Weatherization Assistance:
The Single-Family Study

Marilyn Brown and Linda Berry are researchers at Oak Ridge National Laboratory in Oak Ridge, Tennesee.

In 1990, DOE initiated a nationwide evaluation of the program with assistance from Oak Ridge National Laboratory (see The Reach of Low-Income Weatherization Assistance, HE May/June '93, p. 21). As part of the evaluation, DOE has collected enough data to generate savings and cost-effectiveness estimates for the largest portion of its client base--low-income households that occupy single-family dwellings, mobile homes, and small multifamily dwellings. This is the subject of the Single-Family Study and the results are in.

The most important finding is that the Program is a cost-effective government investment. Total costs (including materials, labor, overhead, and management) averaged $1,550 per weatherized dwelling in Program Year 1989. The net present value of the energy saved per dwelling is $1,690 (in 1993 dollars). This results in a benefit-to-cost ratio of 1.09. When conservative values are included for some of the program's various non-energy benefits, the benefit-to-cost ratio increases to 1.72.

These average benefit-to-cost ratios mask a great deal of diversity in weatherization approaches and effectiveness. For instance, the program is most cost-effective in the cold and moderate climate regions of the country where programs are concentrated, but in the hot region of the country, improvements are needed.

Researchers at Oak Ridge National Laboratory examined a representative national sample of 14,971 dwellings weatherized under DOE guidelines during 1989, and compared them with 3,655 control dwellings drawn from agency waiting lists. For this national sample they collected weather data; utility data on fuel consumption; agency-level cost data on overhead and management costs; and specific data on dwellings and their occupants, measures installed, and weatherization costs. This data was used to estimate program impacts, describe factors associated with high versus low savings, and identify opportunities.

Measures installed and procedures used during 1989 varied widely among local agencies and differences across climate regions were quite pronounced. In cold climates, for instance, we noted high installation rates for insulation, water heating, and space heating measures, and low installation rates for storm and replacement windows as well as doors. Integrated energy audits, blower door testing, and space heating diagnostics were used more often in the cold climate region. In the moderate climate region, there were higher installation rates for storm windows, space heating measures and air leakage control. In the hot climate region, there were lower installation rates for wall insulation and space and water heating measures, but higher installation rates of window and door replacement. (Integrated audits, blower doors, and space heating diagnostics were hardly used in the hot climate region.)

Local weatherization agencies in the cold climate region emphasize many of the measures and procedures recent literature suggests produces the best results--measures like integrated audits, wall insulation, and space heating system retrofits and replacements. In contrast, housing rehabilitation measures, which cannot be expected to significantly lower energy usage, are emphasized more by agencies in the hot region, reflecting the more dilapidated state of housing in the South.

Energy Savings

Using the Princeton Scorekeeping Method (PRISM), a weather normalization procedure, we estimated heating and cooling energy savings for all buildings weatherized by WAP during 1989. Gas-heated dwellings accounted for 90% of those for which fuel consumption records were available, and represented half of the dwellings weatherized by the program during 1989. We calculated savings as a percentage of the gas used for space heating during the year before weatherization. The results indicate that the program saved an average of 13% of the total gas use and 18.3% of the gas used for space heating. Variations in savings by dwelling type were significant. For instance, single-family detached dwellings (the dominant dwelling type served by the program) saved over 50% more natural gas per dwelling than mobile homes.

Electrically heated homes represent only 10% of the dwellings weatherized under WAP during 1989. Weatherization of these dwellings saved an estimated 12% in total electricity consumption, and 36% in electricity used for space heating. As with gas-heated homes, both single-family detached and small multifamily dwellings saved more electricity than mobile homes. Measured savings for electrically and gas-heated homes were combined with indirect estimates of energy savings for other fuels, such as fuel oil, propane, wood, and coal (see Table 1).

During 1989, 198,000 single-family or small multifamily homes were weatherized by the program, resulting in a total (estimated) savings of 3.5 billion Btu during the first year after weatherization. Assuming there are 5,800 Btu per barrel of oil, the program saved the equivalent of 601,000 barrels of oil during 1990-91, or 1,650 barrels of oil per day. Over the 20-year lifetime of the measures, that amounts to 69.7 billion Btu, or 12 million barrels of oil.

Nonenergy Impacts

Selected nonenergy benefits were assigned a dollar value in our research, but the methods used to estimate their value varied. Estimates of environmental benefits relied on a literature review and on information about the proportions of weatherized dwellings using various fuel types and the average savings of different fuels. Estimates of employment benefits combined a literature review with data on program employment, the skill levels of workers, and managers' judgements concerning the job market for weatherization workers. Data on WAP expenditures for home repair were used to quantify the benefits associated with maintaining or enhancing property values and extending the lifetimes of dwellings. The monetary benefits of reducing the incidence of fires were quantified using insurance industry data. Our estimate of reductions in arrearages was based on a literature review and data on payment histories collected on the dwellings included in the study. For each benefit included in the estimate, we developed an average value per weatherized dwelling (see Table 1).

Costs and Cost-Effectiveness

The program-wide average total installation cost per dwelling was $1,050 in 1989, though 8% of dwellings had installation expenditures of less than $300 and 9% had expenditures of more than $1,800. Costs didn't vary significantly by climate region, but the proportion of expenditures spent on types of measures did. In the cold region, investments were highest for insulation. In the moderate region, the highest expenditures were for windows and doors. In the hot region, structural repairs had the highest investment level, and windows and doors consumed nearly as high an amount. Thus, the cold region puts more resources into the measures most likely to save money.

The evaluation examined cost-effectiveness in detail from three perspectives:

• The installation perspective, where the only benefit valued was net energy savings and the only costs included were installation expenditures.

• The program perspective, where the only benefit valued was net energy savings, and costs included installation, management, and overhead costs.

• The societal perspective, where benefits included both net energy and nonenergy benefits and costs included installation, management, and overhead.

   

Perhaps the most striking result of the Single-Family Study is the tremendous diversity among local weatherization agencies. Some weatherize 15 homes in a year, while others weatherize thousands. Some agencies achieve savings of 30%-40% of pre-weatherization consumption, while others produce no measurable savings. Some employ state-of-the-art procedures, leverage a wide variety of financial and technical resources, and perform sophisticated self-evaluations. Others follow the same procedures year after year, do not evaluate their impacts and rely only on DOE funding.

A second phase of the Single-Family Study which is now underway will describe and analyze the practices used by ten high-performing agencies selected from each major geographical region on the basis of measured energy savings. It will also compare and contrast features of high- versus low-saving agencies and dwellings. n

This article is based on the report National Impacts of the Weatherization Assistance Program in Single-Family and Small Multifamily Dwellings, Oak Ridge National Laboratory, Oak Ridge, Tennessee. Tel: (615)574-5939, Fax: (615)574-4747. The publication of this article in Home Energy was underwritten in part by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy.

Service delivery procedures that correspond to higher-than-average savings include

• Weatherization of households with high gas consumption.

   

• Integrated energy audits.

   

• Distribution system diagnostics.

   

• Heating system efficiency tests.

   

Weatherization measures that correspond with higher-than-average savings include

• Distribution system air leakage control.

   

• Air sealing without blower doors.

   

• Attic insulation (particularly first time).

   

• Wall insulation (particularly high-density).

   

• Floor insulation.

   

• Water heater tank insulation, pipe insulation, and temperature reduction.

   

• Furnace replacements.

   

• Mobile home underpinning and skirting.

   

Figure 1. Energy saved by high versus low energy users in the three climate regions.

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