By Dave Miller · off-grid sparky · 22 years wiring solar, batteries and sheds in central QLD
“After losing my entire battery bank to Queensland's wet season in year three, I learned that passive solar orientation is useless without proper ventilation and moisture control.”
— Dave. Measure twice, buy once.
ArticlesCalculatorsSite PlannerShopForget fancy gadgets. If you're going off-grid in Australia, passive solar design isn't optional – it's survival. Get this wrong and you'll be sweating through summer or shivering in winter. Here's how to do it right, bluntly.
Forget fancy gadgets. If you're going off-grid in Australia, passive solar design isn't optional – it's survival. Get this wrong and you'll be sweating through summer or shivering in winter. Here's how to do it right, bluntly.
Point the long side of your house north. Period. No exceptions. In Australia, the sun is in the north. If your house faces east or west, you're wasting money and energy.
Practical tip: Position your main living areas (kitchen, lounge) on the north side. Put bedrooms on the south. If you're building, don't put big windows on the east/west – they'll cook you in summer.
Supplier tip: Use a compass app (free) to check orientation before you pour concrete. No point arguing with the sun later.
Thermal mass (concrete, stone, brick) absorbs heat during the day and releases it at night. But too much = oven. Too little = fridge.
Practical tip: Concrete floors under north-facing windows are gold. 100mm slab = $80-$120/m² (Boral, Cement Australia). No need for fancy stone – concrete is cheap and works. Avoid timber floors on north side – they don't store heat.
Don't do this: Putting thermal mass in a room with no sun (like a bathroom). It'll just sit there, cold and useless.
Windows are your solar collectors. But cheap single-glazed windows are useless. You need low-e double glazing to let sun in winter and block heat in summer.
Practical tip: Get AS 2047 compliant double glazing. Standard low-e double glazing: $180-$250/m² (Glass & Glazing, Pella). Don't buy cheap "solar" glass – it's a rip-off. North-facing windows should be 30-40% of wall area max. More = overheating.
Supplier note: Boral's "SolarGuard" glass is $220/m². Check with local suppliers – prices vary by state.
Shading is non-negotiable. In summer, the sun is high – block it. In winter, the sun is low – let it in. Trees on the north? You're kidding yourself.
Practical tip: Use fixed overhangs (eaves) for summer shade. Depth = 0.5m for every 1m of window height. For adjustable shading: Retractable awnings ($120-$280/m²) from Awnings Australia. Install them 600mm above windows.
Don't plant big trees on the north. They'll block winter sun. Use deciduous trees on the east/west – they lose leaves in winter.
Real Talk: If you're building a tiny home or shed, skip the fancy glazing. Just use a 300mm deep fixed overhang + north-facing windows. It'll save you $500+ and work better than half-baked solutions.
While many off-grid projects are achievable as DIY, certain situations require licensed professionals:
Always check local regulations and obtain necessary permits before commencing work.
Worth a watch: Understanding Passive Homes: Insights from Paul Kealey's Walkthrough · EkoBuilt Passive Homes