One evening last winter, I parked at a big box store near Boston. I’d never met this Jim person – didn’t even know his surname. But he’d texted me particulars of his sports utility vehicle. I found him parked under a security lamp. I pulled out three twenties, a ten, and a five and fanned them out in my hand. He pocketed the cash, slid my purchase out of the rear hatch of his SUV, and helped me load it into my car.

We shook hands. Deal done.

Thousands of these transactions occur daily, mostly through web marketplaces such as Craigslist. Climate change experts look forward to more and more like them.

For far less than I’d have spent at a lumberyard, I’d bought a used walnut newel post – the sturdy upright that holds up one end of a stair rail. I drove it home, crow-barred out my house’s wobbly rotten old newel post, and bolted in the replacement. Jim had told me he spends his working day prying out hardwood flooring, kitchen cabinets, mantelpieces, and other parts of houses slated for demolition. I’d given him part of his day’s pay.

Yard sales + ‘estate sales’ = CO2 emissions reductions

It’s not just the frugal who re-use construction materials – and clothing and household goods; it’s a national pastime, for many a passion or a weekend ritual. All sorts of people prowl thrift shops and used bookstores, pass weekends browsing house sales, yard sales, and self-styled “estate sales,” and repurpose strangers’ and neighbors’ trash. In New York City alone, Salvation Army stores sold 1.8 million articles of used clothing, 140,000 books, 140,000 pairs of footwear and 9,000 games in a recent year.

But far more could be saved from the trash, especially apart from small consumer items.

Anne Nicklin, executive director of the Building Materials Reuse Association, which represents suppliers of used construction parts, says that only a “a very tiny percentage” of useful items currently is salvaged from building demolitions. Times are changing, though, she says.

Governmental officials, mostly at the municipal and county levels, are discovering that reclaiming stuff from torn-down buildings helps them conserve landfill space and avoid the economic and environmental downsides of trucking waste to far-off disposal sites. “They realize that they have a problem and that this is the best available solution.”

Re-use has many benefits, not just for local administrators with limited room in dumps. For instance, when salvaged materials find new uses, less ore is mined for metal, less oil refined for plastics, and fewer trees felled for lumber. Jim, who sold me the newel post, proclaimed proudly that it makes both economic and environmental sense. “Instead of somebody paying 3,000 bucks for a brand new set of kitchen cabinets, for $400 or $500 they get a perfectly usable unit. And it gets a second life.”

Re-use saves a lot of energy, avoiding the attendant CO2 emissions. First, obtaining and then processing virgin materials for new stuff uses energy, and it takes more energy to transport and re-transport things. Moreover, by cutting back on disposal, re-use reduces another large source of greenhouse gasses. Organic wastes, such as cotton cloth and wood, rot when buried, emitting methane – a greenhouse gas more powerful than CO2. Avoiding disposal also cuts back on the amount of poisons spewed into the environment, as dumps often pollute groundwater, and incineration creates toxic ash.

The case of the Vermont home deconstruction

Not so long ago, four workers in hard hats parked by an abandoned ranch house slated for demolition in Burlington, Vermont. Normally they’d have smashed it with heavy equipment and trucked the rubble to a landfill.

In the U.S. most unwanted buildings are disposed of this way. Crews each year ship about 80 million tons of concrete, 35 million tons of wood, and four-million tons of steel construction debris to dumps. Only metal is routinely salvaged, and only about one-third of that is saved.

But these Vermonters were a deconstruction, not demolition, crew.

For three weeks the workers painstakingly took apart the old house. They unbolted and sawed off plumbing fixtures, pulled out pipes and wires, unscrewed doors, pried off plywood decking. Finally, they unhitched the studs, joists, and trusses that had held the structure up, leaving behind only a bare, clean foundation. Monitoring their work were two undergraduate students working for Vasil Diyamandoglu, a professor of civil engineering at City College of New York. They inventoried and weighed each item.

The students counted 16 kitchen cabinets, 10 windows, 12 doors, and several large appliances, and trucked them to a nearby used-building-parts store. They also tallied several tons of sound wood and recyclable metal, also shipped-off for re-use. Resale value of salvaged materials brought in about $7,000. All in all, counting also disposal costs and labor, the deconstruction cost about $12,500 less than a standard demolition.

Looking at the benefits beyond this lowered cost, Diyamandoglu and Lorena Fortuna – then a graduate student of his – wrote a scientific paper analyzing the environmental advantages. They took into account production of raw materials (such as timber); manufacture of building supplies (such as lumber) and of finished goods (such as cabinets); transportation; and final disposal. They calculate that the deconstruction saved 19,000 kilowatt-hours of energy – twice an average family’s annual electricity usage.

Looked at another way, deconstructing that old house also saved about 10 tons of CO2 – about 60 percent of an average American’s annual carbon footprint. Their research validated “the economic and environmental benefits of deconstruction of wood frame houses,” Fortuna said. The Burlington house was a representative U.S. house, with three bedrooms and nearly 2,000 square feet. There are 100 million more single-family houses in the country. Many of them will also come down someday.

Emerging view on reducing GHG emissions?

Diyamandoglu and Fortuna’s research reflects an emerging perspective on how to account for (and reduce) greenhouse gas emissions. Historically, energy use (and greenhouse gas production) has been conceptually allocated roughly by where fuel is burned – in factories, power plants and homes. Climate analysts generally consider about 10 percent of energy to be residential in its use. But some researchers say this way of looking at energy use devalues the impact individuals can make on their carbon footprints. Consumers in our society are usually encouraged to curb their energy appetites by buying efficient products – such as LED light bulbs and electric cars – that consume electricity or fuel most efficiently. Many consumers are advised to adopt conservation-minded habits – such as lowering the thermostat and driving less. Far less often is anyone asked to consider the impacts of the very fabrication of their possessions.

The approach evolving over recent decades focuses not only on energy spent in the use of products but also on the energy embodied in their manufacture and shipping. It attributes a much greater share of total energy consumption – in the range of 50-80 percent – to decisions about what individuals in the U.S. own. And it highlights how and how often we replace our possessions – including our houses. The United Nations Environment Programme estimates that construction and upkeep of buildings produce one-third of all greenhouse gas emissions globally. The walls and roofs that shelter us turn out to be our biggest aggregate contribution to global warming.

Fortuna says paying more mind to embodied energy leads to effective reductions, and she’s studying some at the Center for Materials Reuse, a research branch of the New York Department of Sanitation. Questions, as always, remain. For instance, does buying a used newel post displace production of a new one, or simply increase the amount of newel posts in circulation? And, when technological advances increase energy efficiency – as it has with refrigerators – when is it best not to re-use older and less efficient models?

“We still have a lot to do,” says Fortuna earnestly.