Passivhaus
Castlecrag
Agathē builds to the certified Passivhaus standard in Castlecrag — architectural craft for the suburb Walter Burley Griffin designed around the landscape.
Agathē builds to the certified Passivhaus standard in Castlecrag — architectural craft for the suburb Walter Burley Griffin designed around the landscape.
A certified Passivhaus is measured, not promised. An airtight, highly insulated envelope with continuous filtered fresh air keeps the whole home within a few degrees year-round — without leaning on air conditioning. The result is a home that is quiet, free of draughts and condensation, dramatically cheaper to run, and independently certified to perform exactly as designed.
Castlecrag was designed by Walter Burley Griffin to sit inside its landscape rather than on top of it — stone, bushland, and homes that follow the contours down to Middle Harbour. That legacy makes it one of Sydney's most architecturally literate suburbs, and one of its more demanding building environments: bushland humidity and harbour moisture from below, shaded southern slopes that never quite dry out, and design covenants that rightly expect better than the ordinary. Passivhaus belongs here. It is architecture-first building science — envelopes engineered to keep bush and harbour damp out of the fabric, glazing that opens to the landscape without bleeding heat, and filtered ventilation that keeps shaded, tree-wrapped homes dry and healthy. We work alongside your architect from the first sketch, in the suburb that has always expected architects and builders to think together.
Builder-led delivery of custom homes and Passivhaus builds, managed end to end.
Start the right way with our PAC-certified process — aligning design, budget and timeline before you build.
We work alongside your architect from the first sketch, so Passivhaus performance is designed in, not bolted on.
Scandinavian-inspired homes and cabins built to a healthy, high-performance standard.
Partial to full-scale renovations that transform your existing spaces into healthy, beautiful family living environments.
From design to delivery, we manage every detail for a smooth, on-time, on-budget build.
Yes. AGATHĒ builds architectural custom homes and Passivhaus projects across the North Shore, including Castlecrag. Our team includes a Certified Passivhaus Tradesperson, we are members of the Australian Passivhaus Association, and every project starts with our structured pre-construction process so design, budget and performance targets are resolved before construction begins.
Because warm indoor air is meeting cold glass — the mechanics are laid out in the Australian Government's YourHome guide to condensation. Castlecrag's humid coastal winters keep plenty of moisture in the air, and single glazing gives it a cold surface to condense on. High-performance double or triple glazing keeps the inside pane warm so there is nothing for moisture to cling to, and heat-recovery ventilation removes humidity at its source — cooking, showers, breathing.
In a certified Passivhaus, streaming windows simply do not happen.
Because cleaning removes the mould, not the moisture that feeds it. As NSW Health puts it, the lasting fix is finding and fixing the source of the moisture — a surface that stays damp will simply grow mould again, and around Castlecrag there is no shortage of moisture.
The answer is building fabric that stays warm and dry: insulation without gaps, no cold corners for condensation to form on, and continuous ventilation that holds indoor humidity in the healthy range. That is exactly what Passivhaus construction is engineered to do.
Because most Australian homes leak. Gaps around windows, doors, floors and downlights let the air you have paid to heat or cool escape, so the heater and the air conditioner never stop working — it is why the Australian Government's energy.gov.au guidance puts insulation and draught-proofing ahead of bigger heating and cooling systems.
A Passivhaus takes the opposite approach: a continuous, airtight, insulated envelope that holds a stable temperature year-round, verified by independent testing. The house itself does the work, not the equipment.
It is the exam a Passivhaus has to pass. A fan pressurises the home and measures exactly how much air leaks through the envelope — certification requires no more than 0.6 air changes per hour, one of the strictest airtight construction standards in the world.
The point is proof. Anyone can claim a home is well sealed; a blower-door result is measured by an independent tester. It is the difference between a promise and a certificate — and it is why a certified Passivhaus performs exactly as designed.
Yes — any window, any time. The difference is that a Passivhaus does not depend on open windows to stay fresh. The heat-recovery ventilation system supplies filtered fresh air around the clock, so the home stays comfortable and healthy even when it is sealed against a southerly, a heatwave or a week of rain.
It depends on the design, the site and the performance target, which is why we resolve cost early rather than guessing. Our pre-construction process starts with an early feasibility estimate against your concept plans, so you know whether the project is viable before committing to full documentation.
Running costs then work in your favour: a certified Passivhaus needs a fraction of the heating and cooling energy of a conventional home.
Often, yes — the certification pathway for existing buildings is called EnerPHit, and it is genuinely demanding work: airtightness, insulation and ventilation all have to be re-engineered together. Not every home is a candidate, and we will tell you honestly if yours is not.
Many renovations land on a middle path: applying Passivhaus principles and components where they deliver the most benefit, without pursuing full certification.
Whether you are at the early thinking stage or ready to move, we are happy to have an honest conversation. No obligation. We will tell you if we are not the right fit.