Japan Sustainable Building Database

Multifunctional slab

Diagram of a multifunctional slab

To achieve a pillar-free space of 1,500 m² which is named "three-dimensional One- Office", we have adopted a large PC (Precast Concrete) floor that has sufficient structural intensity. In the office zone, the ceilings are formed by the undersides of these PC floors in exposed finish. This dispenses with the usual above-ceiling cavity, thus achieving a high ceiling space.
To make this large PC floor lighter, the planned structure has hollow layers, void slabs and other crevices at the PC floor joint sections. These crevice spaces are used as air-conditioning flow channels (ducts), thereby achieving an air-conditioning system in harmony with the structural system. Furthermore, the unsuspended ceilings created by the PC floors also contribute to indirect lighting, and the slabs themselves are planned as "multifunctional slabs".

Seasonally responsive double skin

Double skin operation mode

Around the double skin, several types of ventilation dampers are installed, namely upper and lower ventilation dampers, atrium top light ventilation dampers and the ventilation dampers on each floor. Our intention is to create a "seasonally responsive" double skin that can fulfil proper outer skin functions by turning each of these ventilation dampers on or off via automatic control, according to the season and state of use.
In summer, the upper and lower ventilation dampers are opened and external air pre-cooled via the seismic-isolation pit is introduced, thereby reducing sunlight load. In winter, the upper and lower ventilation dampers are closed to improve thermal insulation performance. In other seasons, when the impact of external load is smaller, top light ventilation dampers in the atrium, lower ventilation dampers in the double skin, and the ventilation dampers on each floor combine to provide natural ventilation (night-time ventilation) via the double skin, as well the effect of discharging internally generated heat. The plan also takes account of measures against external noise when natural ventilation is in progress.

Task and ambient air-conditioning

Task and ambient air-conditioning system

Pressurized floor-blower air-conditioning is used for the whole of the office space. The plan is for spiral airflow from the floor to reach occupied zones (generally FL + 1,700) , so that, with a zoning rationale, non-occupied zones and occupied zones are divided vertically via temperature stratification. For the occupied zone, moreover, the zoning plan takes the inside of a booth surrounded by partitions as the task area and divides it from passage sections and other ambient areas. The task air-conditioning method using partition blower outlets has been introduced for the task area. Meanwhile, by carrying out zoning with the area around the perimeter facing the double skin as a perimeter buffer zone, the system relies on VAV-type floor blower outlets using the same floor blower air-conditioners as in the interior, as perimeter-less air-conditioning.