Radiant
Heat
Retro Fit Radiant
Heating Into Your Older Home
By Ruth Rowland
|
You
can retro fit radiant heating below hardwood flooring by installing
the system between the floor joist under the subfloor.
|
Imagine yourself
curled up at home on a typical cold, rainy Northwest autumn afternoon.
You put your feet to the floor, expecting the usual bone-chilling
arctic freeze. Instead, your toes touch a warm surface that radiates
gentle heat up toward your limbs like asphalt on a summer night.
This is radiant
floor heat.
The Romans didn't
have the Oregon chill to reckon with, but they were the first on record
to catch on to the benefits of heating from the ground up. They used
wood-fire exhaust to warm their raised stone floors to radiate heat
to the rooms above.
Two millennia
later, Portland homeowners are discovering the comfort of radiant
floor heating, which HVAC experts agree is unparalleled.
While the city
of Portland doesn't track radiant systems per se, permit office technician
Andrew Millard says he's definitely seeing more applications. "A few
years ago we saw almost none of them," he said. "Certainly they're
an in-vogue item these days."
Radiant floors
work on a simple design. A heat source - typically a domestic hot-water
heater warms up the water. A pump circulates the warm water through
a lattice of tubing, which may be tacked to the underside of the floor,
or, alternately, embedded
in a layer of concrete flooring. As heat transfers out through the
piping, the entire floor becomes a giant low-temperature radiator,
commonly in the range of 80 to 90 degrees F.
With
a radiant heating system you can re-claim the
space in your basement. |
This type of
system, using steel and copper piping, was popular in the United States
up through World War II. In the '60s and '70s, however,
labor costs rose and forced-air systems, which could double for air-conditioning
use, elbowed radiant heat out of the market.
Just when radiant
heat appeared to be on the brink of extinction, however, a new material
rode to the rescue: cross-linked polyethylene tubing, a.k.a. PEX.
Also used for
plumbing, PEX is flexible, inexpensive, easy to install, and can take
the pressure and temperatures required for heating use. The result:
a resurgence of interest in warm floors.
Benefits of radiant
systems are legion. First, there's comfort. While the typical furnace
system heats the air in a building, radiant systems heat objects,
including people. They also keep the heat close to the ground, where
our toes are, instead of letting it drift up to the ceiling. The result
is a temperature curve that's close to the ideal (see diagram above).
In addition,
radiant systems avoid re-circulating air, which reduces dust and allergen
flow. They don't exacerbate the draftiness of leaky vintage houses.
System operation is virtually silent, and, because water holds heat
much better than air, they require much less space to move warmth
around the house. say goodbye to cumbersome ductwork.
"I can transport
- easily - 10,000 BTUs through a half-inch pipe," says Eric Sherman,
designer of hydronic systems for All Temp Professional, a Portland
heating contractor. "A [forced-air] duct would be something like five
to six inches."
In ideal installations,
radiant floor heat can also shave up to 30% to 40% off heating bills,
though not all users see these benefits.
Tom Kelly, owner
of Neil Kelly remodelers, sees a fair amount of demand from clients
for the systems. Bathroom floors are a special favorite. "It's kind
of the neatest heating there is, if you can afford it," he said.
Heat
Distribution Comparison
Heat distribution
with forced-air is uneven. Most of the heat is concentrated
at the ceiling. With radiant floor, the heat is concentrated
at the floor where it is needed. So, you are comfortable at
a lower thermostat setting... that saves money on your monthly
fuel bills. |
Affording it
is the bugaboo of radiant heating today. While costs vary widely depending
on the specifics, homeowners going for a retrofit can expect to pay
roughly double the cost of a good-quality forced-air system. In one
example, the preliminary estimate for a 900-square-foot Portland bungalow
came in at $8,000 to $9,000.
Installation
time is the biggest factor, says Sherman, the system designer. "It's
much more labor intensive," he says. For a typical old-house retrofit,
installers must drill one and one-half inch holes through all the
floor joists to run tubing.
Some resources
exist to help homeowners who want to tackle the job - or parts of
it - themselves. With a cooperative contractor, the adamant do-it-yourselfer
could reduce costs significantly by taking on some of the less-entertaining,
more time-consuming tasks while still leaving the calculations to
a pro.
Just finding
a contractor can be a challenge. "We really don't have a lot of competition,"
Sherman states frankly. All Temp saw a lot of its HVAC colleagues
dabble in radiant heating during the mid-'90s, but most swiftly realized
that the math didn't work out for them. "Right now, it's really good
for buyers, 'cause what's left are guys who have been successful,"
Sherman says.
Sources
for Radiant Heating Information
http://www.eren.doe.gov/consumerinfo/refbriefs/bc2.html
This consumer information sheet from the U.S. Department of Energy
provides an excellent overview of radiant-heat issues.
http://www.thisoldhouse.com/toh/heatingcooling/article/0,13422,216711,00.html
Richard Trethewey, HVAC specialist with ÒThis
Old House,Ó offers his take on the advantages of radiant-heat systems.
http://oikos.com/esb/43/radiantfloor.html
Oikos, an information clearinghouse on sustainable design and construction
issues, gives a green-building perspective on radiant heating.
http://www.radiantec.com/
Radiantec, a Vermont company, specializes in design assistance and
complete, factory-direct equipment packages for radiant floor do-it-yourselfers.
http://www.radiant-floor-heating.com/
For the hydrophobic, Warmly Yours manufactures electric radiant floor
heating products Ð like an electric blanket for your floor.
http://www.spnwsupply.com/
Shelter Products NW of Tigard is the locally based radiant-heat supply
company. |
