Friday, December 5, 2008

Passive solar & sustainable... but how leaky?

Ric Butt, of Strine Environments, designs unique, passive solar sustainable houses that are typically warm, bright and spacious, with full glazing to the north. The thermal design of Strine homes virtually eliminates the need for heating and cooling throughout the year, even in the Canberra region. They are made from heavily insulated, precast concrete panels with a high quality finish. The panels are made to exacting standards (by Strine Products in Queanbeyan, NSW) to ensure that they fit together perfectly on site, and incorporate all necessary conduits for cables and services.

Yesterday, we put one of Strine's homes to the test with our blower door and thermal camera... and the results were impressive.

Our testing of Canberra homes (new and old) has so far shown the average number of air changes per hour (ACH) at 50 Pascals to be around 20. Modern European homes, built using advanced sealing techniques, aim for 1.5 - 3.0 ACH at 50 Pa (ie. they are very air tight, energy efficient and comfortable) and require mechanical ventilation systems to maintain healthy indoor air quality.

The three bedroom Strine 'Milennium' home, completed in 2006, had just 6.2 ACH at 50 Pa. At normal pressures of ~ 1 - 4 Pa the house was having roughly 1 - 1.5 ACH. For healthy indoor air quality 0.5 - 1.0 ACH are recommended. So the house is very air tight by Australian standards and if efforts were made to tighten it even further the homeowners would need to consider installing a heat exchange, mechanical ventilation system (to ensure good air quality when all the windows, doors and solar chimneys were closed).

The temperature of the precast concrete walls was remarkably even. Comparison of the external and internal temperatures of a section of eastern wall at 11.30 am on a sunny, 25 degree day showed a 20 degree difference (40.8 & 20.6 degrees, respectively).

Strine Environments is a unique partnership between Strine Design, Strine Products and Strine Building and can provide a leading edge, seamless environmental design and construction process.

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