Demonstrative studies of improved greenhouse for post-disaster restoration in coastal Iwate area: 1. Climate assessment for environmental applicability of new pipe-framed greenhouse for saving energy and greenhouse using scaffold materials

In Rikuzen-Takata in Iwate pref., agriculture and horticulture was thriving by utilizing comparatively genial climate and abundant sunshine among the region. However, the huge tsunami on 11 March 2011 seriously damaged the agriculture and food industries of the region. Since 2013 we have been participating in the post-disaster restoration project in order to improve rural agricultural activities by means of technological innovation of the greenhouses. We have conducted substantive empirical research to introduce our thermal-enhanced and low-cost greenhouses that strengthen the weatherability to cold climate. This paper confirms the suitability of the greenhouses built in Rikuzen-Takata based on the climatological data. In this region they experience temporary shortage of sunshine due to specific sea fog in summer. On the other hand they receive more than 140 hours/month of sunlight in winter. Therefore it is important to improve lighting of greenhouses to compensate the shortage of sunlight in summer by utilizing transparent covering materials instead of covering materials that diffuse sunlight in order to improve the overall transmissivity. Additionally, it is also essential to improve heat retention of the greenhouses in order to reduce the cost of heating in winter. Even under micro-thermal climate they have approximately 10 tropical days in summer. As average ice day in winter is more than 25 days improvement of thermal condition of the greenhouse and reduction of the cost of heating is essential under such cold condition. The maximum snowfall of 18cm in 2014 did not cause any problems. The design load of 338.8N/square m (34.6kgf/square m) based on the twenty-year probability snow depth (25.6cm) gives sufficient margin for the actual designed load of 50cm snow depth. However, in order to introduce those greenhouses to the neighboring mountainous area it is necessary to take more snowy condition into consideration. Greenhouses under construction are more susceptible to wind pressure due to insufficient structural strength. Therefore it is necessary to draw up an implementation manual regarding the procedure for structural reinforcement during construction. Since strong seasonal wind with the constant wind direction in winter was observed, windbreak is expected to improve the heat retention of the greenhouses markedly and consequently reducing the cost of heating.