Commercial Multi-Story Building Carbon Footprint Model

This section provides information on the commercial multi-storey building used in the NZ Wood carbon footprint model.

Many modern buildings tend to make extensive use of timber, steel, and concrete materials in construction, all of which can be energy-intensive to produce, via processes that have the potential to cause adverse environmental impacts and give rise to CO₂ emissions.

However, recent developments in wood technology and engineered timber products, seismic and acoustic design, fabrication and construction techniques have enabled timber to be utilised much more extensively for instance in the basic structure of medium-rise, multi-storey buildings, such as a typical ‘down-town’ office block.

While there is a tendency for buildings to be labelled according to the main material used for their sub-structure and super-structure, the vast majority of buildings use a large number of different materials, from a variety of sources, both national and international. From a materials perspective, a building becomes a very complex system and it is often not immediately clear which materials or combinations of materials provide the best environmental performance.

Studies have indicated that when considering the environmental impacts of building materials, the structural components used in a building are of significant importance. 

The building designs covered by the NZWood carbon footprint model emphasise alternative structural design options where the predominant structural material is either timber, steel or concrete.

Description of multi-story building

The multi-storey building, designed as a simple, commercial office building with open plan floor spaces, is based on an actual new six-storey, 4,250 m² science laboratory for the School of Biological Sciences at the University of Canterbury in Christchurch. 

The six storey building is approximately 36 metres by 20 metres in plan with one stair and one elevator.  For all structural design, the current New Zealand design codes have been used. 

The buildings have two distinct seismic systems in order to resist loading; in the long  direction, a moment resisting frame is used and in the short direction, walls are used.

The four alternative buildings are summarised:

• Timber building - The main structural components are prefabricated laminated veneer lumber (LVL) columns and beams, the walls are prefabricated solid LVL members, floors are timber / concrete composite and the external cladding is fibre-cement.

• TimberPlus building - As for the Timber building above but with greatly increased use of timber throughout including timber external cladding and cedar windows and louvres, solid timber internal walls, timber ceilings and other features which maximise the use of timber throughout the building.

• Concrete building - Pre-cast reinforced concrete exposed in structural shear walls, with the same external fibre-cement cladding in the light weight façade walls.

• Steel building - All the main structural components are steel, with the use of Eccentrically Braced Frames (EBF) resisting lateral loading in both (short and long) directions. Framing and cladding are steel.

View multi-story building comparison data - Excel document

Perspective view of the new Biological Sciences laboratory at the School of Biological Sciences, University of Canterbury

 TimberPlus building, North-east and South-west perspective views

 ‘Common internal finishes’ of the TimberPlus building

 Plan used for energy calculations, and cross-section through the ventilation chimneys