books, 2005.

[11] http://www.ecohabitar.org/PDF/strawbalebuildinguide.pdf

[12] Christopher Alexander, The Timeless Way of Building, 1979

[13] Cengiz Bektaş, Türk Evi, Bileşim Yayınevi, Haziran 2007