Facade of Optical Glass House, Hiroshima, Japan, 2012, Hiroshi Nakamura & NAP

The Optical Glass House is a 3-story house nestled among the high-rises of downtown Hiroshima. The shimmering glass-block façade provides a semi-transparent barrier to a tree-filled courtyard. From inside, the crystalline curtain appears like a waterfall flowing downward, scattering light and filling the air with freshness.

This 8.6x8.6m façade uses cast borosilicate glass blocks to produce high transparency. Two stories are covered with over 6,000 custom-made glass blocks, each one a standardized 50 x 235 x 50mm. The heavy façade is suspended by 75 threaded stainless steel rods from a pre-tensioned steel beam on the top, which is covered with concrete for fireproofing after the façade weight is applied. Instead of piling up on each other, each glass block sits on a horizontal 40x4mm stainless steel bar, so that its weight is transferred directly to the vertical rods. The continuous horizontal bars on every other horizontal joint and hidden in the joints are primarily meant to withstand the wind load. Two 28mm thick, 230mm deep, vertical steel mullions are also added to shorten the span of small bars from 8.6m to less than 3m.

Photography: Koji Fuji / Nacasa & Partners Inc