The Airtight Case for Passive House
The thermal comfort of our homes depends on the balance of energy flowing in and out through our ceilings, walls, floors and windows. This energy moves via convection, conduction, radiation and air leakage. Combined, these flows determine our total heat loss and heat gain, influencing overall energy efficiency.
This is where Passive House principles come into play.
Understanding Heat Flow in Homes
Heat loss and gain are driven by several factors, including:
- Conduction – heat transfer through solid materials such as walls and windows.
- Radiation – the transfer of heat via infrared waves, such as sunlight warming a room.
- Convection – heat carried by moving air, which can be controlled through proper ventilation.
- Infiltration and Exfiltration – uncontrolled air leakage that causes unwanted heat loss or gain.
Unregulated airflow through gaps and cracks in a building envelope leads to inefficiency, temperature fluctuations and discomfort. In conventional homes, these factors contribute to excessive energy consumption and inconsistent indoor conditions.
How Passive House Eliminates Uncontrolled Heat Flow
Passive House construction is designed to address these issues by achieving an optimal balance of insulation, airtightness and ventilation. Here’s how:
- Airtight Construction
Unlike conventional homes, Passive House homes use a meticulously sealed building envelope to prevent unwanted air leakage. This significantly reduces infiltration and exfiltration, improving indoor comfort and energy efficiency.
- Advanced Ventilation with Heat Recovery (MVHR)
Since airtightness limits natural airflow, Passive House homes use mechanical ventilation with heat recovery (MVHR) systems. These systems maintain optimal air quality while efficiently recovering heat/coolth from outgoing air, further reducing energy demand.
- High-Performance Insulation
Passive Houses incorporate continuous, high-quality insulation to minimise conduction and radiation-based heat loss. This ensures stable indoor temperatures year-round with minimal reliance on heating and cooling systems.
- High-Performance Windows & Doors
High-performance windows and doors are a key element of Passive House homes. They are extremely well sealed, are either double or triple glazed and are sized, orientated and shaded appropriately. Combined, they optimise heat gain and loss throughout Melbourne’s changing seasons.
- Eliminating Thermal Bridges
A thermal bridge is essentially a “shortcut” for heat through a building’s envelope (otherwise known as “the path of least resistance”). It occurs when a section of a structure—like a corner, window frame or junction between materials—has a significantly higher thermal conductivity than the surrounding insulated areas. These are carefully minimised in Passive House design. Strategic detailing and material selection prevent unwanted heat transfer, improving overall thermal performance.
The Benefits of Passive House in Melbourne’s Climate
Melbourne’s varied climate presents unique challenges. A Passive House home offers solutions by:
- Keeping homes warm in winter and cool in summer without excessive energy use.
- Reducing heating and cooling costs by up to 90% compared to conventional homes.
- Enhancing indoor air quality through controlled ventilation and filtration.
- Preventing condensation issues that lead to mould growth and structural deterioration.
Conclusion
The case for Passive House is clear—by controlling heat flow through advanced building techniques, these homes deliver unparalleled thermal comfort, energy efficiency and durability. For homeowners in Melbourne looking to future-proof their living spaces, Passive House represents the gold standard in sustainable construction.