Environmental Impacts of Multi-Storey Buildings Using Different ...

- 32 -lightweight timber and steel framed roof is built with metal roofing. The plant room roof isconstructed in timber and steel frame and is clad in the same material as the main roof.4.3.3.3 Structural WallsThe east wall, west wall and part of the south façade are a 310 mm thick “Thermomass” wall;a composite wall with 60 mm concrete on the exterior, 50 mm of extruded polyurethaneinsulation in the core, and 200 mm of exposed reinforced concrete to the interior of thebuilding. The service area walls are 200 mm reinforced concrete walls.4.3.3.4 Internal PartitionsThe light weight walls on the south face of the offices and the walls to the ventilationchimneys are timber framed containing 90 mm thick fibreglass insulation and a 25 mm aircavity for the exterior walls. Internally, the timber framed walls are lined with gypsumplasterboard. Acoustic insulation is required between partitions of the main body of offices.Generally, a plaster acoustic tiled ceiling is used in all office areas. The solid concreteexposed walls have a clear sealer applied; plasterboard walls have paint finish and all pre-castconcrete walls have an external finish.4.3.4 Steel BuildingFigure 4.6 shows the north-east and south-west perspective views of the Steel building.The structure of the Steel building consists of a concrete foundation supporting steel beamsand columns. Both internal and external walls are non-structural elements, being light weightsteel stud walls supported between floors. This is the only design in which the east and westend envelope walls are not part of the structural system.Figure 4.6: Steel building, north-east and south-west perspective views.Both curtain walls in the north and south façade are the same as in the Concrete and Timberbuildings.4.3.4.1 Structural SystemThe Steel building is a column and beam steel structure braced by eccentrically braced frames(EBF). Figure 4.7 (one of the drawings provided by Steel Construction New Zealand (Xiao &Fussell, pers. comm.)) sketches the proposed layout of the recommended steel structure forthe simplified Steel building. There are three frames of columns and beams running along thebuilding, one at each long edge and one internal frame. Transverse secondary beams connect