Energy spent in construction is water under the bridgeWe should save historic buildings because they are beautiful and because they are important to the fabric of our communities. Relative to the environment, they are often located in central, downtown locations that are pedestrian and mass-transit-friendly. While they aren’t usually super-efficient, they are more energy-efficient than you might think. According to the quadrennial study of buildings in the U.S. by the Department of Energy (CBECS), buildings built before 1960 use less energy per square foot, on average, than buildings built since then.However, when it comes to the energy expended in the 19th century to build that structure, that’s not a good reason for saving a building from demolition — it’s water under the bridge. Energy spent 2, 20, or 200 years ago to build a building simply isn’t a resource to us today. The real question: Does reuse conserve energy today?On the other hand, energy that we might use today or in the next 100 years is a resource that we need to conserve. A better way to look at the issue is whether reusing buildings can save us energy compared with demolishing and building new.Given a choice between reusing and starting fresh, which process will use more energy in construction? Once a building is operating, which building will use less energy to operate — the reused building, or the new one? How do the financial costs compare? If energy is saved, but at great cost, is it really worth it? These are questions any owner should ask if faced with that decision.Let’s take a scenario where it costs us extra energy to build new, but saves us energy in terms of operation. How many years before the energy we save during operations makes up for the extra energy spent during construction? If that point is decades down the road, then perhaps we’d be better off reusing the historic building and putting our energy elsewhere today. Only by really thinking through these questions can we decide if saving a historic building really saves us energy. A surreal magazine ad just got even more surreal for me.After learning of the fire at the historic 1871 Brooks House here in Brattleboro, Vermont last week, I quickly got to wondering: will the owner be put in the painful position of choosing to salvage a beloved historic property or to build new? Similar choices are faced with sad frequency in historic downtowns across America. Some other “embodied” concepts that are more usefulThe “embodied energy” concept isn’t dead, by the way. In fact, it has grown and been expressed in more and more flavors over the years. In the 1970s we had an “energy crisis” — today we also have a “climate crisis,” so accordingly, people are talking about the “embodied carbon” in everything from our building materials to our bike frames. Water quality and water shortages are also worldwide issues, so some people are looking at the “embodied water,” a.k.a. “virtual water” of those Egyptian cotton sheets, or the morning cup of coffee. (That’s 2,600 gallons per sheet, and 37 gallons per cup, respectively, according to some calculations.)These measures could be much more useful than “embodied energy” ever was. That’s because “embodied water” relates to agricultural and manufacturing processes for consumer goods being made and used today. Focusing on reducing that use, and making our goods more durable, would have immediate environmental and economic benefit.Another exciting development is the 2030 Challenge for Products, which was launched in February of this year. Recognizing the immediacy of the climate crisis and the large amounts of carbon emitted to make our building materials, the challenge calls for a 50% reduction in the embodied carbon of products by 2030. Because we don’t yet have reliable carbon numbers for building products, the immediate question is, “50% reduction from what?” Establishing baselines for different product categories will be a project taking several years, but I’m excited to see the results.Maybe we’ll even see an ad campaign that makes these abstract concepts more concrete. My advice: put down the gas can!If you want to read more about greening historic buildings, check out “Historic Preservation and Green Building: A Lasting Relationship” in EBN.What are your thoughts on saving historic buildings and their embodied energy? Let us know below.Tristan Roberts is Editorial Director at BuildingGreen, Inc., in Brattleboro, Vermont, which publishes information on green building solutions. Read more Energy Solutions columns, including columns by Alex Wilson, for whom Tristan is filling in, on the Energy Solutions homepage. You can also keep up with Alex’s adventures on sabbatical at ATWilson.com. A second look at a surreal magazine adThe question brought to my mind an iconic poster from the 1980. The ad depicts a “jerry can” style gasoline can — red, rectangular, with a metal nozzle coming out the top.The surreal thing about this poster was that the gasoline can was drawn in the shape of an archetypal three-story, brick “Main Street” building, with a storefront below and offices and apartments above. The tall rectangular building becomes a tall gas can, with the red brick looking like the red metal can. The fuel nozzle sticks out of the roof.Believe it or not, this poster was run by the National Trust for Historic Preservation. It remains a touchstone today in preservation and green building circles.After seeing one of our iconic downtown brick buildings go up in flames, I had to ask myself, why would any responsible organization ever want to equate an aging building with an explosive, flammable fuel? The National Trust updates its dataThese analyses can get complex and emotionally laden, so it’s fortunate that the National Trust is working to update its story using life-cycle assessment (LCA) methods that look at costs and benefits from numerous angles. The study, begun last year and expected to net results soon, should give us a good idea whether reuse makes sense, in several different typical scenarios.I’m hopeful that the study may help bridge a gap between the historic preservation and green building communities, who have sometimes clashed over the fate of existing buildings. Although plenty of middle ground has been staked out over the years, environmentalists have tended to focus on energy efficiency even at some cost to historic fabric, while preservationists insist that the “greenest building is the one that’s already built.” Both sides have a point, but each needs to learn from the other. Saving buildings saves their “embodied energy” — or does it?The answer is in the form of an argument often made in preservation circles that we should save historic buildings because of their “embodied energy.” The idea is that it takes a lot of energy to build a building. Firing bricks, sawing wood, making windows and doors and door hardware, trucking those materials in, and getting all the workers to the jobsite every day — all the ingredients in a building, and every step in putting those ingredients together, takes energy. That’s energy that we have to get from somewhere, most often burning coal, oil, or other irreplaceable fuels.When a structure is completed, you have not only that building, but you also have a pile of energy in the shape of a building. That was the simple idea expressed by the National Trust in its magazine ad. The text with the ad read, “It takes energy to construct a new building. It saves energy to preserve an old one.”The National Trust was arguing that saving old buildings isn’t just good for the historic fabric of our communities — it also preserves the energy value of the materials involved. I’ve heard preservationists go so far as to talk about how many gallons of gasoline are represented in each square foot of a historic building.I think it’s time for a new metaphor, and not just because of the fire.