Trends New Zealand NZ New Home Trends Vol. 30/10 | Page 65

As well as having totally airtight doors
and windows, and extra insulation in the roof,
walls and floor, the design depends upon a heat
recovery ventilation system. This brings in fresh
air from outside, but a German heat exchange
system ensures inbound air temperature is
nearly the same as the outbound air, so the
temperature in the house remains constant. This
is maintained at around 23°C in this house, and
is never lower than 20°, even without any form
of heating.
“We kept the building envelope fairly
simple, and kept the garage outside of this,”

says Smith. “The ratio of the outside wall area to
the volume inside maximises energy efficiency.
And the low monopitch roof is the most efficient
for rainwater harvesting. At the front the roof
soars up to gain optimum benefit from the sun’s
heat in winter.”
Photovoltaic panels (8kW) on the roof of the
house, from Ideal Electrical, supply more than
the home’s energy requirements, with excess
energy fed into the national grid.
Murray Durbin says data concerning power
usage and internal versus external temperatures
will be published on a regular, ongoing basis.

Above: Architect Stephen Smith of
S3 Architects says the simple shape
of the building envelope maximises
energy efficiency. The garaging is
contained outside of this airtight
volume. Matt Wilson from S3
Architects carried out the Homestar
assessment.

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