Passive building may seem like the cutting edge in energy-efficient construction, but its principles are far from new—and in an industry where the stakes are too high to take a chance on a fad, that’s a good thing. Fortunately for builders, people around the world have been using passive building to keep their homes comfortable for more than a thousand years. Why? Because they work, and free energy doesn’t go out of style.

Due to their highly technical requirements, today’s passive building programs can seem complex, but the basic premise is simple: Rather than heating and cooling a home with active systems that take energy to produce and run, and which are often expensive, passive building takes advantage of climate controls that nature provides for free—sun, shade, earth, and wind.

So how well does it work? According to the Passive House Institute U.S. (PHIUS), homes built to the institute’s standards boast savings of between 80% and 90% on heating and cooling costs compared to a traditionally built house—offering shelter from high energy bills, something virtually no resale home can offer.

And unlike active renewable energy systems, such as solar panels, which must rely on government subsidies to be cost effective, passive building has proven its ability to make a return on the initial investment.

"How you determine your incremental cost increase depends in part on your baseline," says Michael Hindle, principal at Baltimore-based INDRAlogic Architecture and a certified Passive House consultant. "If you typically use the cheapest windows and aim for minimally code compliant, then yes, it will be more expensive. But if you’re going to build a good house anyway, Passive House doesn’t have to add very much."

However, even compared to code-compliant construction, Hindle maintains that building to Passive House standards makes economic sense. He points to projects that have been done for as little as a 2% cost increase yet still deliver the promised 80% to 90% savings on heating and cooling. According to case studies, he says, a typical Passive House pays off in six to eight years. "It’s comparable to other pretty moderate energy-efficiency standards such as Energy Star, but the payoff is a lot higher."

The cost also depends on the region, says Matthew Howard, president of M.C. Howard Builders Corp., in Two Harbors, Minn. Because the energy savings are fueled by reliance on the elements—and the mix of what nature provides changes dramatically around the country—what a home will need to be able to draw on passive energy savings will change based on its location and climate.

For those looking to earn a Passive House label, a home must meet a rigid set of requirements, including a blower-door test reading of no more than 0.6 ACH at 50 pascals; an annual heat and cooling requirement of no greater than 4.75 kBTU per square foot per year; and primary energy use of no greater than 38.1 kBTU per square foot per year.

Despite the hard and fast standards, "it is not a prescriptive methodology," says Hindle. "It has very precise targets, but it's not prescriptive in how you get there."

To help guide builders through their options, the Passive House Institute offers the Passive House Planning Package (PHPP), a 30-page Excel spreadsheet that calculates the impact of individual elements on the home’s overall performance, guiding builders to the standards the home needs to meet for certification.

But for those builders not yet ready to make the full leap, there are still ways to cut down on the heating and cooling necessary to keep a home comfortable. Hindle recommends four steps builders can take to harness some of the power of passive principles.