(2ー2)Thatched roof

For thatching a variety of materials like water reed, rice straw, wheat straw, zebra grass can be used. Tree skin, especially that of the Japanese cypress, is used in Japan. At the experimental house, bulrushes, growing in some wet fields locally, were used. Because we were unable to collect enough for thatching the whole roof, only one side could be thatched.

 Thatching a roof with bulrushes 

The thatch is 30cm thick and has a 10cm air gap underneath. The overall coefficient of heat transfer of the roof is estimated at 0.17 when the thermal conductivity of bulrushes is 0.17. It will be measured at a later stage on the roof. Because of the bulrush shortage, the other side and the top of the roof were covered temporarily by a sheet of tin with an air gap of 30cm. The overall coefficient will be measured later on and will give us a good comparison with the thatched part. Bulrushes are thin and the finished roof look was very beautiful. However, the higher slope has been damaged by worms and birds. If you have a good idea to solve this problem, please let us know!
Hiwadabuki, a type of thatched roof with Japanese cypress bark from Japan, is also an interesting material. But because this is not available in NZ, we were unable to take this option. These methods of thatching are very precious ways which blend in nicely with nature.

Repairing a thatched roof in Japan

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

(2-1) Cobbed walls

(2-3) Rain water for drinking