What is Passive House?

What is Passive House?

Passive House, also know as Passivhaus, is a performance-based standard that incorporates rigorous design and construction requirements to achieve 5 key design principles and performance criteria. This ensures a high performance building with optimum occupant comfort, health and hygiene.

It is a recognised standard, world wide. Any project claiming to be Passive House certified, must meet the requirements of, be implemented and built correctly, and then be assessed by the Passivhaus Institute (PHI), Darmstadt, Germany.

The term “Passive House” should not be misunderstood. A “Passive House” design is an integrated design process created to maximise building performance and benefits the well bring of its occupants. Any Certified Passive House building will be a high efficiency and high comfort building. Theres a subtle, but significant difference between a Certified Passive House, and ‘Passive Solar Design‘,  a building that uses ‘Passive House Principles‘ or similarly misleading terms. If its not Certified as such it’s not a Certified Passive House.

Passive House includes whole-of-building energy control, including heating and cooling, hot water, lighting, fixed appliances and an allowance for consumer electronics. The Passive House Institute (PHI) defines a Certified Passive House as:

“… a building, for which thermal comfort (ISO 7730) can be achieved solely by post-heating or post-cooling of the fresh air mass, which is required to achieve sufficient indoor air quality conditions, without the need for additional recirculation of air.”     Passivhaus Institut (PHI)

To achieve this Passive House Standard, ANY building must meet the following minimum criteria (for NSW and Victoria):

  • Internal thermal comfort must be not less than 20°C and no greater than 25°C (with not more than 10% of the hours in a given year over 25°C).
  • Heating demand is no greater than 15k Wh/m2/yr or a heating load 10 W/m2.
  • Cooling (if installed) demand is no greater than 15k Wh/m2/yr or a cooling load 10W/m2
  • plus controls on airtightness of the building envelope, plus overall energy usage (including renewables).

These requirements apply to new buildings, as well as adaptions of existing buildings (also known as “retrofits”). It is much easier to integrate the Passive House requirements into a new building (home, multi-residential building, shopping centre,, and other building typologies). Retrofitting a building (terrace, standalone home, other building) is definitely possible, but there are limits to how much change can be made and how much it will cost.

The Five Basic Principles of a Certified Passive House project.

More on the fundamentals of Passive House design and certification standard is explained here.

How would a Certified Passive House standard (home) benefit me?

Thermal Comfort, Health and Wellbeing

As a Passive House Certified home owner, you can be assured of a high quality home that will be comfortable to live in, and will have predictably low energy bills.  Your home would be warm and cosy to live during winter, cool and comfortable in summer (and yes – you can open a window!). Also, due to the combination of achieving optimum temperature and humidity levels, your home would not develop mould, minimising risk of developing asthma or skin irritation.

Not only is this good for the environment, it ensures a safer, more comfortable living or working space as we experience increasingly volatile weather conditions in Australia.

Here’s an excellent graphic that collates the individual and greater benefits of Passive House, provided by the Australian Passivhaus Association.

Costs, and Return on Investment

Design Efficiency

The cost to construct any home design is highly contingent on size and complexity of the design; the quality and detailing of finishes, fixtures and materials; as well as site constraints such as location, slope and topography of the land, soil conditions, existing building (renovations), site access (for construction). These costs occur whether a home is a conventional build, or to Passive House Standard.

To design and construct to Passive House Standard should be considered from the very beginning of a project – even at the time you are selecting your project site. Things to consider, and aspects that will influence the cost of your project will be:

  • Capturing views and the sun – orientation of the site is important – not just for appreciation of views, but to achieve optimum energy balance for the performance of the building envelope
  • Size, scale, format – there are optimum ways to design efficiently and effectively (resulting in minimising construction costs). The more building envelope (surface wrap), corners and complexities, the more challenging it will be to achieve the Passive House Standard. This applies to the layout of spaces in plan as well as how each floor level connects with adjacent floor levels and features
  • Existing buildings on site – renovating and extending a building is complex (and highly reliant on your design and project brief requirements)

“Designing in” the Passive House criteria – from the beginning of your design – should ensure the design and construction process will become more cost effective in the long run. Consideration of orientation, building envelope, size, etc, will inform the design as it develops. This in turn creates a more rigorous but effective process and a constructive collaboration between client, architect, Passive House Certifier and builder. Your team is critical to achieving your optimum outcome, and successful Certified passive House home.

Costs and Funding

Most of us though will require a mortgage to build our new home or renovation, internationally there is funding to incentivise construction of buildings to have lower emissions and Certified Passive House projects. In the US there are multiple programs to fund or subsidise multi-family buildings that achieve PHI Certification. Here in Australia, we are lagging behind on the incentives front. Currently, Bank Australia offers a Clean Energy Home Loan to support those that are “looking to do things like add solar panels, window glazing and insulation to your home, or even buy or build a planet-friendly, energy efficient home“.

Reduced Running Costs, Lower Emissions, Better Health

Remember the Passive House Criteria for energy use? Heating demand cannot be greater than 15k Wh/m2/yr or a heating load 10 W/m2. And cooling (if applicable) demand cannot be greater than 15k Wh/m2/yr or a cooling load 10W/m2. This means that for the duration of the time you live in your Passive House home, the cost of running your home (and bills) are minimal as compared to a conventionally built home. While energy bills continue to soar in Australia, your bills will only increase as inflation occurs, that is to cover the cost of pretty much a fixed and predictable cost per year.

The 3 classes of Certified Passive House buildings (Photo courtesy of the Passivhaus Institute)

Exceeding Minimum Standards and Your Return of Investment (ROI)

There is no doubt it’s expensive to design and build these days. Construction costs have increased astronomically over the last few years due to Covid-19 supply chain shortages and the increased costs of labour (and builders existing the industry).

On top of that and within a ever-growing risk averse industry, the National Construction Code (NCC) continues to include additional compliance requirements and procedures for designers and builders for construction conformance. While these measures are to protects us, and the investments that are built, it adds to an increasing load of complexities to an already complex series of design, statutory Planning and Building Regulations. It’s a tough time to design and build and home – its a fragmented and frustrating process. It’s hard to find good builders, and even harder to find a good builder committed to build to what’s designed and specified fully and completely.

The benefits of the Passive House Certification process is that the technical design and construction process requires excellent Quality Assurance procedures, including checks and measures throughout the design, the assessment of the design documents, and then throughout the construction process. The architect, the Certifier, and the builder are committed to ensuring that the building created at the end of the whole process does meet the Design Criteria (and is tested to prove it).

The means you are assured you receive what you expect, and what you are paying for. And considering the rigour and high expectations of achieving the Passive House Standard, your building will match and exceed the minimum standards of Building Fabric, Condensation Management and Housing Energy Efficiency as set out in the NCC.

Black Beauty, Fitzroy North (alterations and additions to existing home). Architecture and Interiors by Cathi Colla Architects. Photography by Emma Cross Photographer


Return on Investment

In the past 10 years, there’s been a steady and strong increase of those aware of Passive House projects. When mainstream media features a Passive House feature, such as on “Grand Designs Transformations”, its here to stay (and is almost mainstream).

Passive House, as a movement, has done its time through testing and experimenting, its trials and tribulations (and its bad wrap). Now we can see, experience and prove it’s benefits. It’s here to stay. It’s good for us, it’s good for reducing carbon emissions, and its good for raising the quality of our building stock (and expectations for better living).

Due to its popularity, its also forcing greater availability of particular components required to obtain greater thermal performance. For instance, 20 years ago we found particular builders would complain about the availability and additional cost of double glazing. Now, as more projects demand better glazing and frames, the relative cost is reducing.

The same goes for building components. According to the Passive House School, additional investment required when building the first passive houses in the early 1990’s “was 18-20%, compared to no more than 5 to 10% in 2015″. This is only going to improve as Passive House becomes more in demand.

Note also that there is a growing availability of Passive House Certified builders and tradespeople. This area is growing exponentially, thereby likely reducing comparable construction costs as the market becomes more competitive.

And the long term economic benefit to you?

It still costs to design and build a home. Its the additional items required to achieve the great thermal performance that should be considered, rather than the whole cost of project.  Any added costs (compared to conventional construction cost) should be considered in the context of the economic benefits of investment of those extras, as compared to the significant energy costs (compared to running a conventionally built home).

There’s a nifty, but comprehensive, summary and calculation at Passipedia, which considers the long term cost and energy efficiency savings for a single family home in Germany.

One should also consider the ‘big picture’ benefits such as healthier living (lower health bills), and of course the even larger benefits to our community as a whole.

By nature of the relative savings on ongoing bills in the future would deem your ROI higherm, thn the average conventional cost of living. Consider that in 30 years time your mortgage is paid, yet at that point in time, your cost of running your home should still be that defined as Heating demand cannot be greater than 15k Wh/m2/yr or a heating load 10 W/m2. And cooling (if applicable) demand cannot be greater than 15k Wh/m2/yr or a cooling load 10W/m2. That means life, and costs, are pretty simple. Savour the thought of the costs of running a conventionally built home in comparison.

Consider then the relative value of owning a Passive House in the future. Surely this will be much more a valuable asset, than a conventional build?

Our Future, and Our Children’s Future