| Back to Contents Page | Home Energy Index | About Home Energy |
| Home Energy Home Page | Back Issues of Home Energy |
Home Energy Magazine Online September/October 1993
The Single-Family Study
by Marilyn Brown and Linda Berry
Marilyn Brown and Linda Berry are researchers at Oak Ridge National Laboratory in Oak Ridge, Tennesee.
Single-family retrofits by the Weatherization Assistance Program are more cost-effective in cold and moderate regions than in hot climates, but program improvements can balance the map.
Since 1976, the U.S. Department of Energy (DOE) has operated the Weatherization Assistance Program, the nation's largest energy conservation program (WAP). The aim is to increase energy efficiency in dwellings occupied by low-income households, reduce their energy consumption, lower their fuel bills, increase comfort in their homes, and safeguard their health.
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.
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.
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:
Comparison of dwelling types showed that weatherization of single-family detached and small multifamily dwellings was cost-effective from all three perspectives, while weatherization of mobile homes was not cost-effective when the definition of benefits was limited to energy savings (the program perspective). Thus, cost-effectiveness and energy savings per dwelling were greatest where program activity was concentrated--in the moderate and cold regions and in single-family dwellings.
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.
Factors Associated with Savings
Service delivery procedures that correspond to higher-than-average savings include
In contrast, the energy savings benefits of blower door-assisted air sealing and client education were not discernable.
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
These findings are consistent with previous research. The one finding that is least substantiated by other research is the questionable energy-savings benefits of using blower doors to assist air sealing. Our finding is attributed to the fact that blower doors were just being introduced into local agency procedures in 1989, when 18% of completed dwellings received blower door-assisted air sealing. Today blower doors are used more extensively, and most state agencies offer training in their use. In fact, low-income weatherization agencies have become leaders in the application of blower doors.
Distribution system air leakage control.
Air sealing without blower doors.
Attic insulation (particularly first time).
Wall insulation (particularly high-density).
Water heater tank insulation, pipe insulation, and temperature reduction.
Mobile home underpinning and skirting.
Figure 1. Energy saved by high versus low energy users in the three climate regions.
Table 1. WAP's Single-Family Evaluation
Energy savings and cost-effectiveness
Indicator Program-wide value
First year energy savings per dwelling 17.6 million Btu
Energy savings as a percent of
total energy use 13.5%
Energy savings as a percent of energy
used for space heating 18.2%
First-year dollars saved per dwelling $116
Installation-related costs per dwelling $1,050
Total weatherization costs per dwelling $1,550
Program benefit-to-cost ratio 1.09
Installation benefit-to-cost ratio 1.61
Societal benefit-to-cost ratio 1.72
Cost per million Btu of conserved
natural gas $4.60
Cost per kilowatt-hour of conserved
Value of the impact
Type of nonenergy impact per dwelling
Increased property value $126
Reduced incidence of fire $3
Reduced arrearages $32
Federal taxes generated from
direct employment $55
Income generated from indirect
Avoided costs of unemployed benefits $82
Environmental externalities $976
Keeping a Running Score on Weatherization (Hill)
Measuring the Performance of the National Energy Audit (Sharp)
Moisture and Mobile Home Weatherization (Tsongas)
Profiles of Multifamily Weatherization Projects: A Tale of Five Cities (Kinney, Wilson, and MacDonald)
'Read Me Your Thermostat': Short-Term Evaluation Tools (Kinney)
Selecting an Infrared Imaging System (Snell)
Ten Highly Effective Weatherization Programs (Brown and Berry)
Weatherization Assistance: The Fuel Oil Study (Ternes and Levins)
Chasing the Golden Carrot (Frantz)
Checking Out HUD's Proposed Mobile Home Performance Standards (Judkoff)
Hauling in the Culprits: Michigan's Bounty Pilot (Witte and Kushler)
How Accurate Are Yellow Labels (Meier)
Making Energy Mortgages Work (Luboff)
Managing Large-Scale Duct Programs (Downey)
New Group Hunts Bad Ducts (Obst)
New Standards Begin, But Will Rebates Continue? (Morrill)
One Size Fits All: A Thermal Distribution Efficiency Standard (Modera)
Telecommuting: An Alternative Route to Work (Quaid)
What's Wrong with Refrigerator Energy Ratings? (Proctor)
| Back to Contents Page | Home Energy Index | About Home Energy |
| Home Energy Home Page | Back Issues of Home Energy |
Home Energy can be reached at: email@example.com
Home Energy magazine -- Please read our Copyright Notice