This is a question I do get asked a lot. Sadly, there is no simple or straight forward answer to it. And no matter who you ask you will get a very different response.
Does it cost more than building a normal home? Again, not an easy answer.
Does it cost more than a home from a volume builder? Yes.
Does it cost more than a highly energy efficient home following passive solar design principles? Yes and no. Will elaborate shortly.
Does it cost more than a custom designed home with a high-end builder? Not necessarily.
I know, what I’m saying here does not make much sense yet but please bear with me.
I can assure you even a lot of people in the industry are debating this exact same question. And the biggest question of all. How can we make passive house more affordable? This is definitely one of our main drives.
But back to the current build cost.
Please note, the numbers below are just a rough guide and can vary a lot.
A project home can cost you something in between $1200 and $1400 per m2.
An individual home can sit between say $1800 and $2500 per m2.
Having said this there are lots of builders out there that won’t even touch a project for less than $3500 – $4000 per m2 even without taking energy efficiency into account.
When it comes to passive house construction, Australia is still in its baby shoes. Even though there have been quite a few homes certified or built according to the passive house principles, there isn’t much data yet available about the build cost. On top of that, everyone is still trying to figure out the most effective building methods. There is still a lot of trial and error happening. Depending on who you talk with they will tell you that you will need to allow $3500 per m2, others are quoting $4500 and above.
However, I’m not quite willing to accept this. I do believe it must be possible to design and build a passive house for less even though some think I am a bit crazy?
At least in my opinion, the build cost depends on quite a few factors:
- Size of home
Actual house area, size of driveway, outdoor living, decking, paving etc.
- Site access
Easy or difficult site, sloped or flat site, inner city – tight sites
- Complexity of the design
This has nothing to do with the size of the home, but whether the design and layout is straightforward or has intricate / complex build elements
- Level of finishes and materials
Using off the shelf products, standard colours and materials versus custom made
- Project location
Remote locations can add to the build cost, sadly same applies for a Toorak or Brighton postcode.
- Construction materials
Off the shelf products rather than custom made. Some builders might also charge more if they are not familiar with a product
- Choice of builder
Builders can charge very differently. A highly experienced and established builder would also have a higher profit margin than a young / new builder, that has just started out his business. Like I explained before, some builders won’t build a house for less than $3500 per square metre, no matter how much you try to simplify your build.
Obviously, you cannot influence some of the above factors. You can’t make site access easier, or you can’t change the slope of the site. However, with a smart but simple design you can overcome some obstacles.
I actually do believe that it can be cheaper to build a passive house than a highly energy efficient home following passive solar design principles. A home following passive solar design principles relies heavily on thermal mass. Meaning when you are building on a sloping block you have to spend quite a lot of money to get your concrete slab working.
Whereas when you are building a home according to the passive house principles, thermal mass is not important. You can build your house on a timber subfloor, following the slope of the land, saving quite a lot of money, which can then be spent on better performing windows.
I’ve explained more about potential cost savings when building a passive house in my blog post: “How building a certified passive house can be cheaper than building a regular energy efficient home”.
BUT there are quite a few factors that can be influenced:
- Coming up with a compact floor plan, that feels spacious but minimises unnecessary circulation space
- Having a simple yet beautiful build form, with a simple roof structure to minimise cost for steel or other complex elements
- Using off the shelf and standard colours and materials. I’d personally rather get a flat pack kitchen or save on my tiles than skimp on the windows or the insulation (remember, you might update your kitchen or bathroom in 15 years, but you will never ever touch your windows or insulation)
- Use simple yet efficient construction materials (avoid using too many different types)
- Get a builder on board early in the process. One that is not only keen on building you the most beautiful energy efficient home, but is also willing to explore options to build your house the most cost effective way.
- Try not to reinvent the wheel. Use standard construction details and certified passive house components to make the design and build process easier.
Another quite interesting factor is that a lot of builders don’t know how to quote a simple design. What do I mean by that?
Most builders are used to highly complex and beautiful architectural designs with lots of intricate details and custom built-in joinery and finishes throughout. They know how to quote and allow for those items. But when you come with a very simple structure and flat pack kitchens or vanities they often don’t quite know how this will influence their labour and build cost. This makes it hard for them to predict how much savings there will be compared to the other custom designed homes they are building.
As most of you might know, we are currently in the process of getting a building permit for my very own passive house, the 20 / 20 house (please check out my blog if you want to follow our journey).
Our house is 213m2, and we are aiming for a build cost of under $600,000. Which would equal to a cost of about $2800 per square metre. Like I said, quite a few people think this is not achievable, but I am determined to prove them wrong. And find out how much money can be saved by keeping the house simple by sticking with off the shelf products where possible.
We are on a mission to find ways to design and build affordable healthy, comfortable and sustainable buildings.