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How Green Is HUD-Assisted Housing?

As part of its commitment to increase the energy efficiency of its assisted-housing stock, HUD is sponsoring a series of research studies to inform its efforts to go green. One study, “An Evaluation of Affordable Housing Using the National Green Building Standard,” identifies the incremental actions and costs of bringing existing HUD-assisted housing units into compliance with the National Green Building Standard (NGBS).1 NGBS, developed in 2007 by the National Association of Home Builders and the International Code Council and approved by the American National Standards Institute, is a set of standards for green building and remodeling of residential buildings.2 These standards consist of practices, requirements, and environmental performance levels for green buildings and developments.

NGBS has four green rating levels ranging from Bronze (the lowest) to Silver, Gold, and Emerald (the highest) based on each of six categories of green features that provide economic benefit to homeowners or the surrounding community: lot design, preparation, and development; resource efficiency; energy efficiency; water efficiency; indoor environmental quality; and operation, maintenance, and building owner education. According to the U.S. Office of Management and Budget, NGBS is a preferred tool for updating the sustainability and green building features of HUD’s existing housing stock.

Evaluating Affordable Housing Designs

To evaluate designs used for HUD-assisted housing units and determine how to make them greener, researchers selected a sample of affordable housing units supported with HOPE VI, HOME, and Alternative Housing Pilot program funds for analysis. The study evaluated single-family, multifamily, and disaster relief housing. Researchers focused their assessments on the architectural designs and specifications of these units, which were located in four different climate zones and six states. All the units were built in accordance with state or International Residential Code (IRC) building codes dating from 2003 to 2009 with the exception of one 1950s-era multifamily apartment building. The NGBS system was applied retroactively to assess the extent of the units’ conformance with green design principles, and the steps and costs needed to bring them into compliance with the green standards were projected. These projections were made to determine the feasibility of bringing these homes into full compliance with a nationally recognized green building standard.

The first step was to give each housing design a baseline green rating. After researchers determined the baseline rating, they selected green products or practices that could incrementally improve the design to satisfy the requirements of each level in the NGBS rating system. The research team made these selections while adhering as much as possible to both the original design and the most affordable improvements. To receive a rating, the design needed to meet the mandatory NGBS practices as well as threshold requirements for all of the green categories.

For each green product or practice used to bring a design into compliance with each of the six NGBS ratings, the total cost was calculated by estimating the cost of the green product(s); labor; and any related operating, maintenance, and replacement expenses. Whenever possible, cost savings that the green product or practices could be expected to generate were identified, as were any benefits that would be likely to accrue in terms of reduced environmental impact, exposure to pollutants, and waste.

A Louisiana Disaster Relief Home

A single-family, one-story home in Baton Rouge, Louisiana developed and built as part of the Hurricane Katrina recovery effort, illustrates how the assessment was conducted. This 3-bedroom, 910-square-foot home was built by the Louisiana Recovery Authority as part of the Hidden Cove Development using the 2006 IRC building code. Although the home was not designed according to any particular set of green building standards, it did contain some green features. A baseline rating of the original design fell short of an NGBS Bronze rating. To qualify the home for a Bronze rating, the researchers identified low- or no-cost practices that would ensure compliance with mandatory green requirements and added some others: a construction schedule that minimized the length of time the soil was exposed, an integrated pest management plan, a construction waste management plan, green materials that could be substituted for original materials at comparable costs, water-efficient fixtures, energy modeling, caulking and sealing, a maintenance plan for vegetation, borate-treated oriented strand board to combat termites, and educational materials for the owner. The initial cost of achieving the Bronze rating was estimated at $2,794, and the benefits included a 15 percent decrease in energy use and a 16.4 percent reduction in water usage.

Researchers systematically followed this process through each of the six NGBS categories to arrive at a comprehensive set of practices that would satisfy the eligibility requirements for a Bronze, Silver, Gold, and Emerald rating. Table 1 shows the estimated costs of reaching each rating level.

Table 1. Cost To Achieve NGBS Green Ratings

Baton Rouge, Louisiana Single-Family, 3-BR, 910 ft² Baseline Bronze Silver Gold Emerald
Total Initial Green Cost ($) NA $2,794 $7,877 $15,102 $34,515
Annual Maintenance Cost ($) 409 409 409 456 456
Annual Energy Operating Cost ($) 1,052 1,022 909 785 758
Annual Water Usage Cost ($) 578 570 570 536 536
30-Year Lifetime Replacement Cost ($) 18,412 18,412 19,772 30,157 35,515

Source: U.S. Department of Housing and Urban Development, “An Evaluation of Affordable Housing Using the National Green Building Standard,” 28.

The progression of green rating levels can be better understood by comparing the examples of initial steps (described above) to reach a Bronze rating with examples of higher-order practices that could move the rating of the Baton Rouge house from Gold up to an Emerald level. Emerald-qualifying practices included the installation of a rainwater collection and distribution system, a whole-building ventilation system, low-VOC hardwood surfaces and wall coverings, and upgraded cooling/heating systems. Among the benefits projected for achieving an Emerald rating for the Baton Rouge house design: a 61 percent reduction in energy use and a 26.7 percent decrease in water use.


After applying this assessment and green rating process to eight different affordable house designs and four multifamily apartment units in HUD’s assisted housing stock, researchers found that achieving compliance with a green standard is possible with modest design enhancements and an investment of up to $3,600 per unit. The researchers found that the designs and specifications of these units could be significantly strengthened with NGBS mandatory green building requirements, a greater emphasis on cost-effective water conservation practices, education of homeowners on the correct use and maintenance of green technologies, and consistent attention to all categories of green building in the NGBS. Improvements in energy efficiency, water conservation, and indoor environmental quality for older homes can be very cost effective.

Although green construction methods are beneficial at any stage — design, construction, or renovation — the best approach is to integrate them during the earliest stages of a building project. In particular, the researchers recommended that affordable green housing designs be improved with the use of construction practices that minimize physical waste (for example, using factory-assembled wall sections), durable materials that require little maintenance, and products incorporating more than one green element, such as cabinets made from recycled materials with no (or low) formaldehyde emissions. Other recommended improvements included greater use of Energy Star-rated appliances and low-flow plumbing fixtures that could be added at little or no cost. Finally, the designs could be improved by optimizing the overall house design and the interconnectedness of many green practices. Examples include installing ductwork inside conditioned space to improve energy and resource efficiency and ensuring that energy-efficiency plans incorporate indoor air quality and moisture management features.

Future Green Research

This evaluation provides an in-depth look at the costs of greening diverse residences, both new and old, and offers useful data for future sustainability efforts in affordable housing. To expand on this study, the researchers suggest developing a system for monetizing the benefits of green renovations that improve features such as indoor air quality, land and lot use, and resource efficiency. Further research is also needed on green building strategies for multifamily housing that make use of economies of scale, on residences in all climate regions of the United States, and on the cost of converting non-green affordable housing designs. Finally, additional long-term demonstration studies would be valuable for learning how green education of owners and residents would affect energy savings and green amenity performance.