Koji Itonaga

Nitrosomonas communis strain YNSRA, an ammonia-oxidizing bacterium, isolated from the reed rhizoplane in an aquaponics plant

An ammonia-oxidizing bacterium (strain YNSRA) was isolated from the rhizoplane of the reed (Phragmites communis) used in an aquaponics plant which is a wastewater treatment plant. Strain YNSRA was identified as Nitrosomonas communis by taxonomic studies. The hydroxylamine-cytochrome c reductase (HCR) of strain YNSRA was found to have a higher activity (25.60 u/mg) than that of Nitrosomonas europaea ATCC25978T (8.94 u/mg). Ribulose-1,5-bisphosphate carboxylase (RubisCO) activity was detected at very low levels in strain YNSRA, whereas strain ATCC25978T had definite activity.

The Influence of Passive Ventilation on the Interstitial Hygrothermal Environment of a Straw Bale Wall

The greatest challenges for straw bale construction in Japan are moisture and straw′s susceptibility to microbial decay. In order to mitigate excessive moisture, some straw bale architects and builders in Japan have utilized passive ventilation. This paper examines the influence of passive ventilation on the interstitial hygrothermal environment of the straw bale walls of a building in Chiba Prefecture, Japan, known as Furyu. Furyu′s walls consist of straw bales surrounding a conventional timber frame. Underneath the bale wall is a ventilation chamber vented to the outside. The bale wall is exposed to the ventilation chamber below and air passes freely between the outside and sub-wall ventilation chamber. Twenty-three temperature and relative humidity sensors monitor the hygrothermal environment of Furyu. The study found that the relative humidity of the ventilation cavity is strongly influenced by the outdoor environment. The lower bale wall is in turn strongly influenced by the ventilation cavity. The results suggest that passive ventilation is not an effective means to control interstitial moisture in straw bale walls. Rather, passive ventilation appears to be a source of interstitial moisture during warm summer months.

An Evaluation of WUFI-Bio to Predict Mold Growth in Straw Bale Walls in Japan

The greatest challenges facing straw bale building in Japan, and many other countries with high humidity and precipitation, are moisture and the susceptibility of straw to microbial decay. WUFI-Bio, developed by the Fraunhofer Institute for Building Physics, is a computer program that assesses the risk of mold growth in buildings based on measured or computed climatic conditions. Researchers in Japan have monitored the hygrothermal conditions of six straw bale buildings in Japan and evaluated the risk of mold growth based on an interstitial temperature and relative humidity guideline. The purpose of the present study is: (one) reevaluate the potential for mold growth in the six buildings using WUFI-Bio and (two) evaluate the accuracy of Holzhueter and Itonaga′s interstitial temperature and relativity guideline vis-à-vis WUFI-Bio. As a result of the study, the potential for mold growth was found to vary by structure. Buildings utilizing rainscreens were found to have a lower risk of mold growth. Holzhueter and Itonaga′s interstitial temperature and relativity guideline was found to over exaggerate the potential for mold growth. Also, although Holzhueter′s guideline does indicate a potential for mold growth, the number of hours above the guideline alone is not a sufficiently accurate indication of severity.

The Influence of Ventilated Rainscreens on the Interstitial Hygrothermal Environment of Straw Bale Walls

Abstract The greatest challenges facing straw bale building in Japan, and many other countries with high humidity and precipitation, are moisture and the susceptibility of straw to microbial decay. Researchers in Europe and North America have found the use of ventilated rainscreens to help control interstitial moisture in straw bale walls. The indoor, outdoor and interstitial hygrothermal environment of six straw bale structures in Japan have been monitored. The six buildings are organized into two groups. The first group includes buildings consisting of straw bales walls with an earthen or lime plastered exterior finish applied directly to the bale walls. The second group includes buildings consisting of straw bale walls utilizing ventilated rain screens. The purpose of the present study is: (one) evaluate the potential for mold growth in the six buildings, (two) clarify moisture dynamics, and (three) determine the effectiveness of ventilated rainscreens to control moisture in straw bale walls. As a result of the study, the potential for mold growth was found to vary by structure. Buildings utilizing rain screens were found to have lower interstitial relative humidity and a lower risk of mold growth.