An Architect's Guide for Sustainable Design of Office Buildings
3. Site and Landscaping
3.0 Introduction
Buildings modify or transform a previously existing natural system. New construction or renovation work should ideally be extended to the surrounding landscape, with the primary goals of:
- Transforming the landscaping to enhance the microclimatic conditions around the building;
- Mitigating the adverse environmental impacts of the building on the site.
These activities must be consistent with the requirements of the Canadian Environmental Assessment Act (CEM).
Since the landscaping surrounding buildings is typically highly visible, improvements provide an excellent opportunity to demonstrate a changing emphasis toward environmental responsibility.
Site/landscaping environmental strategies include:
- Use of site resources;
- Restoring site ecology;
- Enhancing site microclimate;
- Re-examining surface parking;
- Using efficient irrigation;
- Controlling storm water;
- Ensuring sound construction practices.
3.1 Using Site Resources
The transition to sustainability will require increased use of renewable resources.
Each site offers varying degrees of opportunity to use solar heat gain, natural ventilation, daylighting and rainwater advantageously.
Maximizing the use of site resources will involve:
- Examining the complete site for potential access to solar energy and daylight throughout the year;
- Examining the rainfall potential on the complete site;
- Examining the seasonal sun path and prevailing wind directions characteristics of the site and assess potential benefits and problems.
3.2 Restoring Natural Ecology
For those existing buildings where the immediate surrounding natural systems are relatively undisturbed, the goal must be to minimize any potential adverse environmental impacts associated with the building and its operation.
For highly developed sites which are often so transformed and degraded, the opportunities to reconnect a building with natural systems are more difficult, if not, impossible. New landscaping in these cases should be a conscious act of rehabilitation by incorporating landscaping strategies into the project that repairs past environmental damage.
The site ecology can be enhanced by:
- Examining the existing water courses and drainage patterns across the site;
- Understanding the natural behaviour of the ecosystem that embraces the site, consistent with the requirements of the Canadian Environmental Assessment Act (CEAA);
- Considering the ecological aspects of the site that are going to be affected and whether the changes are detrimental to their survival, consistent with the requirements of the CEAA;
- Creating critical connections to any adjacent habitats;
- Promoting the establishment of biodiversity;
- Supplementing existing natural vegetation, but avoiding monoculture;
- Clustering plants where space is available to promote large common root systems and protect other plants from wind, sun and reflective heat;
- Considering plant root systems in the design process.
3.3 Enhancing Site Microclimate
The effects of the surrounding landscape can have a profound effect on the solar heat gain, external air temperature and air quality in the vicinity of the building. This landscaping can also improve acoustic conditions.
The choice of ground surfaces and the type and placement of trees and other vegetation provides many opportunities to positively influence the climate stress on the building and the thermal quality of the spaces surrounding buildings. The significance of the immediate surroundings in modifying the microclimatic conditions is greatest in low-rise facilities. [1]
The microclimatic conditions can be modified positively by:
- Planning the new landscape strategy integral to the energy strategy;
- Planning shade walls and paved areas adjacent to the building to reduce solar radiation striking the building during the summer;
- Planting deciduous trees for their summer shading and winter windbreak effects for buildings up to three stories;
- Planting coniferous trees for summer and winter sun shading and windbreak effects;
- Planting shrubs or other vegetation between the building perimeter and sidewalk to reduce heat build up;
- Consolidating or relocating paved areas away from the building perimeter and replace with vegetation to reduce outdoor temperature build up;
- Using ponds and water fountains to reduce ambient outdoor air temperature around buildings, considering their impact of water conservation and maintenance.
3.4 Re-examining Surface Parking
Significant areas of site landscaping is typically devoted to the parking of motorized vehicles. The current provision of large areas of impervious asphalt limits the amount of water penetrating the subsoil and leads to elevated surface temperatures during the summer.
The use of site landscaping surface parking can be reassessed by:
- Developing alternative transportation strategies and conveniently locating car pooling space;
- Providing options such as covered personnel loading and unloading at building if such options will encourage car pooling or use of mass transit;
- Varying paving materials in parking lots based on traffic use;
- Considering oil grid separators at paved areas.
3.5 Using Efficient Irrigation
Considerable amounts of potable water are used to maintain landscaping, particularly in dry regions. Water consumption for landscape maintenance may be reduced by the use of efficient irrigation systems and on site recovery of waste water for irrigation.
There are four basic strategies for water conservation relating to landscape design:
- Use the water that falls on the site more efficiently;
- Design or redesign the landscape and select plant materials so as to reduce the need for water;
- Apply water to planted areas more carefully and precisely;
- Find sources of recycled water to use for irrigation.
3.5.1 Using Site Rainwater
The efficient use of the rainfall on a site is the best way to reduce the need for costlier sources of water. Water that drains off a site without fully wetting the plant material is wasted and must be replaced later.
Rainwater can be used more effective by:
- Using materials for walkways and parking areas which slow down run-off by allowing the water to percolate into the soil;
- Focusing the flow of water by grading the site to direct water towards planted areas rather than off the property and forming saucers can around the base of trees and shrubs to collect and hold water for the plants;
- Storing water on site. On large sites it may be appropriate to use retention basins to store water for use at a later time;
- Handling rainwater in visible, surface channels integrated with the landscaping rather than in buried pipes.
3.5.2 Redesigning the Landscape
A variety of landscape design and management techniques can be utilized to conserve water through creative landscaping. This should result in landscaping with:
- Lower costs and simpler and less expensive irrigation systems;
- Lower maintenance costs because of lower consumption of potable water, lower mowing and lower fertilizing costs.
Water consumption for landscape maintenance may be reduced by:
- Landscaping with tress, hardy shrubs and indigenous plants which may require little or no watering;
- Grouping plants of similar water needs together into hydrozones;
- Increasing the organic content of the soil to improve its water holding capacity;
- Limiting the amount of turf to small areas or using alternative drought resistant native grass types;
- Using mulch material, such as wood chips, to control weeds and reduce evaporation loss;
- Employing water conserving irrigation system, zoned to allow different watering schedules for areas of different water needs;
- Selecting native plants or plants from areas with similar soils and climates which are able to survive on the amount of water that is naturally available in that region;
- Retaining natural drainage patterns to maintain as much as possible natural contours. Surface drainage rather than subsurface systems.
3.5.3 Applying Water to the Landscape more Precisely
The design and selection of the appropriate irrigation system can reduce water consumption significantly.
Sprinklers are relatively inefficient since a certain percentage of the water is lost to evaporation and run-off. Sprinklers are particularly inefficient during the daytime, when the sun and warm temperatures increase evaporation - on a hot day up to one third of the water can evaporate before it hits the ground. Moreover, sprinkling during hot sun can damage leaf surfaces.
Instead of unselectively flooding an area with water, drip 5 irrigation delivers water directly to the plant. In addition to conserving water, the better control over moisture also promotes better plant growth.
Water consumption for landscape maintenance may be reduced by:
- Using drip irrigation strategies.
3.5.4 Using New Sources for Irrigation
The waste-water generated in a building from both lavatory and kitchen sinks, showers, clothes washers and cooling systems can be reused by means of a dual piping system for irrigating the building's landscape. This reusable waste-water is defined as grey-water and contains primarily soap related wastes which must be filtered out through a cleaning process before reuse.
3.6 Controlling Storm Water
Storm water from large paved sites and roof areas has serious impacts on local ecosystems. Oil and grease, heavy metals, especially copper, lead, and zinc are by far the most prevalent pollutants found in urban run-off. Moreover, storm water management requires storm sewers which are sized for peak periods. Oil accumulation, erosion of natural watercourses receiving peak storm water and flooding of treatment facilities are three of the most common problems.
Storm water from large paved sites and roof areas can be controlled by:
- Design the landscape to retain and filter storm water on-site to protect ecosystems;
- Using large semi-porous areas capable of absorbing water and releasing it slowly, roof ponds or holding tanks specifically designed to reduce peak storm water flow;
- Preserving natural slopes and direction of existing water flows;
- Constructing retention ponds for on-site storm water management, i.e., using large semipermeable areas capable of absorbing and releasing water slowly, or roof ponds or holding tanks;
- Engineering land forms to improve sites ability to catch, hold and absorb water;
- Where feasible, sing roof spaces and terraces for vegetation;
- Minimizing the amount of impervious surfaces and preserving natural areas to retain and filter storm water.
3.7 Ensuring Sound Construction Practices
The construction process is disruptive of natural systems. Although these effect cannot be avoided they can be reduced through careful practices.
Environmental impacts during construction practices can be reduced by:
- Limiting topsoil removal and stockpiling existing topsoil on-site for reuse;
- Exposing the smallest practical area of soil at any one time during development;
- Requiring a waste management plan from the contractor (See Section 7: Waste Reduction);
- Establishing staging areas and travel routes for construction vehicles;
- Protecting areas and vegetation adjacent to development from construction activity and debris;
- Providing and enforcing parking in specified areas for construction worker's personal vehicles;
- Scheduling the installation of features capable of carrying storm run-off prior to removing any existing vegetative cover.
3.8 References
- Guiding Principles of Sustainable Design, US Department of the Interior, National Park Service, Denver Service Centre, September 1993. (back to 1)
- Robinette, G.O., Energy Efficient Site Design, 1983.
- Townshend, A.R., Advancing the Light Grey Option, Research Division, CMHC, April 1993.
- Shrubsole, D., and Tate, D., ed. Every Drop Counts Canadian Water Resources Association, 1994.