They say that walls can talk and if the cold, windowless metal exterior of the Rooftecture OT2 house in downtown Osaka, Japan says anything, surely it's "Leave me alone." Those lucky enough to make it through the front door (complete with forbidding chainlink door handle), however, are in for a bit of a shock. In stark contrast to its outer shell, the family home offers a warm and welcoming diffused light and mixed wood interior comfortably spread over three levels.

Sandwiched between two other buildings, with yet more behind, the Rooftecture OT2 home was designed by the Shuhei Endo Architect Institute. The client having stipulated that the house should have a secure facade but be able to let in both light and air, Endo's project team came up with an outer shell made of perforated steel that lets natural light and air through.

The Rooftecture OT2 houses a family of five (two adults and three small children) over three stories with a total floor area of 127.7 square meters (1,374.5 sq ft). The master bedroom is located to the back of the ground floor, with toilet and storage space out front. Moving up the central Japanese cypress steps brings you to the open-plan kitchen and dining area and the north-facing living room, with the deck outside the walk-through windows.

Continuing up the stairs will bring you to the children's bedroom and the bathroom. A central atrium acts as a focal point for family members and benefits from skylights to brighten the area below, which can also be opened to let in more air if needed. The building's internal walls and ceilings are made from Harvest Panel and oak flooring features throughout.

While by day the family fortress appears impenetrable, as darkness falls and the lights inside get switched on, passers-by are allowed a glimpse of the otherwise secret world within.

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