There are 5 main principals of Passive House.
Insulation helps prevent unwanted heat gain in summer and heat loss in winter. This blanket of insulation requires thick insulation in the floor, walls and ceiling. The amount of insulation required depends on your climate, for example, a house in Auckland will not require as much insulation as a house in Dunedin. A house in the Wairarapa, for example, has to strike a happy medium for the frosty winters and searing heat of summer.
Airtightness helps control the heat and cool air entering the building. Eliminating draughts creates a healthier home and means less heating required in winter and cooling in summer.
Airtightness can be achieved by sealing all joints in the building envelope and ensuring windows are properly installed. The use of products such as Pro Clima are approved for Passive House for use in New Zealand. A blower door test can tell you just how airtight your building is. Airtight means you can control your climate (this is continued further on).
Window and doors need to be triple glazed, with the option of Low E and filled with Argon gas (depending on the climate, it could be double glazed at the top of the North Island). This means that hot or cool air within the home is not lost through the windows, which have a lower R rating (insulation value) than the walls. There are other more important elements of windows, but these can be explored later. The placement of these windows is important for the climate the house is in and how much solar gain is required, as too much leads to overheating in summer.
Thermal bridges must be eliminated or lessened in a passive house. Thermal bridging is most common in aluminium windows, so thermally broken windows are required, timber or UPVC is the choice here. The edge of a slab foundation and corners of the wall framing all need to be accounted for.
Continuous insulation helps prevent thermal bridging.
The final main principle is Heat Recovery Ventilation (HRV)
With an airtight building, airflow must be introduced using mechanical means. Think of an HRV as the lungs of the house. An HRV system takes out the stale air and replaces it with fresh air. So as to not lose all the heat you have created in winter, an HRV system encompasses a heat exchanger. This heats the fresh air to the same temperature as the warm stale air you are expelling so as to not create a temperature drop within the home. (depending on the heat recovery capability of the unit).
Certified Passive Houses are known for their super low energy use, thanks to their super insulation, airtightness, and build quality.
For my own Passive house we will be adding solar panels and rain water harvesting to become more renewable.