When it comes to historic neighborhoods, initiatives to promote sustainability and historic preservation can go hand in hand. The recent development of design guidelines for a proposed local historic district in Davidson, N.C., provided the town with an opportunity to weave sustainability principles into the document from its inception. The result offers a model for other communities eager to add a sustainability component to their historic district guidelines.
Davidson is a small southern college town (home of Davidson College) as well as a growing bedroom community for nearby Charlotte. Its progressive planning department and civic-minded residents are proactive in protecting the small-town character of Davidson from insensitive new construction and teardowns. The designation of Davidson’s National Register Historic District and the proposed expansion of a local historic district are just two of the strategies they have pursued to preserve the small-town charm the community cherishes.
A parallel intent was to reinforce green design and sustainability principles central to the town’s development philosophy in the new district guidelines. As a consultant to the town, I worked with an engaged, dedicated committee of planning staff and local citizens to develop illustrated design guidelines for the historic district that embody these intentions.
Current best practices for historic district design guidelines emphasize the need to put the Secretary of the Interior’s Standards for Rehabilitation in local context by creating user-friendly documents that tailor educational information, specific guidelines, and illustrations to the local community. The guidelines document is usually organized with an introduction that describes the district and explains local procedures, followed by sections addressing changes to building exteriors, new construction and additions, landscaping and site features, and demolition or relocation of historic buildings. Preservation commissions use these design guidelines in reviewing the compatibility of proposed changes in local historic districts or landmark properties, but they also become a reference and educational tool for the community.
In North Carolina, as in many states, the role of historic preservation commissions is defined by statewide enabling legislation. Their role is to “safeguard the heritage of the city or county by preserving any district or landmark therein that embodies important elements of its culture, history, architectural history, or prehistory” and to “promote the use and conservation of such district or landmark for the education, pleasure, and enrichment of the residents of the city or county and the State as a whole.” (See General Statutes of North Carolina, c. 160A, ss. 160A-400.1-160A -400.14.) While the legislation was crafted to promote preservation, the overarching themes of good stewardship, revitalization of neighborhoods, and ongoing use of the built environment clearly provide common ground for linking historic preservation and sustainability in meaningful ways.
Structuring the Guildines
Building from a platform of shared values, the guidelines committee chose to explicitly connect sustainability principles to historic preservation in the Davidson guidelines by: 1) adopting an accepting and encouraging tone toward sustainability, and 2) including examples of and references to sustainable practices in the text and illustrations. As the project unfolded we found more and more ways to link the principles of both, moving beyond the familiar debates about replacement windows or embodied energy to also raise issues such as proactive maintenance, lifespan of traditional building materials, merits of traditional and new energy conserving technology, selective use of new materials, and ecologically friendly landscaping considerations. Design guidelines often address these sorts of issues in an inferred way, but in the Davidson design guidelines the overlap with sustainability values is more explicit and specific.
In the document introduction, the sustainability emphasis in the guidelines begins with an explanation of the mutual values of historic preservation and sustainability. The hierarchical three R’s of the Secretary’s Standards—Retain, Repair, Replace—are compared to the four R’s of Green Design— Reduce, Reuse, Recycle, and Repair. After identifying the mutual principles of good stewardship, neighborhood revitalization, and ongoing use of the built environment, these concepts are then applied through specific, pertinent strategies throughout the heart of the document in the topical guidelines sections.
Changes to Building Exteriors
Although the preservation focus always remains front and center in the Davidson guidelines, the “Changes to Building Exteriors” section includes specific commentary that translates green principles into pragmatic pointers—pointers that reinforce the value of proactive maintenance of traditional building materials and features. For example, when espousing the merits of historic slate, tile, and metal roofs, the guidelines offer the following argument: “If well maintained, these roofs can last up to a century—much longer than the thirty year lifespan of a good quality composition shingle roof.”
Likewise, the discussion of wood points out that “fortunately, wood is a renewable resource; however, new fast-growth wood is not as resistant to decay as the denser slow-growth wood it is often replacing.”
Similarly, guidance offered for brickwork touches on several principles of sustainability by explaining that the preservation of historic masonry walls “represents a sustainable approach given their extended lifespan, high-insulating value, and the embodied energy they represent.”
In a similar vein, the guidelines advocate for window repair versus replacement: “Routinely maintaining and repairing historic wood windows to keep them operable and weather tight is generally more sustainable and cost effective over time than replacing them with new units with a shorter lifespan.” Taking the window issue a step further, the caption beneath a photo of a storm window asserts that compatibly finished storm windows “protect historic windows with minimal visual impact and can improve their overall energy efficiency
as much as double-glazed replacements.”
Beyond making the preservation case for retaining significant historic materials and only replacing deteriorated or missing materials in kind, the guidelines offer additional commentary on contemporary exterior wall materials such as vinyl siding, a petroleum based material. Stepping beyond the issue of compatibility of such materials in a historic district, the guidelines go on to suggest property owners weigh the prorated costs of the new material over its anticipated lifespan as well as the environmental-friendliness of the material.
Utilities and Energy Retrofit
The text on “Utilities and Energy Retrofit” urges optimizing the efficiency of traditional features such as double-hung windows (that can capitalize on breezes and control fresh air input), ventilated foundation walls, gable vents, high ceilings, operable shutters, and retractable awnings as a first step in improving energy efficiency before adding weather-stripping, insulation (in the attics and crawl spaces), storm windows, or an upgraded mechanical system.
The text goes on to offer the low-tech suggestion that property owners may “also want to consider replacing lost shade trees or adding new shade trees in appropriate locations,” and pushes the tree planting idea further for the southern climate with the point that “well-placed deciduous shade trees can provide welcome relief in the summer and are a sustainable way to reduce cooling costs associated with solar gain on south-facing walls.” To assist property owners in landscaping decisions, a list of ecologically friendly trees for Davidson is included as an appendix to the document.
The guidelines also address strategies for introducing and sensitively siting new energy-saving features such as solar panels, new HVAC units, rain barrels, and compost piles. A photo of a corner downspout leading to a rain barrel with a caption discussing screening from the street reinforces the concept of appropriate locations for such elements.
In the discussion of exterior lighting, the guidelines introduce concerns about light pollution and energy conservation and offer suggestions for property owners: “The use of motion sensors and timers can also limit the impact of exterior lighting and conserve energy at the same time. The selection of energy efficient bulbs and fixtures is encouraged.”
The guidelines clearly advocate for a green mindset when designing infill buildings and related site development. This section promotes the idea that contemporary buildings reflecting an understanding of Davidson’s visual and spatial character “add to its continued vitality and viability without diminishing its small-town character.” The section also clearly encourages “incorporation of contemporary sustainability principles in new construction and related landscaping.” Images of new buildings in the district commend the successful retention of mature trees on the site—a principle of both preservation and sustainability—and the guidelines elaborate on the need during construction to limit ground disturbance, protect areas within the dripline of significant trees, and avoid the use of bulldozers and heavy construction equipment within the district. Parallel commentary is provided in the related sections on new secondary buildings and additions.
Landscaping and Site Features
In the “Landscaping and Site Features” section of the guidelines, green principles are woven into discussions on restricting and softening the impact of new off-street parking. The guidelines reinforce the need to limit “new parking areas so that the overall ratio of paved area to green area is not dramatically changed” for a site. For large off-street parking areas they explain the need to “incorporate existing trees and introduce planting medians or islands to minimize both the visual impact of the paved area as well as the environmental impact of the noise, glare, and heat from the automobiles.”
To further minimize the impact of hard paving surfaces, the guidelines recommend brick pavers and other permeable paving materials that “are environmentally friendly choices appropriate for new residential
driveways and parking areas.”
The intent to preserve and enhance the pedestrian-friendliness of Davidson’s historic district obviously aligns with sustainability’s push for walkability. Concerned that short term strategies for slowing vehicular traffic might be thwarted or delayed by the design review process, we decided to explicitly encourage the introduction of “temporary and reversible traffic calming features” in the public right-of-way. Though a logical extension of both camps’ values, this specific recommendation is one of the more unusual results of incorporating sustainability principles into the guidelines document.
Demolitions and Relocations
The guidelines on demolition and relocation of historic buildings deal explicitly with the effect of wasted energy and wasted resources: “Beyond the loss to Davidson of a historic building, the loss of the embodied energy inherent in the existing building as well as the tremendous amount of materials added to the local landfill from a demolition make it an inherently environmentally unfriendly act.” From the same perspective, the guidelines advocate for the salvage of reusable building materials if demolition is imminent and also encourage relocation of historic buildings as a desirable alternative to demolition.
In the proposed Davidson design guidelines, the compelling case for preserving, revitalizing, and respecting a historic district as a valuable multidimensional community resource is enhanced by also incorporating concerns for sustainability of the built and natural environment. The intentional adoption of an accepting and friendly tone toward sustainability in these guidelines offers more opportunity for broader support of shared goals. Although there is nothing truly radical about the Davidson guidelines, they do provide an expanded model for historic districts advocating good stewardship, neighborhood revitalization, and ongoing use of the built environment. Publication Date:
Spring 2009#historicdistricts #ForumJournal#GreenGuidelines