On June 22, the shortest day of the year, at 12pm, the Melbourne sun at its zenith will be shining down from the north at an angle of 29 degrees.  For a tall window, say 2m high, the direct sunlight at this angle will penetrate around 4 meters along the floor into the house.  This is the maximum penetration for the year.  This penetration is fine for rooms on the direct northern side of the house, but for the rooms further to the south, they will typically get darker and cooler without the access to the warm northern light.

This is where clerestories and popped ceilings can be so useful getting northern sunlight deep into the belly and southern rooms of the house.  With a bit of thought popped ceilinng areas can also be used to delineate, and give character, to spaces in open planned layout, as well as bringing the sunlight into these spaces to warm the internal rooms in winter.

In summer, clerestories provide a very effective passive cooling strategy.  While the general strategy of setting out floorplans and openings to facilitate entry of prevailing cooling breezes works much of the time, sometimes nights in summer are still.  This is where clerestories can be used to induce a flow.  By opening up clerestory windows on such nights, you allow the more bouyant warmer air to escape out the window.  This makes a slight lower pressure inside.  If you also then open ground level windows, the cooler night air is then drawn into the house to replace it.  This air then flows across the slab floor, and along the brick walls, and as it does so, it is heated by these hotter masses.  This warms the air, which expands, becomes more bouyant, rises and goes out the open clerestory.  This in turn creates a low pressure at ground level, which draws in more cool night air.  And so on.  

Over the course of night, this circulation pattern effectively takes the heat out of the house, through the high clerestory window.  Come the next summer morning, you can shut the clerestory, and be ready, cool, for the next hot day.

© Positive Footprints