Selecting a Good Site for a Green Home
Many aspects must be considered when choosing a good site to build a green home. A site has the potential to limit green building options. This section details aspects that must be considered.
Types of Sites
There are many different types of sites. The following section broadly defines the most common sites builders and developers encounter and the role each site type plays in building a green home.
Brownfield sites are previously developed areas that have some contamination present that needs to be cleaned up before the site can be used again. Not all brownfields are created equal; some need little or no clean-up, while others may need extensive work. Builders should consider the benefits (typically prime locations and government subsidies) and balance these against the clean-up costs and disadvantages of a site. Many organizations, like the U.S. Environmental Protection Agency (EPA), offer grants for contamination assessment, clean up, and site remediation job training. After Hurricane Katrina in 2005, environmental remediation of contaminated land became a common construction practice in New Orleans.
Greyfield sites are those that have been previously developed but are not contaminated. Typical examples are demolished schools, amusement parks, old malls, and, at the largest scale, airports (although these invariably contain pockets of brownfield sites). These sites offer the possibility of providing a carefully planned mixed-use development within or close to existing development, filling in a "missing tooth" in the urban fabric, and avoiding the development of outlying farmland. In large projects, there are often excellent opportunities for developing sizable wildlife core refuges and linking corridors.
Greyfield Case Study: The Stapleton Airport
In 1988, the Stapleton Airport in Denver, Colorado, was decommissioned in response to growing complaints from the nearby community and the need to add an additional runway. The airport was replaced by the Denver International Airport about 20 miles away. The decommissioned land was then transformed into a redeveloped residential and retail center. The old airport now serves as the site of 12,000 homes, six schools, a light-rail station, offices, retail space and over 1,000 acres of park. The once greyfield is now one of the largest and most sustainable developments in Colorado.
Scattered-Lot Infill Sites
One way to raise settlement density and avoid the development of open space or farmland is to "fill in" vacant lots. Infill sites are typically more expensive to develop than greyfield sites because they are scattered, access is sometimes constrained, and permits must be obtained one-by-one. The added costs are partly balanced by savings from using existing infrastructure and from local incentives (mentioned previously). Local small builders can typically build on scattered-lot infill sites more economically than larger companies, because they can shepherd permits through the official channels and pay attention to the complexities of building non-repetitive homes in tight quarters.
Clustering homes enables parks and other open spaces to be preserved for recreational or environmental purposes. Developers have found that they can cluster well-designed homes into a more densely populated community and preserve open space at a greater profit than if they had developed the area in a more traditional manner. Most home buyers are attracted to, and some are willing to pay a premium for, homes that are adjacent to open spaces, recreational areas, or other amenities. Clustering can also foster an increased sense of community.
Generally, builders should try to reduce paved areas for streets, alleys, sidewalks, and parking lots. It is possible to reduce the paved area in a subdivision by as much as 50% (15% of the land being developed rather than the more typical 22-27%). Where paved areas are created, consider using pervious materials to reduce storm water runoff or using lighter colored paving materials to reduce the "heat island effect." In addition, take advantage of recycled materials, such as less-expensive aggregates that reuse asphalt and concrete. Planting trees in the parking strips may help reduce the heat island effect.
During the development phase, consider narrower streets to reduce paving materials. However, the reduction in paved area can often only be achieved by adopting incentives that allow reduced road widths and parking requirements. A side benefit is that motorists slow down, allowing pedestrians and children to more safely use sidewalks, lawns, and, in smaller communities, even the street, as impromptu community gathering areas. As always, design decisions require integrated thinking. Consider this simple but interesting example. Most sidewalks are 48 to 54 inches wide, just wide enough to accommodate two people walking past one another. However, designing sidewalks to be up to 72 inches wide could help meet other goals, such as to accommodate people with disabilities or to encourage children to play on the sidewalk rather than in the street. In any case, consider placing a sidewalk on only one side of the street.
Other Important Site Considerations
Besides the site characteristics itself, there are many other factors when selecting a site for a green home. In particular, a site's density and proximity to services are both important aspects to building a green home.
Smart Growth and Community Connectivity
Community growth and development can be controversial. Issues of traffic, schools, open space, and environmental protection are just a handful of the Smart Growth concerns that home builders and local governments are grappling with. Many local home builder associations have found that a green building program changes the tenor of relations and improves opportunities for substantive dialogue on Smart Growth issues.
Principles of Smart Growth
Increased density of housing is the most important way to cut the use of resources in developing land. Not only does it reduce the need for certain types of infrastructure and its long-term maintenance, it also reduces the energy consumption of the home by decreasing the exposed surface area in the homes (particularly for town houses, apartments, and mixed-use structures). Properly planned higher-density development, such as the increasingly popular Traditional Neighborhood Development projects, are designed and built for easy access to schools, work, shopping, and public transportation. This type of development reduces automobile use.
Smart Growth Case Study: The Crossings, Mountain View, California
This 18-acre infill project was transformed into residences in 1994 and today serves as a great example of smart growth. The Crossings offers affordable high-density living, access to several transit options; and walkable streets just minutes away from shopping.
Street orientation should be controlled to provide properly oriented buildings, whenever allowed by density and view considerations. On east-west streets, homes can be closely spaced, with their major openings facing front and back (north and south). On north-south streets, lots should be shallower and wider, with homes set to the north side of the lot, again with major openings to the north and south. This strategy is unusual, as builders may forget that homes do not have to "face" the street to be welcoming.
Protection and enhancement of natural systems can play a key role in maintaining and enhancing the natural environment. One way builders can help is by configuring development or selecting sites that connect open spaces in ways that preserve or create wildlife corridors of forested, wetland, prairie, or other undeveloped lands. This is far more effective than creating isolated "wildlife islands." Builders can turn these lands into a home buyer asset by creating or planning for walking trails or educational signs and kiosks. Local nature-oriented nonprofits are excellent partners for such efforts. Small parcels of disconnected land or water do not provide enough sustaining habitat for area birds, mammals, and other wildlife and vegetation.
Consider clustering homes and other buildings in a manner that preserves undeveloped lands for use as parks, with or without trails. Builders can also develop sites that promote biodiversity by landscaping, using meadows, ponds, trees, and other features while minimizing lawn areas. Implementing these natural environment strategies will add value to nearby homes and ease storm-water runoff.
Access to public transportation is especially important in a previously undeveloped area. Because rapid transit is generally not available in outlying areas, building in areas with high-speed bus service linked to rapid transit or other transit centers is possible. Developments should also be designed to encourage walking, bicycling, and carpooling as a means of reducing conventional individual auto use.
Traditional Neighborhood Development
Traditional Neighborhood Developments (TNDs), sometimes also known as neo-traditional communities, seek to rediscover the principles of small towns built before World War II. Some common features of TNDs are the following:1
- an interconnected network of streets to give motorists alternate routes and avoid concentrating traffic onto a single busy road;
- a town center with a small grocery store or convenience store and other essentials (including, ideally, mass transit links);
- formal plazas and greens, the most prominent of which are usually located in the center of the community;
- a mix of uses and housing types in close proximity, usually including detached houses, row houses and apartments and, in the town center, apartments built above the stores;
- higher density; and
- pedestrian-oriented design, achieved through the combination of narrow street widths, sidewalks, street trees, houses that are close together (and close to the street), and alleys, which relocate the garages to the rear of the lot and remove the clutter of garage doors and driveways from the streetscape.
Designing a Site for a Green Home
No matter what the density of a development, the site a home occupies determines major aspects of the home's design. For example, in a typical subdivision on relatively flat land, homes are almost always designed with most windows facing the street and the rear yard, with only secondary bedroom, bath, or kitchen windows facing the narrow side yards. Homes are typically designed in specific widths so they will fit on specific sizes of lot with the required setbacks. This section delves into the design aspects associated with different site characteristics.
Design for High Density
As the density increases, the lot and street layouts determine the size and orientation of the homes more and more. The site planning (except for detailed landscape design) and the amount of solar access are determined entirely during the land development stage. In a typical site plan, the builder should take advantage of the solar opportunities made available during land development, compensating in the detailed design of the home for less than ideal circumstances.
What can a builder do when setting homes in a medium- to high-density subdivision if solar access and views have been ignored in laying out the lots and streets? Suppose, for example, that the street side of a relatively wide lot happens to be on the west. The simplest measure is to develop home plans with enough flexibility in the design so that some of the windows can be placed on the south side instead of the front or rear and so that living spaces and bedrooms, instead of closets and bathrooms, end up on the south. This may require flipping the plan right to left, or in a two-story home, flipping one story relative to the other (if that is possible). Home styles that feature informal, asymmetrical elements are easier to work with than classical "colonial" homes that emphasize symmetry at the expense of flexibility in plan layout and window placement.
Another approach that works on relatively wide lots is to orient the home sideways on a west- or east-facing lot so that its major facade faces south instead of west (toward the street). In most cases, turning the house requires some ingenious landscaping (fences, hedges, pergolas, etc.) to guide the visitor to the front door. What seems to be a problem can often turn into an opportunity for inventive design, and the end result may prove more interesting than a conventional, street-facing design.
Design for Low Density
As density goes down and building sites become larger, there are more options for locating and designing a house to take full advantage of desirable sun, views, and breezes. Homes can more easily be protected from undesirable sun, views, wind, noise, rain, and snow. Along with freedom comes responsibility, and large sites raise new issues that must be considered during site planning. A large rural site, for example, is not likely to be served by urban utilities, and may need a septic system, a water well, and a long, paved entrance driveway. On the other hand, on a remote site, an array of photovoltaic solar cells may be selected as a source of electricity instead of a diesel generator, with the advantages of being quiet and not relying on any fossil fuel.
Of the wide variety and extent of issues that must be considered to build green on a generous site, some of the most important are the following:
- How the sun moves across the sky at the latitude of the site
- Shading by mountains, slopes, or large trees
- Shading by regular morning or afternoon fog
- Direction of prevailing snowfall and drifting (for example, entries facing northeast in New England can become completely plugged with snow, so New England Colonial farmhouses nearly always had the front door facing south or southeast)
- Direction of cold winds in winter (so protected outdoor spaces can be located out of the wind)
- Direction of cooling breezes in summer (so the home can be cooled by natural convection without mechanical air conditioning)
- Surface water drainage
- Underground water drainage and soil type
- Existing wetlands
- Attractive car access without excessive grades (especially in areas requiring salt or heating), without disrupting drainage on the site, and with areas to pile plowed snow without damaging native plants or trapping runoff water
- Attractive car parking that does not dominate the site and create large paved areas
- Location uphill from the septic field to avoid the need for pumping sewage
- Orientation toward desirable views and away from undesirable present or future development on adjacent sites
- Understanding of soil types and the type of plants best suited to each
- Preservation of desirable plant material, especially true native plants, and thinning or removal of undesirable plants (it pays to have a landscape architect decide which is which)
- Providing reasonable and attractive ramps or slopes up to the home's entrances, for accessibility.
Passive Solar Case Study: Amory Lovin's Home
Design for Solar Access
Site planning should take solar access into consideration. With solar access, builders can incorporate passive space heating and daylighting. These features can significantly reduce energy needs and can contribute to occupant comfort. Over the years, developers and builders have come up with flexible ways to guarantee that homes have access to the sun for the life of the building. Of course, it is not possible to always provide optimum solar access, so it is important to carefully assess shading patterns to make the best compromise. Subdivisions that have streets running within 30 degrees of east-west will have building lots that face or back up to south, which is best for sun control. Subdivisions that have existing north-south streets can consider adding east-west cul-de-sacs.
In northern climates, taking full advantage of solar energy in the design of a home tends to stretch out the house's form in the east-west direction so that most living spaces can be on the south, with service spaces such as bathrooms, garage, storage, and corridors on the north, and with few east and west windows. In southern climates, the same approach to home design applies, because it is easier to control sunlight on a south-facing facade than on one facing east or west. But additional attention must be given to the use of overhangs and landscaping for shading during the cooling season.
Design for Storm Water Management
Storm water is defined as precipitation that does not soak into the ground or evaporate, but flows along the surface of the ground as run-off. The management of storm water involves a combination of strategies to reduce both the run-off and the amount of pollutants that enter the run-off. Federal and state regulations require most construction sites to manage any storm water leaving the site. Typically the site operator will be required to obtain a permit to discharge storm water from the site. Check with the U.S. EPA or your state environmental agency. A storm water analysis will include soil analysis, topography mapping, peak flow calculations, and run-off characteristics. It will also help measure pollutants such as fertilizers and other lawn treatments, as well as vehicular pollutants. Important aspects of managing storm water run-off include:
- Minimize land disturbances on the site.
- Preserve existing topography, vegetation, and landforms as much as possible.
- Separate impervious surfaces with turf, vegetation, or gravel to increase filtration and reduce run-off.
- Use pervious paving materials and avoid curbs where possible.
- Use grass paving systems as an alternative for driveways, streets, and alleys.
- Minimize the amount of road salt, animal waste, and vehicle fluids.
- Avoid using pesticides and fertilizers on landscaping.
- Switch from channeling and paved drainage ways to systems that encourage sheet flow, thus reducing the need for expensive storm water piping.
- Use open grass swales, pervious paving materials, and natural vegetation to reduce the total hard paved areas in a development.
- Ensure compliance with local and state drainage master plans and sediment control requirements.
- Remove or isolate any hazardous material on the site to prevent it from getting into the storm water run-off.
Designing a Green Site—Rules of Thumb
- Lower density developments require careful design decisions in order to take full advantage of the green possibilities available on larger sites.
- Provide solar access to as many homes as possible during the planning process.
- Provide a solar orientation for homes on developed lots whenever possible.
- Minimize compacting of soil during construction by keeping equipment on areas that will be paved and by stockpiling topsoil.
- Well-designed landscaping can lower a home's heating and cooling load costs by as much as 25% through proper placement and species selection.
Creating a Green Site during Construction
The average home generates 3 to 5 pounds of construction waste per square foot, costing builders anywhere from $250 to well over $1,000 in disposal costs. Reducing waste lowers disposal costs. The key point to remember is, if you do not generate waste, you do not have to deal with it. Builders can reduce waste through design and planning. Any money saved by developing and executing a waste management plan can be added directly to a builder's bottom line. By weight or volume, 60% to 80% of a builder's jobsite waste stream may be recyclable (wood, drywall, and cardboard). Metals are generated in much smaller quantities but have good recycling values. However, waste placed on the jobsite by someone other than the contractor or subcontractor, "drive-by contamination", can be a factor.
Reduce Site Disturbances
When grading, plan activities so that heavy equipment compacts a limited area of soil and stays as much as possible where paving will occur. Prior to construction, develop a site access plan to minimize damage to the site. Indicate areas for scrap/reusable, recyclable and waste materials; areas for staging and storing building materials, and areas where soil compaction is prohibited. During the construction phase, preserve vegetation by storing materials and performing work outside the drip line of existing trees. Transplant valuable vegetation that must be removed. Stabilize soil during and after construction by using filtration barriers, soil erosion fences, and wood chip mats at entrances. Before beginning construction, save topsoil for reuse and replace the topsoil at the end of the construction phase. During construction, avoid creating erosion by minimizing the steepness of temporary slopes, planning ahead for temporary site drainage, and placing runoff barriers and sediment collectors. Use silt fences or other suitable methods. Incorporate language into subcontracts to ensure that other trades respect these same rules.
Develop a Waste Management Plan
Effective waste management begins with a company waste management policy. The policy should be a general document that acknowledges waste management as an issue and sets forth the company's general approach to waste reduction, reuse and recycling. The waste management plan can be tailored to meet the conditions the builder faces in the community, or even on a specific site. It should address the design of homes; material purchasing practices; disposal and recycling costs; availability of outlets; and feasibility of changing worker habits. The plan should be posted on the jobsite, in the office, and given to suppliers and subcontractors. Suppliers, workers, and subcontractors should be informed of its importance. The three basic steps to developing a waste management plan are:
- Identify components of the waste stream and learn conventional disposal costs.
- Understand conditions affecting waste management decisions.
- Establish a plan that follows the waste management hierarchy of Reduce, Reuse, and Recycle. See "Waste Minimizing Guidelines" later in this page for specific suggestions.
On-site waste reduction is a three-step process: reducing the amount of materials purchased and subsequently wasted, reusing as much construction waste as possible, and recycling whatever waste remains. Reducing construction waste begins with minimizing the amount of scrap and packaging materials. Recycling and waste disposal costs vary greatly from region to region and from month to month. Builders should note that developing new approaches to waste management can become profitable in the long term due to changing waste disposal fee structures, even if immediate conditions may not be favorable. Builders will need to evaluate all the conditions affecting their waste management in order to develop the most advantageous plan.
Waste Minimizing Guidelines
The biggest opportunities for builders to reduce waste are through designing homes efficiently, optimizing purchasing, and minimizing packaging materials. These can be incorporated into contract language with suppliers and subcontractors. On-site, efficient framing techniques and reuse of materials are the best waste reduction opportunities. Wood waste is the single largest portion of the construction waste stream by both weight and volume.
Waste reduction techniques include the following:
Reduce packaging. Packaging can account for up to 25% of a jobsite's waste by volume. Require suppliers to keep packaging materials or ask suppliers and product manufacturers to limit the amount of packaging. Look for materials packaged in easily reusable or recyclable materials such as cardboard.
Reduce waste factors when making material take-offs. Generate comprehensive, detailed construction drawings.
Increase spacing of joists and studs. This technique can reduce the amount of framing material required by 30%.2
Create a central cutting area for wood.
Separate reusable lumber, such as 2x wood cutoffs which can be used for bridging, stakes, bracing, shims, drywall nailers, and blocking. Similarly, cut off sheathing waste can be used for drywall stops and furring. Grind remaining wood on-site into wood chips to use as an erosion control mat at the site entrance or as mulch.3
Use cardboard or drywall off-cuts by grinding up for use as a soil amendment.
Require subcontractors to remove their own waste from the jobsite, rather than supplying a dumpster for their use. While subcontractors may increase their contract price to include disposal, eliminating waste dumpsters from the jobsite eliminates drive-by contamination; facilitates waste separation and recycling; promotes more efficient use of materials; and improves jobsite appearance.
Consider precast or poured concrete or insulating concrete forms (ICF), because they create little or no on-site waste.
Establish set work areas for each trade, especially framers, to aid in separating and reusing materials.
Assign and empower individuals on your staff to facilitate waste reduction and management.
Perform a waste audit on each job to determine where waste can be eliminated on future jobs.
Site-separate waste for recycling when sorting materials that cannot be reused. Sort into wood, cardboard, metals (wiring, steel, copper, brass, aluminum, zinc), cladding, flashing, plumbing, drywall, glass, plastics, and non-recyclables. Plastics may have to be further separated into polystyrene, polyethylene, and PVC. Check with local recycling facilities to see what they can accept.
Waste Recycling Guidelines
Recycling programs can vary greatly from location to location. Below are some general guidelines to minimize waste either through conservation, design, or recycling. There are four approaches to waste recycling, (check your local recycling center for more detail):
Jobsite clean-up service. Requires waste management contractors to establish the service schedule and separate, transport, and tip the material. Fee structures are based on the size of the house.
Jobsite commingled recovery. Requires builders to put all waste in a conventional container and schedule service for the waste management contractor to transport and tip the materials. The materials are commingled in the container and delivered to a facility that accepts mixed waste.
Jobsite separation. Requires builders to separate the material and schedule the container service. The waste management contractor transports and tips the materials. Fees are similar to the above two approaches, but savings can be realized through separation of higher value materials.
Self-hauling. Requires builders to handle all phases of waste management: separation, containers, transport, and tipping. Disposal costs and recycling revenues are determined by vehicle cost, tipping fees, and required labor.
Hazardous Waste Disposal
There are two approaches to active construction hazardous waste management:
Use or switch to nonhazardous substitutes. An example is water-based paints, which have seen dramatic improvements in performance and price. Using these paints eliminates solvents and clean-up materials that can be considered hazardous. Make sure your painting subcontractor has a waste management plan.
Recycle or dispose of hazardous waste at permitted facilities. Given the complexity of federal, state, and local statutes, it can be difficult for builders to shift potential liability for hazardous waste materials generated on their jobsites. The largest sources of residential construction materials that could be considered hazardous are waste solvents, paints and coatings and adhesives. Given the contractor's exposure under federal law, it is prudent to require subcontractor documentation of disposal methods for hazardous wastes or to directly oversee the disposal yourself.
Construction Waste Management Procedures—Rules of Thumb
- A builder's jobsite waste is 60% to 80% recyclable.
- Create and post a waste management policy and plan.
- Incorporate waste management language into subcontractor agreements.
- Evaluate and update your waste management plan periodically.
- Insist that subcontractors adhere to the waste management plan.
- Properly deal with hazardous waste.
Organizations / Associations
- National Ready Mixed Concrete Association
- Northeast Midwest Institute
- Portland Cement Association
- Savings By Design
- Smart Growth Online
- Southeast Cement Promotion Association
- Urban Land Institute
- Building with Trees recognition program is presented by the National Arbor Day Foundation in cooperation with NAHB. The program outlines tree protection practices and provides builders with opportunities to receive recognition.
- Planning Commissioners Journal online publication and resource Planners Web
- U.S. Department of Energy Building Technologies Office on using the whole building design approach.