Building Thermal Performance Assessment (NatHERS)

Nationwide House Energy Rating Scheme (NatHERS) is the National Assessment and Monitoring authority operating the building  and housing energy scheme. A compliant NatHERS building thermal performance assessment increases your building's thermal efficiency, producing savings of about $250 per year for an average home as a reduction in heating and cooling costs. This saving is expected to at least double in the next 3 years.[1]

Shading of the building and outdoor spaces reduces summer temperatures, improves comfort and saves energy. Direct sun can generate the same heat as a single bar radiator over each square metre of a surface. Shading can block up to 90 percent of this heat.[2]

Fixed shading devices can regulate solar access on northern elevations throughout the year, without requiring any user effort.[2]

Summer sun from the north is at a high angle and is easily excluded by fixed horizontal devices over openings. Winter sun from the north is at a lower angle and will penetrate beneath correctly designed fixed horizontal devices.[2]

Awnings and pergolas need to extend beyond the width of the north facing opening by the same distance as their outward projection.[2]

For locations north of the Tropic of Capricorn (23.5°S) in hot humid climates or hot dry climates with warm winters, the building and outdoor living spaces should generally be shaded throughout the year.[2]

Fixed horizontal louvres set to the noon midwinter sun angle and spaced correctly allow winter heating and summer shading in locations with cooler winters.[2]

Midwinter and midsummer noon sun angles for locations can be calculated using the formulas below, where L is the latitude of your home.[2]

Midwinter noon sun angle = 90 – (L+23.5)
Midsummer noon sun angle = 90 – (L–23.5)
Equinox noon sun angle = 90 – L

The Geoscience Australia website allows you to find the latitude of more than 250,000 place names in Australia, and will calculate the sun angle at any time of the day, on any day of the year.[2]

As a rule of thumb, the spacing (S) between fixed horizontal louvres should be 75% of their width (W).[2]
The louvres should be as thin as possible to avoid blocking out the winter sun.[2]

ANGLES OF LOUVRES TO THE HORIZONTAL
Hobart 24°
Melbourne 29°
Sydney, Canberra, Adelaide 31°
Perth, Broken Hill, Port Augusta 34°
Brisbane, Geraldton

 

Download fact sheets (143Kb PDF file)

References

1. Build Sustainable, Boost your buildings thermal performance. Retrieved 10 December 2010.

2. McGee, Caitlin, Australia's guide to environmentally sustainable homes, Chapter 4.4 Shading Retrieved 10 December 2010.

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