Many people have heard about the term passivhaus in Australia, but not everyone fully understands what it entails. To give you a quick passive house definition:
Passive house design is a unique approach to house building that vastly improves a home’s functionality and energy efficiency—sometimes by as much as 90%! The result is a more comfortable, healthy and liveable home.
The design process relies on a range of considerations and techniques to achieve continuous insulation, quality glazing, airtightness and heat recovery ventilation, while eliminating thermal bridging.
Okay, that was a lot of information and many terms that you have probably heard of, but are not super familiar with. That is why we want to dive in a bit deeper and make sure you fully understand why we are so passionate about passive houses.
On this page, we want to tell you a bit more about:
- the history of passive house design
- passive house vs passive solar design
- the passive house principles
- the passivhaus concept in Australia
- why energy efficient house building is good for you—and your bank account
- how you can build your own passivhaus in Australia
So, without further ado, let’s talk passive house!
THE HISTORY OF PASSIVE HOUSE DESIGN
The passive house concept was developed in the late 1980s by German building physicist Wolfgang Feist and Swedish structural engineer Bo Adamson. The two men were having a (literally) heated conversation about how to increase the energy efficiency of buildings.
Feist and Adamson wondered if there was a better way to cool and heat houses than by using heaters and air-conditioning. They came up with a concept that would increase the energy efficiency of a house by up to 90%, massively reduce energy cost and therefore the environmental impact while increasing the comfortableness of a home.
Their concept was further developed through a number of research projects, and by 1990, the first passive house residences were built in the German city of Darmstadt.
Fun fact: As this construction concept was developed in Germany, you will often see the original German spelling Passivhaus in Australia.
PASSIVE HOUSE VS PASSIVE SOLAR DESIGN
Many Australians have stumbled across the term passive solar design, but only few are familiar with the concept of a passive house. However, due to the perceived similarity of the words, they are often used interchangeably, when in reality, they are two very different approaches to energy efficient building design.
Passive solar design is a broad umbrella term that describes a range of different measures to increase a home’s energy efficiency and comfortableness without following the rigid rules of passive house design.
So, passive solar design basically takes some of the approaches and standards of passive home design to increase the performance, but it doesn’t meet all the criteria you would need to have a certified passive home.
You can look at it this way: Passive solar design follows all the guidelines and rules for residential construction, and then adds in some smart optimisations to have better insulation and a more comfortable indoor home. But it does not offer the high standard and guaranteed performance of a certified passive home.
To make matters a bit more clear, here are the main differences in a comprehensive overview:
PASSIVE HOUSE PRINCIPLES
Passive houses are distinguished by a number of elements that all together help to massively increase the energy efficiency of homes.
1. INCREASING INSULATION
Insulation acts as a buffer between your home and the outside, making it easier to maintain a consistent and comfortable temperature throughout the home regardless of the weather and climate.
Think of it this way: In winter, the outside temperature is usually colder than the inside temperature, but if you don’t have the appropriate amount of insulation protecting your home, the cold will find its way inside and eventually cool it down. The same principle applies for hot summer days, where the heat travels through uninsulated walls and windows and heats up your home.
Heat loss through walls, roofs and floors account for more than 70% of the total heat loss in buildings. Therefore, improving thermal insulation is an extremely effective way to save energy, while improving thermal comfort and preventing structural damage at the same time.That is why passive houses are built to a very high standard of insulation. This includes insulating all parts of the thermal envelope around the house, meaning walls, ceilings and floors using well-insulating materials such as glass wool or other common insulation materials.
As an interesting comparison, you can also use concrete, brick or softwood for insulation, however the thickness required to achieve a comparable level of insulation varies from approx. 1 meter of softwood to more than 17 meters of concrete, while you would need less than 0.50cm of straw or only 0.30cm of typical insulation material to achieve the same effect.
2. ELIMINATING AIR LEAKS AND THERMAL BRIDGES
A lot of Australian houses are not built airtight and therefore let cold or hot air enter the house through thermal bridges as well as air leakages.
A thermal bridge is a physical pathway from inside to outside of the building through which heat can move easily. Common thermal bridges are:
- poor quality windows
- uninsulated concrete slab edges
- steel framed buildings
On top of that, there are a number of very common air leakages that enable unwanted heat transfer, such as:
- gaps around doors
- gaps between and around windows
- unsealed vents, skylights, downlights or exhaust fans
- gaps between floorboards
- gaps around wall openings (e.g. pipes, power outlets, switches, air conditioners and heaters)
- gaps between walls and cornices or floors and skirting boards
Passive houses are designed to be airtight and with no thermal bridges, keeping heat out in summer, and cold out in winter. Airtight construction also ensures that only fresh filtered air enters your home.
Side note: Not having any holes in your house also means that you won’t have any unwanted visitors such as snakes, spiders or cockroaches coming into your home.
3. UTILISING THERMAL MASS
Thermal mass refers to a material’s capacity to store heat. For instance, concrete, bricks and tiles can store a relatively large amount of heat, whereas materials such as timber can only store a small amount.
Where possible, passive design utilises materials with high thermal mass because they help to maintain comfortable temperatures throughout the home, and reduce reliance on heating and cooling devices.
4. THINKING ABOUT A HOME’S ORIENTATION
Orientation plays a significant role in maintaining a comfortable home throughout the year. Given the high intensity of the Australian sun, it’s an important consideration when designing a home, and ranges from smaller measures such as eaves and awnings to larger features like pergolas and plantings.
Passive design relies on cleverly positioned orientation that utilises shade during summer, but embraces the sun in winter.
5. USING DOUBLE OR TRIPLE GLAZED WINDOWS
Windows are the biggest source of heat loss and gain in all buildings. That shouldn’t be surprising, as they are basically big holes in your house. What is surprising though, is thinking that one thin layer of glass will help in protecting your house from the weather conditions outside.
In some Australian climates, double glazed windows might be sufficient, while in others, triple glazing is the way to go. Either way, on average, passive house windows transmit just one-sixth of the heat compared to a typical Australian window. The critical element is high quality insulated frames that seal tight and have more than one closing point.
If you want to know more about and glazing, we have a comprehensive guide on windows here.
6. ENSURING PROPER VENTILATION
Passive houses use heat recovery ventilation (HRV), a system that draws filtered outdoor air into living spaces and bedrooms and exhausts stale air from bathrooms and kitchens. This type of active ventilation removes moisture, odours, dust and pollutants, which can result in improved physical health and wellbeing.
In warmer climates, an energy recovery ventilation (ERV) system can do the same with the addition of humidity balance.
PASSIVE HOUSE DESIGNS IN AUSTRALIA
Many Australians believe that due to our climate, we don’t need better insulated houses and windows. But with climate change being a major issue—and energy consumption being one of the main sources of Australian greenhouse emissions—the government has stepped in to make Australian houses more energy efficient.
In 2012, the Greenhouse and Energy Minimum Standards (GEMS) Act came into effect. The new law not only provides a national framework for product energy efficiency in Australia, but also sets new standards for Minimum Energy Performance Standards (MEPS) and Energy Rating Labelling (ERL).
SIX-STAR ENERGY RATING STANDARD
Ever since then, the Australian government has introduced more and more regulations in an effort to reduce energy consumption and costs. The Building Code of Australia (BCA) Volume Two for example, states that all new homes and some renovations, alterations and additions must comply with the energy efficiency requirements, including specifications around insulation, external glazing, sealing, services and ventilation.
Under the Nationwide House Energy Rating Scheme (NatHERS), houses are now also given a star rating based on the energy efficiency of their design, with 6-stars being the new standard. The rating considers factors such as the building envelope (the roof, walls, floor and windows), the orientation and type of glazing.
SAVING MONEY WITH A PASSIVE HOUSE
Building a home is a highly individual undertaking, meaning the price will vary based on many decisions along the building process. Therefore, we can’t definitively say that your new passive house will be more or less pricey than a standard built.
However, what we can say is that down the road, you will absolutely save money in regards to heating and cooling costs. Let us explain.
Based on the average energy cost (electricity, gas) in Victoria, a house with a 2-star energy rating roughly spends $7,330* a year on operational cost. If you opt for a 7-star energy rating, your cost goes down by over 75%.
To take it one step further, a 10-star energy rating passive home basically won’t cost you anything in heating or cooling, leaving you with an average annual bill of only $23.71. Amazing, right?
*OUTLIER energy calculations
HOW TO BUILD YOUR OWN PASSIVE HOUSE
Do you want to reduce your energy cost? Are you sick of wearing a jacket inside to stay warm? Do you want to build a healthy home that will keep you comfortable all year round? Then hop on the passive train and embrace the future of building in Australia!
Drop us a message or give us a call to start your own passive journey. We are here to help.