Last week’s post showed that about one-fourth of the typical homes built by a sample of 246 single-family builders in 2016 had enough green features to quality for a bronze rating under the 2015 National Green Building Standard™ (NGBS). A major reason is the high marks the homes tended to receive under the energy efficiency section of the NGBS.
The NGBS is organized into six chapters: lot design, preparation, and development; resource efficiency; energy efficiency; water efficiency; indoor environmental quality; and operation, maintenance, and owner education. To achieve an NGBS rating, a home must not only satisfy a total point requirement, but also point requirements in each chapter. The chart below shows the average points earned in each chapter by the typical homes built by the builders who responded to NAHB’s 2017 Green Practices Survey.
Builders’ homes tended to score higher in some areas than others. The average number of points earned for energy efficiency under the 2015 standard is 51, or 21 above the threshold needed for bronze. Similarly, the average number of points earned under water efficiency is 17 points above the bronze threshold, and the average for indoor environmental quality is 7 points higher. In contrast, the average number of points earned in the lot design chapter of the 2015 NGBS is 15 points below the threshold needed for bronze, and the resource efficiency average falls 13 points short.
Lot design scores tended to be higher under the 2015 than under the 2012 version of the NGBS, because the 2015 standard awarded more points for some relatively common location and transit features. For example, 31 percent of the homes were built an infill site, which is worth 8 points in the 2012 NGBS and 10 points in the 2015 NGBS. Forty-seven percent were built on sites connected to existing sidewalks, which earns 5 points in the 2015 NGBS, but none in the 2012 version.
On the other hand, resource efficiency scores tended to be slightly lower under the 2015 than under the 2012 version of the NGBS. This due entirely to the 2012 awarding somewhat more points if the homes are under 2,500 sq. ft. In the last three chapters in the NGBS, scoring is identical under the 2012 and 2015 versions of the standard.
Looking at energy efficiency in more detail, under the 2015 NGBS, 74 percent of builders’ typical homes hit or exceeded the 30-point threshold for a bronze energy-efficiency rating, 58 percent hit or exceeded the 45 points needed for silver, 36 percent hit or exceed 60 points for gold, and 34 percent even had the 70 points needed for emerald.
Although still quite high in absolute terms, energy efficiency scores tended to be somewhat lower under the 2012 version of the NGBS. As discussed in last week’s post, the reason for this is the points awarded for HERS ratings in the 2015, but not in the 2012, version of the NGBS. One reason energy efficiency scores are as high as they are under both versions of the standard, is that about two-thirds of the homes were built to either the 2012 or 2015 International Energy Conservation Code, worth 30 points in both 2012 and 2015 NGBS
For more details, please consult the full Green Practices Survey report, available free of change on NAHB’s web site.