Direct-Vent Fireplaces / Ventless Fireplaces
You don't need a chimney with ventless gas fireplaces & electric fireplaces
Although they look very much like traditional fireplaces,
direct-vent units are, in many ways, the fireplaces of the future.
Through technology, they have solved many of the problems associated
with their wood-burning forebears.
Unlike traditional mortar-and-brick masonry fireplaces with
foundations and chimneys, direct-vent units take advantage of
zero-clearance technology. They are prefabricated from metal and
designed to be installed in wood-frame construction without a
foundation and this is the big difference between these and any
other fireplace--a chimney. They burn so efficiently, they can be
vented directly out a wall. This means they're much easier and less
expensive to install than masonry units and you have much greater
flexibility in their placement.
Direct-vent fireplaces burn natural gas or propane, not wood. But
direct-vent models are different from conventional gas-fired
fireplaces that require a through-the-roof, Class B flue to carry
away hot, combustion gases. They burn efficiently, extracting most
of the heat from the combustion gases and sealing the combustion off
from interior rooms. A direct-vent model has a glass door that is
securely sealed to prevent leaks of combustion products into the
room. Air to feed the flame enters from outside and the relatively
cool combustion gases are exhausted through the wall-mounted vent
(if you prefer, you can also vent it through a roof).
Because they are gas-fired, these units address the serious problem
of wood-smoke pollution that grew to crisis proportions in some
regions about a decade ago. Unlike wood-burners, these gas
fireplaces give off virtually no particulates.
Like all gas-burning fireplaces, they're much easier to use than
wood-burning units because you don't have to buy, haul, chop, start
and continually feed wood to the fire. And you don't have to scoop
out the ashes or sweep the chimney. With gas, you just turn on the
fire with a knob, a switch or even a remote control. Or you can let
a thermostat do the job. When in use, they only cost pennies per
hour to operate.
Heating
Up
Most of these units have passageways that direct room air around the
firebox /heat exchanger, then return it to the room. Some come with
fans to boost this circulation; with others, fans are an option.
These fireplaces garner efficiency ratings that approach those of
gas-fired furnaces --in the 78 percent range. (This means they
convert 78 percent of the fuel's potential heat to usable heat.)
Gas-fired fireplaces, like other gas appliances, are measured by
their "Btu" per hour input or output capacity, depending upon the
manufacturer. A Btu (British thermal unit) is equal to the amount of
heat required to raise 1 pound of water 1 degree Fahrenheit.
Input capacity refers to the amount of gas burned without taking
into consideration the percentage of heat lost through the flue.
Output capacity refers to the total usable heat generated. Most
manufacturers use the input capacity figure because it's always
larger than the output. If you're concerned about how much heat a
fireplace will generate, the output figure is the one that's
important. If you want to know how efficiently it will use its fuel,
figure the Steady State Efficiency rating by dividing its output
rate by its input rate.
Input ratings vary, and some units have a range, depending upon the
flame's setting. If supplemental heat is important, choose a model
with plenty of output. The Mendota DXV fireplace, for example, has a
thermostatically-controlled, variable two-level burner that can
deliver from 25,000 to 40,000 Btus per hour with 75% efficiency.
What about vent-free?
In some parts of the country, codes allow the use of vent-free
fireplaces. Vent-free or "no-vent" fireplaces, made by several
manufacturers, have an oxygen depletion sensor to shut off the gas
if the oxygen level ever drops below a preset level. In addition,
their burners produce only very low levels of carbon monoxide.
Because all of their heat is recirculated into the room, these have
very high efficiency ratings. On the downside, they have a much
smaller and less realistic fire than other fireplaces. Also, product
directions usually require you to leave a window slightly open
during use.
Log technology
Of course, all gas-burning fireplaces have artificial logs, so the
big question is: Does the fire look like a wood fire? The only way
to set your mind to rest on this issue is to visit a couple of
dealers and check out their offerings. You're likely to discover
that, although early gas fireplaces had phony-looking fires, new
burners and artificial logs are surprisingly realistic. Many produce
a very authentic fire with tall, dancing flames and have logs and
embers that glow. And, to heighten the effect, you can even buy
incense that imitates the aroma of a wood fire.
Styling
Direct-vent gas fireplaces are made in many different designs.
Standard one-sided models are the norm, but you'll also find
two-sided, three-sided (peninsula) and four-sided (island) styles,
as well as bay-window shaped and corner units.
Sizes vary. You'll find units from about 30 to 48 inches wide and
about 24 to 30 inches high. They are typically quite shallow --from
13 to 18 inches deep.
Nearly all manufacturers make both top and rear-venting models.
Where you need to vent a unit upward because there isn't a straight
shot out a wall, top-venting types work well. Depending upon the
model, vents may run vertically or horizontally for quite a distance
--up to 25 feet or more.
When
shopping for a new gas fireplace, be sure it is lab-certified by an
organization that is accepted by your local codes, such as the
American Gas Association (AGA). Also be sure that the fireplace is
installed according to the manufacturer's directions. If you intend
to put it in a bedroom, a mobile home, or at relatively high
elevation, be sure it's approved for that usage.
Controls and options
Controls and options vary from one manufacturer to the next. Some
models have a standing safety pilot light that burns continuously to
light the main burner whenever the gas is turned on. Others have
electric spark ignition, to save energy, or a piezoelectric
ignition, often chosen when there isn't an electrical hookup at the
fireplace. Some of these types use a millivolt generator so the
fireplace can operate even if the power goes out.
But if the pilot isn't lit, the main gas valve won't open. In fact,
the ODS or Safety System shuts off the gas within one second if the
pilot light goes out.
As mentioned above, you can use a wall switch, a thermostat a remote
control to operate many types. Some remote controls have adjustable
thermostats, blower speed controls and flame-height adjustments.
Other
options for direct-vent fireplaces include variable-speed fans to
boost circulation, special trim kits, propane gas conversion kits,
decorative screens, firebrick-style fireboxes and more.
Because installation is relatively easy, it usually costs about
$200. Prices for the fireplaces, of course, vary widely, depending
upon size, style, finish and various options. You'll find they start
at about $450 --a small price to pay for the value, comfort and
enjoyment a new fireplace will bring your family.