The term “rain-screen” refers to the use of a drainage plane/air gap between exterior siding and bale wall. Permeable plasters tend to be porous and absorb exterior moisture. In many cases, this moisture is then transferred to interstitial bales through capillary action. In order to prevent liquid water, i.e. rain, from direct contact with a plastered bale wall, rain-screens can be used. The author has found that rain-screens help control interstitial moisture in straw bale walls.
Madeinoie, a studio in Iitate, Fukushima Prefecture, was designed by Yoshiyuki Toyota. Construction of the straw bale wall was led by Kyle Holzhueter and Koji Itonaga of Nihon University. Construction began in November 2009 and was completed in February 2010. Madeinoie consists of straw bales stacked to the inside of a conventional Japanese timber frame. Cellulose insulation was blown in between the posts. The building was designed for passive solar gain, and with no supplemental heating, the average indoor and outdoor temperatures in January, 2011 where 12C and -3C respectively. Madeinoie is located in the nuclear evacuation zone near Fukushima Daiichi Nuclear Power Plant. For this reason, the brown and finish coats of plaster were never applied. The earth used for the base coat was recycled from a 150 year-old farm house. And although Iitate experienced a Shindo 6 on Japan’s seven-point scale for measuring the intensity of earthquakes, and the concrete pavement around the building cracked, there was no cracking in the straw bale wall.
Leyenda, an antique store and gallery located in Toyama City, Toyama Prefecture, was designed by Shoko Yoshimoto and built by Hiroaki Yoshimoto of the Toyama Straw Bale House Association. Hiroaki Yoshimoto and Kyle Holzhueter led the construction of the straw bale walls and finish plastering. The bale walls are plastered on both sides with lime plaster. The ventilated rain-screens consist of wood lath, roofing, metal lath, a layer of cement plaster and a layer of lime plaster. Construction began in August 2010 and was completed in September 2011.