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|Island Presentation Partnership Snapshot
||Dewees Island, South Carolina
||Island Preservation Partnership
||150 homesites for single-family detached permanent and vacation
residences; 32 homes built, 1,600 to 5,000 sf, average 3,000 sf.
||Homesites $320,000 to $850,000; furnished homes $895,000 to $1,125,000
||Conservation in land use, passive climate design, SIPs,
shared wastewater treatment, small-diameter sewer lines, rock filters, Energy
Star appliances, low-VOC finishes and adhesives, low-flow plumbing fixtures, rainwater
harvesting, permeable pavement, electric vehicles, xeriscaping
Can profitable development be not only harmonious with the environment but actually enhance it? John Knott of Dewees Island thinks so. Claiming that "the environment and development are natural allies," he set about developing an island protected by conservation law. Combining local climatic responses with new materials, Dewees Island contains a growing population while protecting its sensitive ecosystems.
When the development company, Dewees Island (DI), set out
to develop the island, located 10 minutes by ferry from the mainland
and 12 miles northeast of Charleston, they found a natural area
with just three existing homes. About 65% of the scenic barrier
island is set aside for permanent conservation by law. So DI
started with an inventory of the island's natural resources (wind,
vegetative covering, topography, orientation, and view), believing
that harmonizing with them would reduce construction and maintenance
With seven geological zones on the island, it was decided
that all houses would be in the sturdiest zone, buffering the
homes from storm surge while preserving the more sensitive areas.
Dune fences (like snow fences), measures for new vegetative rooting,
and beach access paths, are created to deter eventual erosion,
common to many beachfront properties. In this case, dispersed
home sites were determined to be less disruptive to the wildlife
zones than clusters. DI asserts that this measure, together with
creating additional ponds, triples the water habitat. And by
limiting development to 150 homesites at two acres each, effectively
92% of the island is conserved, far less than the 65% conservation
law. This leaves more vegetation to absorb massive rains, protecting
For the building systems themselves,
the designers relied heavily on industry information from DOE,
Energy Design Update, Environmental Building News, and the Rocky
Mountain Institute. A vertical, closed loop geothermal
heating and cooling system was chosen for many of the homes,
and the geothermal company assisted in energy modeling.
Passive solar climatic design figured largely in the initial
planning stages of the community, and the architect was required
to do a study of the sun and prevailing breezes for all four seasons.
By orienting the houses to collect cooling breezes and incorporating
deep overhangs and vegetation for shading, the air conditioning
load could be reduced, saving construction and energy costs. The
tight structural insulated panel walls and roofs, coupled with
high-performance windows on the south and west sides, save additional
energy. Transom windows in the interior walls enhance cross ventilation.
The net result of these measures is that the homes are often cooled
with ceiling fans.
The choice of wastewater treatment can be either a boon or
a barrier to sustainability. If conventional methods were used,
the leaching fields alone would take up much of the space set
aside for houses. The difficult site conditions meant that a large
number of lots couldn't even get a septic system permit.
To reduce the size of the treatment areas while still protecting
the groundwater, the health department worked with the developer
to design a system in which a combination of technologies was
employed. Each residence has a septic tank/rock filter pretreatment
system that feeds into a small-diameter pressurized sewer line,
leading to a central disinfectant area, and finally a shared absorption
field Shared Wastewater Treatment Systems. To regulate the amount of effluent
going into the soil, a below-ground tank holds disinfected effluent,
which is pressure-dosed to the absorption field. By these treatment
methods, the entire absorption field for 150 houses is kept to
100 feet by 700 feet. A single absorption field is much easier to monitor
for quality than many scattered fields.
Areas around the homes xeriscaped with native plants require
little fertilizer or watering. This not only reduces maintenance
and protects groundwater supplies but also allows efficient low-drip
irrigation to be used, from harvested rainwater. High-efficiency
dishwashers and horizontal-axis clothes washers save additional
water and heating energy. All the appliances in the homes meet
the EPA Energy Star Rating. Rounding out the water conservation
aspect with low-flow plumbing fixtures, these homes use 70% less
water than comparable homes.
Although Dewees Island includes its own construction outfit,
Dewees Builders, home site buyers are permitted to hire any architect
and builder they want, as long as resource-efficiency guidelines
are followed. Buyers are encouraged to choose from Dewees' approved
list of architects and suppliers if they choose not to go with
some variation of the official Dewees Island Home.
Construction crews are trained in waste reduction. Lumber is
minimally cut, and scraps from lumber and pilings are used as
landscaping posts and mulch. This reduces both landscaping and
carting costs. In areas of the walls and roof in which air gaps
have been created during construction, an expanding spray foam
is added to stop air infiltration.
With oceanfront property in South Carolina at a premium, the
home sites are fetching $325,000 to $850,000. Fully furnished
Dewees Island Homes go for $895,000 to $1,125,000. These prices
reflect the market more than the cost of building in environmental
performance. DI actually saved money with environmentally benign
practices, enriching an already profitable venture. For example,
the decision to cut back paving reduced other costs including
storm water drains and regional ponds. And mounting outdoor lighting
on existing trees eliminated the need to clear them and install
massive lampposts. Although monthly bills are not the first concern
of these homeowners, efficiency measures yield 60% energy savings,
70% water savings, and 60% household waste savings. Dewees Island
Homes are built to exceed Energy Star standards.
Barrier islands typically present difficult wastewater problems
with their fragile, sandy soils and high water tables. The nearby
shellfish waters posed a particularly delicate situation. Before
the state Department of Health and Environmental Control (DHEC)
issued a variance for the space-saving wastewater treatment system,
the developer went through a period of groundwater monitoring.
Still, the DHEC mandated the absorption field be at least 4' above
the water table. This and the high water table in the island required
a mound absorption field, built 10 feet above sea level. This required
filling and grading, adding costs.
Water transportation is a way of life at Dewees. But the extensive
sitework needed for private docks would close shellfish hatcheries.
A community docking design was much less disruptive, but only
approved for commercial facilities. So another variance was sought
To ensure future preservation and resource efficiency, Dewees
Island established its own architectural and environmental guidelines.
For example, every plumbing fixture in every building has to be
low-flow, and any watering of vegetation must be drip irrigation
via cistern. Kitchen wastes are composted and garbage disposals
are prohibited. Individual homes are limited to 5,000 sf. There
is an absolute island limit of 150 homes.
The development is meeting sales expectations. In Fall 1996
there were 15 residences built on the Island, with 10 to 12 more
expected the following year. As of Fall 1998 there were 32 homes
built, with eight more in various stages of design and construction.
At this rate, home sites are expected to sell out in two years.
According to the developer, the buyers appreciate the beauty and
tranquility of the place, and feel they have a personal stake
in its preservation.
Developers attribute the Island's success to an exclusive,
but wide-ranging, marketing campaign. The approach is described
as more personal and one-on-one, directed at a buyer with an environmental
ethic. Ads are placed in specialized publications, and a substantial
response has come through the company website. Additional interest
is channeled through local realtors and friends of current Dewees
homeowners. And a certain amount of P.R. is generated through
the enthusiasm of John Knott, the company's CEO and managing director,
who travels extensively to give talks about the project and related
Do you have a specific question? Try the contacts listed below:
46 41st Ave
Isle of Palms, SC 29451-2662
Burt, Hill Assoc.
1056 Thomas Jefferson St., NW
Washington, DC 20007
Mailbox 6202 J
Washington, DC 20460
Environmental Building News
28 Birge St.
Brattleboro, VT 05301
Energy Design Update
Cutter Information Corp.
37 Broadway, Ste. 1
Arlington, MA 02174-5552
Rocky Mountain Institute
1739 Snowmass Creek Rd.
Snowmass, CO 81654-9199