Australian Passive Solar Home

When designing and/or building an energy efficient house, be wary of fads and fashions.

Many people working in the industry are heavily invested in promoting the latest and greatest things. In short, that’s how they make their money. Traditional passive solar technology and ideas are simple and longstanding.  They are not cutting-edge, ground-breaking, innovative breakthroughs.

I can pick up a book on passive solar design from 50 years ago and see all the fundamental ideas explored. The only real change worthy of note has been the development of effective energy modelling software – and that is indeed a very major improvement over hand calculations and rules of thumb.

I have found that professionals in this space seldom want to discuss basic ideas like thermal mass, orientation, fibreglass insulation, interior house zoning – or even the interior temperatures at which different people feel comfortable. Instead they’d rather discuss heat recovery ventilation, minimising thermal bridges, testing airtightness, internal air quality, creating new building regulations, training tradespeople in new skills, the development of new materials, and so on.

I am not suggesting that these things aren’t worthy of discussion; what I am saying is that these are the cream on the cake. Let’s get the cake right first before worrying about its topping.

The corollary of this is that many people thinking about building an energy efficient home see all the complex stuff being discussed and promoted – and think that’s what is most important. But nothing could be further from the truth!

While researching for our house, Georgina and I saw it happen many times – and to be honest, we found it quite disheartening. The process seemed to be this. (1) A person was interested in building an energy-efficient home. (2) They had some sound ideas (e.g. orientation) but also some gaps in their knowledge (e.g. thermal mass).  (3) They went to an expert… and here the story is not clear, as no homeowner would explain to me where it started to go wrong. But in short, it appears that at this point, things suddenly became complex and expensive.

“Oh what you need is a sealed house and mechanical ventilation.”

Or “Hebel blocks are your answer.”

Or “Of course you need these ultra-high efficiency windows.”

One owner, describing to me this stage in his house building project, shrugged resignedly and said, “At that point of course the price of the house went up 30 per cent.” 

I also suspect that some designers and architects have more than one eye on winning design competitions. As an architect friend said to me, “Residential architects are always about self-promotion. That’s how they get clients, and clients are their whole business.”  Otherwise, I find it difficult to explain why certain decisions were taken that were, on a cost/benefit basis, so poor.

Of course there are some approaches that, depending on your criteria, are justifiable. If you want a home with low embodied energy, some materials will be more expensive. If you have a difficult site, to gain good passive solar results may indeed need very expensive windows. I recently saw wall insulation made from recycled denim. If you want to use such a material because it is a natural fibre, it will cost you more (and likely give poorer results) than fibreglass – but yes, it will use a natural material. 

But what we have now seen many times are people who have ended up with a house that cost a lot, and yet has only adequate – not excellent – thermal performance. Why? I think the number one reason is that the focus on the fundamentals was lost during the design and development process.

The fundamentals?

• orientation
• thermal mass
• insulation
• shading

These are the criteria against which all design and build options should be assessed.