Economic Development

Greening Historic Buildings

Dubuque, Iowa's most sustainable buildings are a century old--and older. The Victorian homes, aging storefronts and 19th-century warehouses are sustainable in that they're positioned to...
by | April 1, 2010

Dubuque, Iowa's most sustainable buildings are a century old--and older. The Victorian homes, aging storefronts and 19th-century warehouses are sustainable in that they're positioned to take advantage of the sun's warmth in winter and the trees' shade in summer. With their thick brick walls and old-wood window frames, they are beautiful structures, and for the past 30 years, the city has been actively preserving them--as an economic-development strategy and as a way to remember its manufacturing past.

Now it is upping the ante. In 2006, city officials designed a plan to turn Dubuque into an economically, socially and environmentally sustainable city. A key part of that plan relies on existing historic buildings for both good community design and green-building ideas. In addition to the hundreds of old Victorian homes and storefronts that have been carefully restored by their new owners, Dubuque's stock of old and sustainable buildings includes a group of commercial buildings--more than 1 million square feet of space--that make up the Historic Millwork District in downtown Dubuque. These old facilities--factories, warehouses, stores and loading docks--once were the driving force behind a thriving timber business. Wood products were made here and shipped all over the world via the Mississippi River, which flows right by entrances to some of the buildings.

The millwork business is long gone; many of the warehouses and factories sit nearly empty and forlorn. But as part of the city's overall revitalization plan, the warehouse district will capitalize on its old infrastructure, developing a multiuse complex where residents can live, work and play. The project's old buildings will, in short, be rehabbed to embody the new principles of smart growth.

Cindy Steinhauser, Dubuque's assistant city manager, says the city's stock of old buildings showcases how the earlier settlers and city elders knew how to place a building to maximize its efficiency, such as using sunlight for natural light and heat. "These are practices that our grandfathers and grandmothers used when they designed their storefronts," she says, "so they could live above them and take advantage of natural lighting." Combined with some modern tweaks, such as energy-efficient heating and cooling systems, and adding insulation to walls, these older buildings could be as environmentally friendly as sleeker, shinier new construction.

Dubuque is one of a handful of cities featuring historic preservation as a key part of sustainability efforts. As such, these cities are the opening wedge of a movement that believes older building stock could be the way to becoming a greener city--a means to becoming sustainable without wasting resources, energy and history. But history and policy may need to catch up to each other if other cities are to move in the same direction.

More than 200 localities have adopted guidelines requiring that buildings become Leadership in Energy and Environmental Design (LEED) certified--the recognized standard for measuring building sustainability in terms of site development, water savings, energy efficiency, materials selection and indoor environmental quality. Many are targeting not only the basic LEED certification, but also the higher levels. A look at some key statistics suggests, however, that a central part of any city's effort in that direction should key in on existing building stock. Buildings, it turns out, are huge energy users and carbon dioxide emitters. According to the U.S. Green Building Council, buildings in this country account for 39 percent of total U.S. CO2 emissions and 40 percent of energy consumption.

In the pursuit of sustainability goals, however, there may be an unintentional focus on new construction. Many believe that to have a green building, everything must grow out of the newest technologies. This approach solves one problem by introducing another: Demolishing old buildings is inefficient. When a building is torn down, its "embodied energy"--the energy already exerted to create and gather the materials, and then construct the structure--is wasted. Moreover, materials from that demolished building could end up in a landfill. The National Trust for Historic Preservation estimates that one-quarter of the municipal waste stream consists of construction debris. And according to a 2004 report by the Brookings Institution, such demolition could add up to a big problem: About one-third of the U.S. building stock will be taken down and replaced by 2030.

Meanwhile many older buildings are as energy efficient as newly constructed facilities. According to U.S. Energy Information Administration data, buildings constructed before 1920 have about the same energy efficiency as buildings constructed between 2000 and 2003.

Older, historic buildings have several energy efficiencies built into them: Window frames, for instance, are often made of old-growth wood, which preservationists say is very durable and can have a high R-value, meaning the window is good at containing heat. "If you look at the life cycle of a vinyl or aluminum window," says Patrice Frey, director of sustainability research at the National Trust for Historic Preservation, "usually it lasts 10 to 20 years tops, and then ends up in the landfill." A wood window, she says, can be retrofitted and used for up to another 100 years--saving a window from that trip to the landfill.

Many older buildings also are positioned to catch sunlight, helping to heat and bring in daylight, and the floor plan may have been designed to maximize airflow and ventilation. In addition, older and historic buildings are often part of walk-able neighborhoods or near public transit, reducing the need for cars.

In the LEED guidelines' newest version, the U.S. Green Building Council allows for older and historic structures to achieve additional points toward LEED recognition by giving more weight to categories such as energy efficiency and sustainable sites. "Existing buildings," says Roger Limoges, director of advocacy for the U.S. Green Building Council, "are where we are going to see the transformation we need."

Green-building advocates and preservationists recognize that each other's aims are self-complementary, and preservation as a sustainability strategy has potential pitfalls. One challenge is that developers must find ways to make the numbers work for financing such a project. Federal and state historic tax credits help. But developers may not be able to use both a federal historic tax credit and a federal energy tax credit on the same project. At the state level, there are 30 states with historic tax credits on the books. At one point in 2009, Maryland had considered adding a 5 percent bonus if the commercial rehab achieved LEED Gold, but the legislation didn't pass.

Even if the financing is successful, prevailing codes and policy may not recognize the means by which older and historic buildings are green. Cities' prescriptive codes may require buildings to achieve energy efficiency or environmental sustainability in such a rigid way that the developer might have to compromise a building's historic character.

The National Trust for Historic Preservation, recognizing that there are minimal models cities can look to in "greening" historic buildings, launched in 2009 the Preservation Green Lab--a public-private partnership that shows how cities deal with various challenges in helping historic buildings meet sustainability criteria. For instance, Seattle, where the Preservation Green Lab is based, is a partner in creating an outcome-based energy code. This would give older and historic buildings more flexibility in achieving the right energy efficiency per square foot.

Dubuque is also a partner with the lab in a project to create an energy-efficient heating system that would work throughout its Historic Millwork District. Previously the district's buildings were connected by a system of tunnels and pipes; a steam system heated all the buildings. The majority of the district was eventually sold to four owners, who now must determine how they will heat their buildings: Should they all buy their own boilers? Or would it help to introduce a districtwide geothermal system? If the developers come together, there could be some cost-effectiveness. But then, the developers must decide whether to make it a "pump-and-dump" system, a "closed-loop" system or a hybrid of the two. And Dubuque will have to review what it will allow regarding filtration and entrenching for such a system.

Despite the challenges, Steinhauser remains optimistic about raising Dubuque's historic buildings to a solid green level. "Just because it's an old building," she points out, "doesn't necessarily mean that it's going to cost you more or it can't be done."

Cities may have to take baby steps at first, but Dubuque is betting it can lead to a giant step forward.

Tina Trenkner
Tina Trenkner  |  Deputy Editor,  |  @tinatrenkner

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