In December 2004, Meridian Energy identified the need for larger premises, and initiated a project to develop office accommodation that met its immediate and long-term operational needs, and reflected its commitment to renewable energy and sustainability.

The construction project adopted Ecologically Sustainable Design (ESD) objectives to ensure the Meridian building would respond to and utilise external environmental conditions.  To help achieve the ESD objectives, designers referred to the Australian Green Star office building rating tool.

case study 5_photo2.jpgThe designers’ efforts to optimise energy use and year-round comfort included extensive use of natural light and ventilation, as well as insulation.  In the building, solar gains are controlled by active shading systems, while the natural air supply is sourced entirely from the outdoors.  These innovative features have been integrated into an overall passive design through the thermal mass properties of the building’s concrete shear wall core and other exposed concrete surfaces.

The designers of the Meridian building were aware that concrete walls, columns and floors have the capacity to store and release heat.  This function has the effect of regulating the internal environment by reducing and delaying the onset of peak temperatures, to create healthy working environments for the occupants and reduce energy consumption costs for building tenants and owners.  This can also be cost-effective if the concrete utilised is already part of the building’s structural components.

The use of exposed concrete as part of an integrated passive design to achieve low energy thermal comfort has been widely used in commercial offices throughout the UK and Europe.  The Meridian building’s focus on ESD, and its profile at the forefront of sustainable building design, should increase the understanding and appreciation of concrete’s thermal mass properties within New Zealand.

The Meridian building’s ESD credentials have also been increased by the use of Holcim New Zealand’s Duracem.  Duracem is blended cement with an iron blastfurnace slag content of around 65%.  The decision to utilise concrete containing a supplementary cementious material enabled a reduction in the Portland cement content and therefore an increase in the building’s “green” rating.  

Used in the Meridian building’s jump-formed concrete shear core and the external precast elements, Duracem’s unique blend reduced the permeability of the concrete, inhibiting chloride ions from reaching and corroding the reinforcing steel, and therefore preventing any resulting expansion, cracking and spalling of the concrete.  Duracem cement was also used in the Meridian building’s concrete piles, which are submerged to a depth of around 18m.
 
The Meridian building has created a new environmental performance benchmark for New Zealand’s commercial buildings.  To help realise the objectives of their sustainable design philosophy, the building’s planners have looked towards concrete’s thermal mass properties and the benefits of concrete incorporating an SCM, such as blastfurnace slag.