A Bay of Plenty tourism company is on a mission to make locally made hot tubs more environmentally friendly - with the help of New Zealand wool.

Outdoor Gravity New Zealand manufactures Zorb balls which have become a well-known tourist attraction in Rotorua.

But during Covid-19 when the tourism industry was flipped on its head, company general manager David Akers said they started looking at how to diversify the business - and saw an opportunity with hot tubs.

He said the materials used to make spa pools were unsustainable in the long run.

"We use hot tubs here on our Zorb site and we realised that when they come to the end of the life, you take the entire thing to the landfill, and it's a big, big product that ends up taking up a trailer and a half and just gets dumped," he said.

"We thought that's not very satisfactory, there must be a better way of doing it."

The company manufactured its own hot tubs featuring materials like recycled native timber, hemp fibres and wool.

After starting the one-year project last February, the company's $146,000 investment into the project was boosted by a further $97,000 from the Ministry for Primary Industries' Sustainable Food and Fibre Futures Fund.

The project was a pivot for the company during the tourism slowdown brought on by the Covid-19 pandemic.

"Throughout Covid, we were looking at some different things, seeing as tourism wasn't going terribly well," he said.

"And so we looked at the idea of making a more sustainable hot tub and spa cover as well, because spa covers can be made of polystyrene and spa pools can be made of plastic and all sorts of nasties in terms of the insulation."

The company was testing water temperatures in the tubs - comparing wool insulation with none at all.

Akers said so far the results had been positive.

"We're definitely getting a degree or two of extra warming from having that wool layer in there, which is great.

"A rough estimate in terms of how much that might save you in electricity costs, we're looking at something like $400 a year saved in electricity for the heating by having that wool insulating layer inside the hot tub."

Akers said with more testing needed in different environments, he hoped the spas could soon be scaled up and sold domestically and possibly even internationally.

-RNZ.