Their houses may also be carbon negative over their lifetime, with Auckland University finding an 180sq m home made with their system could sequester five tonnes of carbon, when a traditional home would generate 50-60 tonnes.
"It's completely unheard of in New Zealand," Heller said.
He started his business after moving back to New Zealand from London several years ago and realising he couldn't afford his first home, and that the local housing market was poor value for money.
He won a place in The Settlement's Start Up incubator in 2019 funded by Hutt City Council, and began coming up with a strategy for home building that allowed all the building components to be interchangeable.
This meant the building could be modified and reconfigured over time with relative ease and very little waste.
Customers could build a one-bedroom home and simply add rooms as needed, he said. People could even sell components of their home secondhand on Trade Me.
One key difference is the lack of Gib plasterboard, a particularly convenient absence amidst the current national shortage.
Gib, which makes up the vast majority of plasterboard in New Zealand, has been almost impossible to source, leaving a long delay on building projects.
"We're using a plywood interior lining. It's a pre-finished plywood, which means we don't have to coat it, we don't have to paint it, which means we've actually eliminated most of our wet trades on site."
They also use screws and bolts to fix the components, rather than nails or glue, meaning the house can be disassembled and reassembled, rather than needing demolition to renovate.
The mass scale and repeatable system also meant price points would decrease.
The business' first house is being built offsite and has taken about six weeks. Soon it will be sent to Cromwell where it's expected to take two weeks to assemble before it will be ready for the owners to move in.
Customers will be able to use Flexi House's online tool to design and order the house they want.
Heller said he has had discussions with Kāinga Ora about doing projects with them.
"We would build them a few houses and measure different aspects of our build compared to traditional housing.
"If the government really wants to scale houses and build them fast, they need to mass manufacture. This is a solution to the issues we are currently grappling with, and they aren't going to go away anytime soon."
Heller said it was frustrating to see homes being built cheaply and "to bare minimum code".
"We are in desperate need of better quality homes due to having some of the highest asthma rates."
Kāinga Ora construction and innovation general manager Patrick Dougherty said they had completed about 6400 public and supported homes over the past three years.
"We currently have almost 4700 homes contracted or under construction. In addition to this, we have about 6000 homes in the pre-construction phase that are expected to be delivered over the next two years," he said.
"Offsite Manufacturing (OSM) isn't new to New Zealand, or to Kāinga Ora. Around 15 per cent of public homes under construction or in design within our build programme utilise OSM techniques."
OSM had a role to play in addressing the home shortage and had numerous efficiency benefits, he said.
"We've proactively reached out to OSM suppliers around New Zealand.
"If there are other suppliers of new and alternative products out there who believe they have capacity, we'd love to talk with them."
Ministry for Business Innovation and Employment manager of building performance and engineering Dave Gittings said OSM had potential to lift productivity and reduce building costs and delays.
"This is why the Government has consulted on and introduced a new voluntary Modular Component Manufacturing certification scheme that supports this type of construction."
Modular component manufacturers will be able to apply to be certified after new regulations commence in September 2022.
