Page 84 - Build 152

Departments/Sustainability
By Hugh Byrd NZRAB, University of Auckland, and Phil Howard ANZIA, Paci c Environments NZ
Towards a zero- energy building
Clever passive design in the new Waiheke Community Library has removed the need for air conditioning, while rooftop PV panels provide energy for lighting, fans and equipment. Will it be a zero net energy building?
Automated windows on both sides of the building enable air ow.
THE COMMUNITY LIBRARY on Waiheke Island was completed in mid-2014 with an intention from the outset to produce a very low-energy building.
The installation of a modest 128 m2 of photovoltaic (PV) panels in mid-2015 means the building can now be benchmarked against a net zero energy building. It is currently generating more electricity than it uses, with an excess yield during the summer
months. Further monitoring will reveal how close the library is to being a zero energy building with increased output from the PVs and additional energy savings.
Passive design, not air conditioning
In order to reduce energy consumption, an important environmental design principle was to avoid air conditioning by using passive cooling techniques (see Figure 1).
Temperatures and sunshine hours in Waiheke are marginally higher than in Auckland, and annual cooling degree-days exceed heating degree-days. If air condi- tioning had been installed, it would have resulted in higher energy use for cooling than for heating.
Passive design features were included throughout the building:
● Extended eaves to the north that were
calculated to completely shadow the glazed elevation over the summer while allowing the sun to penetrate into the building in the winter.
● A polished concrete floor around the perimeter that gives a high thermal mass to reduce overheating.
● Automated windows, controlled by internal air temperature, on both sides of the main library that allow through- ventilation and air ow at both high and low level.
● Large 2.4 m diameter ceiling fans that can silently supplement air movement for use on summer days with low wind speed.
● Windows on all sides in the main library that, together with skylights in the centre, give an even distribution of daylight throughout. Arti cial lighting is controlled by both daylight and occupancy sensors.
● Heating in the winter by a radiant under- oor water system heated by heat pumps.
Positive sta feedback
Feedback from library sta indicates that internal temperatures have remained comfortable throughout the year without overheating.
82 — February/March 2016 — Build 152
ARCHITECTS – PACIFIC ENVIRONMENTS