Passive House Design
This is a concept you may come across if sustainability is important in your renovation or new build. "Passive house" (German: Passivhaus) is a voluntary standard for energy efficiency in a building, which reduces the building's ecological footprint. It results in ultra-low energy buildings that require little energy for space heating or cooling.
It is the practice of taking note of the local climate and site conditions and making sure your home design maximises the benefits these can offer to create a comfortable internal environment.
What areas does it address?
Solar passive design
It considers the direction the sun is coming from and how it can be utilised to heat and cool the dwelling. Typically, this means opening up living areas to the north for all day sun and thinking about shading certain areas in summer using eaves or trees to protect the home from the harsh afternoon sun. These changes may not be drastic or noticeable but can have a huge impact on how comfortable a home is to live in.
Layout
The design should have living areas facing north for all day sun. South-facing rooms receive less sun so these should be used for storage and garages, while east-facing rooms gain morning sun and are cool in the afternoon, making them ideal for bedrooms.
Thermal mass
Aka using different materials around the home to absorb, store and release heat. Ie concrete, brick, and tiles are great examples for capturing warmth and are ideal for the morning sun. If you want to minimise heat use timber, which cools down quickly.
Natural ventilation
The home should be orientated to take advantage of the breeze and create natural circulation. This cools areas down and airs out all parts of your home. Window choice will play a factor with the best designs able to open wide for maximum ventilation. Cross ventilation should also be considered. This is where windows are placed on adjacent walls to encourage the air to travel right through the space
Do Passive Houses cost more?
Passive Houses can cost more up front, because the home takes more time and expertise to design. However in the long run, due to the focus on efficiency it can also result in big long term savings when it comes to the bills.
Why are conventional Australian houses less efficient and why do they end up costing more than Passive Houses?
Three words…minimum building code! More specifically, insufficient insulation detailing, vapour barriers that are inevitably punctured, uncontrolled thermal bridging, poor quality windows (80% of the market is single glazed!) and dated construction techniques. To make up for these subpar practices, air-conditioners and heaters are required to make up for all that energy loss which ends up costing homeowners each and every year. Ref: Passive House Australia.
Do you need professional assistance to achieve a Passive House?
Yes. In order to achieve the Passive House standard, it is vital that the building design is tested and verified using the specialist PHPP software. At present there are now over 90 Certified Passive House Designers and Tradespersons providing dedicated full Passive House services in Australia. Ref: Passive House Australia.
Does a Passive House have to follow a certain design?
With the right team in charge, passive design does not dictate aesthetics. A Passive House can be traditional or contemporary but the key to a Passive House is the simplicity in its plan. It is best (most efficient and cheapest to construct) to create a compact shape (two storey is more efficient than a bungalow) with optimal solar gain, but the Certified Passive House Designer should otherwise be free to create any bespoke design according to the Client’s needs. It is important that the Passive House concept can be adapted to local cultures, styles and building traditions. Ref: Passive House Australia.
Can you have an open fireplace in a Passive House?
The answer from an Australian perspective is very likely to be no. Having an open fireplace would introduce too much heat into the space and may dramatically reduce the efficiency of the mechanical heat recovery ventilation system (due to lack of airtightness). However, there are other really clever means of having a real flame effect in your Passive House, including bio-ethanol fires as well as wood burning boilers or stoves with glass fronts. Ref: Passive House Australia.
Why is a Passive House a good idea?
There are a few reasons why people are designing their homes in this fashion:
They are seen as healthier homes: mandatory ventilation systems supply filtered fresh air continuously
They are seen as a more comfortable home with smaller variations in temperature year round
They are seen as more environmentally friendly (with reduced carbon emissions from your home)
They are seen as a more robust home, as they are less likely to attract mould, like a traditional house might.
They are seen as having less ongoing maintenance as the homes are more ‘self sufficient’ and doesn't have a lot of ‘bolt on’ technology.
They are seen as a cheaper home to run long term, as they consume up to 90% less heating and cooling than compared to a standard build.
Even if you don't want to go ‘all in’ with this concept, there are some great takeaways. So if you’re in the process of planning a new build or renovation, take into consideration Passive House practices and enjoy the fruits of your labour for years to come!
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