Union Mill

Another great example of how APG’s high-performance HVAC systems have solved unique building needs is the Union Mill installation.

About Union Mill:

  • Union Mill is a 146-year-old nineteenth-century Baltimore mill.
  • The building was closed in 2002 and declared a sick building due to alleged ventilation issues.
  • The development company wanted to adapt the old industrial space to a mixed-use facility that would contain 56 one- and two-bedroom apartments, 30,000 square feet of office space and a 1,500-square-foot café restaurant in the former boiler house building.


  • The stone walls were more than 2-feet thick, making a ducted option impossible.
  • The building’s pitched roof would not support boilers, chillers or outdoor condenser units.
  • With its urban setting, outdoor space surrounding the building was limited, making outdoor unit size of paramount importance.
  • Considerable load variation between open-air retail space and individual apartment units.
  • Need for individual zone control.


  • VRF zoning equipment costs were less than expected.
  • The outdoor units are among the quietest available.
  • The outdoor units’ small footprint would preserve the public outdoor space.
  • The indoor units come in many diversified configurations, which provided the architect with numerous choices for installation in a variety of zones.
  • The  R2-Series has simultaneous cooling and heating capabilities for the varied spaces.
  • Ductless capabilities would accommodate the wall thickness.
  • The TG-2000™ software allows the HVAC energy consumption for each zone to be monitored and individually billed.
  • A single Seawall PC (from a remote office) can control and monitor all functions.


  • The equivalent standards of LEED Silver.
  • $164,258 cash rebate through Baltimore Gas & Electric’s “Smart Energy Savers Program.”
  • Average apartment energy use only $50/month.