The Charleston Single House: Vernacular Solutions for Sustainable Design
By Mitchell H. Lowe, A.I.A., NCARB, LEED AP BD+C
As the sun touches the Tropic of Cancer and the
Summer Solstice arrives, New Englanders start to worry about warm weather and how to protect themselves from its effects. How are we going to stay cool on those days when the temperature hits 90°F and the humidity is over 50%? The region dreads these days. On the other hand, what would happen if it hit 90°F in the early spring and the temperature and humidity just kept on climbing throughout the spring, summer, and continued well into the fall? It might not happen here in New England, but it certainly does in the South. The average high temperature in Charleston, South Carolina is above 80°F from May until September, while the highs in December and January are still in the upper 50s and 60s.
When you have temperatures and humidity in these ranges, the design of buildings is
profoundly influenced by the local climate. In fact, in order for buildings in any region to provide an energy efficient solution, the analysis of local climate should be one of the first tasks undertaken in the design process. Look at what was designed before the advent of modern heating and cooling systems and see what choices were made by local designers in response to local climate conditions. If you can design your structure to work with the climate, you can cut down on the size of heating and cooling systems in your buildings.
How did builders in Charleston design their houses to address climate issues and what can this
tell us about how to design structures in other parts of the country suitable for the climate? The Charleston Single House is one of America’s best examples of vernacular design solutions dealing with local climate issues. The City of Charleston was founded in the late 1600s, the Single Houses were developed in the early 1700s, and the greatest era of construction of this building type was in the early to mid 1800s. Charleston was a wealthy town. It was situated near the coast with a well protected harbor and was ready for trade with the British and other European powers. The Charleston peninsula, surrounded on the east and west by rivers and on the south by the harbor, has a grid of streets with the major streets running north-south away from the harbor toward the mainland, and the secondary streets running east-west from river to river. Prevailing breezes come in off the ocean from south and from the mainland to the west. The breezes are what help keeps the heat bearable enough for residents in the summers.
A typical lot in Charlestown has narrow street frontage, but extends deep from the street with the house on the north or east side of the lot. These houses are known as Single Houses
because they are one room wide. They are generally narrow with tall proportions. There is a porch (in local terminology, the piazza) on the south or west side of the house. The piazzas are generally two or three stories high with a garden on the south or west side. A garden wall separates the piazza and garden from the street and the garden wall becomes the main street façade of the house. The main entry to the property is through a door in the garden wall that leads onto the piazza, not into the house. The entrance to the house is from the piazza into the stair hall. The stair hall is in the center of the house and runs side to side, not front to back. There is one room on each side of the stair. The rooms open both to the piazza and onto the stair hall. The first floor houses the drawing (living) room in the front and dining room in the back, with bedrooms and other family rooms on the second and third floors. The kitchen is either in a separate structure at the back of the house or attached to the house at the rear, adjacent to the dining room. Each room has doors and windows on the piazza side, and windows either at the rear of the house or facing onto the street. By contrast, the north and east sides, which back up to the adjacent lots, are solid walls with fireplaces and few windows. The architectural styles of the homes vary based on the era in which they were built, but each home adapts their style to match the prototypical plan.
Since the prevailing winds are from either the south or west, the houses are oriented on the
north and east sides of the lots so winds help keep the house cool. The orientation of the piazza on the lot is the most important factor in controlling and guiding the breezes to keep the house cool. The breezes flow through the long direction of the house, from the room in the rear, through the stair hall, and then into the front room. The gardens are shaded by the houses to their south or west, and then the garden trees provide shade to the piazza. The east and north sides of the houses are relatively solid so they provide privacy to the garden on the abutting property. The piazzas are generally deep enough so they provide shade to the interior rooms during the warm months when the sun is high in the sky, but still allow light into the rooms for activities to occur. However, during the winter months when the sun is lower, the porches are not so deep that they keep the sun out of the rooms. In the summer months, the piazza is a refuge from the warmer interior rooms. It is used as the dining porch, the living porch, and the sleeping porch. The kitchen is separate from the living quarters so the heat from the stove does not warm up the rest of the house.
It gets very hot and uncomfortable in Charleston; but, the design of the Single House has
evolved over the years to provide natural cooling. The major components of cooling via Sustainable Design principals are air movement and shading. The more natural air movement and natural shading can be introduced into any building in any location, the less the structure will need to rely on powered systems to keep the building cool.