Cobbed walls

The clay at the excavation of the basement of the experimental house was kept for cobbing. The main structure of the house is 2 x 4. The inside and outside walls were plastered with a clay mix. Komai, which is a traditional bamboo net used for cobbing in Japan was tried out, but it took too much time. Therefore, only an inside wall was done in this way. The other surfaces were nailed with battons. Following the Japanese way, a mixture of clay and cut grass was used. But due to miscommunication, sand was added to the first coat. In the second and third coats, cement was added to the mixture.

In the Japanese way, a mixture of clay and cut rice straw grass are plastered over a Komai net as the first coat, making keys on the back side. Time has to be allowed for the first coat to dry, after which there will be some cracks which serve as keys for the second coat. Some sand has to be added to the mixture of the second coat, and the surface cracks are smaller. After drying, the third coat with more sand and finer fiber is applied. For a finishing surface, rice gruel or glue from sea weed, for instance, gloiopelitis, can be mixed as a bond.
At the experimental house the 2 x 4 structure contains an air gap of about 14cm wide. A variety of porous material was used in separate sections to fill the gaps to avoid air convection. Later on each section will be compared with a heat rate meter. The materials used for filling include crinkled newspaper, crinkled plastic, bulrushes, fiber glass and wool fleece. The windows and doors are triple glazed in different styles. Later, heat flow will be measured in different styles. When the thermal conductivity of bulrushes filled in a 12cm width of the 2 x 4 wall is estimated at 0.063, the overall coefficient of heat transfer is 0.43 - which compares equivalently with that of a commercial modern wall.

(2) Using nature-friendly material from the local area.

(2-2) Thatched roof

(2-3) Rain water for drinking