More than 30 million Americans live in multifamily housing. A disproportionate number of them are poor, renters, minority, single parents, and children. While buildings with five or more units account for only 9% of residential energy end-use in the United States, the energy burden—i.e., the percent of household income spent for energy—is several times higher for these households than for single-family households. Historically, multifamily buildings have been the most neglected building sector for retrofit activity in utility and federal programs, but the last ten years have seen impressive advances in improving the energy efficiency of these buildings.
Figure 1. The Margolis Apartments in Chelsea, Massachusetts, was designed in 1973 and is typical of high-rise construction from that period. This USHUD project is the site of ventilation and infiltration measurements to improve comfort and energy performance.
A new book, Improving Energy Efficiency in Apartment Buildings, by John DeCicco, Rick Diamond, Sandy Nolden, and Tom Wilson, funded by the U.S. Department of Energy and the Energy Foundation and to be published by the American Council for an Energy Efficient Economy in early 1996, documents much of this work. It is the result of collaboration by practitioners and researchers active in multifamily retrofit research. One area that continues to block retrofit efforts has been our lack of understanding of how ventilation and infiltration occurs in these buildings. Unlike single-family buildings, where our knowledge of ventilation and infiltration has benefited from such tools as blower doors and tracer gas measurement, the more complex configurations of multifamily buildings challenge our ability to measure and model the air flows and their resulting energy costs.
We have been working for the past two years at the Margolis Apartments (Figure 1), the site of a collaborative venture among DOE, HUD, the Boston Edison Company, and the Chelsea Housing Authority, to demonstrate energy-efficient retrofits of public housing as part of a utility DSM Program.
We made a series of visits to the building in which we performed ventilation and air-leakage measurements using tracer gases and blower doors to determine the performance of the energy-saving retrofits and to determine if adequate levels of ventilation for air quality were being met throughout the building. Following these measurements, we modeled the air flows in this building using the computer simulation program COMIS, which allowed us to understand the complex air flows under different weather conditions.
Figure 2. A simulation of the air flows in the Margolis Apartments under different wind speeds. The model shows that even apartments on the windward side of the building are not receiving sufficient outside air (according to ASHRAE Standard 62, see dashed line) during periods of low windspeed.
Our findings to date illuminate the asymmetric nature of the air flows in highrise buildings. Depending on the side of the building and the height above the ground, the unit may be under- or overventilated (Figure 2). We have also been studying the relative importance of the stair towers and elevator shafts and how they interact with both the mechanical and natural ventilation in the building. One disturbing finding is that the designed mechanical ventilation often performs poorly, both in exacting a greater energy penalty and in not providing adequate ventilation.
We plan to continue our study of ventilation in highrises by looking at additional buildings and making recomendations for both retrofits and new construction. One goal of this research is to develop protocols and guidelines for measuring and improving ventilation as efficiently as possible.
—Rick Diamond, Helmut Feustel, and Darryl Dickerhoff
Indoor Environment Program
(510) 486-4459; (510) 486-6658 fax
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