Sea Glass: Designing a Sustainable Community – Sanibel, FL

Project Objective

Sea Glass is a unique, resource responsible community of homes gathered around an ecologically rich commons that promotes sustainable, social, and culturally connected living. This development is a collective of twelve homes organized around a well-designed commons.

Suburban Ecology: Ecological sensitivity has been a Sanibel tradition dating back to the 1890s as the earliest settlers managed with the resources that naturally flowed to the island — sunlight, fertile land, breezes, and ample rainfall.  Jay Norwood “Ding” Darling’s personal discovery of Sanibel in 1935 continued the lineage of conservation in the form of the J.N. “Ding” Darling National Wildlife Refuge.  The Pulitzer Prize-winning political cartoonist’s efforts to preserve the character of Sanibel led to federal protection of more than 6,300 acres of ecologically sensitive land in 1945.

During the late 1970s, when most of Florida was engaged in rapid, ecologically destructive development, Sanibelians partnered with environmentalist and Landscape Architect Ian McHarg — author of the 1969 book Design with Nature; founder of the University of Pennsylvania’s Department of Landscape Architecture; and recognized pioneer of the concept ‘ecological planning’ — to protect the character and environmental quality of the Island from incompatible development. 

Typical Sanibel Development

With McHarg’s direction, the citizens of Sanibel developed a long-term land planning and development strategy that is still in place today and after 30 years, won the American Institute of Certified Planners (AICP) 2007 National Planning Landmark Award for projects with at least 25 years old that are historically significant, initiated a new direction in planning or impacted American planning, cities or regions over a broad range of time or space.

Arranged for Community

The result seems to be more like ubiquitous suburban development rather than something inspired by natural or sustainable living.

Initial design scheming investigated the interaction of automobile circulation, preservation of existing specimen trees, nature areas, recreational activities, and civic engagement as themes that could influence the organization and spatial distribution of activities on the site.  This led to five unique planning strategies: Auto Court, Butterfly Meadow, Civic Promenade, and Eco Villa. 

Auto Court- This scheme uses the more traditional suburban cul-de-sac form adapted as ‘auto-courts’ that mix parking with natural vegetation and permeable paving (shell) to expand the ‘street’ as a civic place.  Nature and recreational areas are separated from homes.

Butterfly Meadow- The meadow provides a diverse grass, insect (butterfly) and bird ecology with a clean rectilinear form drawing from the more formal renaissance ordered gardens and taking cues from the Sanibel Historic Village.

Civic Green Promenade- With an open program for the central green space, the focus is on the formalization of the pedestrian circulation with both civic (promenade) and natural (paths) walking/recreation areas.

Eco Villa- The centralized recreational area is optimized linking vegetable gardening, bocce ball, citrus groves, tennis, and swimming (off-site) with walking paths and ecology niches forming the civic realm.

Neighborhood Development

Sea Glass continues and extends this tradition of conservation and stewardship on Sanibel Island.  Drawing from the precedents of the past, Sea Glass also engages state-of-the-art technologies that are just now entering the mainstream in terms of residential development.  Sea Glass leverages the ‘cluster development’ land use designation in McHarg’s vision to provide a more compact suburban form that allows the marginal spaces (typically lost to setback areas and drainage ditches) to be organized as a centralized nature area. 

This provides a unique neighborhood amenity and in this case acts as a public foyer, buffering between Periwinkle Way and the individual homes.  Centralizing a storm water garden with bioswales as part of the commons, rather than as dispersed vacant ditches, provides visual amenity through hydric planting while extending the habitat diversity — actually improving the site rather than just minimizing the negative impact.

Planning strategies were critiqued and vetted during a two-day design charrette and then synthesized into the Eco-Marsh and Auto-Hub variations present.  Amazingly, five independent teams during the charrette identified the Eco Villa scheme as preferred for a variety of reasons within the first 15 minutes of evaluating the schemes.  Charrette’s recommendations were integrated within the Eco Villa scheme including preferred elements from the other less desired schemes and enhanced stormwater strategies to ultimately achieve the Eco-Marsh/Auto-Hub schemes.

Site Design as Ecological Response

Site Planning- “Cluster” land-use regulations are utilized to implement LEED-ND (Leadership in Energy and Environmental Design – Neighborhood Design) ecological planning strategies.  This allows typical setback and separation requirements to be reduced allowing more aggregate natural habitat and ultimately a smaller built footprint with less ‘residual’ underutilized space.

Garden and Grove- Harvested rainwater is used to irrigate vegetable gardens and citrus groves.  Symbolic and practical, ‘gardening’ is part of the ‘closed loop’ ecological lifestyle of Sea Glass.  Composting of outside inputs, on-site biomass, on-site rainwater, and resident nurturing, as a form of civic engagement, provides useful resources and a sense of connectedness with the place.  

Gardening is highly valued for its physical and psychological therapeutic benefits in sustaining the mind and body — Journal of the American Medical Association (JAMA) & American Horticultural Therapy Association (ATHA). Native Vegetation- Sea Glass has many plant specimens and examples of species of plants native to the Sanibel including the interesting Strangler Fig, majestic Royal Palm, and the more common Sabal Palm. 

The design team will work closely with the Sanibel-Captiva Conservation Foundation to preserve native species and promote diversity of flora habitats as an ongoing aspect of the community.  Homes and roads have been designed around this important ecology and spaces have been planned to engage existing trees as part of the civic experience as landmarks, gathering places (shaded), and habitats.

Strategies Implemented

Non-Native Vegetation

As a former plant nursery, Sea Glass has a variety of beautiful, nonindigenous plants ranging from bamboo to magnolia.  So long as the plants are not considered invasive, they have been incorporated into the design.  Invasive species are removed as a process of development and replaced with native plants to the extent possible.  In this case, the Sea Glass design team is working closely with the Sanibel-Captiva Conservation Foundation.

District Cooling

Mechanical cooling is required for modern living in Florida.  Typically, homes have self-contained dedicated split system units.  Although great advancements have been made in terms of efficiency (high Seasonal Energy Efficiency Rating – SEER), residential units still do not compete with commercial-scale systems.  Furthermore, traditional residential heat-pump/condensing units must be located near each home and they generate substantial noise often disturbing neighbors who might be trying to enjoy natural cooling — or their ‘sleeping porch’.

The Sea Glass district cooling strategy has three primary components.  First, the heat sink (where the heat that is ‘extracted’ from the homes ultimately goes), will be the earth rather than the air space around the home (as is traditionally done).  The earth provides a more stable ambient temperature to absorb heat in summer and provide heat during the limited heating times — dramatically improving efficiency.  Second, high efficiency, variable speed chillers (two) will be housed in a central location to provide chilled water. Third, chilled water will be provided to the homes for cooling.  Billing will be similar to billing for electricity – a meter will monitor flow.  An alternative that may prove more viable is to connect each home directly to the earth loop heat sink – eliminating the chilled water loop but requiring compressors in each home.  Of course, this will be decided by the optimal available technology at the time of construction.

District cooling will maintain the natural sonic environment for those opting for the ‘sleeping porch’ mode during temperate times; will optimize the efficiency of heat flow; and, coupled with a backup generator, will provide more reliable cooling during power outages and post-storm conditions.  Lastly, it will eliminate the heating of already hot ambient air around the homes.

District Power

Back-up power is an important feature in storm-prone coastal areas.  Even though the storms are quite survivable (home in-tact), long periods may pass before electricity is restored, particularly on barrier islands.  The centralized backup power plant will provide power to the homes during these periods.  Underground distribution will provide storm protection.  This will also power the chilled water supply to provide cooling to homes an important feature during the summer storm season.

Stormwater management

In traditional suburban development, the flow is gathered at swales and ditches along the sides and rear of homeowner yards traveling around the perimeter of the property to finally be discharged at a single location — dispersion and re-collection.  A more ecological or ‘closed-loop’ approach, is to gather the stormwater at a central location, store the water as an aquatic/hydric habitat and utilize the waste as an irrigation source for gardens.  Overflow is filtered and discharged as needed during storm events.  This harvesting strategy is the genesis of the ‘Eco-Marsh’ scheme.

Plantings will be selected to promote ‘phytoremediation’ a process where the reedy plants absorb hydrocarbons and other pollutants that wash from roads during the initial phases of a rain event.  As these plants sequester chemicals in the plant biomass, the water becomes cleaner.

The diagrams below illustrate two approaches to managing stormwater on the site.