Solar elevation/altitude and solar access

North-facing windows do not guarantee good solar access - obstructions to the N, NE or NW can block your free solar heating. Solar access is measured by the number of hours that the sun can shine into north-facing windows between the hours of 9 am and 3 pm on the shortest day of the year (22 June). In the cooler parts of the warm humid zone, a few hours of solar access during midwinter would be desirable. In the temperate zone, the cool temperate zone and the hot summer, cool winter climatic zone, you need to have the sun shining in your windows during the entire 6 hours. It's particularly important in the cool temperate zone, where solar access to east-facing windows would also be a good idea.

Case study in Melbourne

The diagram below (picture1) shows the sun positions at 9 am and 3 pm in Melbourne in midwinter. Even though the third bedroom has a north-facing window, its solar access is limited by obstructions to the east and west. The living room and kitchen have good solar access. Picture 2 shows how the sun's elevation or altitude changes from winter to summer.

You can use the AUSLIG web site (or contact the State Museum or Observatory in your capital city) to check the sun's position in midwinter. You need to know the solar azimuth angle (position in the horizontal plane) and the solar elevation or altitude angle (position in a vertical plane) at 9 am and 3 pm on 22 June (see pictures above).

Some useful telephone numbers are: -
Western Australia - the Perth Astronomical Observatory, Bickley, on (09) 9293 8109 or email perthobs@iinet.au
Victoria contact the Planetarium at Scienceworks on (03) 9392 4800.
Tasmania - the Planetarium at the Queen Victoria Museum and Art Gallery at Launceston (03) 6323 3777. CSIRO bookshops also have a useful publication, SUNSHINE AND SHADE IN AUSTRALIA.

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