Optical Glass House / Hiroshi Nakamura & NAP

      project name: Optical Glass House

      main purpose: Housing

      Design:　Hiroshi Nakamura & NAP Co.,Ltd.

      structure design :　Yasushi Moribe

      contractor :　Imai Corporation

      location: Naka-ku, Hiroshima-shi, Hitroshima, Japan

      Site area: 243.73m2

      Total Floor area: 363.51m2

      completion year: March,2012

      structure : R.C.structure 

      Photographer：　

      (c)Koji Fujii_Nacasa & Partners Inc

      (c)Hiroshi Nakamura & NAP Co.,Ltd.

     This house is sited among tall buildings in downtown Hiroshima, overlooking a  
     street with many passing cars and trams. To obtain privacy and tranquility in
     these surroundings, we placed a garden and optical glass façade on the street
     side of the house. The garden is visible from all rooms, and the serene soundless
     scenery of the passing cars and trams imparts richness to life in the house. Sunlight
     from the east, refracting through the glass, creates beautiful light patterns. Rain
     striking the water-basin skylight manifests water patterns on the entrance floor.
     Filtered light through the garden trees flickers on the living room floor, and a super
     lightweight curtain of sputter-coated metal dances in the wind. Although located
     downtown in a city, the house enables residents to enjoy the changing light and
     city moods, as the day passes, and live in awareness of the changing seasons.

     A façade of some 6,000 pure-glass blocks (50mm x 235mm x 50mm) was employed. The pure-glass   

     blocks, with their large mass-per-unit area, effectively shut out sound and enable the creation of an 

     open, clearly articulated garden that admits the city scenery. To realize such a façade, glass casting 

     was employed to produce glass of extremely high transparency from borosilicate, the raw material for 

     optical glass. The casting process was exceedingly difficult, for it required both slow cooling to remove 

     residual stress from within the glass, and high dimensional accuracy. Even then, however, the glass 

     retained micro-level surface asperities, but we actively welcomed this effect, for it would produce 

     unexpected optical illusions in the interior space. 

 

 

 

     Waterfall

     So large was the 8.6m x 8.6m façade, it could not stand independently if constructed by laying rows of       

     glass blocks a mere 50mm deep. We therefore punctured the glass blocks with holes and strung them 

     on 75 stainless steel bolts suspended from the beam above the façade. Such a structure would be 

     vulnerable to lateral stress, however, so along with the glass blocks, we also strung on stainless steel flat 

     bars (40mm x 4mm) at 10 centimeter intervals. The flat bar is seated within the 50mm-thick glass block    

     to render it invisible, and thus a uniform 6mm sealing joint between the glass blocks was achieved. The 

     result — a transparent façade when seen from either the garden or the street. The façade appears like    

     a waterfall flowing downward, scattering light and filling the air with freshness.

     Captions

     The glass block façade weighs around 13 tons. The supporting beam, if constructed of 

     concrete, would therefore be of massive size. Employing steel frame reinforced 

     concrete, we pre-tensioned the steel beam and gave it an upward camber. Then, after 

     giving it the load of the façade, we cast concrete around the beam and, in this way, 

     minimized its size.

Hiroshi Nakamura

1974    Born in Tokyo

1999　Master’s degree, Graduate School of Science and Technology, Meiji University

1997    Worked at Kengo Kuma & Associates (-2002)

2002   Established Hiroshi Nakamura & NAP Co., Ltd.