The restoration of historic buildings in Charleston, SC, shows how sustainability and preservation issues can be solved.
By Ralph C. Muldrow, RA
Historic Charleston, SC, has weathered more than its share of traumas since its founding in 1670. The city has survived numerous fires, frequent hurricanes, bombardments, a major earthquake and a hot, humid climate. Like many southern cities, Charleston experienced burgeoning growth in the post-World War II era, not only because of the Naval Yard as an employer but also, importantly, because of the new availability of air conditioning that facilitated growth throughout the South, although at the price of increased energy use.
All along the way, Charleston's ethos has been intertwined with the veneration of the past, especially the architecture. The seal of the city has a Latin phrase that translates, "She guards her buildings, manners and laws." Charleston created the first historic district in America in 1931, and continues to stringently guard the buildings of the old and historic district. Protecting the historic buildings is a sustainable practice, utilizing the 'embodied energy' that it took in terms of materials and labor to build and maintain this sought-after historic city.
Of course, the buildings do present a range of styles, but the pervasive typology is that of the single house. In the 18th and 19th centuries, the single house was the dominant typology. The plan has the narrow end facing the street with a false door which leads to a real front door half way down the side of the house. This was greatly augmented by about 1800 when the false door became the entryway to a long, often double-height side porch, called a 'piazza' in Charleston.
We find this floor plan recurring from the Georgian period, through the Adam (Federal) Style, the Greek Revival Style, Victorian styles, etc., but in all of these exotic garbs the floor plan, fenestration and formality remain constant, with only a few elements giving the house a discernable 'style.' The distinct urbanism created by the repetition of the single house is a very sustainable model in and of itself.
The survival of the underlying form of the single house over large areas of the city is an embedded 'sustainable' urban form. These older blocks provide a syncopated rhythm to the street, with the sustained intervals of house, piazza, garden, house, piazza, garden, etc.
Post-Bellum Charleston was not a prosperous place. The local saying was, "too poor to paint, to proud to whitewash." Yet these weathered remainders of times gone by largely remained standing. Thus in the 1920s there was a phenomenon now called 'the Charleston Renaissance,' wherein the crumbled stucco and naked wood siding of the day became a tourism magnet. Spurring this movement were the evocative etchings of Elizabeth O'Neill Verner, the lyricism of "Porgy and Bess," and even the African-American derived dance, "The Charleston," with its raw energy.
It was in that era that many gardens were designed for the single houses – beautiful parterres with shaped boxwoods and trellises. This glorious layer veils the truth about these back yards, which historically usually functioned as 'urban plantations,' with cows and hogs and chickens raised at the homes.
This 'weathered city' utilized her unique, long-standing architectural layout of houses turned longways into their sites to create a shelter appropriate to the climate. The piazzas all face south and west, which allows them to catch prevailing breezes and allows for the shading of windows when the sun is high in the summer. And in winter the sunbeams drench the house with much needed warmth.
There is a 'louver effect' in which the houses themselves provide shade to the neighboring house and/or garden, just as the louvers of a vent shade each other. The side garden also functioned as a firebreak.
The formal fenestration allows for numerous windows on the south and west sides of the house (facing the prevailing breeze) which feed the few windows (mostly in the staircase) of the north-facing side, allowing for cooling breezes through the single room depth of the house. And despite earnest attempts by the government throughout Charleston's history to require the use of brick for fire resistance, many houses are wood frame, clapboarded houses built originally with no insulation to allow cooling air movement within their walls. Even the chimney stacks, which facilitate air movement, aided in cooling the single house in the summer.
For the purposes of this study, "sustainability" will be defined as an approach to construction that strives for efficiency in its use of energy, water and other resources. It is also an approach that favors occupant health and improved employee productivity, and it strives to reduce waste, pollution and environmental degradation.
Green products are those that further the cause of sustainability through recycling and low environmental impacts. Even green products may cause some friction with sustainable building. For example, should one buy a 'green' adhesive product from California? Or should you instead purchase a normal adhesive locally, saving the carbon footprint associated with the transportation of the product, and promoting the economic health of the community? Should you buy the adhesive product at a national chain store like Home Depot for a slightly lower price than the locally owned building supply store, or should you pay the extra money to sustain the viability of a local company?
Now add to the equation a host of preservation issues involved in a building rehabilitation project and other questions arise. The preservation approach to a significant historic building would be to save as much of the extant fabric as possible, or to agree on a period of significance to aim for in the course of making rehabilitation decisions. Which priority trumps the other? This inevitably differs from one project to the next.
Preservation approaches include issues that are less quantifiable but just as important in their own right. For instance, aesthetic considerations may not be optimizing energy use but may instead be highly important for the perpetuation of a building, avoiding demolition, which negates all of the embodied energy in such a structure.
The same goes for significance. For instance, a plain cinderblock structure may be an iconic talisman for the civil rights movement. Should we load up the roof with photovoltaic panels to lower the use of electricity, or will that be an unacceptable incursion on the historic structure?
#93 and #97 Broad Street
Some current construction projects in Charleston are grappling with marrying sustainability with preservation – two important but sometimes differing agendas for the betterment of society. A high profile case in point is the two-building project at #93 and #97 Broad Street.
The first building, #93 Broad Street, was constructed ca.1800, while #97 was built in 1835. The goals for the much altered and deteriorated buildings were that they may be used as offices and that they will be historically correct and constructed sustainably with 'green' products. In addition, appropriate reconstructions should be based on historic photos (rather than expanding over every last square footage on the site). The two buildings were extremely deteriorated and had been unoccupied for many years.
One example of sustainability and preservation is exemplified by the mechanical systems. Instead of one or two large condensers, #93 Broad has been fitted out with six condenser units, all with a SEER rating of '16.' They are mounted on heavy timber dunnage with rubber blocks to dampen the inevitable vibrations. A filtering system dehumidifies the sultry summer Charleston air and cleans it as well.
This number of condensers allows for them all to operate at about 60 percent of their full strength so as not to wear out easily. This also allows for a number of different zones in the building that can then be adjusted as necessary for specific needs instead of cooling the entire building needlessly.
Many other sustainability items have been addressed with the target being LEED Silver certification. Meeting preservation requirements as well has been a challenge. The windows, for instance, have all been repaired instead of being replaced, including matching glass panes where the original ones are missing. This painstaking work is appropriate for such prominent historic structures, and it fulfills sustainability goals concerning 'embodied energy,' respecting the reuse of the windows instead of sending them to a landfill.
The original windows were made from slow-growth wood, which is much sturdier than most wood today. The sills were replaced with solid mahogany – a wood that resists decay naturally. They are connected to the jamb with mortise-and-tenon connections. Yet with all of that going for them in the preservation process, a purely sustainable approach might encourage the provision of new windows with higher R-values, to save energy. One way to meet both goals would be to apply interior storm windows.
The historic brick was another issue. An important part of reusing and re-pointing historic brick is the understanding that early bricks were softer than later 19th-century machine-made bricks. Conservation practice emphasizes the need for lime-based mortar which would have been used initially, rather than the Portland cement-based mortar. The latter is harder than the soft bricks and can lead to spalling.
The use of lime mortar, however, is not a 'fix all' in every case, and it carries with it a higher need for maintenance in our present day market where labor is very expensive. (The hands that built the brick walls worked for lower wages and probably included slaves). The solution was to use salvaged bricks from a ruined 19th-century addition, with equal amounts of Portland cement and lime in the sand aggregate. The use of Portland cement will significantly extend the life of the mortar with these harder, machine-made bricks.
Insulation is obviously an important component of the energy-saving approach advocated by LEED. #93 Broad has a new rear addition which is a replica of the earlier addition that was a ruin. In the new addition Charleston-based Meadors Construction used spray foam insulation on the back of the roof sheathing.
In the historic section, rigid insulation was used to create airspace to allow airflow through the rafter plenums. Closed-cell spray insulation was used to provide a redundant layer of waterproof material and to prevent mold.
The roofing is standing-seam copper on plywood sheathing with insulation as described above. Copper has a long life expectancy and is historically accurate, but it costs significantly more than an asphalt shingled roof and comes from distant sources, possibly even from China.
Sustainability precepts would recommend that materials be local or at least from within a 300-mile radius, minimizing the fossil fuel costs to transport the material. Instead the copper has a big 'carbon footprint' due to the transportation factor. However, preservation precepts call for the historically correct roofing material, and it could be argued that the copper roofing is a 'sustainable' product because of its long life.
Green products used in the rehabilitation of these severely damaged historic buildings included a fire-rated water-resistant sheathing made by National Gypsum Company, the use of stainless-steel screws to strongly secure the framing in perpetuity, lumber purchased from local forests, low-flush toilets, hot water on demand (to keep from having a hot water heater going all of the time), electrical elements such as lights are on a clock or a timer, insulated ductwork and numerous others. The exterior walls are thick brick coated with true lime stucco and painted with mineral pigment paint which allows for vapor to exit the wall.
In terms of the sitework, a silt fence contains run-off of pollutants from the construction site. Metal scraps were recycled and plaster was sent out to be crushed and reused. This high-profile site may serve as a model for others.
As these case studies indicate, sustainability and preservation don't always go hand-in-hand, but knowledgeably made decisions allow us to utilize new technologies and materials to allow sustainability goals for historic structures. Perhaps a new LEED category for historic structures should be created. The Charleston single house has built-in sustainable characteristics out of necessity. We can learn from the sustainable aspects of historic buildings and we can then augment their sustainability with emerging 'green' technologies. TB
Ralph C. Muldrow, RA, is the Simons Chair Professor of Architecture and Preservation at the College of Charleston. He has degrees in architecture and preservation from the University of Pennsylvania and undergraduate degrees from the University of Virginia. He has worked at a number of preservation architecture firms including John Milner Associates. He teaches architectural design and architectural history and has lectured widely on architectural and preservation topics.