How radiant differs
From other Heating
Radiant heating generally refers to heat-delivery systems that rely on electromagnetic
waves to warm surfaces. The sun’s energy that
hits the earth is electromagnetic energy, including visible waves we know as sunlight. Sunlight
is radiant energy that transforms into heat
energy when it contacts a physical surface, like
the absorber plate in a solar thermal collector.
The heat is conducted through the metal of the
absorber to a heat-transfer fluid, which then is
pumped to where it is needed or will be stored
for later use.
Radiant heating systems rely on electromagnetic waves that we cannot see, but we can feel
them as warmth. Imagine a flat panel that is like
the absorber plate in a solar thermal collector.
If we circulate a hot fluid through our flat panel
and if the panel is warmer than the surrounding
air, then the panel will emit radiation in the form
of electromagnetic waves into the surrounding
space. When this radiation hits a solid object,
the object will get warm. When the object gets
warm it will, in turn, warm the air that surrounds
it. In other words, radiant heating systems heat
things rather than directly heating air. By contrast, traditional forced-air heating systems and
traditional hydronic heating systems heat air,
and the warm air heats things it comes into con-
Solar radiant Floor Heating
Aluminum heat-emission plates fit between
floor joists to transfer to flooring heat delivered via a solar-heated liquid. Here are two
design options.
Heat-Emission Plate
Track Plate
tact with through convection and conduction.
The point of the above descriptions is to
clearly show how fundamentally different radiant heating systems are from conventional heating systems. Conventional systems have to fill
the conditioned space with hot air to achieve
the desired temperature, while radiant heating
systems heat the objects in the space.
Any heating system comprises two main
components: the heat source and the heat-delivery system. Most radiant heating systems
rely on a boiler to heat a liquid that is then piped
to some type of heat-transfer device, like baseboard radiators or radiant floor, wall or ceiling
panels. Resistance electric heating could also
be used where heating cables are embedded in
floors, walls or ceilings, in which case the heat
source and delivery system are the same heating cables. Baseboard radiators and most old-fashioned radiators actually work on the principle of convection, whereby the radiators heat
air that is then circulated throughout the room
by convection.
The operating temperature of the heating system and the heat load of the room being heated
determine the size of the radiator needed. The
warmer the operating temperature, the smaller
the radiator need be to deliver a determined
amount of heat. Conversely, the lower the temperature of the heating system, the larger the
radiator needs to be to deliver an equal amount
Radiant floor heating has
been refined in Europe for 50
years, but it’s only caught on
here in the last 15 years.
leIF ramlow
Radiant wall panels are an excellent way to distribute solar heat in a building. Running the piping is a little more difficult than for floor systems, but note that
these panels can be mounted either on interior or exterior walls.
