Net-Zero For a Competitive Price

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Net-Zero For a Competitive Price

A California model home comes in at $150 a square foot — demonstrating that net-zero doesn't have to cost much more than conventional construction

Posted on Nov 26 2012 by Patrick McCombe

The designers of a 1,700 square-foot net-zero-energy demonstration home in Irvine, California, claim that a similar home can be built by virtually anyone for less than $150 per sq. ft., a figure that’s price-competitive with conventional homes in this market.

The developers of the home — Southern California Edison and Green Homebuilder magazine — call the three-bedroom, two-bath model home “the ABC (Affordable, Buildable, and Certified) Green Home.” The home’s energy features should reduce its estimated monthly utility bills by $150 to $200 compared to a similarly sized conventionally built home.

John Morton, project manager for Southern California Edison, says that the ABC home’s energy-saving strategies are mainstream and so they shouldn’t scare off buyers who might be leery of unfamiliar technology. The mild climate means the house can achieve net-zero status with 3 1/2 inches of Demilec closed-cell spray foam in the walls (in addition to 2 inches of EPS on the exterior side of the wall sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. ) and 5 1/2 inches of closed-cell spray foam in the ceiling. The roof deck is insulated to keep the ductwork within the conditioned spaceInsulated, air-sealed part of a building that is actively heated and/or cooled for occupant comfort. .

The water-resistive barrierSometimes also called the weather-resistive barrier, this layer of any wall assembly is the material interior to the wall cladding that forms a secondary drainage plane for liquid water that makes it past the cladding. This layer can be building paper, housewrap, or even a fluid-applied material. (WRB) installed on the walls is a vapor-permeable membrane (Henry BlueSkin VP).

The wall panels were built by high school students

The house was built in conjunction with North Orange County Regional Occupational Program. Students in seven high-school construction classes designed and built the wall panels as part of their training. The panel sections were then brought to the site (in Irvine’s Great Park), where they were assembled by a contractor. The partners spent $204,000 to build the house — about $120 per sq. ft., a figure they say could be lower with a large builder’s efficiency of scale factored in.

For a virtual tour of the ABC Green Home, click here.

The house will be on display Mondays, Wednesdays, Fridays, and weekends from 9 a.m. to 4 p.m. until October 2013. At that time, the house will be separated from its slab foundation and donated to Habitat for Humanity, which will move it to a new site. The next ABC home will be a similarly sized two-story model. California is trying to make all new homes net-zero by the year 2020.

Notable features of the ABC Green Home

  • One story, three bedrooms, two baths, a den, no fireplace or chimney
  • 1,695 sq. ft. with a 440-sq.-ft. attached garage
  • 2x6 wall studs on 2-ft. centers
  • AMX home automation system controls lighting and window shading
  • 5-kw PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow. array
  • “Smart” electric appliances for use with “smart” electric meter
  • Hot-water recirculation
  • Gray-water recycling
  • Rainwater collection
  • Air-to-water Daiken Altherma heat pumpHeating and cooling system in which specialized refrigerant fluid in a sealed system is alternately evaporated and condensed, changing its state from liquid to vapor by altering its pressure; this phase change allows heat to be transferred into or out of the house. See air-source heat pump and ground-source heat pump.
  • Permeable paving stones
  • Drought-tolerant plants
  • Universal designDesign that makes a building accessible to as many individuals as possible, including older people and those with physical handicaps.
  • Plug-in stations for electric cars
  • Meets the NAHBNational Association of Home Builders, which awards a Model Green Home Certification. Green Building Standard and requirements for the California Advanced Homes Program, USGBCUnited States Green Building Council (USGBC). Organization devoted to promoting and certifying green buildings. USGBC created the LEED rating systems.'s LEEDLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. program, and Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners.

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Image Credits:

  1. ABC Home