Meet the eco-housing standard that demands attention to detail.
HOUSEHOLD energy use accounts for nearly one-fifth of the Victoria’s greenhouse gas emissions. And while our residential efficiency standard will rise to six stars next year, we’re still lagging behind many parts of the US and Europe.
If you want your home to stand above the rest, you could take your cues from one of the most rigorous standards of all: passive house.
Founded in Germany and Sweden in the 1990s, passivhaus (in the original German) is a voluntary standard for building energy efficiency. It aims to create homes that don’t need any conventional heating – even in the bitterly cold winters of northern Europe.
Christoph Begert, from eco-consultancy Sustainable Built Environments, has studied the way passive house principles apply to Australian homes. He’s speaking this week at RMIT’s Green Building and Design Conference.
The concepts involved are nothing new: they include all the usual suspects of passive solar design, such as good orientation and shading. But they’re combined without compromise. “The rigor of the requirements is what makes passive houses successful,” he says. “They effectively decouple the internal climate from the external climate.”
Mr Begert, originally from Germany, says the criteria are such that the power of a hair dryer is sufficient to heat a 100-square-metre home. “The houses often end up not requiring any heating system at all, because a few people and electrical appliances produce more heat than a hair dryer does.”
There are three crucial elements of a passive house. Firstly, the homes are ‘super-insulated’ to two or three times the level required here. Windows are usually triple glazed.
Secondly, they’re sealed like a snap-lock bag. Gaps and cracks must be comprehensively stopped, to the point where the air change rate is less than 0.6 of the volume of the house per hour. That’s up to 30 times less than the rate in a typical Victorian home when a strong wind is blowing.
Finally, to make sure there’s plenty of fresh air inside, passive houses have mechanical ventilation systems. They often use a heat exchanger, which captures the heat from exhaust air to keep the temperature constant inside.
The result, according to Mr Begert, are homes that rate beyond nine stars.
He has examined the performance of passive houses in Spain and Italy and compared them to conditions here. “From our analysis, we found that Melbourne has a very good climate for passive houses,” he says.
Because of our warmer climate, the insulation need not be so extreme and windows only double-glazed. Good shading is compulsory to avoid baking in the hotter months. “Passive houses perform extremely well during winter, but you have to be sure you don’t make an oven during summer,” he says.
In Europe, homeowners have found that building a passive house costs between 10 and 15 per cent more than a standard home. But with little or no heating and cooling, ongoing expenses are low.
The theme of the RMIT conference is “Greening the Existing Building Stock”. Mr Begert argues that the passive house principles can be applied to renovations as well as new homes.
“You don’t renovate your house very often. When you go to that effort, it’s worthwhile getting it right. You’ll spend a bit more money, but you get really good value for it.”