The diversity of multifamily buildings—from new "supergreen" apartment buildings to aging public housing, from semi-detached townhouses to 100-unit high rises—presents an equally diverse range of opportunities for energy savings. These buildings offer numerous energy and environmental advantages over single family dwellings. Energy efficiencies are intrinsic to shared structural and mechanical systems such as roofs, exterior walls, water, and climate control. Since less of the building envelope is exposed, heating and cooling a multifamily building is typically less energy intensive per unit when compared to a single family home.

There are significant environmental benefits to multifamily buildings as well. Concentrating residential units in one building or complex conserves land and transportation resources. Sharing outdoor areas can minimize landscaping and maintenance efforts and reduce yard waste and water usage. And multi-use swimming pools and playgrounds are certainly more cost effective than privately-owned ones.

Still, energy and water costs tend to be high in multifamily buildings, particularly those built before 1970. In fact, 65% of public housing units fall in this category. Many of these units feature old, inefficient appliances and heating and water systems.

The Good News?

In New York City, the first green apartment building is currently under construction, designed to take maximum advantage of energy-efficient building technologies as well as renewable energy systems and water conservation features. The building design features efficient windows, roofing, insulation, lighting, and mechanical and ventilation systems. In addition, the building will produce its own solar energy and will recycle water for flushing and irrigation. All the appliances—refrigerators, ovens, compactors, dishwashers, washers, and dryers—will be energy-efficient as well. This high-performance high rise will serve as a model for sustainable apartment building design and operation, and demonstrate the cost-saving benefits of energy and environmental features.

The same opportunity exists in public housing, where energy-efficient building improvements can help public housing authorities save big on utility bills and maintenance costs. Even better, many of the same improvements that lower energy consumption also help to make buildings more livable, with improved temperature and lighting control, ventilation, and indoor air quality.

Energy-efficient renovations in multifamily buildings usually target inefficient heating and hot water systems. New boilers, improved or new distribution systems, conversion from electric or oil heating to natural gas, improved system controls, and improved motors can make a huge impact on building energy consumption. Improvements to the building envelope—windows, roofs, and insulation—boost savings even further by minimizing heat gain and loss.

Replacement of inefficient equipment and appliances represents another substantial source of savings. For example, today's refrigerators are twice as efficient as those built 10 years ago. Bulk purchasing agreements reduce the cost of replacing old refrigerators, and the energy cost savings provide a fast return on a modest investment.

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