All-water distribution systems provide flexible
zoning for comfort heating and cooling and have a relatively
low installed cost when compared to all-air systems.
The minimal space required for distribution piping
makes them an excellent choice for retrofit installation
in existing buildings or in buildings with significant
spatial constraints. The disadvantage to these systems is
that since no ventilation air is supplied, all-water distribution
systems provide little or no control over air quality
or humidity and cannot avail themselves of some of
the energy conservation approaches of all-air systems.