What the Heck Is a Carbon Positive House?

Now this is a zero energy house. (Photo: Bruce Damonte for Zero Energy Building Consortium) .

It's a lovely thing, the little prefab sitting in a Melbourne square, designed by Archiblox and called Carbon Positive House. Matt Hickman introduced you to it. Dwell calls it "the world’s first carbon positive prefab house" and claims that it produces "more energy than it uses." On Sploid, the post is titled "I would totally live in the world’s first carbon-positive house." But it made me wonder: What the heck is a carbon-positive house?

archiblox house carbon positive house
It's carbon positive — I'm positive. Tom Hall for Archiblox

The website for Archiblox, the prominent and successful prefab builder in Australia responsible for the abode, notes that “The CPH has moved beyond carbon zero by making additional ‘positive’ contributions by producing more energy on-site than the building requires.” Oy, now I have to figure out what they mean by carbon zero.

The whole nomenclature is confusing and intimidating. I have heard net zero energy, net zero carbon, carbon neutral and zero energy building. In fact, the Australian Sustainable Built Environment Council set up a task force to figure out definitions and came up with a whole pile of different categories:


To make it all more confusing, in North America and the U.K., they tend to use zero-energy rather than zero-carbon; they are not really interchangeable, but there you go. In a brochure for the Archiblox house, the builders note:

A Life Cycle Assessment has been carried out on the proposed design, calculating the carbon emissions due to materials’ manufacture, materials’ transport, building material, building maintenance and building operations. The boundary of the assessment includes the building foundations, floors, walls, roof, internal finish, external finish, services and basic fittings.

The implication I read from that paragraph is that they did indeed build what is defined in Australia as a carbon positive house that takes into account all of the embodied energy built into the house during its construction, and that the house generates enough excess power to compensate for this over the life of the building. And given that it is an Australian proposed standard, it may well be the world’s first.

section through carbon positive house
Section through a very clever and green prefab,. Archiblox

One certainly cannot complain about the design of this prefab — it has everything going for it, from earth sheltering, careful solar design, low embodied energy insulation, photovoltaics and solar hot water, a green wall. It is a great model for green building, and I hope they do very well with it.

zero energy house another view
Zero energy house is built on a tilt. Bruce Damonte for Zero Energy Building Consortium

But it's not the world’s first carbon positive house or the first carbon positive prefab house if you ignore the Australian term and look at the North American or European equivalents, which are truly confusing. There are lots of houses that have achieved the same thing. The most interesting one is the Zero Energy House in Norway, which not only generates more energy than it needs, but has enough to power a car and will, over the life of the house, produce enough excess energy to pay back the carbon debt of all the embodied energy it took to build the house. Most of the prefabs built as entries for the Solar Decathlon meet these criteria.

net zero energy

It's really astonishing how complicated this has got; it’s no wonder that people throw up their hands in confusion, and no surprise that there are such dramatic headlines. Next, we will look at the meaning of net zero, and why it really is not only confusing, but also not very helpful.

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