Chapter 5.4 - Radiant Hydronic Heating Systems

4.1 Introduction To Radiant Hydronic Systems

Radiant hydronic heating systems accomplish heat delivery by means of panels that
transfer 50 percent or more of total panel energy radiantly, a characteristic by which
the ASHRAE Handbooks define all radiant systems. The distinguishing feature of
radiant hydronic heating systems is the use of a liquid or fluid to transfer heat from
the originating source to the radiant panel at the location of heat delivery.The focus
of this chapter is the development of information about hydronic heating panel
design, performance, and control characteristics.

Radiant hydronic systems employ a broad range of radiant panel configurations
located on or in the floor, wall, or ceiling. The performance characteristics are
impacted by the planar selection. Occupant proximity to the heat source, the split
between radiant and convective heat transfer, and potential for heat-obstructing or
surface-covering materials—all are important considerations in plane selection for
radiant heat delivery. Each location can accommodate a broad selection of hydronic
equipment and design options.

Common radiant hydronic panels encompass a variety of floor design options to
accommodate the complex range of new and existing building architectural requirements.
Even though radiant hydronic floor systems normally embed the heat transfer
conduit directly into the floor as the panel, the heat transfer conduit may also be
placed on the underside of the floor. Each radiant floor panel design should be analyzed
carefully to determine its unique performance requirements, as planned, as it
could be installed, and as it might later be used.

Radiant hydronic wall panels include embedded and surface-mounted systems.
Old-fashioned radiators are, in fact, not considered radiant panels, as heat transfer is
often more than 70 percent convective. However, large-panel-face, narrow-profile,
wall-mounted radiant hydronic panels transfer a larger portion of heat radiantly
than the cast-iron radiators that heated the buildings of yesteryear, and are included
in the review of radiant hydronic systems.

Embedded radiant hydronic ceiling systems were more common in the United
States in the 1940s, when ceilings were composed of lathe and plaster, in which copper
or iron piping was embedded. For such applications, narrow-profile polymeric
conduit and mats have replaced metal for embedded radiant hydronic ceiling systems.
A less expensive design routes flexible conduit through the ceiling joists above
the topside of the ceiling surface or under the subfloor for floor heating. Insulation
is placed above or below the conduit to maximize panel face heat output.

Metal panels are more common for hydronic ceiling heating in commercial and
institutional applications. Metal panels transfer heat radiantly that is delivered by
copper conduit routed through heat transfer brackets integral to the panel. Manufactured
radiant hydronic ceiling panels are made of various metal alloys and
designs. Metal radiant hydronic panels may be installed flush with the ceiling or
surface-mounted on the ceiling.The performance characteristics of each of the radiant
ceiling panel equipment and design selections are unique. Each alternative
should be carefully designed to ensure that desired comfort and energy performance
is achieved.

4.1 Introduction To Radiant Hydronic Systems

Radiant hydronic heating systems accomplish heat delivery by means of panels that
transfer 50 percent or more of total panel energy radiantly, a characteristic by which
the ASHRAE Handbooks define all radiant systems. The distinguishing feature of
radiant hydronic heating systems is the use of a liquid or fluid to transfer heat from
the originating source to the radiant panel at the location of heat delivery.The focus
of this chapter is the development of information about hydronic heating panel
design, performance, and control characteristics.

Radiant hydronic systems employ a broad range of radiant panel configurations
located on or in the floor, wall, or ceiling. The performance characteristics are
impacted by the planar selection. Occupant proximity to the heat source, the split
between radiant and convective heat transfer, and potential for heat-obstructing or
surface-covering materials—all are important considerations in plane selection for
radiant heat delivery. Each location can accommodate a broad selection of hydronic
equipment and design options.

Common radiant hydronic panels encompass a variety of floor...