Renewable Energy Information Consultation Centre
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National Association for Ecological Building
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Reprinted from North Sun2007
Abstract – This article describes the current straw bale building situation in the project “Promotion of Straw Bale Building for Climate Change Mitigation” and presents countries, advantages and methods to build with straw. The future opportunities of straw bale building are impressive, as society starts looking for more efficient and economic forms of construction.
Straw bale construction offers many advantages, from super insulation and reduced heating and cooling costs to the use of renewable, local materials and great aesthetics. Straw is a natural product, grown by photosynthesis during a half or one-year period, fueled by the sun. Straw is currently produced in surplus to requirements, so it is cheap and easily accessible in most countries. It is the end product of growing crops; so using it for building purposes is a very sustainable and ecological way of recycling. The first straw bale houses, built more than 100 years ago in the USA, proved the durability of the material and reliability of technology. Straw as a building material offers a lot of possibilities and lots of them are not yet discovered. The building method itself is based on a block system, making the designs very easy to implement, and giving great flexibility in its use. The most important advantages of straw bale building are energy efficiency, low-embodied energy, greenhouse gas emissions reduction, saving resources and a healthy microclimate.
Buildings and Environment
The buildings’ impact on the environment
Modern buildings have a tremendous impact on the environment in all life cycle stages. It results in different problems and has a significant influence on climate change because of energy use producing building materials, building, maintenance and demolition of buildings. The building industry uses 40% of stone and gravel, obtained annually worldwide, 25% of timber, 16% of fresh water, and 40% of the energy and materials produced annually. 30% of newly built and renovated buildings have Sick Building Syndrome [1, 2]. Citing the example of Europe, more than one-fifth of present energy consumption and up to 45 million tonnes of CO2 per year could be saved by 2010 by applying more ambitious standards to new and existing buildings .
Advantages of straw bale building
Straw bale walls exceed building insulation requirements. A typical rendered straw bale wall has an R-value of 7 m2·K/W .
Building with straw bales produces no waste. Straw is renewable and easily accessible; it is a by-product of a basic food source. Excess straw is currently being burnt in Lithuania and other countries. Straw bale buildings provide a safe and healthy living environment. The houses are warm thereby reducing heating costs. Buildings are durable: some of the first Nebraska style houses are still being occupied and reveal no problems. They have good acoustic properties, so it’s possible to build houses in noisy territories, to use technology for building studios in residential areas. After demolition, straw could be recycled back to the garden. Straw is a carbon sink that collects CO2 while growing and stores it in the walls of a building.
Technological Aspects of Straw Bale Building
Methods to build with straw
There are several methods to build with straw: the load bearing straw bale wall where the roof loads are transmitted into the foundation directly via the straw bales; a frame structure, usually consisting of timber posts and beams with straw bale infill; and hybrid systems, combining the previous two methods [4,5]. These methods are used widely, but there are possibilities to discover new techniques. In several years period straw panel technology was developed in Great Britain, Germany and other countries. This promises wider use of straw as a building material.
Load bearing or Nebraska style is the original method of building, pioneered by the Nebraskan settlers more than 100 years ago in the USA .
Straw bales are placed together like giant building blocks, pinned to the foundations and to each other with hazel sticks (or other), and have a wooden plate on the foundation and on top of the wall. This is the simplest and cheapest method to build with straw. Some limitations of the method are the length of walls and openings’ area: the longest wall could be 6 m; openings for windows and doors should not exceed 50% of the wall surface area.
Frame and infill technology
Straw bale building practically has no limitations when the frame (wood, metal) is used to carry the roof weight and straw bales are used for infill and do not carry any weight. It is possible to build 3-, 4- and even more storey buildings.
Firstly, the frame is being built; the roof is being made, then straw bales are used for infill.
This method is more expensive and not so quick in realization, comparing with load-bearing technology. On the other hand, straw is protected from rain, when building under a roof.
This is the combination of framing and load bearing.
This technology can be used to build bigger buildings and to save some money by using less wood for the frame.
Some other aspects of building with straw
Straw is a natural material, so for the plastering and painting of walls, natural materials should also be used. Straw is light in comparison to bricks and other building materials, so the foundation could be light, made from recycled car tires or other alternative materials. The straw must be dry if we use it for building purposes. This means care must be taken when storing the bales and the use of wider roof overhangs to protect built walls and to raise the ground floor over the land surface.
Contrary to public opinion, straw bale walls are fire resistant. In a 30-minute test with a 1000ºC fire on an exposed side, the unexposed side raised just 1ºC. A plastered straw bale wall has a 90 minutes rating (F90, or ASTM E-119 test) .
Promotion of Straw Bale Building for Climate Change Mitigation
Beginning in December 2006, the project– “Promotion of Straw Bale Building for Climate Change Mitigation” –has been going on with the main aim – to inform and educate Lithuanian, Estonian and Latvian society about straw bale technology, to teach a group of professionals about building with straw, and to contribute to reducing the impact of building on climate change in Baltic countries. Sponsors of the project are: UNDP Global Environment Facility’s Small Grants Program, the Lithuanian Republic Ministry for Environment, the British Embassy in Vilnius and The Nordic Council of Ministers Office in Lithuania. The Renewable Energy Information Consultation Centre (Lithuania) coordinates the project; international partners are ECOTON (Estonia) and National Association for Ecological Building (Denmark). Latvia is looking for partners in Latvia. The project website is www.siaudunamai.lt.
Straw Bale Building Development in Partners’ Countries
Straw bale building has been part of the ecological building tradition in Denmark since the mid 1990s. The first one was built in 1998 at The Nordic Folkecenter for Renewable Energy in Northwest Jutland. From 1998 to 2001 straw bale building spread very fast through owner-builder networks, combined with frequent conferences.
In 2001 a national test programme was initiated by SBI- Danish Building Research Institute. It was funded by the Danish Government. This test programme verified results about heat insulation, sound insulation, moisture, fire resistance, compression and other characteristics were received.
There is now a network of independent professional straw bale builders who each year build 10-20 new houses, and who share their experiences and thereby develop quality at a fast speed.
It is estimated there were ~150-200 straw bale houses in Denmark in March 2007.
The first straw bale experimental building in Estonia, a sauna, was built in 2004. The real start of Estonian straw bale building though, can be considered to be the summer of 2006, when the building of at least eight structures is known to have started, several straw bale building articles were published and in autumn introduction seminars of straw bale building were organized. Besides using straw bales, the use of reed-bale has been in experimentation, and encouraging results have been received. Estonian straw bale building developers have practiced straw bale building outside Estonia. Mikk Suursild has practiced straw bale building in New Mexico, USA; Kermo Jürmann – on the eastern coast of Australia– and there are some Estonians known to have practiced straw bale building as volunteers in Spain.
In 2006 Riina and Knut Klais started building their own straw bale house. The structure of the house is hybrid – sixteen wooden beams carry the roof. Walls will be self supporting. The roof is covered in shingles; the house will be rendered with clay found in the surrounding area. Riina and Knut are planning to build the house with the price of 1000 EEK/m2. At the end of summer in 2006, Mikk Suursild started to build three straw bale houses in Nina village. His aim was to build very simple, low-cost and independent cabins. Houses were built on existing concrete poles.
Straw was used in the floors, walls and ceilings as well. These are hybrid structures: the roof leans only on the four corners and straw bale walls are without any frames. Walls are rendered with lime plaster, scaffolding has been hammered on the wooden framework attached to the lower and upper belts (there is an air gap between the scaffolding and the straw bale wall), which is covered in tar paper. Energy is obtained from a wind generator (1, 5 kW). The heating system uses wood. The price of construction of one cottage was 200 000 EEK, 10 000EEK/m2.
In the summer of 2006, the architect of the local parish government Andres Toome built himself a straw bale sauna in Sompa, East-Estonia. He built the house on the foundation of a former manor vault and gathered the necessary material from the field of a farmer he knew. A cubic meter of straw cost him only 30 EEK for transportation. In comparison, a cubic meter of rock wool insulation costs 400 EEK. A wooden frame carries the roof; straw is laid between this for heat insulation. For building the wooden frame floorboards from a demolished house were used. The house is rendered with clay and painted with lime. The price of the sauna was 2000 EEK/m2.
At the moment there are three companies in Estonia connected with straw bale building – these are Säästvad Ehituslahendused OÜ, OÜ Unite and OÜ Natuurehitus. Straw bale building is combined with renewable power solutions (solar panels, wind turbines etc.) and water saving systems (water reusable, water heating in solar panels, foul water cleaning in artificial wetland etc.). The building of five straw bale houses is known to begin this summer, but this number can quite easily be doubled, as there are surely builders we do not yet know about. It is presumed that in two years, there will be at least 25 finished straw bale houses in Estonia.
The first straw bale house was projected in Camphill village Rožkalni in 2000 by Norwegian architect Rolf Jakobsen .
Vilnis Neimanis initiated the idea and coordinated implementation with the help of a Norwegian ecological construction school, “Brobygger skolen”. In the autumn of 2000, the house was assembled.
In 1996, the architect Petras Devizis discovered straw bale building himself, without knowing about other examples of this construction in the world. This kind of serendipity happened also in several other countries around the world.
The first straw bale dwelling was built in Taraldziai village . As there was a lack of public trust in the technology and no knowledge about other examples of straw bale building in the world, the second building was built only in 2002, also by Petras Devizis. This is the symbolic one – the boat, which symbolizes the salvation from the flood of waste. Other straw bale houses were built with lessons learned from Lithuanian examples and ones from the world. In 2005 Jonas Kacerauskas, who is a jurist and has nothing in common with the building industry, built his family house himself with several consultations from Petras Devizis. His successful home construction proved that the simplicity of the technology is a real fact and everybody who wants to build with straw could learn this very quickly. The house building budget was very low – 15000 ltl (125 ltl/m2).
The house is very warm and cozy. The family uses electricity from PV. This example is popular among journalists, so they help spread the knowledge about straw bale building in Lithuania. Builder Domantas Surkys, inspired by P. Devizis’s straw bale boat, first tested the technology in 2003, building an extension to a wooden house. Now he is preparing to build two straw bale dwellings.
Several people’s plans to build with straw in 2006 were stopped by a very bad straw harvest because of a dry summer and heavy rains in August. This showed the need to develop the production and storage of straw bales. This is an additional opportunity for farmers. Also it is very important to involve more professionals (architects, builders) into straw bale building development in Lithuania. The project, “Promotion of Straw Bale Building for Climate Change Mitigation”, started in Lithuania and gathered up to 500 people to seminars in the period from January to April 2007. It is known that 10 straw bale buildings are to be built this summer.
The future opportunities of straw bale building are impressive, as peoples’ interest in building with straw is noticeably increasing. The building industry in Estonia, Latvia and Lithuania is growing at high speed; consumers and builders start looking for more efficient and economical forms of construction. Straw bale building reduces green house gas emissions so should be widely promoted and supported by the attention of researchers and governments. Exchanges of information and experience all over the world could speed up the development of straw bale building industries and contribute to sustainability in building.
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