Rethinking DHW Systems: Why Better Floorplans Deliver Better Performance

Domestic hot water performance is often treated as a mechanical problem, but many of the most impactful decisions are made much earlier at the floorplan level. In this session, Gary Klein reframes DHW system design through the lens of architectural layout and infrastructure efficiency, showing how compact floorplans, stacking and back to back layouts, and right sized plumbing systems can dramatically reduce water volume, energy use, wait times, and pressure loss, often at lower cost.

Drawing on decades of research, code work, and real world projects, the session explores why time to tap and volume until hot targets should be set during schematic design, how architectural compactness improves system performance, and which plumbing layout decisions have the greatest impact on efficiency and occupant experience. Attendees will also learn best practices for integrating air source heat pump water heaters into high performance homes, specifying pressure independent flow regulators, and right sizing systems using the IAPMO Water Demand Calculator. This session is especially relevant for architects, engineers, and builders looking to align layout decisions with performance goals and rethink DHW systems as a shared architectural and mechanical responsibility.

About the Speaker
Gary Klein is the principal of Gary Klein and Associates (GKA), an international consulting firm focused on water, energy, and carbon footprint issues with a particular emphasis on high performance hot water systems. GKA works with architects, engineers, builders, and organizations to design efficient domestic hot water systems, including providing redline drawings to optimize plumbing layouts at the floorplan level. Gary has been deeply involved in national codes, standards, and incentive programs including ICC, IAPMO, ASHRAE, EPA Energy Star and WaterSense, LEED, and NAHB, and has collaborated with Masco, BASF, and the U.S. Department of Energy to implement best practices across a wide range of building types.


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