"There's so many business opportunities we just don't know what to do next," Mr Iliffe said.
EcoBuild Developments started in 2010, with the two directors researching green building methods. Mr Iliffe was influenced by his time in Europe and they decided on the German Passivhaus method. They trained in it and became certified consultants.
Passivhaus involves a highly insulated, airtight building, with a heat-transferring ventilation system that replaces all the air in the house every three hours. The houses are more expensive than average to build, but they need 80 per cent less heating. The EcoBuild directors called their version of a Passivhaus an eHaus.
The first eHaus was a showhome built in Webster Pl on St John's Hill. Mr Iliffe's family has been living in it for the last year. He said they spent a total of $130 on heating - for pellets to fuel a wood burning stove.
The house has just sold at the asking price of $569,000. The Iliffe family is moving out and looking to build another eHaus to live in.
A three-bedroom, two-storey private eHaus (pictured) is going up for clients in Brunswick Rd.
It was designed by Wanganui architect Duncan Sinclair and will be partly finished and open to the public for a day in November.
Another house being built in Marangai is an eHaus Zero. It will make all its energy on-site, through solar water heating, photovoltaic panels and a domestic wind turbine designed for New Zealand conditions. Apart from the carbon emitted in the building process, it will be carbon zero.
The other local eHaus project is for commercial clients who are earthquake strengthening and improving a building in Taupo Quay.
The Wanganui men act as consultants for builders in other centres, and have trained builders in New Plymouth, Wairarapa and Rodney to build to eHaus specifications. In Wanganui Mr Brown's company does the building, and a Palmerston North team will soon be trained.