The Optical Glass House overlooks the typical environment of downtown Hiroshima. The name comes from the glass facade that covers the street side of the building. The garden and the glass wall provides privacy to the inhabitants while ensuring a natural connection with the environment. Patterns of refracted light from the east show up in the interior of the house that adds aesthetic appeal to a relatively simple design. Raindrops engaging the water-basin skylight manifests water patterns on the floor at the entrance. Filtered light through the garden trees appears on the living room floor, providing ample lighting during the daytime. Overall, this design enables the inhabitants to feel the changing seasons while sitting in a city brimming with traffic.
A façade of some 6,000 pure-glass blocks (50mm x 235mm x 50mm) stands out as the main attraction of the design. The pure-glass units, provide ample sound-proofing and allows a view of a garden coming off as a respite from city life. Glass casting was employed to produce a glass of high transparency from borosilicate (the raw material for optical glass). The casting process was a huge challenge and required very high accuracy temperature variations. With little asperities in the glass bricks, the glass facade produced different optical patterns in the interiors.
The glass facade consists of glass blocks punctured with holes and strung on 75 stainless steel bolts supported by the beam above.
The structure was not stable at first because of lateral stress; therefore, along with the glass blocks, stainless steel flat bars (40mm x 4mm) at 10-centimetre intervals also hung from the beam. The flat bar sits within the 50mm-thick glass block to conceal it. Thus a uniform 6mm sealing joint between the glass blocks came into existence.
The facade provides the appearance of a waterfall, scattering light and filling the interiors with an aesthetic play of colours. The supporting beam employs the use of steel frame reinforced concrete, holding the massive weight of the glass.
Pictures: © Koji Fuji / Nacasa & Partners Inc