I'm in Wilmington, Delaware this week, where I was asked (and honored) to speak to an EPA-sponsored symposium on green historic preservation.  I spoke yesterday afternoon, and this is what I said.

I started with the wonderful phrase attributed to Carl Elefante, "the greenest building is the one that is already built."  (Carl, whom I just met, is also speaking at the conference, so I hope I got it right.)  There is much truth in that statement, since a new building, no matter how green its technology, will often be on a new site, sometimes in sprawl; it will also need to use new material and energy that have already been invested in an older building; and chances are the new building will lack some of the traditional green wisdom that, over the centuries, informed building performance and efficiency "before the thermostat age," as Steve Mouzon (another conference speaker) puts it.

That said, though, the greenest building will not be the one that's already built if it has been abandoned, and rendered nonfunctional and deteriorating because its community or neighborhood has been disinvested by the flight of people and economic resources to the fringe of the region.  I have long thought that the greatest contribution that the National Trust's visionary former president, Dick Moe, made to the cause was to understand that sprawl is antithetical to saving older communities, neighborhoods, and buildings.  He believed it was in the interest of preservationists to fight sprawl and support revitalization, and I do, too.

Of course, disinvestment and sprawl are not just preservation issues.  If you care about green preservation, you also have to take into account that households in centrally located properties and neighborhoods use far less energy and emit far less carbon for transportation than their counterparts in sprawl.  And you have to take into account that, for many households and office buildings, carbon emissions from transportation exceed those emitted by operation of the building.  The poorly planned spread of development that characterized so much of the late 20th century also eats up culturally and environmentally significant landscapes, farmland, habit, and watersheds.

These are regional issues, not just building-centric issues, and I believe that green preservation means, among other things, thinking about how we want our metro areas to be shaped as we go into the future.  Will our development patterns be supportive of older communities and neighborhoods?  Green preservation requires it.

In addition to the serious problems that accompany abandonment and are properly addressed at the regional scale, preservationists who care about green performance must also care about the neighborhoods that surround the properties we wish to preserve.  If a historic building, even a functioning one, is not within a strong, supportive neighborhood context, it will not perform well environmentally.  These issues are in some ways analogous to those that concern the larger region, but they are less about broad policy objectives and more about the character of the immediate, close-at-hand environment.

I only had 30 minutes, so I didn't go into as much wonky detail as I would have enjoyed (!), but I emphasized six neighborhood factors that affect the environmental performance of buildings, including historic ones.  These are all backed by research:

• Location.  The centers of regions and older suburbs perform better than the fringe, even if other factors are held constant.
• Connected streets.  A well-connected street network (featuring smaller blocks and lots of intersections) shortens travel distances and makes walking more feasible and pleasant.  It is the single most important determinant of how much walking will take place in a neighborhood and the second most important determinant (after location) of how much driving will take place.
• Places to go.  A mix of conveniences such as shops, schools, and places to eat and socialize encourages walking, promotes fitness and health, and reduces emissions from driving.
• Ways to get around.  The more transportation choices, the better.  If you're lucky enough to be within walking distance of rail transit, for example, the number of automobile trips during rush hours can be up to 50 percent lower than what would otherwise be expected under standard engineering forecasts.
• Density.  As I have said before, it doesn't necessarily have to be high density to reduce driving and watershed-damaging pavement per household.  We see substantial improvements in performance as we move from large-lot sprawl even to ten homes per acre; beyond 40 to 50 homes per acre, we continue to see improvements, but at reduced increments.  Moderate density helps a lot.
• Green stormwater infrastructure.  While runoff per household goes down in denser neighborhoods, runoff per acre can go up unless mitigated.  Green infrastructure, when in the form of publically accessible green spaces, can also bring an array of additional benefits to a neighborhood.

One could go on with additional factors, but in the interest of time I stopped there.  I believe that green preservation must include strengthening the neighborhood environment around what we want to preserve.  Maybe we can't do all of these things in every place, but we can do (or support others who can do) at least some of them in many places.

I then turned to a delicate issue:  both environmentalists and preservationists need to protect our credibility.  We have created a system of safeguards and laws that are entirely appropriate but also can be misused, even by those who do not have our interests at heart.  Every puddle is not an ecologically significant ecosystem, particularly if what can replace it is a building or development with great green infrastructure that can also add density and strengthen the environmental performance of the neighborhood.  Every vacant lot isn't well-suited to be a park or garden (some are).  I believe environmentalists need to speak up when our cause is invoked to block something that actually would be environmentally beneficial, just as we need to speak up when something would truly harm the environment.

Preservationists face a similar situation:  every building that is 50 years old is not worthy of protection.  Within walking distance of my house, some people tried to block a great development (see rendering) by asserting that the ugly, plain, dysfunctional supermarket on the site was historically significant.  They didn't care about the building at all.  They wanted it replaced, actually, just not with what was proposed.  So they played the historic preservation card, in my opinion damaging the reputation of a movement that needs to be taken seriously when the property in question is truly worthy.  (Their petition was eventually withdrawn.)

In other words:  green preservation also means being discerning in asserting our cause and vigilant against those who hurt us by abusing it.

I'm sure some conference participants were surprised and perhaps even disappointed that I didn't talk much about individual building performance.  Instead, I tried to talk about the context of green preservation more than about preservation per se.  Because I think the context matters, both to preservation and to the planet.

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