Building Green: Sustainable Sites – An architect looking at a site for the first time, considering the job of designing their client’s dream home, will begin by addressing the important and fundamental issues concerning the relationship of the building to the land and the wider environment.

It is likely that the owner will have given some thought to questions of the location, size, and orientation of the future building. However, the design professional ultimately delivers a solution that maximizes the potential of the site and at the same time minimises any negative impacts of the building on the environment, through sound advice and guidance.

    
On the steep sloping hillsides of the BVI, it is particularly important to carefully consider the driveway access from the road to the building with a view to achieving a comfortable gradient, which reduces the need for destructive excavation.  A driveway cut is likely to require some degree of retaining structure; however an ideal solution would require as little excavation as possible, reducing or eliminating the need for excessive and costly concrete retaining walls.

It pays to be as aware as possible of the natural drainage patterns of the site.  A careful observation should be made of the existing drainage systems such as the ghuts on the hillsides; this is best done by visiting the site during a rainstorm. Flash floods are not uncommon and can cause a lot of damage if not accounted for in the site layout and design.  An environmentally sensitive design will seek to limit the disruption of these hydrology patterns by minimising the amount of impervious materials, maximising the amount of on-site water infiltration into the ground, managing stormwater runoff, and protecting existing stream channels from excessive erosion. Consideration can also be given to capturing stormwater in tanks for re-use in landscape irrigation.

In locating the building on the lot, a sensitive design would seek to minimise disruption to the existing natural landscape.   A topographical survey will identify important natural features such as large trees and boulders, which should be protected if possible.  The contractor should be encouraged to work carefully and limits of site construction disturbance should be established. During construction, the contractor should implement effective erosion and sedimentation control measures.   A properly installed silt fence will prevent soil from escaping and reaching the sea, preventing damage to ocean ecosystems; and temporary or permanent seeding of unstable slopes with plants with aggressive root structures, such as Weledia, will rapidly help to control surface erosion.

In our tropical climate, water should be considered a valuable resource not to be wasted. Our culture of incorporating a cistern to capture rainwater helps to encourage an awareness of efficient water consumption and conservation. Many homes now have a number of cisterns to harvest roof water runoff, stormwater runoff, and, increasingly, to store and re-use “greywater” from washing machines, bathroom sinks, showers and tubs for use in landscape irrigation. In a well-considered design, use of “town water” in landscape irrigation should not be necessary and is to be avoided if possible.

In order to conserve water, and to protect and preserve the BVI’s natural ecology, the landscape design should be made up of native or “adapted” vegetation; plants that are indigenous to the islands or are adapted to the local climate and are not considered invasive species. Native or adapted plantings typically reduce maintenance costs over their lifetime by minimising inputs of fertilisers and pesticides. Irrigation requirements can be drastically reduced through thoughtful plant selection, and a good landscape designer will also consider the microclimates of a site and give careful thought to selecting practical plant groupings.

Modern irrigation technology can allow for a broader plant species palette, while still conserving water supplies. High-efficiency drip systems will apply water slowly and directly to the roots of the plants, using 30 to 50 percent less water than conventional sprinkler irrigation and moisture and rain sensors ensure that plants only receive water when necessary. A healthy landscape can be encouraged by carefully moderating the supply of water to the plants, training the plants to “look” for moisture, helping them to establish good strong root systems.
    
Whatever the topography of the site, with careful and sensitive consideration, the home can blend with the landscape and the owner can feel comfortable that they are living in harmony with the natural environment.

Next month…
In the next installment of the Building Green series, we will discuss building materials.

By: Steve Fox, OBM International – Steve Fox is a Senior Architect for OBM International’s BVI office. He is a Leadership in Energy and Environmental Design (LEED) accredited design professional and co-founder of the BVI Sustainable Living Network. Thanks also to Anthony Blake of Green Thumb Landscape Services.

OBM currently has design offices located in Antigua, Bermuda, British Virgin Islands, Cayman Islands, Madrid, Miami, Trinidad and Tobago and Turks & Caicos Islands, a strategic alliance in the Bahamas, and a business development office in Bath (UK).