This article was originally published in the September/October 1995 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.



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Home Energy Magazine Online September/October 1995




Citizens Conservation Corporation studied savings from high-efficiency boilers and controls installed in public and assisted multifamily housing in New England. They found that savings from equipment retrofits can and do persist well beyond the first retrofit year.

In a study funded by the U.S. Department of Energy and the Department of Housing and Urban Development, we looked at the savings persistence from equipment retrofits that Citizens Conservation Corporation (CCC) installed in low-income apartment buildings over the past decade. We also explored the key factors that affect whether savings erode after the first postretrofit year.

The study included 15 retrofits in which existing boilers were replaced with high-efficiency condensing boilers and controls. Three of the projects involved steam-to-hydronic conversion of the distribution system. Each project also included some or all of the following measures: air sealing; attic insulation upgrade; temperature-limiting thermostats or fail-close zone valves; and hot water-saving measures, such as faucet aerators and low-flow showerheads. Total natural gas consumption after the retrofit was analyzed, weather-adjusted, and compared to the pre-retrofit baseline usage. Table 1 shows, for each retrofit, the projected savings, the first year savings, the most recent year savings, and the most recent year savings as a percentage of the first year savings. Figure 1 shows the savings over time for four of the projects we will discuss here.

Table 1. Persistence of savings from retrofits in 15 multifamily buildings              
Site Retrofit
# of
Installed Measures Projected
(% of preretorfit
gas usage)
First year
Most recent
year savings
Most recent
year savings
as % of
first year
#1 1986 48 new boilers, controls, air sealing, attic insulation, pipe insulation 39% 26% 17% 64%
#2 1986 157 new boilers, controls, air sealing, insulation upgrade, water-saving measures, non-electric zone valves 26% 20% 31% 156%
#3 1986 104 new boilers, controls, air sealing, setback thermostats 31% 39% 44% 111%
#4 1986 16 new boilers, controls, air sealing, storm windows, water-saving measures,
non-electric zone valves
48% 41% 38% 91%
#5 1987 151 new boilers, controls, setback
thermostats, door weatherstripping
20% 16% 1% 4%
#6 1987 124 new boilers, DHW system, controls, setback thermostats, attic insul., air sealing 35% 25% 28% 114%
#7 1987 123 new boilers, controls, pipe insulation,
air sealing
14% 19% 18% 97%
#8 1988 36 new boilers, controls, weatherstripping, low-flow toilets, pipe insulation 27% 21% 16% 77%
#9 1988 90 new boilers, controls, replacement of indiv. gas A/C with central elec. 53% 46% 45% 98%
#10 1989 161 new boilers, controls, water-saving measures 27% 35% 24% 69%
#11 1989 40 new boilers, controls, air sealing,
insulation, water-saving measures
27% 42% 43% 103%
#12 1990 38 new boilers/piping, controls,
non-electric zone valves, weatherstripping
54% 49% 45% 91%
#13 1990 10 new boilers, controls, non-electric zone valves, insulation, steam-to-hydronic conversion 40% 51% 45% 88%
#14 1990 10 new boilers, controls, non-electric zone valves, steam-hydronic conv. 40% 75% 81% 109%
#15 1990 292 new boilers, controls, non-electric zone valves, steam-hydronic conv., new water heaters 60% 68% 69% 102%
Avg.       36% 38% 36% 92%
Note: Sites in bold are discussed in this article.              

Savings Do Persist

For each project, we had at least three years' worth of monitored, weather-adjusted savings; for some buildings, we had up to seven years' worth of data. The savings from the boiler retrofits have been substantial. The average postretrofit savings for the 15 projects was 37%, slightly greater than the average projected savings of 36%.

To evaluate savings persistence, we looked at first-year savings and compared them to savings in subsequent years. The average first-year savings was 38%, compared to the average savings for the most recent year, which was 36%. In other words, savings declined an average of only 5% from the first year to the most recent year. In 10 of the 15 projects, savings declined less than 10% over the monitoring period.

Success Story

In 1990, CCC retrofitted a 292-unit inner-city low-rise brick public housing development (Site 15). We converted the old steam-heating system to a hydronic distribution system and installed high-efficiency condensing boilers, indirect-fired domestic hot water systems, and nonelectric zone valves. We calculated a simple payback of 11 years for the $2.66 million project, which was funded through a $1 million energy performance contract supplemented by a state grant and weatherization funds. In the four years since the installation, savings have remained steady, averaging 68%, or approximately $230,000 annually.

Prior to CCC's retrofit of the development, the public housing authority had installed high-quality replacement windows. The new windows were more attractive and easier to operate than the old ones, but they provided no energy savings. This was because, due to the lack of temperature control, residents had to open their windows in the winter to keep their apartments from overheating. It was evident that no shell measures would produce energy savings unless the heating system and its control were addressed.

Since CCC replaced the heating system, the savings have persisted in large part because the on-site maintenance team has been supportive in making sure that the new system has run smoothly. Meanwhile, CCC and the housing authority have engaged the residents' interest in the benefits of saving energy through the resident energy education program and through a drug prevention program--funded in part by energy savings--for the young people at the development.

Planning for Persistence

In this and the other cases, we found that savings persistence from boiler replacement retrofits depends on three main factors: appropriate measure specification, proper maintenance of the equipment, and resident behavior.

Pick the Right Equipment

High-efficiency boilers are more complex than moderate-efficiency boilers and require special maintenance, without which they may fail. In some cases, despite good maintenance, equipment may malfunction because of faulty manufacturing. The most efficient boilers available on the market are relatively new and unproven, and there is some risk involved in specifying high-efficiency boilers. For example, boiler failures were largely responsible for savings erosion at Site 8. Specifications should take into account a manufacturer's track record.

Care should also be taken when specifying temperature-limiting thermostats. If the thermal comfort of a building is not addressed, the residents will be uncomfortable, and they may disable their thermostats. Be especially careful in specifying temperature-limiting thermostats in buildings with poor thermal comfort, such as brick buildings with single-pane windows and no wall insulation.

Maintain the System

Once the equipment is selected and installed, proper maintenance of the new system is essential to the persistence of savings. The maintenance staff should be trained to maintain the equipment, especially when high-efficiency condensing boilers are specified. At Site 10, savings erosion was due largely to maintenance problems, in particular to maintenance staff overriding controls.

Upon completion of an installation, CCC has furnished maintenance teams with customized manuals designed to facilitate upkeep and repair of the new heating or hot water system. Thereafter, CCC has provided troubleshooting and monitoring of savings for the life of the loan. By tracking the energy savings of every site, CCC can assess the performance of every project, and can develop a plan of action if savings are not accruing as projected.

Involve the Residents

Savings persistence also depends on the behavior of the residents in the retrofitted buildings. In order for savings to accrue and persist, residents must accept the changes to their living environment that result from the installation of the energy efficiency measure package. Residents accustomed to having unlimited heat, regulated by opening and closing windows, must adjust to a limited indoor temperature (usually 75deg.F) with the new heating system. If the residents do not accept these changes, they may disable zone valves or thermostats. At Site 5, where savings erosion was the worst of all the projects in the sample, residents used the override button on their thermostats as the default setting.

CCC has built resident energy education into its contracts, institutionalizing annual or semiannual on-site resident energy education workshops for the life of the energy loan. Before the installation, the residents are told about upcoming changes to their apartments and buildings and why those changes are being made. After the retrofit, residents learn how to save energy and water without sacrificing comfort, and where appropriate, how to operate the new thermostats or zone valves.

Because residents of low-income multifamily buildings typically have little or no incentive to save energy or water, CCC has sought to create incentives. In many cases, a portion of excess savings is used to fund social programs exclusively for the benefit of the residents. At some sites, residents have received a cash bonus when they achieved a certain level of savings.

Savings can and do persist from equipment retrofits, as CCC's experience with boiler replacement has shown. Specifying high quality equipment, ensuring proper maintenance, and recognizing the importance of resident behavior will help keep savings from eroding.

Figure 1
Figure 1. Savings over time for four retrofit sites.

Sandra Nolden is a policy analyst with Citizens Conservation Corporation.

Note: For a copy of the unpublished report on which this article is based, contact Michael MacDonald, Oak Ridge National Laboratory, P.O. Box 2008, Bldg 3147, Bethel Valley Road, Oak Ridge, TN 37831-6070. Tel:(615)574-5187.


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