The financial consequence of getting this wrong is substantial. Typical annual electricity bills for a Canberra household range from $1,500 to $2,100, among the highest in Australia, driven primarily by heating. Heating and cooling represent the largest portion of residential energy consumption in the ACT. Passive solar design addresses this at the source, not with a more efficient heater.

In the Southern Hemisphere, the sun tracks across the northern sky throughout the day. Positioning the main living areas to face between 15° west and 20° east of true north is the single most important passive solar decision and costs nothing if made at the design stage.

At Canberra's latitude (35.3°S), the sun's altitude varies dramatically between seasons: 29–33° above the northern horizon at the winter solstice and 65–67° at the summer solstice. This 35+ degree variation is what makes fixed horizontal shading so effective and why orientation is the cornerstone of passive solar performance.

When main living areas face north, the same window that captures winter warmth receives minimal direct summer sun — not through any mechanical adjustment, but through geometry. This is the elegant logic of passive solar design.

What If My Block Doesn't Face North?

Most Canberra blocks can achieve excellent passive solar performance regardless of street orientation. The challenge is greater on some sites — east-west blocks, south-facing slopes, narrow inner-suburb lots — but the strategies that address them are well-established.

•       East-west blocks: clerestory windows, skylights, and split-level designs to capture northern light over the roofline

•       South-facing slopes: two-story designs with upper-level north-facing glazing above the slope's shadow line

•       Narrow urban infill: internal courtyards or light wells creating north-facing zones within a compact footprint

•       Hemmed-in sites: high-level windows and reflective surfaces to redirect light into living spaces

We have delivered 7-star and 8-star NatHERS-rated homes across challenging sites in Denman, Throsby, Gungahlin, and Canberra's inner suburbs. The solutions require more considered design thinking, but the performance outcomes are achievable on almost any ACT block.

"Thermal mass" refers to the ability of dense materials, such as concrete, brick, stone, and rammed earth, to absorb, store, and slowly release heat. In a Canberra home, correctly positioned thermal mass charges during sunny winter days and release warmth throughout the cold night, functioning as a silent, cost-free radiant heating system.

The relationship between north-facing glazing and thermal mass is the most critical balance in passive solar design. As a design guideline, north-facing glass should represent approximately 15–25% of the area of exposed thermal mass in a room. For Canberra's cold climate, we typically target the upper end of that range, around 20–25%.

Common Thermal Mass Mistakes That Undermine Performance

•       Too much glazing, insufficient mass — daytime overheating and rapid cooling after sunset

•       Mass in the wrong position — covered by carpet or rugs, or located away from direct winter sun

•       Uninsulated slabs — heat drains into the ground rather than being stored and released into the room

•       Slab without edge insulation — a common ACT construction problem that allows captured heat to escape at the perimeter

For Canberra projects we typically specify polished concrete slabs in north-facing living areas, internal brick or masonry walls positioned to receive winter sunlight, and dark or mid-toned surface finishes to maximise solar absorption. The mass must be thermally isolated from the ground beneath and exposed on both surfaces — to the sun for charging and to the room air for heat distribution.