When Rob Harmon had an energy audit done on his home a few years ago, he discovered that 43 percent of the heat from his garage-based furnace was getting lost between the garage and his house.

A committed conservationist, he realized that if he were to lighten his carbon footprint, a message he’d preached for years, he had to do something about the energy waste in his own house.

“The greenest unit of energy available to us is the one we don’t use,” he noted.

But perhaps most important, it wasn’t particularly hard or costly for Harmon to address the problem. The air ducts under his house that took the heat from his garage to his home were leaky and uninsulated; so last October, he spent a small amount of money taking care of the problem — funds he expects to recoup in a few years of reduced energy costs.

Now, said Harmon, a Vashon resident and the chief innovation officer for Bonneville Environmental Foundation, many Islanders can do what he did and take a closer look at what’s happening to the resources within their own homes.

Thanks to a recent eight-week course taught by Islander Dan Auer at South Seattle Community College, three Vashon residents have been trained to conduct home energy audits using the latest technology, the best gadgets and a growing understanding of building science to determine what happens to virtually each BTU in a person’s house.

Michael Laurie, who has a business focused on water conservation called Watershed LLC and has long been in the energy conservation business, will add home audits to his list of conservation services. Charlie Rogers has started a new company, Habitat Home Energy Audits, now that he has completed the course; he and Laurie will often work together, he said. And Eddee Edson is looking to work full-time teaching about home energy use and has already begun working with local grassroots efforts on energy issues.

It’s a profusion of resources on an Island that only a couple of months ago had very few, Harmon noted. And it’s a significant step on Vashon, where the housing stock is notorious for its draftiness and less-than-stellar craftsmanship.

“If people care about climate change, we now have people on the Island who can help us figure out what we can actually do about it,” Harmon said.

“Earth Day,” he added, “is all about how human beings interact with the planet. What better way to heal that relationship … than to reduce the amount of needless energy waste in your house. It’s on-the- ground action.”

What these three Islanders have been trained to do is figure out — in a nutshell — how “leaky” one’s home is. They use a variety of means, though the most significant tool in their tool chest is what’s called a “blower door” — a piece of nylon fabric that covers a doorway, leaving room only for an industrial-sized fan that blasts air into the house.

That blast forces air out of the house, and as it gets replaced, the auditor walks through the home, literally feeling where the air is coming in. An infrared camera — a $4,000 tool that Rogers and Laurie plan to rent — also enables auditors to create a map of a home’s energy leakiness.

The problems they find with these tools can often be easily fixed. And using sophisticated software from the building science industry, they can even calculate how long it will take for the homeowners to see a return on their investment in the form of smaller energy bills.

Rogers, 25, recently demonstrated how these tools and his training can be put to use in a building. A resident of Vashon Cohousing, he audited the 3,000-square-foot common house that serves the community and found several problems that make the structure “astronomically off the charts” in its energy consumption, he said.

Some were seemingly minor; rock rimming a large fireplace in the living room, for instance, was not tight against the floor, creating small openings directly into the crawlspace.

Others were significant. By using the blower door and detecting air movement, he found out that the first floor in the three-story structure was quite leaky. When Rogers went down into the crawlspace to investigate, he stuck his arm up through the insulation and found a nearly six-inch cavity between the insulation and the subfloor. A layperson likely wouldn’t notice the insulation problem, Rogers said. In fact, most homeowners would be happy to see insulation, held securely in place by string zig-zagging across the floor joists. But a problem like this one could suck a lot of heat out of the building, he said.

“It’s like wearing a sweater that doesn’t touch your skin.”

Laurie, a veteran of conservation with 25 years in the business, said he’s struck by the power of these tools to illuminate what’s happening in a home. During the course of the eight-week training session, he said, he and his classmates went to 14 homes, all seemingly well-built — and all, it turned out, very leaky.

“It was not obvious to the untrained eye,” he said. “They all looked like good quality houses.”

Edson, who took the course after getting laid off from Washington Mutual, decided to direct her training toward her own home — and has reduced her energy consumption by 75 percent, she said. The changes she made were relatively minor, she noted — like using her gas fireplace less (she was losing a lot of heat through the chimney) and getting more heat into her kitchen.

“It’s an analysis,” she said. “It’s building science.”

Janie Starr, an Islander who has worked extensively on energy issues over the past several years, said this kind of home energy conservation is at the forefront of what needs to happen to make Vashon a more sustainable place.

Solar is sexier, she said. It’s much more exciting to see photovoltaic panels on a house than well-caulked windows or insulation that’s properly installed.

But Starr, a strong advocate of alternative energy, said it makes little sense to put solar panels on a home that is inefficient.

“It’s an area where we’re behind on this Island,” Starr said of home energy conservation. “I think we need to catch up.”

“It’s exciting to have these three people trained and certified on the Island,” she added. “They come in with all this equipment and figure out where the leaks are in your house. And then you get the caulk gun out. And it’s not an expensive tool, the caulk gun. These are not complex solutions. But they can make a world of difference.”