In this article:

Types of Direct-Vent Fireplaces
Direct-Vent Fireplace Heat Capacity
Direct-Vent Fireplace Options
Vent-Free Fireplaces

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 or—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.

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.

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.

When shopping for a new gas fireplace, be sure it is lab-certified by an organization that is compliant with 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 a relatively high elevation, be sure it's approved for that usage.

Prices for direct-vent fireplaces, of course, vary widely, depending upon size, style, finish, and other 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.

Types of Direct-Vent Fireplaces

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 shapes and corner units. Heat-N-Glo even makes a three-sided Pier Bar unit that can go at the end of a bar.

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.

Direct-Vent Fireplace Heat Capacity

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 one 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 the output rate by the 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 percent efficiency.

Direct-Vent Fireplace Options

Controls and options for direct-vent fireplaces 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, Blaze King's Split Second(tm) Safety System shuts off the gas within one second if the pilot light goes out.

You can use a wall switch, a thermostator, or a remote control to operate many types of direct-vent systems. 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.

Vent-Free Fireplaces

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 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.

Photos courtesy of Heat & Glo