What is a passive house (PassivHaus)?

 

Passive House (or PassivHaus) is essentially about high performance design that can be summarised by 5 principles or performance criteria.  The system ensures a design delivers very high performance and comfort for the lifetime of the building, pluging the “Performance Gap” often experienced in building operations.

 

It relies on building physics and carefully integrated, minimal building services and technology. By eliminating the need to bolt expensive additional technology onto a poorly performing building, it eliminates the risk of bolt-on green-bling compromising the architecture.

 

The 5 concepts or building blocks that Passive House is built upon are:

 

Insulation

Passive houses must be insulted extremely well.  This can be achieved in a number of ways.  Some are wrapped in a “blanket” of insulation; where the insulated is used in the walls, floor and ceiling. Alternatively the home will be built from insulating materials, such as prefabricated insulated panels, or even straw bale. Excellent insulation is the first step in minimising heat gain in summer and heat loss in winter.

 

High-quality windows and doors

The Passivhaus Institut stipulates that window frames must be well insulated, and fitted with double glazing or low-emissivity glass.

The main goal here is to reduce unwanted heat loss through the window, and to increase the surface temperature of the inner pane to reduce the sensation of cold draughts.

 

Eliminate thermal bridges

The third requirement is to address “thermal bridging”. Thermal bridging refers to points in the building shell that conduct heat or cold more quickly than the rest of the structure, for example where metal wall framing “bridges” between interior and exterior wall linings. Heat or cold will transfer along this point, and it compromises the overall performance of your insulation.

Junctions and connections between building elements typically provide a thermally conductive bypass route for heat loss and must be reduced or eliminated wherever possible.

 

Air-tightness

This means ensuring every joint is perfectly sealed over, and there are no gaps within the building envelope.

An airtight, insulated building will successfully retain any warmth or coolness generated within, which is, essentially, why these houses require so little energy to heat or cool. Passive House standards require air leakage to be no more than 0.6 air changes per hour at 50 pascals of pressure – a typical Australian home would measure around 15-20 air changes per hour.

This is a big issue in Australia.  We’ve all experienced homes that have a cold draught that comes through the floorboards and have learned to just deal with it.  This definitely shouldn’t be the case and violates a core principle of a Passive House.

 

Heat recovery ventilation

Because the building is airtight, and there’s no draughts or leakages, we need to get fresh air into the house.  This is achieved and controlled with a heat recovery ventilation (HRV) system, which is the fifth design component.

The HRV is crucial to the functioning of the passive house, flushing stale air out and replacing it with a constant supply of fresh, temperature-controlled, filtered air.

It’s so important to properly ventilate your home because indoor quality can be significantly worse than outdoor. Moisture and pollutants encourage growth of mould and mildew which can cause illness and allergies.

 

To learn more about Passive House principles, watch this fantastic 90 second video below.  If you’d like to go deeper again, click here to download the Passive House brochure.

 

 

Once you’ve finished digesting all that information, get in touch with us to discuss your new building project!