Passive House Principles

Passive House (also known as Passivhaus where it originated in Germany) is an international method or technical standard of designing and constructing a building to achieve a very high level of energy-efficiency (with little or no heating or cooling required). Passivhaus buildings are the most comfortable, healthy, durable and efficient buildings in the world

It is similar in concept to solar passive heating, letting sun in to warm dense parts of a building such as a concrete floor. However it builds upon this and is an overall or holistic approach to the entire climate and wellbeing of a home.

It is a method of designing and thinking, perfect for any climate in Aotearoa wether it be cool and dry or damp and warm. A common misconception is that passive-house standards are not applicable in warmer parts of our country. This is not true as a proper passive house is dry, cool when it needs to be and healthy. 

It is not an architectural style, but more concerned with the building science of how the building is put together and how it performs - and has a rigourous and robust thermal-modelling to ensure quality-assurance of the result. This means you are not really restricted by how you want your home to look and feel but there are some overall design principles to keep in mind.


A home is one of the largest investments we will make, and we're finding more and more people want a home that will last lifetimes and look after its occupants while avoiding costly yearly upkeep. The passivhaus thermal modelling has been proven to be very accurate in terms of understanding heating and cooling requirements, in addition to ensuring high quality indoor environment (healthy air quality with low C02 levels, ideal temperature and humidity levels, and no condensation/mould-growth) - all with minimal heating/cooling requirements and savings.\
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It is a science driven approach to building health modelling which means it is clear to prove if it works or not. There is no hiding behind vague green star ratings.


Courtesy of Hans Jorn-Eich, here a 90 second explainer of these concepts:

THE BASIC ELEMENTS OF A PASSIVHAUS:

1. Highly insulated building envelope. This is to walls, roof and floor - so the building is like a thermos where the inside climate is separate from what is happening outside.
2. Great windows. In our climate, high-quality and well sealed double-glazed windows should suffice, sometimes triple-glazing is preferable. Windows are the weakest point in the thermal envelope of your building - we don't want to compromise on these.
3. Airtight envelope. If you have gaps in your building, it is like trying to have a warm bath without the plug in - you have to constantly keep filling it up with more hot water! We want to control how air enters and exits our buildings. A draughty home is the standard in New Zealand, and well sealed but poorly designed homes are the exception. A passive house lets air move where we want it to move to ensure a healthy, dry and warm home.
4. Solar orientation. Passive Solar Design Principles that are fundamental to all our projects – allow for northern solar gain in winter, and shade windows to prevent hot summer sun from entering house. We are always careful to balance the harsher afternoon light while letting in winter morning sun as soon as possible. 
5. Controlled Ventilation. An air-tight building still needs fresh air - but it must be controlled - no leaky drafts and air gaps all over the place. You can still open in windows in a Passive House, but also a low-energy and highly-efficient mechanical ventilation system is required to ensure fresh air circulates throughout the building.
6. Elimination of Thermal Bridges. This is one of the most ignored issues with current buildings - especially with steel/aluminium framing that conducts heat/cold through the building fabric - particularly aluminium-framed windows! Construction details are important here. Where there is a difference of temperature, condensation forms and has the possibility to create mold. 
7. Form Factor. Consideration of size and shape of the building. Less surface areas of walls means less surface area for heat to escape. Conversely, more surface area towards the sun in hotter climates means overheating issues. Designing with the climate in mind is the first step in the right direction. 

Passivhaus aims for a comfortable indoor air temperature between 20-25 degrees celsius all year round, and uses 60% to 90% less energy for heating/cooling than a 6 star house. It is a life-cycle costing approach - so although it will cost a bit more up front in construction costs (while passivhaus is still new in New Zealand), it will have reductions in the cost of heating/cooling building for over 60 years (not to mention the amount of carbon emissions saved). It is worthwhile to note that energy to heat and cool is still the MOST energy consumed over a building's lifetime - much more so than the embodied energy of the construction materials.


What's the main reason people love living in Passivhaus homes?
They are so comfortable and healthy, providing year-round comfort for New Zealand homes, even in our changable climates. They stay a passively comfortable temperature all year round, with no cold drafts and no cold surfaces (even in the middle of winter) - this seems almost unimaginable when around 90% of our housing stock are essentially "wooden tents"! There is also a very real and frightening issue with the indoor air quality of many of our current buildings - which includes the high levels of pollutants, dustmites, chemicals, and mould... that many occupants breathe in everyday (this is causing a lot of ill-health effects). A passivhaus provides a constant supply of fresh filtered air, and is calculated with building physics to ensure a healthy indoor environment that is much better for our well-being.