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A LOOK AT RADIANT FLOOR HEATING—AN AGE-OLD
TECHNIQUE FOR MODERN-DAY HOMES, USING THE
LATEST TECHNOLOGY. By Kim J. Gifford
Winter is upon us in the Upper Valley—and
yet you no longer have to wake up in the morning,
get out of bed, and step onto a freezing tile or
hardwood floor. Advances in radiant floor heating
technology, a method of heating homes by heating the
floor, have increased its availability. Radiant heat
is currently used in 50 to 80 percent of new home
construction in Europe and is catching on in the
United States.
Although radiant heat may be transmitted by heating
elements placed in walls and overhead panels, it is
most effective when used in flooring, where it
radiates upward, focusing its energy on the surface
of the floor and the occupants of the room—as
opposed to directly heating the air.
Duffy Orr of Orr’s Plumbing and Heating in Bethel,
Vermont, compares the sensation of radiant heat to
sitting on a large stone in the middle of a field on
a spring day. “You might feel the cool air around
you, but you are warm sitting on the stone because
of the heat radiating from it,”
he explained.
A Brief History
Rick Dickinson of Dickinson & Son, Inc. in Hanover,
New Hampshire, notes that radiant floor heating has
been around for ages. “It has only really come on
strong here in the U.S. within the last 25 years,
but it has been in existence for a long time,” he
said.
As early as 670 A.D., the Romans heated their villas
and baths by directing hot gases and air from fires
in pipes beneath slab floors. More recently,
architect Frank Lloyd Wright employed radiant
heating in the houses he designed; and in the 1950s,
tract homes built at Levittown on Long Island used
this method of heating. Many of these early systems,
however, relied on copper piping, which eventually
corroded under the cement. Today’s hydronic systems,
based on heated water, rely on durable cross-linked
polyethylene (PEX) tubing. PEX tubing is less
expensive than copper and more resilient. It will
not corrode from concrete additives and can stand up
to water conditions better over time.
System Types
Radiant floor heating relies on either an electric
or hydronic system within the floor to generate
heat. Electric systems are typically used for spot
heating in areas such as a workroom, entryway, or
garage. This is because they don’t take as long to
heat up as hydronic systems, and are not as
efficient over long periods and bigger spaces.
Electric systems are based on cables or thin mats,
similar to electric blankets. If electric systems
are being installed in a new home or with a new
floor in an existing home, they are often set in
cement. Otherwise, they can be inserted in an air
space beneath the floor.
Hydronic systems use hot water, heated by boilers,
which runs through a system of tubes that radiate
heat to the floors. Experts agree that the design of
hydronic systems is better for heating large areas —
or a whole house — than the isolated mats that
typically make up electric systems. Hydronic systems
can be installed in a number of ways. The first
method is called a “wet” installation and involves
embedding the tubing within a solid floor, such as a
concrete foundation slab. This requires a new floor,
and for this reason it is easier, and sometimes only
possible, to perform a wet installation in a home as
it is being built. The other method of installation
is referred to as “dry” and involves running tubing
in an air space beneath the floor. The tubing can
also be suspended between the joists underneath the
sub-floor. In this case, insulation must be
installed under the pipes to ensure the heat
radiates upwards. “As a rule of thumb you want to
have one-and-a-half times the insulation underneath
the tubing to force the heat up,” said Perry.
“Any wood floor that still has moisture left in the
wood is going to give you a problem. It’s going to
shrink and crack. Generally, hardwood floors that
are well dried and uniform are compatible,” said
Dickinson. Some experts discourage the use of
carpeting over radiant flooring, but Perry
disagrees. “Even though [carpeting is] a form of
insulation and takes a little longer to come up to
temperature, it eventually does, and it radiates the
same as wood, or anything else.”
Pros and Cons
The primary reason to choose radiant floor heating
is comfort. The biggest drawback for most people is
its initial expense.
According to Dickinson, “Radiant heat is probably
the most comfortable heat ever devised. But it’s
also the most labor intensive and expensive to
install.” Most estimates suggest that it will cost
$500 to $700 to install a timer-controlled
thermostat and an electric mat in an average-sized
bathroom. Estimates for hydronic heat systems vary,
running the gamut from 20 to 60 percent more than
conventional heating systems.
Another drawback is radiant floor heating’s slow
recovery. “It can take up to six, seven, or eight
hours to initially feel the heat, but once it’s warm
it takes just as long to cool off,” said Orr.
Another drawback? Radiant heat systems do only one
thing, heat. Unlike many conventional heating
systems, they cannot be used to generate and deliver
cool air as well.
Radiant floor heating may save
energy in the long run.
Although radiant floor heating is initially more
expensive than conventional systems, industry
insiders suggest that it may yield a small savings
in the long run via energy usage. Because it focuses
first on warming objects and your body as opposed to
the air, most users find themselves feeling
comfortable at a lower temperature, and this allows
them to turn down the thermostat.
Radiant floor heating is also quiet and clean,
reducing possible allergens such as dust. Because
there is no need for radiators, it opens up more
decorating options.
But when asked why it really matters most, Dan Ryan
of Dan Ryan Heating in Braintree, Vermont, said,
“It’s just the pure comfort of it.
“As anyone knows, when your
feet are warm, you are warm.”
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