The group says more than 97,000 such homes have been built since the mid-1990s. That pales in comparison to the 1.4 million total housing starts expected in 2007, even in a punk real estate market.

That niche may be significant and most pundits predict the green share will rise in the years ahead.

But who’s to say what a “green” home means? Well, the NAHB for one. Last fall, the trade group announced plans to create a National Green Building Program. It intends to unveil this program (www.nahbgreen.org) at the International Builders’ Show in February.

But not so fast, says the U.S. Green Building Council (www.usgbc.org). Already well-known for its LEED certification for commercial construction, the USGBC rolled out a LEED program for new residential construction (LEED for Homes, www.usgbc.org/leed/homes) at its Greenbuild Convention & Expo last November in Chicago.

Let’s sort through some of the basics of the two programs and other green initiatives.

Q: ‘Green building’ - what’s the big deal?

A: Mainly energy savings. While an SUV is the poster child of wasteful energy use, the Department of Energy says the residential sector accounts for 22 percent of the total energy consumed in the nation and three-quarters of its water use. More than 20 percent of the country’s carbon dioxide emissions are from the residential market. Just as an aside, the emissions are better known as “greenhouse gas emissions,” so you have to figure we’ll be in for a new name, if green building takes off as expected.

While today’s homes are built more efficiently than, say, 20 years ago, there’s still room to improve.

Q: Who did what first - the USGBC or the NAHB?

A: The USGBC says it started planning the home program in 2000, and began the pilot program in August 2005. As of May 2007, about 375 builders representing 6,000 homes across the United States were participating in the pilot program, and more than 200 homes have been LEED-certified. The pilot test concluded last fall; the USGBC is expected to make the program official, although no date has been set.

The NAHB says it started working on green building guidelines for its members in 2004. But some of its local affiliates have been at it longer. For example, the Home Builders Association of Metro Denver began a “Built Green” program in 1995 and expanded it to cover the state in 1997. Since then, the program has constructed more than 33,000 homes. Following its initial success, the HBA of Metro Denver licensed the name and other homebuilding associations, mostly in the West, adopted the program.

But do a search and you can find other programs that may have been at it longer. You can build a home to the standards of Energy Star, Earth Advantage, Health House, Build It Green or EarthCraft programs. Many already have successful track records. The federal government’s Building America program says the partnership between the Department of Energy and private businesses has built more than 32,000 energy-efficient homes.

Q: OK, so which one is better?

A: We knew you were going to ask that. We’re not going to pick favorites, but we will give you a general rundown of each.

Builders using the USGBC’s LEED for Homes program earn points under a set number of categories to earn either silver, gold or platinum status, just as they do with LEED for commercial projects.

Residential projects are rated on a 130-point scale and can get a rating of silver, gold or platinum. A minimum of 45 points is required to be certified, with a minimum of 90 for platinum.

Here are the categories:

• Innovation and design (9 possible points) - Includes integrating green strategies and planning for durability.

   

• Location and linkages (10 possible points) - Includes environmentally sensitive site selection; development near existing communities; development within walking distance of transit and basic services; and access to open space.

   

• Sustainable site (21 possible points) - Includes site “stewardship”; landscaping with drought-tolerant plants; management of storm water runoff; nontoxic pest control; and use of high-density development.

   

• Water efficiency (15 possible points) - Includes reuse of rainwater and indoor water (grey water); reduction of water use in sinks, toilets and showers; and use of high-efficiency irrigation system.

   

• Energy and atmosphere (38 possible points) - Includes use of basic or enhanced insulation to minimize air leakage; energy-efficient windows; proper insulation around heating and cooling systems; programmable thermostat and high-efficiency heating and cooling systems; efficient hot water heating system; energy-efficient lighting fixtures and appliances; and renewable energy systems.

   

• Materials and resources (14 possible points) - Includes reducing waste from building framing; use of local or “certified tropical” wood and environmentally preferable material, such as bamboo and linoleum; recycling and reuse of materials; and reducing waste from construction process.

   

• Indoor environmental quality (20 possible points) - Includes proper sealing to minimize leakage from space and water heating systems; proper ventilation of fireplace and woodstove; moisture control system; proper ventilation to outdoor air; exhaust fans for bathroom and kitchen; filtration; sealing off garage from home; and contamination control.

   

• Awareness and education (3 possible points) - Includes training of occupant; owner’s manual; and ongoing management.

Q: And how about the NAHB program?

A: Projects are also rated on a point system in to qualify for bronze, silver or gold status. Builders must meet a minimum number of points for each the following seven “guiding principles.” After reaching this point, builders then still have to earn another 100 points from any of the seven principles.

Here are the principles, along with the minimum points needed to qualify for bronze status:

• Building lot (minimum 8 points) - Includes minimal impact; conservation and preservation of natural resources; minimal slope disturbance; maximum use of solar resources; management of storm water, low water; and energy landscaping.

   

• Resource efficiency (minimum 44 points) - Includes reducing construction materials and waste; improving durability; using recycled, salvaged and renewable materials; and recycling of construction waste.

   

• Energy efficiency (minimum 37 points) - Includes appropriate heating and cooling equipment; proper insulation; energy-efficient windows; energy-efficient water heater; energy-efficient lighting; and potential use of solar power and other renewable energy sources.

   

• Water efficiency (minimum 6 points) - Includes reducing indoor and outdoor water use in sinks, appliances, toilets and irrigation systems.

   

• Indoor environmental quality (minimum 32 points) - Includes proper ventilation of heating, hot water supply, stove, bathrooms and fireplaces; proper sealing between garage and home; use of low-toxicity adhesives and materials; and proper vapor barriers in walls and under floors.

   

• Operation and maintenance (minimum 7 points) - Includes providing an owner’s manual and training in building controls.

   

• Global impact (minimum 3 points) - Includes using low-toxicity paint and sealants.

   

• Additional points (minimum 100 points) - To qualify as a green home under the NAHB proposed standard, builders also would have to accumulate an additional 100 points in any category above.

Q: Sounds like they’re exactly the same – points for this and points for that.

A: Maybe. To hear it from the USGBC, however, only its programs offers proof - namely documentation, performance-tested products and third-party verification - that a house has been built in a number of green ways.

Q: I bet the NAHB has something to say about that, right?

A: Right you are. The NAHB says its new program will be based on a new American National Standards Institute-accredited national green building standard. The model for residential construction and renovation will be written by a consensus of builders, architects, environmentalists and product experts.

This standard will be a cooperative effort between NAHB and the International Code Council and based on NAHB’s Model Green Home Building Guidelines, introduced in 2005. More than 20 state and local green building programs, such as Green Built, already incorporate these guidelines.

Technically speaking, the whole program will be organized by the NAHB Research Center, an accredited ANSI developer. However, ANSI also accredited the USGBC November 2006, so it could also submit its LEED program to be a national standard.

Q: OK, really now. Which one is better?

A: We’re still not going to say. But we will add that for NAHB’s part, it appears that its program will try to appeal to the largest audience and offer less costly and more streamlined ways of “proving” a home to be green. The program largely leaves it up to the builder and subcontractors to manage.

Of course, that means green purists are concerned that the association’s approach - which allows those greedy, nickel-and-dime builders to self-certify that they have followed along with a 200-page green checklist - might water down the overall effort.

Meanwhile, the USGBC plainly states that its market for the new LEED for Homes campaign is the top 25 percent of homes.

The LEED home program even takes into account that some of these homes, mansions actually, might not inherently be green. That’d be like drinking a Diet Coke in a Humvee. Something called the “Home Size Adjuster” factors in size, making it harder for above-average homes to reach each LEED point. However, the adjuster also compensates for smaller homes than “average,” making it easier for these structures to earn LEED points.

Of course, that means green purists are concerned that the group’s approach, which requires thousands of dollars in fees and man-hours of documentation, might turn off anyone but the Forbes 400 from building a green home.

Regardless of which group you want to pick on, neither picked the greatest time to unveil a green program. We’ve read enough press releases that sugarcoat the added costs of building green. The fact of the matter is, anything out of the ordinary costs more than the run of the mill. And with each day bringing more bad news about residential real estate, builders are going to have to cut prices on plenty of already built nongreen homes before investing in a good cause.

Q: Enough with the politics. Tell me more about what both these programs say about plumbing and heating.

A: Of the two, the USGBC is the more stringent. When the LEED folks says their intent is to “minimize indoor demand through water-efficiency fixtures,” they’re not kidding. You don’t get any points unless you install toilets that flush with less then 1.3 gallons. Flow rates for lavatory faucets must be less than 2 gpm and showerheads must be less than 2 gpm. You get one extra point each for installing less than 1.1-gpf toilets, 1.5-gpm lav faucets and 1.5-gpm showerheads.

In other areas, four points can be earned for installing a rainwater and/or grey water reuse system. The water can be used either for irrigation or indoor water use.

It does recognize hydronic heating systems, but puts them on an even point basis with its recommendations for HVAC systems. For potable water heating, homes earn points for reducing waste by minimizing plumbing runs, including minimizing the distance between fixtures within a home.

LEED for Homes recognizes solar for generating electricity, but does not address using the sun to heat potable water.

Over at the NAHB, the program offers more options to save. For plumbing, builders do get points for installing 1.6-gpf toilets, 2.2-gpm lav faucets and 2.5-gpm showerheads. They’ll also earn points for reusing rainwater, but grey water systems are under “Innovative Options” along with sensor faucets. Radiant and HVAC earn the same point, but the NAHB program takes in account more power options, such as ground source heat pumps. And it recognizes not just passive solar design, but active solar power to heat water.

Keep in mind that each group may change parts of any current plan before making them official nationally.