This is a house that was renovated from a 30-year-old steel-framed building with ALC exterior walls in Tokyo, Japan. The first floor was an office for a newspaper company, and the second and third floors were company housing. The site was an acute triangle overlooking the river to the east, and the existing plan was a simple triangle that followed the shape of the site.

First, to check the condition of the existing building, the existing interior finish was demolished to reveal the steel frame and ALC walls. It was found that the frame was sound, but there was no insulation in the exterior walls. It became necessary to renovate the insulation of the exterior skin, but by taking advantage of the simple exterior shape and wrapping the entire building in external insulation, the exterior skin had fewer thermal bridges, and the interior was left exposed with the steel frame and ALC exposed, allowing the interior to be used as widely as possible. The exposed steel frame can be thought of as a heat storage body, and various metal fittings such as clamps and full screws and magnets can be attached, so it can be used as a starting point for freely customizable ad hoc construction.

For the windows, a resin inner sash was added to the existing aluminum sash, but the depth of the cavity was made wider to cut direct sunlight during the peak summer season like a canopy. In the piano room on the first floor, a multi-layered window made of FRP and polycarbonate was devised to replace the existing large glass window. The triple air layer provides high insulation, the folded plate shape diffuses sound, and the translucent surface protects the privacy of the first floor. The first-floor wall is equipped with a sound diffusion and humidity control device that reuses the peeled core material generated during the LVL manufacturing process.

Overall, the design is such that the exterior skin, structure, and interior are linked. By renovating the exterior, the structure can be exposed, which improves its maintainability, creates an opening for the interior, and makes it easier to show the structure's value as a building that will not change even when it is handed over to the next resident. Not finishing the structure and walls will also be a measure against internal condensation. The interior was kept as simple as possible, allowing for future versatility and reducing costs. Fixing the existing steel frame with full screws and metal fittings does not require special tools, is easy to install by oneself, and is easy to adapt to changes in lifestyle.

The exterior renovation makes use of the structure and creates versatility for the interior. Existing buildings with steel frame construction and ALC exterior walls are common, but we aimed to add value to them and create a type of renovation that can continue to be used for a long time, even if the residents change.