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Coatesville House, Rodney District

27 Nov 2016

The Coatesville (passive solar and environmental) house in the Rodney District is a four-bedroom family home designed a bit like an old saw tooth-shaped factory roof — but smarter!

The 270m2 home, situated on a 2.4 acre property with bush and valley views, is a series of stacking saw tooth roofs designed to capture every possible bit of sunlight during winter, and naturally exhaust warm air during summer. The result is high energy efficiency and comfortable internal environments all year round.

Typically, a passive solar house works on an East-West axis following the seasonal sun path. This site has a narrow east-facing flat platform located on the downward side of a hill, meaning that the designers worked within a restricted footprint which functioned on both an East-West and North-South axis for maximised solar gain and view.

The house relies on exposed insulated concrete slabs and large insulated vertical precast concrete walls for optimised passive solar gain and heating during winter. The roof shapes and windows allow a natural stack effect to cool down the interior and naturally ventilate the bedrooms and living spaces over summer. This is further assisted by the summer winds which enter the house from the North-East.

A commitment to sustainable construction is clearly evident in the passive solar design components — 140mm-thick insulated concrete slab (thicker slab than normal) with an R-value of 8, 240mm-thick insulated precast exterior concrete walls with an R-value of 7, 240mm uninsulated precast interior walls, roof insulation with an R-value of 5, wall insulation (140mm framing) with an R-value of 3.2, and U.44 insulated glass windows. The house also boasts an array of other ‘green’ features that align with the overall pledge to sustainability.

From the period June 20, 2015 to June 20, 2016, internal temperatures passively peaked at 24° Celsius during late afternoon in mid-winter, with the extreme low being 17° Celsius during early morning. So far the house has thermally performed as calculated, and will be further monitored.


This modest family home offers (and superbly executes) a core design principle entirely accessible and applicable to the vast majority of yet-to-be-built homes. Passive solar design, built around the thermal mass of concrete, in this case exposed interior slab-on-grade and precast panels, has the potential to enhance future building stock through “built-in” energy efficiency. The merit of Coatesville House is elevated in that it achieves its sustainable objectives despite a challenging site, managing to secure a pleasant outlook while optimising the sun’s energy to replace active heating and cooling mechanisms. In principle, passive solar design is relatively simple, yet to accomplish it as well as Coatesville House has deserves applause.


CLIENT Home Owner

DESIGNER Solarei Ltd

CONTRACTOR Selah Construction Ltd