An energy-positive home

Green Lifestyle

Marc Bernstein talks us through the Melbourne Design Studios’ 10 Star PassivHaus, a new house he helped design that generates more energy than it uses.


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Can you tell us about the eco-friendly and energy saving features of the house and what impact they have?

The whole house is designed as being eco friendly and energy saving, rather than just having features added on at a later stage. And I think that's partly what makes this house so special. Some of the main points incorporated are:
- The footprint of the house is 145 sqm, between that of the average Australian home (220 sqm) and the average UK home (75 sqm). It allows generous room sizes Australians are accustomed to while saving about a third of the average footprint size.
- Because it’s in Melbourne where about 90 per cent of energy is used for heating and 10 per cent for cooling, all living spaces and bedrooms are orientated to the north to maximise solar heat gains. Service zones to the south create a 'thermal buffer'.
- Lots of thermal mass (concrete slabs, reverse brick veneer construction, etc.) store heat and release it later, helping level out temperature fluctuations.
- Eave overhangs minimise solar heat gains in summer (steep sun angle) and maximise them in winter (less steep sun angle).
- Active sunshading is enabled via sliding timber shutters upstairs, a retractable awning and external pull-down louvres downstairs.
- Cross ventilation helps flush out hot air.
- Ceiling fans help reduce the need for airconditioning.
- Triple-glazed windows and high performance insulation minimise 'energy leakage'.
- Forestry Stewardship Council-certified timbers and sustainably forested local timber cladding minimise the carbon footprint and adding a contemporary, warm feel.
- Concrete with recycled crushed aggregate is eco-friendly.
- A rooftop swale/rainwater garden provides water attenuation and filters the water before it enters the water tank for use in the laundry, toilet cisterns and garden taps.

I guess the important thing is, that the building works as a whole. We created the thermal energy model at a very early stage in the process, and that helped to inform the design a lot. Generally, we approach sustainability from a holistic point of view, taking into consideration environmental, social and economic benefits that we require our designs to deliver. We also endeavour to create 'healthy and happy family homes' which means avoiding and/or dealing with potential off-gassing of any levels of toxicities - hence the low VOC (volatile organic compounds) or no VOC approach - and creating a loveable atmosphere through material selection and design.

Could you explain how the house also produces energy?

Being a 10 Star energy rated home means the house requires next to no energy for heating or cooling for the average resident. Part of that is that the house 'passively' produces energy, for example by using the sun rays to warm up the concrete slab. Running energy efficient appliances will then help to minimise other energy required. This in turn means any additional active measurements take the house very easily from energy neutral to energy positive. These are simple techniques that are readily available in Australia at the moment, such as solar hot water systems with gas booster, Photovoltaic system to generate electricity, and more. In other words, with this house you can have a green lifestyle that doesn't require you to abstain from anything and it looks really cool too!

I am personally also a fan of other, more advanced 'green techniques' like geothermal heat pumps, which are most efficiently used with a full ventilation system with heat recovery, phase changing materials, co-generation, and so on, but generally these are all still very expensive in Australia and therefore are often financially viable only on a larger scale - so in this house, we've left them out of the equation.

What are the benefits to the family and the environment of living in a home like this?

Charging your energy supplier rather than having to pay them, would be one of the most obvious benefits to the family! Having a well balanced temperature without having to rely on artificial heating or cooling another one. The house creates a healthy indoor climate, no risk of mouldy areas or dust being blown around through ducted heating, very low levels of toxicity through specifications. Using E0 plywood rather than standard E1 MDF for joinery means a huge reduction in formaldehyde emissions. There are no VOC paints, natural Sisal carpet and so on. The family in this residence has not only a greener lifestyle but also a much healthier one. For the environment, the specification of sustainable materials is as important as the high performance building envelope, so the house doesn't require heating and cooling in the first place.

The smaller footprint not only benefits the energy usage and star rating, but it also reduces land use, freeing up valuable garden space for growing vegies and fruit, which in turn helps reducing the environmental impact from commercial production, packaging and transportation of food, which is often not considered by architects and designers. Alternatively, in inner-city locations houses this size would actually allow a much higher density, thereby reducing traffic and sprawling cities.

Social sustainability aspects that form part of the design are also huge benefits to the family. Amongst them are the re-interpretation of a traditional verandah space, allowing for a nice protected spot to sit to interact with your neighbours, helping to create communities. The internal flexibility of the upstairs spaces - with flexible joinery walls - allows for different bedroom configurations that can adapt to changing situations of the residents. The family can therefore stay in the house for longer, getting more benefits out of their gardening work and again improving local communities, which are currently absent in many Australian suburbs."

Do you think design like this will become more popular in the near future?

These spaces and designs need to be very well considered, and if you want to do a house like this you need to make sure that your consultant will look at the whole picture rather than just considering particular parts and/or some eco features. You also need to be confident that the architect or designer fully understands the consequences of what they are proposing. When working with high performance insulation in moderate climates it is really important to include vapour barriers and breather membranes in your walls and roofs, rather than just sisalation foil, to make sure the building won't fail over time.

So, yes, I am sure these designs will become more and more popular, we are already getting a rising number of clients asking for a truly sustainable building like this. If a building can be funky and modern and warm at the same time while allowing you a really green lifestyle, then most people will adopt that readily. At this stage, cost is the only possible hurdle on that - but having said that, one of the underlying principles of the design is 'Build smaller - build better'! In other words, if you look at what you actually need in terms of space and focus on that, then you will be able to build that space to a much higher quality than you would otherwise. And as an aside, you are using less materials which means less embodied energies.

While Melbourne Design Studios generally do individual and personalised designs for each of their clients, they are currently looking at making this house commercially available for a wider group of people. So if you really like it, visit their website, or hit the 'like' button on their facebook page to stay in tune with the latest news.