No conversation about green building can commence without a discussion about the site. “[It’s] mandatory, from where you put the building to how you handle stormwater,” says architect Bill Kreager, principal of Seattle-based Mithun Architects. “It’s critical.” Long after you’ve moved on, the site plan will affect home buyers, local wildlife, drinking water, and a host of other issues that many builders don’t even think about. The Austin, Texas–based Austin Energy Green Building program says in its Sustainability Source Book that the site should get first consideration and be evaluated for all characteristics. It “has a crucial role in future performance of the building and enjoyment of occupants,” the group says. Here, then, are some site items to take into consideration.
Look Before You Leap
It’s easy enough to clear land and drop in as many houses as possible. Surprisingly, this may not be the smartest approach nor the most cost effective. Meticulous planning is better. Before anything else, thoroughly analyze your site for ecological and anthropological conditions, says the Austin Energy Green Building program. It takes a little more time, but it’s worth it. “General climatic data (insolation, temperature, humidity, and wind patterns) should be analyzed in conjunction with specific site elements (i.e., topography, vegetation, water conditions on site, existing built forms, and natural drainage patterns) in the selection of building location, orientation, form, envelope construction, and size and location of apertures,” the group advises. For example, if you use a site’s natural wind patterns you could greatly reduce cooling bills in the summer, says Peter L. Pfeiffer of Austin-based Barley & Pfeiffer Architects.
In the Shade
Before any other decision is made, the site should be assessed for “significant shrubs and trees, which help percolate water to the soil,” says Langley, Wash.–based architect Ross Chapin. Save as many trees as possible and incorporate them into the site plan, architect Peter L. Pfeiffer adds. “They provide shade, [act as] good wind buffers, and enhance the marketability of any home or building,” he says. The Austin Energy Green Building program adds, “Preserving native vegetation can greatly reduce water and pesticide use, and large existing trees add to property value.” It also makes sense to save as many trees as possible. “If you completely clear a site, you will need to rebuild what nature provides for free,” says Chapin. “Have you seen how much trees cost?” Besides, a neighborhood with mature trees simply looks better.
Promote Water Drainage
The architects at the University of Arkansas Community Design Center say that up to 47 percent of surface pollutants such as fertilizers can be removed from a site in the first 15 minutes of a storm event and drain into local waterways. This is not good because much of this rain (or melted snow) runs right into the stormwater system and some ends up in the drinking water. Using pervious surfaces is a better idea because it reduces runoff and manages the water on site. The illustration below shows how the Design Center employed a variety of pervious mechanisms for Habitat Trails, an eco-friendly project of 17 Habitat for Humanity homes in Rogers, Ark.
Keep a LID on it
Typical residential developments manage stormwater with “pipe-and-pond” systems that collect rainwater and discharge it off site. A low-impact designed (LID) site takes a different approach. Modeled after nature, “it manages rainfall on site,” a Massachusetts Metropolitan Area Planning Council low-impact development fact sheet says. “Designers should seek to maintain or create small sub-watersheds on the site and ‘micromanage’ the runoff from these sub-watersheds in small, decentralized structures such as swales, bioretention areas, infiltration structures, and filter strips.” Mithun Architects used a low-impact system for its 120-acre High Point development in Seattle and was able to reduce its pond area from the typical 5 acres to 1 acre. The plan cost $2.7 million, but it allowed 72 additional units, architect Bill Kreager explains.
The Great Xeriscape
How you landscape your houses will affect your buyers a great deal. It could mean the difference between a landscape that requires tons of water and one that’s able to withstand drought conditions. “You can reduce landscaping time and your customers’ water bills through xeriscaping,” says the Partnership for Advancing Technology in Housing. “Disturb as little existing vegetation as practical and choose drought-tolerant native plants.” Vegetation that corresponds to the local rainfall patterns is low-maintenance, requiring less water. Additionally, says architect Peter L. Pfeiffer, “A thicker layer of topsoil will mean a lawn will require less watering.” The U.S. Green Building Council says effective landscaping design could also reduce heat build-up near houses.
Higher Elevations
No need to get fancy to be green—or greener. And achieving an energy-efficient house doesn’t necessarily have to be an expensive proposition with fancy gewgaws and extravagant fixes. A lot of strategies cost very little and some are essentially free. “You have to pick the low-hanging fruit,” says architect Edward M. Binkley, national design director in the Ovieda, Fla., office of BSB Design. The elevation and the building envelope are good places to start. Peter L. Pfeiffer of Austin, Texas–based Barley & Pfeiffer Architects says the primary culprits affecting comfort and energy in most parts of the country are “infiltration of outside air, improper orientation, excess solar heat gain, and internal loads that produce humidity and heat.” Check out these exterior strategies that will help your houses perform better.
Face Forward
Few things are as important in green building as where you put your houses on the site in relation to the sun. “It is fundamental,” says architect Allison Ewing of Hays + Ewing Design Studio in Charlottesville, Va. In short, proper orientation affects its future performance. “Orient streets in a new subdivision to run east-west as much as possible so that the majority of lots can have either a north- or south-facing front and rear,” architect Peter L. Pfeiffer advises. Also orient the building to maximize prevailing breezes. As best you can, put most of your windows on the south side to cut down on heat gain in summer and to allow heat gain in the winter, Ewing says. Ideally, windows should face within 15 degrees of true south to take advantage of solar heating.
Go Deep
Like a hat or an umbrella, a roof keeps a house dry, but it does a lot more than that. “Roof overhangs keep hot summer sun from overheating a home and help protect the home from rain,” PATH says. “The larger the overhang for windows or doors, the less frequently moisture problems will occur on exterior and foundation walls.” In addition to deep roof hangs, also consider a shading porch on the west elevation to help deal with harsh sunlight.
Cover Up
Despite all best efforts, you will still need to put some windows on the east, west, and north sides. For those cases, sun screens, shades, or awnings will help, architect Allison Ewing says. The trick is in locating the shading devices on the outside, rather than the inside, to prevent the heat from coming in, she adds. Once the heat penetrates the window, the house will require fans and air conditioning to work harder to cool the interior.
Color Corrected
The same principles that govern dark- and light-colored clothing apply to your houses as well. In a warm climate, avoid dark siding, trim, and especially roofs. “The roof is the No. 1 heat-gaining product on a house,” says architect Edward Binkley. “So look at Energy Star–approved roofing, use metal, or pick the lighter-colored asphalt or fiberglass shingles.” Dark roofs also require the use of a radiant barrier to cut down on the heat gain, says architect Peter L. Pfeiffer.
Window Dressing
Pfeiffer often notes that a single-pane window in the shade is more efficient than an insulated window in direct sunlight. Super insulated low-E windows are not a substitute for common sense techniques such as window shading and solar control. Still, window technology has come a long way; high performance glass, in the presence of good passive strategies, will make your houses highly energy efficient.
Shell Game
The construction of a home’s walls is very important. As the barrier between inside and outside, the shell is the primary defense against wind, moisture, heat, and cold. It also helps keep the indoor temperature constant. It’s important, then, to construct walls for maximum efficiency, which includes adequate insulation, a good vapor barrier (installed based on regional climate), properly flashed windows, and adequately installed siding. Architect Allison Ewing prefers walls constructed with 2-by-6 framing and sprayed foam insulation. “Sprayed polyurethane insulation is especially effective in reducing infiltration and vapor [humidity] flow,” says architect Peter L. Pfeiffer. Architects Binkley and Ewing also like panelized construction such as structural insulated panels that create an energy-efficient shell. Panelized systems, the Partnership for Advancing Technology in Housing agrees, can be assembled rapidly on site, cutting cycle times and reducing waste. “They provide superior insulation and are often lightweight, making installation easier.”