This technical report applies to water-using cooling and heating systems in buildings.  It provides information for minimizing system damage and operational interference because of corrosion, scale, fouling, and microbiological growth in building heating, ventilation, and air conditioning (HVAC) systems.  This includes open and closed circulating water systems, low-pressure steam boilers and hot water “boilers.”  The document also addresses thermal energy storage systems, but does not address potable water or fire protection systems.  It is intended for use by building owners and engineering, maintenance, and operations management personnel.  It is also intended for use by those involved in the design and construction of building HVAC systems so that corrosion, scale, fouling, and microbiological growth problems described above can be understood, anticipated, and minimized through appropriate design decisions.