The New Zealand house that hemp built

Hemp is turning a new leaf in Taranaki, with a house made of the marijuana-like plant featuring on tonight's Grand Designs NZ.

New Plymouth couple Greg Whitham and Gayle Avery wanted to build a rustic French farmhouse-style home for their extended family - and they wanted to do this using hemp.

But being one of the first hemp homes in New Zealand presented numerous challenges, with the results revealed on tonight's episode of the hit TV3 series.

Bales of hemp were imported from Holland for the build as it is not available in sufficient quantities in New Zealand.

"We wanted a material that is environmentally friendly and hemp fitted the bill," Avery said. "It is tough and durable, and costs about the same as using traditional building materials.

"Once the house was plastered inside and out, you could never tell the walls are made of vegetation."

The plant, however, contains very low levels of THC compared to marijuana. So if a hemp house burned down, none of the neighbors would catch a buzz.

"You would have to smoke a whole plantation of the stuff before you got high," Avery added.

For the episode, Grand Designs NZ host Chris Moller travelled to Holland to visit a hemp plantation.

"I couldn't believe the height of the hemp plants in Holland and the fields of them are enormous," he said. "I have never come across a home quite like this before, it is bold and ambitious."

The house has a few other unusual features.

The couple have shielded their home against electromagnetic frequencies - invisible radiation emitted by radio towers, cellphones, wi-fi and their own electrical circuitry.

"We later had the house tested and the electrical levels inside were minimal compared to outside," Avery said.