SAN FRANCISCO — As the builders of a 17,000-square-foot Newport Beach mansion batten down the hatches on the home’s insulation, a San Francisco startup is tempted to carry someone or something over the threshold in recognition of a landmark marriage between wool insulation and a stunning new residence.

“Why inject your house with fiberglass or foam when you can swaddle it in wool?” said Andrew Legge, founder of Havelock Wool, which is pioneering the use of wool in the United States as a natural building material. “There’s a sea change that needs to happen, and we’re looking at this new residence as the flagship of a whole new way to stay warm — or cool — in the home.”

One might forgive Legge his bullish enthusiasm, but this new mansion in the iconic Corona del Mar neighborhood is a milestone of sorts for his burgeoning company, which he launched two-and-a-half years ago after spending considerable time in New Zealand surveying its business landscape.

Once the province of sweaters, hats and blankets, wool is now making waves as a smarter, more compelling alternative to fiberglass and foam. England’s iconic Palace of Westminster recently turned to wool as its insulation of choice after a trial at Leeds University found the material significantly reduced heat loss.

Legge is attuned to such studies, and he’s leveraging them wisely. Proof is in the showpiece opportunity in Newport Beach. He’s proud to have landed such a deal. But he’s also quick to give credit where credit is due.

“The builder definitely played a role in us getting the job,” Legge admitted. “We had to convince the homeowner that wool was the way to go, and the guys at Corbin Reeves (Construction) were happy to make the recommendation.”

While working his way into the $16 billion insulation market has been challenging for the former COO of an investment firm in Southeast Asia, getting Corbin Reeves to go to bat for Havelock Wool was easy. That’s because unlike other types of insulation, wool requires no protective clothing for installation.

“Working with wool is kind to your skin, eyes and respiratory system,” said Steve Franta of Corbin Reeves Construction. “You could sleep in it if you wanted to.”

Wool also has the ability to naturally manage moisture, reduce noise and resist fire. Its environmental benefits are many, as well, starting with its source.

“Unless sheep decide to stop producing wool, we’ll always have a renewable and sustainable product,” said Legge, who holds an MBA in Finance from the University of Chicago’s Booth School of Business.

What’s more, wool requires no glues or bonding agents, can be composted when a dwelling is repurposed, and lasts longer than other mediums — except for foam, which may never break down, according to the Garbage Project.

The Newport Beach mansion’s owners believe investing in the age-old fiber is a smart decision. Despite the cost of wool — which is about the same price as closed cell foam and twice as expensive as the most popular form of insulation, fiberglass — they found themselves gravitating toward it for two sensible reasons.

“They wanted a natural fiber,” Legge said, “and they wanted something that could stand up to the moisture challenges that come with being right on the ocean. Wool ticks those boxes.”

With Havelock Wool’s biggest project nearly in the books, Legge is doubling down on efforts to increase North Americans’ knowledge of wool and its advantages.

It’s the kind of groundwork he believes will enable Havelock Wool to establish prominence in the insulation marketplace, which finally possesses a solution that jives with America’s ever-increasing desire to make resource-efficient choices.

“The bottom line is, you get what you pay for,” Legge said. “When cost differences stand out, we like to suggest that people at least wrap their bedrooms with the most environmentally friendly, non-toxic insulation available. This has made a real difference in our efforts. It makes the cost incrementally higher, but you get to experience the advantages in a space where you spend so much of your time.

“Those who see the advantages on an absolute basis are often happy to go ahead with the whole job, but what is most exciting for us is watching the repeat business continue to grow.”