HVAC: Retrofitting systems in existing buildings with boilers

August 17, 2023

While the mechanical engineering team has much more control over how HVAC systems are designed and how they fit into the facility for new construction, retrofitting HVAC systems to accommodate existing buildings is considerably more challenging.

Boilers typically are replaced after they have been in service for 20 to 30 years — or more. This relatively long service life, as well as the significant amount of energy a boiler uses, makes all decisions related to boiler replacement critical from financial, operational and sustainability standpoints.

Hot water condensing boilers offer an excellent replacement solution in many applications, and their theory of operation, advantages and disadvantages are well documented. Although the efficiency improvement associated with hot water condensing boilers is significant, in many cases they are not chosen to replace conventional boilers because of a concern that they will not operate efficiently in an existing hot water system.

  • Understand the reasoning behind retrofitting an HVAC system with a boiler.
  • Review boiler codes and standards, such as ASME’s Boiler and Pressure Vessel Code (2021 edition).
  • Gain insights on how to calculate the owner’s return on investment (ROI) and complete a life cycle cost analysis (LCCA) when retrofitting.
  • Gain insight from examples of boilers specified to retrofit an HVAC system.