Green Neighborhood in North Carolina

Durham, NC

Oct 15 2008 By Rob Wotzak | 0 comments

General Specs and Team

Location: Durham, NC
Cost (USD/sq. ft.): $65/sqf

Completed: 1998-1999
Bedrooms: 2-4
Bathrooms: 21/2

Living space: 962-1,974 sq. ft.

Owner/developer: Sherri Zann Rosenthal
Builder: Craig Morrison, Cimarron Homes
Architect/designer: Jeffrey Davis
Landscape architect: Ken Coulter, Coulter Hart Jewell Thames
Engineer: Jim Thames, Coulter Hart Jewell Thames
Environmental building consultant: Arnie Katz, Advanced Energy Corp.
Geothermal contractor: Bill Evangelist, Evangelist Service Co.


Foundation: slab on grade, 1 in. EPSExpanded polystyrene. Type of rigid foam insulation that, unlike extruded polystyrene (XPS), does not contain ozone-depleting HCFCs. EPS frequently has a high recycled content. Its vapor permeability is higher and its R-value lower than XPS insulation. EPS insulation is classified by type: Type I is lowest in density and strength and Type X is highest. insulation at perimeter and extending 20 in. under slab (R-3.6)
Walls: 2x4, 16 in. o.c.; damp-spray cellulose (R-15)
Windows: low-eLow-emissivity coating. Very thin metallic coating on glass or plastic window glazing that permits most of the sun’s short-wave (light) radiation to enter, while blocking up to 90% of the long-wave (heat) radiation. Low-e coatings boost a window’s R-value and reduce its U-factor., double-pane, argonInert (chemically stable) gas, which, because of its low thermal conductivity, is often used as gas fill between the panes of energy-efficient windows. -filled on east-, west-, north-facing; south-facing, clear (not low-e), argon-filled (Caradco)
Roof: 2x8, 16 in. o.c.; vented; blown cellulose on flat ceilings, fiberglass batt in sloped ceilings (R-30)
Garage: None


Heating/cooling: closed-loop 1.5- or 2-ton GSHPs (water furnace)
Water heating: electric water heater
Annual energy use: 19 MMBtu average

Although solar hot water was not included in the initial construction, water heaters were located for future solar collectors.

  • Windows laid out for ample daylightingUse of sunlight for daytime lighting needs. Daylighting strategies include solar orientation of windows as well as the use of skylights, clerestory windows, solar tubes, reflective surfaces, and interior glazing to allow light to move through a structure. and cross-ventilation
  • Passive solar design, including slab floor as thermal massHeavy, high-heat-capacity material that can absorb and store a significant amount of heat; used in passive solar heating to keep the house warm at night.
  • Roof overhangs, reflective roof, and natural cross-ventilation reduce cooling load

Water Efficiency

  • Low-flow plumbing fixtures
  • Drought-tolerant, native plants

Indoor Air Quality

  • Most flooring is concrete or wood


Green Materials and Resource Efficiency

  • 100% recycled PET carpeting
  • Most materials locally sourced


None: (development predates most certification programs)

Twenty-two homes in a cluster made for walking

Eno Commons takes the idea of green homebuilding to another level — the community level. The Durham, North Carolina, project includes 22 energy-efficient homes that, in accordance with the community concept at the heart of Eno Commons, encircle a comfortable walking path while car traffic and parking are kept to the perimeter.

Smart planning makes the best use of space
By clustering the development in the middle of the site, more than 75 percent of the land was left undisturbed, allowing wildlife to freely cross the property. The relatively level home sites made it easy to provide accessibility by bringing footpaths right up to each front door. The homes have well-thought-out open floor plans, with all of the important amenities on the first floor, making the layout equally comfortable for a growing family or a retired couple. The smart layout also means a lot of function is packed into a small footprint.

Well-designed homes can be comfortable and affordable
Sustainable building doesn't have to come at a premium. Simple, traditional details and production building methods kept construction costs low — around $65 per sq. ft. — about half what it would have cost to build a typical single-family house in 1998. The passive solar design of the homes dictated their orientation, but the open floor plans allowed placement of a "front" door on whichever side faced the footpath.

This flexibility gives each home a distinctive identity, even though there are only two unique designs. Ground-source heat pumps and tight building envelopes complement the passive solar heat and make the homes' operation more affordable. Inside temperatures are kept stable by reflecting summer heat with a metal roof and storing winter heat in the concrete floors. Both of these materials will last a long time. The homes illustrate the fact that straightforward designs based on simple principles can make great-looking, affordable houses. In fact, they're among the most energy efficient houses built in the last decade.

Lessons Learned

Even with such a dedicated, team effort, there are usually surprises. Because the first two horizontal loops for the ground-source heat pumps were so destructive to a site that was to be left 75 percent undisturbed, the remaining loops were inserted into drilled vertical wells at significant extra cost. On a less serious note, even though local building officials were uncomfortable with the lack of driveways, buyers were most interested in the home sites farthest from the parking area.

Rob Wotzak is assistant editor at

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Image Credits:

  1. Triangle J Council of Governments
  2. Robert Heinich
  3. Scott Gibson

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