Tutorials and Definitions

I:  Btu's and "what size do I need/want?"
II:  What a "Fireplace" is and is not.
III:  What exactly is the difference between Direct Vent and Natural Vent gas stoves?
IV:  What is better:  Direct Vent or Natural Vent?

I:  Btu's and "what size stove do I need/want?"

Gas stoves are built in an array of sizes; physically and with respect to their heating capacity. Gas stoves are categorized, in accordance to heating capacity, based on Btu input. The Btu (British thermal unit) is a unit of heat defined as the amount of heat-energy necessary to raise the temperature of one pound of water by one degree Fahrenheit.

As a point of reference, 1 gallon of propane contains roughly 93,000 Btu’s of stored heating capacity...and 1.0 therm of natural gas contains 100,000 Btu's.

Large gas stoves (greater than 32,000 Btu’s) are recommended by their manufactures to heat approximately no more than 1,600 to 2,300 square feet.

Medium sized gas stoves (20,000-32,000 Btu’s) are recommended by their manufactures to heat approximately no more than 1,500 square feet.

Stoves smaller than 20,000 Btu’s are generally used to heat smaller homes, or portions of larger homes, such as a bedrooms, dens, kitchens, family rooms, etc.

II:  What a "Fireplace" is and is not.

The term "fireplace" is not as ubiquitous as most people think.  The best way to describe what a fireplace is is to describe what it is not.  In the hearth industry the term "fireplace" does not refer to:

•  an "insert" (which is a gas, pellet, or wood burning unit which installs into a pre-existing masonry or zero-clearance fireplace)...
• it does not refer to a "freestanding stove" (which is a gas, pellet, or wood burning unit that sits out in the room or into an alcove on legs or a pedestal)...
• and it does not refer to "furnace" (which is a gas, pellet, or wood burning unit that is typically installed in a basement or garage in which blowers force that heat produced throughout the house through ducting).

A "fireplace" is for the homeowner/builder who wants to retrofit a wall that does not already have a masonry or zero-clearance firebox with a self-contained gas or wood burning unit that does not require a masonry type chimney.

III:  What exactly is the difference between Direct Vent and Natural Vent gas stoves?

The root of the difference between Direct Vent and Natural Vent is the combustion air, to be more exact, from where the combustion air comes from.  A Direct Vent (abbreviated DV) gas stove uses combustion air that is drawn from outside the house, either through a co-liner or a coaxial vent system.  A Natural Vent (abbreviated NV) gas stove uses air from inside your home for combustion. 

IV:  What is better:  Direct Vent or Natural Vent?

That's a tough question.  And the answer depends on several things:

• the age of your home
• your venting requirements based on necessity and/or aesthetics
• the type/brand stove you want

The age of your home
Newer homes and mobile homes, typically, are more air-tight than other types of homes.  Sometimes these homes are so well insulated and air-tight they're dubbed "Super Good Sense" homes.  This type of home requires the use of appliances that draw outside air (DV) for combustion.  'Why?', many people ask.  Imagine if you will an appliance that uses room air for combustion.  As the oxygen levels in the air are depleted, a pressure difference is created...one in which the pressure inside your home is now lower than that of the pressure outside the home.  Typically this pressure difference is leveled out almost instantaneously when air from outside your home leaks into your home through such places as door jams, windows, and electrical outlets.  But in air-tight homes these sources of "leaks" are almost non-existent.  Thus, the path of least resistance for air outside your home to equalize with inside your home is back down the vent exhaust pipe.  Two of the most obvious drawbacks to this situation is that you're appliance will vent properly and will burn dirty.  Just remember this as a rule of thumb...mobile homes, newer homes, or super-insulated homes should (often required) uses appliance which draw outside air.  

After reading the previous paragraph many homeowners, in well insulated homes or not, wonder why anyone would want a Natural Vent appliance.  Well, in many situations, such as in homes that have a "good draft", a Natural Vent appliance will never create a negative pressure difference in which the pressure inside the home is less than the pressure outside the home.  In almost all instances, Natural Vent appliances are less expensive than their Direct Vent counterparts...and the vent required for Natural Vent appliances are almost always less expensive.  Ignoring these price differences is a good portion of customers who prefer Direct Vent appliances to Natural Vent appliances because they "don't want to replace warm air inside their home with cold air from outside" as would happen when the room air is used for combustion and exhausted up the chimney.  While it is true that outside air replaces lost room oxygen during the use of a Natural Vent appliances, never is a draft felt.  Furthermore, on the flip side of the coin, most new "air-tight" homes are so air-tight that builders install air exchanging devices to replace the home's stagnant air.  So, which either route you go...you end up with the same result.

Your venting requirements based on necessity and/or aesthetics
Some folks don't want any visible vent pipe in their room...in those cases only Direct Vent appliances will suffice, for Direct Vent freestanding stoves can vent off the rear of the stove terminate horizontally or with a "snorkel" on going up at least 14" to 24" up the outside wall.  Natural Vent freestanding stoves can only vent vertically, in fact they must vent 2-feet higher than anything within a 10-foot radius.

Some folks don't like the looks of a Natural Vent stove's chimney pipe, which is typically 3" to4" in diameter, in comparison to a Direct Vent stove's typical 6-5/8" to 7" outside diameter.  This is because the larger diameter pipe more naturally resembles the pipe one would find on a wood freestanding stove.

Some folks want to install a freestanding gas stove on the first floor of a multi-floor building, in which a vertical venting system would be impossible.  In such cases a Direct Vent freestanding stove, which can vent and terminate horizontally, is the easier of the two types of systems to install.

Some folks want to vent into a pre-existing masonry chimney or freestanding wood stove vent pipe already in the ceiling.  Many companies have their Direct Vent stoves tested and approved  to vent into these pre-existing systems...but some have yet to do so.  If you can't find a stove you like that is Direct Vent that is tested and approved to vent into these pre-existing systems...then you might have better luck finding a Natural Vent stove that will, for almost all Natural Vent stoves are tested and approved to vent into these systems.

The type/brand stove you want
Some brands don't offer both Natural Vent and Direct Vent versions of their stoves...some do.