Experimental Study on Straw Bale and Rammed Earth · the initiative of experimental research of rice straw bale building for which the further research is needed, and rammed earth

Experimental Study on Straw Bale and Rammed Earth

Koji Itonaga１, Haruki Fukumori２ Mirai Tono3

1 Prof. Collage of Bioresorces, Nihon Univ., Dr. Eng . 2 Graduate school of Bioresorces, Nihon Univ

3 Architect, Tono Mirai Architecture Office

Keywords: Straw bale building Rammed earth building Heat insulation, Heat storage performance， Natural building

Summary AREDS（Architecture and Regional Ecological Design Studio in Nihon University）has so far verified the

possibility of straw bale building in Japan. In this research, the possibility of ecological building is verified by the initiative of experimental research of rice straw bale building for which the further research is needed, and rammed earth building, which can consider the possibility new from now on.

The experimental construction showed the possibility of self built of straw bale and rammed earth building, and the possibility of reuse of rice straw bales. The heat insulation performance and the moisture regulation performance of the straw bale wall were proved. The moisture characteristic of straw bales has been evaluated. The high heat insulation performance and thermal storage performance of the rammed earth wall were evaluated quantitatively. The possibility of developing the natural, low technical and ecological buildings by straw bale and rammed earth in Japan were suggested. 1. Introduction The correspondence with the environment from the various views, such as selection of material /amenity for

human / construction process, reconstruct, etc, when we construct the buildings, is needed recently in the world. AREDS, which is our researching studio in Nihon University, have so far verified the possibility in Japan of straw bale architectures by building them by us. The straw bale buildings attract attention as ecology architecture in Europe and America.

In this research, the possibility of natural and ecological architectures is verified by the initiative of experimental research of straw bale and rammed architecture in Japan. 2. Method The natural and ecological buildings, such as straw bales and rammed earth buildings, have been

constructed a few times experimentally in Japan. Therefore, we have built the building types for 4 years by ourselves in Japan. For example in the Exhibition of Yamaguchi prefecture in 2001 we built up a small straw bale house and reconstructed the same house for the rural restaurant near the mountain. And after building the model case buildings, it is important to manage and research the condition of the buildings from the view of architectural environment issue. Then, Atom house, which we call the model building on the campus of Nihon University by straw bales and

rammed earth, was constructed newly experimentally by self-built in 2002. We investigated the characteristic of temperature and humidity of three straw bale buildings for the example, such as Atom house, a small one at Bite town in Yamaguchi prefecture and the model house at PCCJ (Permaculuture Center Japan), which

Fig.1 Straw bale house

In Ireland Fig.2 Straw bale house In Denmark

Fig.3 We constructed astraw bale model house inExh. of Yanaguchi prif. Fig.4 Inside wall of the

left straw bale house

The 2005 World Sustainable Building Conference,Tokyo, 27-29 September 2005 (SB05Tokyo)

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were built experimentally until now by ourselves. Simultaneously, the characteristic as building materials of straw bale or rammed earth is clarified by an experiment of constructing and measurement of the building environment. 3. Construction of Atom house Atom house project was started in 2002, in order to pursue the new possibility of new ecological

architecture based on the experiment of the former straw bale buildings. We are building the ecological building by straw bales and rammed earth by ourselves in cooperation with a traditional Japanese plasterer engineers in CNES of Nihon University near Tokyo. We were looking for the natural material near the campus and constructed the building by ourselves with

local people and ecologists. We would like to develop the new construction method, which took in traditional plasterer and bamboo technology of Japan and the possibility of a curvilinear form, which harnessed the feature of straw bale, with a green roof and the construction method of rammed earth with a curvilinear form. First, it designed based on the idea proposed within our team. Atom house was made into the form, which

catches the flow of canal in Permaculuture Garden in CNES. Rammed earth wall was assumed on the heat storage object, which receives sunlight. And the straw bale wall was assumed on the heat insulation object.

Fig6. Sectional view of Atom house

Fig.7. Leveling Fig8. Concrete foundation

Fig.9. Pillar construction Fig.10. TAKEKOMAI

Fig.11. ARAKIDA Fig12. Base plaster Fig.13. Top plastering Fig.14. Mold

Fig.16. Rammed earth wall

Fig.15. Continuation mold

Fig.18. North side of atom house

Fig.5. Plane view of Atom house

Fig.17 South side of atom house


The construction was started from August in 2002 after design determination. First, the site was leveled.

Next, the concrete foundation was created. In this case, in order to raise earthquake resistance, a wooden pillar, which we brought from near mountain area, was used as the structure object.

Straw bales, which were bought from the near farmer who produced the organic rice for his cows, were loaded after completing the structure of a pillar. The bamboos, which were gotten from the same farmer, were knit on the outside of a pillar at that time. This is called in TAKEKOMAI, which is traditional plasterer technology of Japan. Thereby, by using this traditional technology we were able to create the beautiful curve with straw bales. . The base plastering was carried out after loading straw bales were completed. The base coating material is clay which is called ARAKIDA and which carried out fermentation digestion together with cut straws. The sand of the same volume as it was mixed with ARAKIDA. The second plastering was applied on the base plaster, in order to prepare the surface. And the top plastering was applied on the second one in order to raise water resistance. The top plastering material is the mortar with which clay, sand and lime were mixed. The roof was constructed naturally as the roof garden and now, we are testing to plant some vegetables.

The rammed earth wall was also built in parallel with this construction. First, the wooden molds were constructed, the soil and lime (10:1) were paid into it, and it poked, and was hardened. The molds were removed after a wall is completed, it connected with that wall and the next mold was constructed. Now, we have four rammed earth walls which include an inside wall. The inside rammed earth wall was requested the heat storage in winter and the cooler storage in summer. The plastering of straw bale wall outside, rammed earth walls, roof construction and temporary doors and

windows were completed by February in 2004. By the end of 2004 we plastered the inside straw bale wall with lime plaster two times, planted the some vegetables on the roof garden and made the cordwood wall.

4. The relation between the moisture content of straws and the relative humidity of straw bales The moisture content of rice straws was measured from 22 samples which rainwater does not hit. As a result, although variation is seen, it is guessed that the moisture content of straws in the bale also becomes high as relative humidity becomes high. Moreover, in about 90% of relative humidity, the moisture content of straws does not exceed 15 to 20% made into a dangerous value by the guideline of U.S. each state. This is maintaining at the state rainwater's not hitting, and a possibility of saying that Japanese rice straw in the straw bale does not exceed 20% of moisture content is shown.

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Fig.23. The relation between moisture content of straw andrelative humidity of straw bale

Fig.19. Bamboo bones for ceiling

Fig.20 plastering inside in the WS Fig21.Coad wood wall Fig.22. roof garden


5. The characteristic of temperature and humidity inside straw bale wall It showed the stability of temperature and humidity inside of straw bale wall. Furthermore, Inside of the

straw bale wall was behind in the peak of temperature and humidity compared with outdoor. Thereby, the heat insulation performance and the moisture regulation performance of the Straw bale wall were proved. The cooler in summer and the warmer in winter of the complex ecology building by straw bale and rammed

earth are going to be proved by the example of Atom house. It is because sunlight was avoided in summer, and the thermal storage of the sunlight was carried out in winter. Before plastering inside wall, the average humidity inside a straw bale wall was lower by about 13% during

winter than summer. Maybe, because the straw bales were breathing. While we measured the heat flow on the surface outside and inside, we showed the insulation function of

the straw bale wall.

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Fig.24. Summer characteristic of moisture and temperature

Fig.25.Winter characteristic of moisture and temperature


6．The characteristic of temperature of Rammed earth wall of Atom house The temperature sensors were installed in the inside of the rammed earth wall extended from east and west.

The thickness of a wall was 50cm. These positions of sensor are 6.25cm from south face as a south sensor, center of wall as a center sensor and 6.25cm from north face as a north sensor. As a result, in the climate of winter, it showed that average temperature of the south sensor was higher by about 6℃ than the open air. Carrying out thermal storage highly in response to the sunlight of a rammed earth wall is shown. However, since sunlight does not hit, the north side is maintaining low temperature. And it showed the stability of temperature inside of a rammed earth wall. By the time the influence of the temperature of the open air is transmitted in the center of a wall, the heat insulation performance in which it takes 8 hours or more will be shown. While we measured the heat flow on the surface outside and inside rammed earth wall, we showed the heat keeping in the rammed earth wall in daytime and in nighttime the heat ejection.

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Fig.27.The temperature inside and outside of rammed earth

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Fig.26. Heat move characteristic on straw bale wall surface in summer

Outside wall in winter Inside wall in winter Outside wall in summer Inside wall in summer


7. Conclusion Our experimental constructions showed the possibility of self built of straw bale and rammed earth

architecture, and the possibility of reuse of straw bales in Japan. And we could construct the beautiful curve wall by the traditional technology with crossed bamboos. The heat insulation performance and the moisture regulation performance of a straw bale wall were proved, researching for three years. The moisture characteristic of straw bale has been evaluated. The high heat insulation performance and thermal storage performance of a rammed earth wall were evaluated quantitatively. The high level of the thermal storage performance especially by sunlight was clarified. These suggested a possibility of promoting the natural and low-technical ecological architecture by straw

bales and rammed earth in Japan.

References 1) Fukumori,H. Itonaga,K. Miyano,N. Sase,Y. Takagi,A. (2002) Experimental study on the moisture

regulation performance of Straw bale. Oral Paper of Kanto blanch in Architectural Institute of Japan

2) Sudo,T. Itonaga,K. Kurihara,S. Fujino,E. Tono,M. Sase,Y. Fukumori,H. (2003) Experimental construction of Straw bale architecture and Rammed earth architecture. The atom house project of the earth and straw No 1. Oral Paper of Kanto blanch in Architectural Institute of Japan

3) Fukumori,H. Itonaga,K. Kurihara,S. Fujino,E. Tono,M.. Sase,Y. Sudo,T. (2003) Characteristic of

temperature and humidity of Straw bale wall of construction process. The atom house project of the earth and straw No 2. Oral Paper of Kanto blanch in Architectural Institute of Japan

4) Sase,Y. Itonaga,K. Kurihara,S. Fujino,E. Tono,M. Fukumori,H. Sudo,T. (2003) The image to a construction

participant's Straw bale architecture and Rammed earth architecture. The atom house project of the earth and straw No 3. Oral Paper of Kanto blanch in Architectural Institute of Japan

5) Fukumori,H. Itonaga,K. Fujino,E. Tono,M. Kurihara,S. Sase,Y. Sudo,T (2003) Experimental construction

on Straw bale architecture and Rammed earth architecture. Case of Atom house project by earth and straw. Oral Paper in Architectural Institute of Japan

6) Aoki,T. Itonaga,K. Kurihara,S. Tono,M. Fukumori,H. (2004) Characteristic of temperature and humidity of

Straw bale architecture. The atom house project of the earth and straw No 4. Oral Paper of Kanto blanch in Architectural Institute of Japan

7) Barbara Jones, (2002) Building with straw bales, GREEN BOOKS

8) Athena Swentzell Steen,(1994)THE STRAW BALE HOUSE,CHELSEA GREEN PUBLISHING COMPANY

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熱量（kcal/h・m

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Fig.28 Heat move characteristic on rammed earth wall surface in winter

South surface outside wall North surface outside wall South surface inside wall North surface inside wall

Heat volume South surface outside wall

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Documents

Experimental Study on Straw Bale and Rammed Earth · the initiative of experimental research of rice straw bale building for which the further research is needed, and rammed earth