In 2005, the NAHB had actually introduced the NAHB Model Green Home Building Guidelines, giving developers the first national platform to understand green techniques and incorporate them into the single-family homes they were building. Those guidelines were also meant to serve as a baseline so builders could develop local green building programs.

With the intention of "having an approved rating system that's flexible, dynamic and practical," says Martin, the NAHB and ICC started their work with the consensus council two years ago, using those 2005 guidelines as a starting draft. The groups worked on the standard for over a year, holding four public hearings and analyzing more than 3,000 public comments, before presenting it to the Standards Institute.

"ANSI certification confirms that this standard is not an 'industry-generated' document, but was developed through a rigorous process requiring public input, a diversity of participants, consensus and due process," says Eileen Lee, vice president of energy and environmental policy at the National Multi Housing Council.

And because the NAHB worked with the ICC to develop the standard, it is the only green rating system specifically written to be compatible with existing building codes. Not only will the NGBS give apartment developers set guidance on how to approach environmentally friendly projects, says Lee, "it is also important for the growing number of states and localities considering mandatory green building requirements. The NGBS offers a more appropriate alternative for residential properties than other non-standardized green rating systems like the US Green Building Council's LEED criteria."

It was the option of having broader choices that spurred NAHB to become involved in this effort, explains Martin. The organization has been promoting not only "change in the way we build, but also how our building is interpreted and valued by appraisers, realtors, lenders and underwriters and even insurers. We believe that any builder who wants to go green should be able to, and having credible, practical and universally agreed-upon options is part of that process. Builders need to be able to choose options that will allow them to reach a given level of greenness that is appropriate for their practice and makes sense practically. Choice will move mountains, but in a metaphoric, environmentally friendly way."

There has indeed been a proliferation of green building initiatives nationwide, points out Paula Cino, director of energy & environmental policy for the NMHC. To date, there are 31 states, 112 cities and 12 federal agencies that have some sort of green building statutes. However, she points out, "It's important to note that these numbers include many jurisdictions that are either incentivizing green building or only mandate green building in public projects or publicly funded buildings."

Only one state and 18 cities currently mandate sustainability in private construction, but that figure is expected to rise in coming years. That shows "we're pretty early in the game when it comes to green building requirements in private construction, which means there are good opportunities for discussion and education at the state and local level, as mandates are proposed and considered," Cino relates.

That is where the NGBS comes into play. "We strongly believe that this standard is a better tool for green building in the multifamily sector than other green building programs currently available," she says. "Our goal is to have the NGBS specify, as a compliance option, every time legislation or an incentive program says that residential construction has to follow some kind of green building criteria."

In fact, a number of housing bills brought forward last year sought to tie federal requirements with green building. Among the federal proposals in 2008, there were new green building requirements for Hope VI projects and more energy efficiency requirements for building codes in several HUD programs. The 2009 stimulus package has a large allocation to green, and requires that states receiving grant money must update their building energy codes. And this year, comprehensive energy and climate change bills are expected to be brought to Congress.

Structured like LEED and Green Globes, some of the aspects of the NGBS are mandatory while others are point-based options that allow developers to pick and choose what features make the most sense for their projects. Builders must achieve a minimum number of points in each of the six categories of the standard, but its crafters made an effort to tie the mandatory requirements with building code requirements.

"This structure can cause some anxiety for some people, but it's really not warranted," says Cino. "There are some point options that are more suited for single-family construction but not multifamily, and vice versa. The development committee ultimately decided that was fine, so long as there were enough points available collectively for each type of residential building to comply." Plus, the fact that the standard applies to both single-family and multifamily projects helps developers who build both types of projects in terms of time savings and efficiency.

Developments must incorporate a minimum number of features in order to meet the different thresholds of the standard, explains Martin. The standard, however, includes more mandatory elements and higher thresholds be matched in certain categories. Further, in addition to Bronze, Silver and Gold, the standard adds a new threshold--Emerald--to represent the highest level of green construction. The standard also recognizes that different geographic markets have their own environmental issues, product availability and building traditions, so it has flexibility built in that would allow developers to construct regionally appropriate housing.

Developers can accumulate points in the following areas: lot design, preparation and development, which includes infill development, brownfield/greyfield development, proximity to mass transit and community resources, mixed-use development and high-density development; resource efficiency, such as small unit size, stacked stories, green roof installation and the reuse of existing buildings; energy efficiency; water efficiency; and indoor environmental quality, which can mean the exclusion of fireplaces in the project, no garage built or having the garage detached from the dwelling unit and the installation of entry grilles and/or mats.

"This idea has really gone beyond what we've been seeing in the housing market; it's entrenched at the federal level," says Cino. "We expect to see those kinds of provisions attached to many, if not most, of the housing bills moving forward. This idea is here to stay and it's one of the biggest reasons why the NGBS is so critical."

The ANSI process also requires that the Standard must be under continuous maintenance, and go under regular review. The next version of the bill, says Cinto, may include awarding additional points for urban heat island mitigation, light pollution reduction, on-site power generation, energy-efficient elevators and daylighting design--these points were all discussed in the creation of the guidelines but were not included in this version.

Also to be taken into consideration during the next review of the NGBS are multifamily renovations, since the renovation section of the guidelines currently applies only to single-family homes; multifamily high-rise projects, because the current version includes high-rise residential towers but does not fully capture their methods and materials; and giving more credit to urban and infill development.