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


Energy Savings Rise High
In Multifamily Buildings

by Rick Diamond

Air sealing, heating systems, air conditioners, domestic hot water, lighting, fuel bill analysis, customer education.... Sounds like a typical issue of Home Energy. Only this time the focus is on multifamily buildings.

The art and science of multifamily retrofit is in many ways similar to that of single-family houses, but the added complexity of the buildings and their occupants can be daunting. Fortunately, organizations around the country have been doing excellent work in the field of multifamily building analysis and retrofit, and we are fortunate to bring together the work of many of these experts for this Special Issue.

Mary Sue Lobenstein and Martha Hewitt, from the Center for Energy and Environment in Minnesota, sum up 10 years of research on specific measures to increase the efficiency of boilers and domestic water heaters. Victoria Hayes describes how crews from GRASP in Pennsylvania tackle issues of defining and sealing pressure barriers. And Larry Hasterok from the Wisconsin Energy Conservation Corporation explains how compact fluorescent fixtures are the friend of the multifamily auditor.

Given the many variables that go into making multifamily buildings work, do savings from these retrofits persist? Citizens Conservation Corporation studied 15 projects and found that they usually do. Sandra Nolden reveals that choice of the right measures, good equipment maintenance, and occupant cooperation determine whether savings persist in a building. The last of these factors, the behavior of occupants, can be addressed with a good education program, as Fairlie Firari from Syracuse Energy Conservation Company explains.

A fuel bill analysis can help weatherization programs and building owners decide how much to invest in energy savings. F. L. Andrew Padian introduces a method of using a fuel bill analysis to set a draft investment level for multifamily buildings.

To wrap up the section, Larry Kinney and Tom Wilson from Synertech Systems Corporation in New York, and Mike MacDonald from Oak Ridge National Laboratory, give us a glimpse of what's happening in multifamily retrofit in five northern cities; and Kathy Robinson, Mike Myers, and Bert Brown describe a successful multifamily program in Austin, Texas.

But before getting into the nitty-gritty of multifamily retrofit, it helps to put multifamily housing in a national perspective. In the first article of the section, Rick Diamond from Lawrence Berkeley National Laboratory takes a look at the structural, social, and energy characteristics of multifamily buildings in the United States.

An Overview Of The Multifamily Sector

This article is based on a chapter from Improving Energy Efficiency in Apartment Buildings, by John DeCicco, Rick Diamond, Sandra Nolden, and Tom Wilson, funded by the U.S. Department of Energy and the Energy Foundation. The book will be published by the American Council for an Energy Efficient Economy (ACEEE) in early 1996.

More than 30 million people live in multifamily buildings in the United States, accounting for 9% of total residential energy use. Yet federal and utility energy conservation programs are still disproportionately focused on single-family and owner-occupied housing. To determine the potential for, and obstacles to, multifamily conservation, we examined census data and the Department of Energy's 1992 Residential Energy Consumption Survey (RECS), among other sources, in order to characterize the types of structures, social conditions, and energy usage in these buildings. The results, some of which may be surprising, should be useful for those who are working with or planning multifamily programs.

The Buildings

More than one-quarter of U.S. households live in multifamily buildings. These range from duplexes and low-rise garden apartments to high-rise structures occupying entire city blocks. Since the larger buildings are the most different from single-family houses, we looked mostly at the statistics for buildings with five or more units. In 1990 there were one million such buildings, which were home to 14 million households.

Regional and Urban Distribution

Multifamily buildings are found in all parts of the country, with the largest number in the Northeast and the South. Over four million units are located in the Northeast, another four million in the South, and about three million each in the West and the Midwest.

The Northeast and the West have a higher percentage of households in multifamily buildings than the rest of the country (21% and 19% respectively). In the Midwest and South the figure is 13%. The larger multifamily buildings tend to be in the Northeast, where 42% of the nation's buildings with 50 or more units are located. The smaller multifamily buildings tend to be found in the South.

Age of Building

While we tend to think of multifamily units as being in older buildings, in fact less than 20% were built prior to 1950 (see Figure 1). More than half (55%) have been built since 1970, mainly due to a construction boom in multifamily housing that occurred in the South and West in the 1970s and 1980s.

Figure 1. Age distribution of multifamily households (five or more units).

The People

Perhaps the single most defining characteristic of multifamily households is that the residents are renters, not owners. While rental households account for only 30% of the total U.S. households, the majority of residents (90%) in multifamily buildings rent their units.

Household Income

Not surprisingly, residents of multifamily units (both owners and renters) have lower incomes on average than the rest of the population (see Figure 2). More than a quarter of the residents of large multifamily buildings have total annual household incomes of less than $10,000. Over half (54%) make between $10,000 and $35,000, and only 8% make more than $50,000. The median income for a multifamily household in 1989 was $19,100, compared to the median single-family household income of $32,100.

At the same time, census data show that the median monthly housing cost (including mortgages, taxes, rent, and utilities) for a multifamily household was $447, slightly more than the median monthly housing cost for a single-family household ($416). Consequently, apartment residents pay an average of 27% of their income for housing compared to the 16% paid by single-family households.

Figure 2
Figure 2. Annual income distribution of multifamily households (five or more units).

Minority and Elderly Households

Multifamily buildings house a higher percentage of minorities than single-family buildings. A quarter of the black and Hispanic households live in multifamily buildings. Black households account for 17% of the multifamily stock, compared to 9% of the single-family stock. Hispanic households account for 11% of the multifamily stock, compared to 5% of the single-family stock.

The elderly, however, are more likely to live in single-family households. The census data show that only 19% of the multifamily households are headed by someone 65 years or older compared to 23% of the single-family stock. Nevertheless, there are 2.9 million elderly households in multifamily buildings.

Energy Use

Patterns of energy use in multifamily buildings are different from those in single-family houses. The average multifamily household uses less than half as much energy as the average single-family household--51 million Btu (MMBtu) per household compared to 111 MMBtu per single-family household (see Table 1). When compared on a floor area basis, however, the multifamily units are larger users--62,000 Btu/ft2 versus 51,000 Btu/ft2 for the single-family house. One reason for this is that the average floor area of a multifamily apartment (800 ft2) is less than half the average floor area of a single-family house (1900 ft2).

Public versus Private

Public housing units use more energy than private multifamily units per household and per ft2, but use less energy per household member--24 MMBtu per person compared to 27 MMBtu per person in a private multifamily unit. Public housing as defined here follows the Energy Information Administration (EIA) definition, which includes not just federal housing, but also a mix of state and local housing authorities, with a variety of housing types, from duplexes to high rises.

According to the Department of Housing and Urban Development, housing authorities spend $1.1 billion per year for utilities (27% of their operating costs), and public housing residents' utility allowances total about $400 million per year for the utilities that they pay.

Electricity and Gas

Multifamily residents consume much less electricity per household than do single-family households--nearly half as much, in fact. But when compared on a floor area basis, multifamily households consume 40% more electricity annually: 7.1 kWh/ft2 versus 5.0 kWh/ft2 for single-family households. Residents of public housing use the least electricity per household.

Multifamily households also use less natural gas than single family households. As with electricity, gas use is higher per ft2, at 49 kBtu/ft2 compared to 42 kBtu/ft2 for single-family households. Fuel oil consumption follows a similar pattern.

Gas consumption in public housing is significantly higher per household than in private multifamily buildings, but only slightly higher when measured on a floor area basis. Assisted-housing units consume significantly more gas both by household and by floor area.

Table 1.
1990 Total Energy Consumption and Expenditure for Single-Family, Multifamily, Public, and Assisted Housing

    Consumption   Expendature    
Million Btu/
Million Btu/
KBtu/ft2 Dollars/
Single-family 64.4 111 39 51 1321 0.60
Multifmaily(2+) 24.4 69 34 71 815 0.85
Multifamily (5)+ 14.4 51 27 62 677 0.84
Public housing 2.5 57 24 66 646 0.75
Assisted housing 1.7 70 25 75 863 0.93
Source: Data from Household Energy Consumption and Expenditures 1990, p. 59.            

Regional Variation

The energy used, and the price that people pay for it, varies substantially from region to region (see Table 2). Apartment dwellers in the Northeast both consume and spend the most for all fuels both per household and per ft2. The West spends the least on energy, although the South uses slightly less both per household and per ft2.

The South uses the most electricity, however, due to high demand for air conditioning, as well as lower electricity costs. The Northeast, which has the highest electricity costs, uses the least electricity.

Household gas consumption is greatest in the Midwest, where costs are lowest, and lowest in the West, probably due to the milder climate.

Table 2. 1990 Total Energy Consumption and Expenditure
for MultifamilyHouseholds (2+ units) by Region

    Consumption Expendature    
Region Million
Million Btu/
KBtu/ft2 Dollars/
Northeast 6.8 91 83 1084 0.98
Midwest 5.4 86 82 794 0.75
South 6.7 48 56 744 0.88
West 5.4 49 59 588 0.71
National 24.4 69 71 815 0.85
Source: Data from Household Energy Consumption and Expenditures 1990, p. 59.          

Consumption by End Use

Multifamily households also have different patterns of end-use energy consumption than other households. These different patterns are due to differences in building exposure, utility metering, appliance stock, and household behavior. Space heating is typically a smaller fraction of total energy use in multifamily households than in other households (see Table 3). Appliance use is lower in multifamily households partly because there are fewer clothes washers and dryers in these buildings. Refrigerators tend to be smaller, manual defrost models, which accounts for their lower consumption. Lower air conditioning use is probably related to the smaller size of multifamily households and to lower income levels. Domestic hot water is the largest end use after space heating and represents a major target for potential energy savings in multifamily buildings.

Table 3.1990 End Use Consumption for Single-Family,
Multifamily, Public and Assisted Housing

[Million Btu/household]

Housing Total Consumption Space Heating Air Conditioning Domestic Hot Water Refrigerators Appliances
Single-family 111 60 9 18 6 22
Multifmaily(2+) 68 34 5 17 4 11
Multifamily (5)+ 51 19 6 15 4 9
Public housing 57 24 4 17 4 11
Assisted housing 70 36 4 15 4 12
Note: End uses do not add up to total consumption because the number of households differs by end use.
Source: Data from Household Energy Consumption and Expenditures 1990, p. 59.

Multifamily Values

Although this article has presented a lot of numbers, the multifamily sector is more than a statistical compilation of floor areas, numbers of apartments, and units of energy consumption. This sector represents the homes of countless individuals, many of them poor, for whom the trade-offs among better housing, food, and fuel, are very real. The following articles describe how conservation programs across the country are saving energy in multifamily buildings.

Further Reading

Greely, Kathleen M., et al. Baseline Analysis of Measured Energy Consumption in Public Housing, LBL-22854, Berkeley, CA: Lawrence Berkeley Laboratory, January 1987.

U.S. Department of Commerce, Bureau of the Census. American Housing Survey for the United States in 1989, H150/89, Washington, DC: Government Printing Office, July 1991.

U.S. Department of Energy, Energy Information Administration. Housing Characteristics 1990, DOE/EIA-0314-(90). Washington, DC: Government Printing Office, May 1992.

U.S. Department of Energy, Energy Information Administration. Household Energy Consumption and Expenditures 1990, and Supplement, DOE/EIA-0321-(90) and DOE/EIA-0321-(90)/S. Washington, DC: Government Printing Office, February 1993.

U.S. Department of Housing and Urban Development. Report on Review of Opportunities to Reduce Utility Costs at Public Housing Authorities, 95-SE-101-0001. Washington, DC: Office of the Inspector General, HUD, May 1995.

Rick Diamond is a staff scientist at Lawrence Berkeley National Laboratory.
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.


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