Image: getty
Image: getty

ScienceFebruary 9, 2021

The house that climate built

Image: getty
Image: getty

Achieving our emission reduction obligations means changing the nature of our homes. Here’s how we can do that.

New Zealand’s homes need a refresh. Mouldy, leaky, cold homes that leach any semblance of heat to the outside world won’t cut it any more – if they ever did.

Aside from the health benefits, making homes more energy efficient cuts greenhouse gas emissions. Reducing Aotearoa’s emissions is front of mind after the Climate Change Commission released its advice last week.

The commission recommends the country should cut emissions from buildings, both residential and commercial, by roughly 28% by 2035 to meet its greenhouse gas reduction targets.

The commission’s roadmap is a little light on advice on how to do that in terms of the actual physical, built structure. Instead it emphasises the need to move away from heating homes with coal and natural gas.

But there’s a skyscraper-full of ways to make homes less bad for the planet, and ourselves. This is a rundown of some of those options, ranging from the obvious and easy to the downright weird.

Get real windows and insulation

Every view to the outside world is essentially a hole that precious heat seeps from. Make those holes better at reducing heat loss, or heat gain, and you’ve got yourself energy and emissions savings.

One study estimates that you can reduce energy consumption by as much as a third in existing buildings by glazing windows, adding insulation, plugging up gaps in ceilings and putting in awnings, blinds or trees on the sunny side of the house.

Another estimates glazing and shading reduces a building’s carbon emissions by 2.1% every year.

The extreme end of this is a passive house — one that’s super insulated, faces to capture the sun and is air-tight. A passive home could reduce emissions by 30% over its entire life (from sourcing materials, to transport, to final house) compared to a regular dwelling.

Pick materials wisely

Different building materials take a different amount of energy to make therefore affecting the amount of greenhouse gases they let off before they even become part of a house.

For example steel is made through an energy-intensive process that’s pretty much remained unchanged since the 14th century. Timber on the other hand is fairly cheap emissions wise to source and could actually store carbon. Keeping steel to an only-where-needed material and maximising wood use is one of the suggestions the commission makes.

The perfect combination of materials, according to a study from Singapore and China, is porous brick for the walls, windows made from low heat-emmitting glass with plastic frame, a flat roof, a raised floor with natural ventilation, wool or glass cotton insulation, and lots of shade.

Or you could go fully eco and use recycled materials, like the University of Brighton’s Waste House. It uses VHS tapes, DVDs and old denim as insulation, recycled wood as walls and bike inner tubes for sealing windows. No extra production energy needed.

Build up and a little out 

Since the country is in dire need of a few new builds, it’d be wise to consider what shape those take and how that affects emissions. Tall high-rises can fit more people per bit of land and might be able to trap heat better, but they also need more steel for support and extra structures like elevators.

A 2015 study weighed up these various factors and concluded that a four-story building with a centre courtyard had the lowest carbon footprint out of options including a 215, 58 or 16 story high-rise, smaller urban home or larger suburban home.

More people per area of land could also mean less distance between home and work, which would make taking a bike or walking to work easier, meaning more emissions savings.

IKEA-fy houses

The beauty of flatpack furniture isn’t the hours you spend figuring out how to put it together but its emissions savings. Pieces can be cut from materials in a way to minimise waste and, because it packs flat, more boxes of shelves or what have you can fit onto the same transport truck or plane, lowering the emissions per item.

Same idea goes for houses. Instead of lugging a bunch of two-by-fours to the building site and leaving offcuts behind, flatpack houses are partially preconstructed and then assembled on site.

One study compared the total greenhouse gas emissions for building a house the ol’ fashioned way on site and IKEA-style. They found that the flatpack method could be 30% more efficient.

Even if they’re not totally flatpack, just being savvy about not using more building material than is necessary could save around 18% in emissions, according to a UK report.


Cob houses are made from a natural building material, a mix of straw, sandy soil and a bit of gravel. Materials are usually sourced on-site (no or low transport emissions) and those materials have a low carbon footprint.

A cob house could generate around 30% fewer greenhouse gases over its life than a regular concrete house. Most of those savings came from the materials used, even though a cob house needs more of them.

The New Zealand version is whare uku, which uses harakeke instead of straw and has the added benefit of being low cost to build (around $150,000).

Dome sweet dome

Forget about hanging a picture on the wall but dome houses are a potentially carbon neutral housing alternative.

They look like little greenhouses but are made from ceramic tiles which can absorb carbon from the environment. Although the company that’s planning to make them doesn’t promise anything, they think that the ceramic plates could end up absorbing more carbon that it took to manufacture the house.

But their shape is their true selling point when it comes to cutting carbon. The domed roof maximises surface area, while keeping the same floor area. That means the domes naturally have double the insulation properties of a regular house with the same floorprint.

And when you’re done, just pop the tiles into an “emerging vortex wind technology” device or “tornado in a can” to pulverise them to remould into new panels or use as fertiliser.

Plus they look like cities of the future.

Keep going!