There are five key Certified Passive House design principles;
1
Air Tightness
Elimination of drafts.
2
Super-insulated & thermal bridge-free envelope
Retain heat energy.
3
Heat recovery ventilation (MVHR) Recycles heat energy & provides fresh air.
4
Water tightness
Essential for building durability.
5
High-performance joinery
Building enclosure
2. Insulation & thermal bridges –
retain heat energy
Thermal bridges are paths that allow heat to flow through the insulation within the building envelope (the shell or enclosure). In passive houses, thermal bridge-free construction is essential to maintaining the integrity of the insulation layer and preventing energy loss. Proper detailing, such as continuous insulation and careful design at structural connections, helps mitigate this issue.
The entire exterior is highly insulated, including walls, roof, and floor, without any gaps that allow heat to escape or enter the building. High-quality insulation materials are used to minimise heat transfer.
Passive homes well exceed the insulation levels found in conventional construction. Insulation materials like expanded polystyrene (EPS), extruded polystyrene (XPS), fibreglass and mineral wool create a continuous layer of insulation that envelops the building.
In standard construction, windows are usually placed on the outside of the cladding, creating a thermal bridge – with plenty of gaps for heated air to escape (you can read more about windows here).
With a passive house, we pull the window into the insulation line and recess it, putting it in the warm part rather than the cold part of the building envelope. If you put your hand on the inside of a window in a regular home, the glass would feel cold. In a passive home using this method, the inside of the window is warm – the temperature of a recessed window will be the same as any other interior surface temperature. This minimises ‘thermal discomfort’ – the feeling of your body heat being radiated to the cold surface of the window.
Once you have an air-tight structure, you can rely on your insulation. It reduces the bleed of heat energy through the walls, floor, and roof.
Generally, a passive house will have higher levels of insulation than what is required by the New Zealand building code. We also use higher-quality joinery to add to this performance and to manage moisture by preventing water infiltration and condensation within the building structure. Proper moisture control prevents mould growth and structural damage due to decay.
If a concrete floor has been chosen, then the floor slab is completely encapsulated within polystyrene insulation, isolated from the outside ground. A concrete floor has thermal mass properties that can help regulate indoor temperatures by absorbing and releasing heat slowly. By encapsulating the floor slab entirely, it is protected from the cold ground. It integrates with the overall building envelope strategy of creating a continuous insulation layer that minimises thermal bridges and maximises energy efficiency.
Transform how you live and start your passive journey with a consultation with Barefoot Architecture. Simply phone, email or fill in the form here, and we’ll reply as soon as possible.
