Houses built from shipping containers have been on the radar for some time now, but we don't usually associate them with innovative architecture.

They may have clever storage solutions and maximise space well, but usually a shipping container house looks like what it is – a container with windows and a door.

But this could be the decade of a new type of container house made from prefabricated, custom-designed modules, says Bernard Mager of SmartWay Homes in Nelson.

​Mager spent 18 months sourcing an overseas manufacturer (in China) for his shipping container housing, and is now selling his houses internationally – the last two builds before Christmas were shipped to Bermuda and Mexico. Others have gone to clients in Europe, Asia, USA, Canada and South Africa.

One project, about to be built in Ruby Bay, was considered for Grand Designs NZ, but the timing wasn't right.

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Another container house is on offer in Nelson, with a concept plan that shows such homes can be highly architectural. The property, which is being marketed by Martin Wilkie of Ray White Richmond, could accommodate a 120 square-metre house built using five containers, one of which stands on end to provide a tower element.

"People may think of old containers sitting in someone's backyard, but it's not like that at all," says Mager. "We don't use second-hand containers off the wharf – we use new ones straight from the factory that have never been used to carry chemicals or any other item."

The containers are greatly modified and insulated with a spray foam that hardens, increasing the structural strength of each house. "They can easily withstand an earthquake to 8.5 and even 8.6 magnitude, and the insulation not only regulates the temperature, but also the noise," says Mager.

But, it's also the cost differential that is turning heads. Mager says just before Christmas he did a quotation for a potential client in Raglan. "A local building company quoted $460,000 for the project and our quote for the same house (using containers) was $240,000 – near-enough half the cost."

​Mager says his company is usually "about 40 per cent cheaper" than more traditional construction for the same size house. "In my opinion, people end up with better-quality homes (using this method) than those made from a few sticks of pine with chipboard next to it."

"We can fit high-quality materials, a designer kitchen and underfloor heating if that's what people want, but the basic concept is a lot cheaper."

The company's homes are built to meet or exceed the New Zealand building code. The houses are prefabricated, shipped to New Zealand and can be erected within a week.

Grand Designs NZ has already featured a container house – in the second series in 2016. Joyce Wee and David Fitzmaurice of Christchurch sourced used containers and doubled the size of their house (20 containers) during the build, prompting Grand Designs presenter, architect Chris Moller to wonder, "What were they thinking?".

Not surprisingly, they almost doubled their $450,000 budget, and were not completely finished when the programme screened. They also provoked comment on the look of their house, which Moller thought looked more like a warehouse. The containers were left unpainted on the interior.

A year ago, Fitzmaurice said the open-plan layout was working out exactly how they envisaged things right back at concept.

"Initial concerns in design around moisture issues, have been shown to be a non issue because of the open space. The interior is actually a very dry environment. Power bills are very low for a large house."

Brenda Kelly of IQ Container Homes has even lower power bills – her 45 square-metre container home, the first 8 Homestar container house, has solar panels that generate enough power to meet her needs. Excess power is sold to the national grid and in return, the electricity can be "bought back" to be used at night when the solar panels are not activated.

And Kelly has a ready answer for people who like to do cost-per-square-metre comparisons: "I say, don't compare," she says. "People need to scrap such comparisons. I try and educate my clients to help them get out of the mindset of pricing a house on a cost-per-square-metre basis. With a small home you still have the kitchen and bathroom costs, which can't be offset by large, empty rooms that help to bring down the cost per square metre.

"I tell people to look at the functionality, look at the overall cost and look at the longevity – the running costs over a lifetime."

In the meantime, Wilkie is marketing the Nelson property with the concept plan, which he describes as a "very interesting concept". More than 37000 people have viewed the listing in the past three weeks.

"We have had a lot of interest in the whole idea of a container house," Wilkie says. "People are wanting more information, and we are also stressing that these are substantial houses built to code, and not something you can pop up for $30,000."