Saving energy in multifamily buildings is similar to saving energy in homes. The choices become different for multifamily housing as the building increases in size. The fact that one building is home to many people also becomes a factor in selecting energy conservation measures. For example, insulating walls is more difficult in multifamily buildings because you need access to every apartment at approximately the same time.

The most common and cost-effective energy conservation measures are these:

  • Improve domestic water-heating efficiency
  • Tuning up boilers and furnaces
  • Improving hydronic and steam distribution systems
  • Improve lighting efficiency
  • Reducing air leakage
  • Improving windows
  • Insulating attics and roofs

You can’t go wrong with simple improvements to the heating system, cooling system, and water-heating system. In most buildings, problems in these three systems typically waste 10 to 35 percent of the energy they use.
A process called retrocommissioning is one method towards evaluating multifamily energy efficiency.  It starts with an analysis of how the systems are supposed to work. Then a commissioning agent measures performance and makes suggestions about adjustments, additional controls, and operational changes.
For a major change in heating or cooling systems, the building shell retrofits should be completed first so that the contractor can install the smallest heating or cooling plant possible. Reducing air leakage is often the most cost-effective improvement to the building shell. The trick to air-sealing multifamily buildings is to characterize the air leakage into these categories.

  • Leakage directly to outdoors
  • Leakage between floors
  • Leakage between apartments
  • Leakage in the attic and roof
  • Leakage in the lower floors of the building

After evaluating air sealing and insulation, consider new windows or adding storm windows. Doubling the windows from inside the building is a good option if there is space to install another fixed or movable sash.
Lighting is another good retrofit, assuming that the building has an abundance of light fixtures that is easily retrofitted or replaced.