Balancing Hydronic Systems in Multifamily Buildings

More than 50% of units in colder climate region multifamily buildings in the United States are heated by steam or hot water systems (RECS 2009). These buildings often suffer from imbalance: some apartments are too hot and some are too cold. In hydronic systems, distribution issues may be caused by undersized piping, improperly adjusted balancing valves, inefficient water temperature and flow levels, and owner/occupant interaction with the boilers, distribution, and controls. The effects of imbalance include tenant discomfort, higher energy use intensity, inefficient building operation, and decreased equipment longevity. These issues can affect a building’s financial viability as apartments become more expensive to heat, no-heat calls accumulate, and maintenance staff and heating equipment work harder and less efficiently in their efforts to provide enough heat to all units to meet code requirements and tenant expectations. This paper explores the causes for heat imbalance in these systems and discusses potential upgrades and measures to address them, providing guidance to contractors, auditors, and building owners on best practices to improve tenant comfort and lower operating costs.

The research was conducted by The Partnership for Advanced Residential Retrofit in conjunction with Elevate Energy. The team drew upon existing knowledge of retrofits for optimizing distribution in typical multifamily hydronic systems, with the aim of identifying common situations and solutions, then conducted case studies on two Chicago-area buildings with known balancing issues to quantify the extent of temperature imbalance. At one of these buildings the team installed a booster pump on a loop to an under-heated wing of the building and tested the effect of this retrofit on imbalance.