Mark Ternes and Bill Levins are researchers at Oak Ridge National Laboratory in Tennessee.

In 1990, the U.S. Department of Energy initiated a nationwide evaluation of its Weatherization Assistance Program, with assistance from Oak Ridge National Laboratory (see "The Reach of Low-Income Weatherization Assistance," HE May/June '93, p.21, and "Weatherization Assistance: The Single Family Study," HE Sept/Oct '93, p.11). The key finding of these studies was that weatherization assistance is a cost-effective investment.

In the fuel oil study, we focused on a major submarket served by the program--single-family fuel-oil-heated houses. We analyzed program-eligible, single-family houses located in nine Northeast states, during 1991 and 1992. We monitored a total of 337 houses (222 weatherized and 115 as controls) associated with 41 local weatherization agencies. The agencies installed energy-efficiency measures in the weatherized houses in January of each year according to their standard procedures. We used a data logger that recorded inside and outside temperatures and heating system run time, to monitor each house over one heating season. Synertech Systems Corporation technicians performed blower-door tests and steady-state efficiency measurements of the space-heating systems in each house before and after weatherization. They also performed safety inspections of space- and water-heating systems and surveyed all occupants after weatherization.

Our typical test home was a two-story, 63-year old, wood-framed house, with wooden single-pane windows covered by metal-framed storm windows, and with a total floor area of 1,332 ft², a heated area of 1,274 ft², and a 667-ft² unheated basement. Wall insulation was present in 52% of the control houses and in 60% of the weatherized houses following weatherization; attic insulation was present in 82% of the control houses and 91% of the weatherized houses after weatherization. Forced-air furnaces (on average 14 years old) were present in 44% of the houses, and boilers with hydronic distribution systems (on average 18 years old) were used in 41% of the houses. Fifty-five percent of the burners were of the flame-retention type. Most participants said they used no auxiliary heat. Average occupancy per house was three people.

Installed Measures and Procedures

Local agencies in the Northeast weatherized more than 23,000 single-family, fuel-oil-heated homes in 1991 and 1992. The agencies usually used a priority list to select envelope measures and performed space-heating system diagnostics in about 80% of the houses. They installed insulation in 82% of the houses (37% received new attic insulation, 35% additional attic insulation, 37% band-joist insulation, 25% wall insulation, and 23% floor insulation). The agencies performed air-leakage measures in 96% of the houses, space-heating system measures in 53%, domestic hot water system measures in 62%, and energy-efficiency improvements to windows and doors in 41%.

The agencies performed visual quality-control inspections in most houses, and space heating system quality-control inspections were performed in all 53% of the houses receiving space-heating system measures. The agencies also provided client education to more than 95% of the weatherized households.

Fuel Savings

We estimated the average net fuel savings of the weatherized houses (the gross savings of the control houses subtracted from the gross savings of the weatherized houses) at 160 gallons per year, or 18% of pre-weatherization consumption (see Table 1). At $1.01 per gallon, the net annual savings were about $162 per house. Roughly half the weatherized houses experienced a gross savings less than 200 gallons per year. Only 4% had a savings greater than 500 gallons per year, while 17% had negative savings (most between 0 and -100 gallons per year).

Did the occupants "take back" some of the savings in the form of a warmer house? We doubt it. The average indoor temperature change following weatherization was nearly zero in both the weatherized and control houses.

The local agencies spent an average of $1,200 per house, about $750 for materials and $450 for labor. Overhead and management costs amounted to another $630 per house, excluding state costs for implementation of the program. We estimated a benefit-to-cost ratio of 2.26, assuming a measure life of 20 years and considering only installation costs, and 1.48 when we included overhead and management costs (see Table 2). Our estimates show that the program is cost-effective, even without the consideration of any non-energy or societal benefits.

Factors Affecting Savings

Savings were greatest in houses with high pre-weatherization consumption. This can be seen by examining the top and bottom 18 savers (see Table 3). The low savers used considerably less fuel in the pre-weatherization period than the high savers, even though the houses had the same floor areas. Low savers saved -44 gallons per year (-6%), compared to the 498 gallons per year (37%) by the high savers.

The high savers had needed weatherization, while the low savers were more energy-efficient to begin with. The high savers used about the same amount of fuel following weatherization as the low savers did. Almost $1,600 was spent on each of the high savers, which was cost effective, while the average expenditure of $892 for the low savers was not cost-effective. The high savers benefitted more from air-leakage measures, even though both groups had about the same post-weatherization air leakages.

Although the agencies installed similar measures in both groups, the frequencies with which different measures were installed varied. Measures installed more frequently in the high savers' homes were attic insulation, wall insulation, floor insulation, air sealing using a blower door, replacement of broken glass in windows, and heating system cleaning and tune-ups. Replacement windows and new storm doors were installed more frequently in the low savers.

We found that certain aspects of space heating system retrofit and tune-up programs contribute to fuel savings--for instance the steady-state efficiency of new systems was 12 percentage points higher than that of the systems they replaced and the steady state efficiencies of systems with flame-retention burners was higher than those without them. Yet we could not confirm steady-state efficiency increases due to heating system cleaning and tune-ups (see "Space-Heating System Measures," p.14). Weatherization activity reduced house air leakage (see "Air-Leakage Mitigation"), especially in those houses where agencies used a blower door or installed wall insulation.

Occupant Feedback

Our closeout occupant surveys revealed that weatherized house respondents felt their homes were more comfortable, safer, and less expensive to heat after weatherization. Health and safety were the only areas that both weatherized and control groups thought were acceptable before weatherization.

The Moral of the Story

The Weatherization Assistance Program cost-effectively weatherized more than 23,000 single-family fuel-oil-heated houses in the nine northeastern states during 1991 and 1992, with higher-than-average fuel oil savings achieved by higher-energy consumers. We found benefits in addition to fuel savings in our study. For instance, occupants felt better about their houses and indoor environment after weatherization. Most occupants felt that their houses were now healthy and safe, and that weatherization had made their houses less drafty and much more affordable to heat. n

The publication of this article in Home Energy and the primary research were supported by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy.

Figure 1. Distribution of fuel-oil savings for the weatherized houses.

Tune-ups were not particularly effective at improving the steady-state efficiency of space-heating systems, but they may have improved system safety. The Weatherization Assistance program should investigate methods for improving the selection and/or application of space-heating system tune-ups and should actively promote the improved tune-up procedures that have been developed. New, higher-efficiency boilers or furnaces should continue to be installed when warranted and flame retention burners should be installed when a burner is replaced.

Local weatherization agencies performed system cleaning and tune-ups in 38% of houses they weatherized. This was the most-frequently performed space-heating system measure. However, our data show that the current implementation of this measure does not produce desired benefits because it is not long-lasting, not done properly, or is applied to houses that do not need it. Houses that received a cleaning and tune-up did not increase in steady-state efficiency any more than houses that did not receive the measure. Only 4% of the study houses that received a cleaning and tune-up met the performance goals proposed by the Alliance to Save Energy: 80% steady-state efficiency with flue gas containing <=7% oxygen and a smoke number of <=1. We found that fan-on (upper limit) and fan-off (lower limit) switches, which should be adjusted during tune-up, were essentially the same (137deg.F and 100deg.F, respectively) for both weatherized and control houses.

Houses receiving new boilers or furnaces (4% of the weatherized houses) in addition to other measures, had about twice the average fuel savings of other houses. The steady-state efficiency of houses receiving new systems increased from 71% to 83%. We also measured higher steady-state efficiencies (3-5 percentage points) in houses with flame-retention burners, compared to houses without them.

Our visual inspections of the heating systems showed that the weatherized houses were slightly safer than the control houses, with few serious problems noted in either group. Our visual inspections also showed, though, that safety deficiencies were identified and corrected during weatherization. For example, at least three houses initially had no return air systems, a potentially dangerous situation that was rectified during weatherization.

               Annual Consumption     Gross      Percent     Net      Percent 
                  Pre     Post       savings      gross     savings     net 
Houses         (gallons)(gallons)   (gallons)    savings   (gallons)  savings
_____________________________________________________________________________
Weatherized       905      783         122        13.5%       160      17.7%
Control           918      956         -38        -4.1%         -       -

Indicator                                         Region-wide value
___________________________________________________________________
Installation-related costs per dwelling                $1,192     
Total weatherization costs per dwelling                $1,819     
First-year dollars saved per dwelling                    $162     
Installation benefit-to-cost ratio                       2.26     
Program benefit-to-cost ratio                            1.48

                                                 Top 18          Bottom 18 
Variable                                      (high savers)     (low savers)
____________________________________________________________________________
Annual fuel savings (gallons)                      498              -44     
Percent fuel savings                               37%              -6%     
Annual pre-weatherization fuel use (gallons)     1,392              873     
Weatherization cost                             $1,604             $892     
Heated floor area (ft2)                          1,467            1,457     
Pre-weatherization air leakage (CFM50)           3,856            3,580     
Post-weatherization air leakage (CFM50)          3,191            3,290     
Annual pre-weatherization fuel use               1.055            0.672
    (gallons per ft2)
Annual post-weatherization fuel use              0.658            0.705
    (gallons per ft2)
Installation benefit-to-cost ratio                4.01               -
    (15-year measure life)

Blower doors should be used more often, and also more effectively, by weatherization personnel during air sealing. Air-leakage measurements showed that weatherized houses were tighter after weatherization, especially when blower doors were used during sealing, but still leakier than what is achievable. A blower-door guidebook would be a useful document for technology transfer and training.

Weatherized houses averaged a statistically-significant reduction of 570 CFM50, while the controls showed a 164-CFM50 reduction. The average post-weatherization air leakage for the weatherized houses was 2,725 CFM50, significantly higher than what is generally accepted as being a tight house. Air-leakage reductions were 240 CFM50 greater in houses where blower doors were used during sealing, compared to houses where they were not used (local agencies used blower doors in about half the weatherized houses). Similarly, reductions were 175 CFM50 greater in houses receiving wall insulation, and 300 CFM50 greater in houses receiving high-density wall insulation. These differences, though, were statistically significant only at an 80% confidence level.

Related Articles