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Quick Answer
Most direct vent gas fireplaces do not require a chimney. Direct vent fireplaces are designed to vent exhaust gases directly outdoors through a dedicated vent pipe system rather than up through a chimney flue. So in most cases, direct vent gas fireplaces can be installed without the need for a chimney.
What is a Direct Vent Gas Fireplace?
A direct vent gas fireplace, also known as a sealed combustion fireplace, is a type of fireplace designed to draw all combustion air directly from outdoors and vent all exhaust gases directly outdoors as well. This differs from a traditional open fireplace which pulls air from indoors and vents exhaust up the chimney.
There are two main types of direct vent gas fireplaces:
Coaxial or Concentric Vented
Uses a single, double-walled vent pipe to simultaneously bring in combustion air and vent exhaust gases. The outer pipe brings in fresh air from outdoors while the inner pipe vents exhaust gases out.
Horizontal or Two-Pipe Vented
Uses separate intake and exhaust vent pipes side-by-side instead of a concentric, double-walled vent. One pipe brings in fresh combustion air, the other vents exhaust gases.
The main benefits of direct vent gas fireplaces include:
– High efficiency – since air supply and exhaust venting is sealed off from the home, heat loss is minimized
– Flexible venting options – direct venting allows both horizontal and vertical vent configurations
– Improved indoor air quality – combustion air is drawn from outdoors, not already heated/cooled indoor air
Do Direct Vent Fireplaces Require a Chimney?
In most cases, no, direct vent gas fireplaces do not require a chimney. Here’s why:
Direct Venting Eliminates Need for Chimney Venting
Conventional fireplaces vent exhaust gases up through the chimney. But direct vent fireplaces are specifically designed to vent through a dedicated vent pipe system directly outdoors. So there is no need for a chimney.
Direct Vent Pipes Can Go Through Walls or Roof
Rather than venting up a chimney, direct vent pipes can go horizontally through a side wall or vertically through the roof. So a chimney is not required for venting exhaust gases.
Codes Do Not Require Chimney for Direct Vent
Building codes and manufacturer instructions generally do not require a chimney for direct vent gas fireplaces. As long as proper clearance distances are maintained, vent pipes can go through combustible walls and roof structures.
When is a Chimney Needed for a Direct Vent Fireplace?
There are a few scenarios where a chimney might be required with a direct vent gas fireplace:
Converting a Wood-Burning Fireplace
If you are converting an existing wood-burning fireplace over to a direct vent gas fireplace, the existing chimney will likely need to be used to run the vent pipes up and out.
Aesthetic Preference
Some homeowners opt to vent their direct vent fireplace through an existing chimney, even though not required, for aesthetic purposes. This avoids the need to add vent caps on an exterior wall or roof.
Challenging Venting Routes
Using an existing chimney to vent a direct vent fireplace can sometimes simplify the venting in cases where exterior venting would be difficult due to construction challenges.
Venting Requirements for Direct Vent Gas Fireplaces
While direct venting eliminates the need for a chimney in most cases, proper venting is still critical for safety and performance. Here are key requirements:
Proper Vent Size
Venting must be sized according to manufacturer specifications for the BTU rating of the fireplace. Undersized vents can lead to insufficient combustion air and ventilation.
Allowable Vent Lengths
There are limits on the total length of vent pipe and number of elbows. Exceeding these limits can impact performance.
Proper Vent Layout
Vents must be routed to provide the straightest path outdoors and proper clearance from combustibles. Horizontal vents require a 1/4″ rise per foot of vent length towards the termination.
Proper Vent Terminations
Vent caps must have proper clearance above the roof and from windows, doors, and intake vents. Specific termination requirements differ between manufacturers.
Sealing Vent Joints
All intake and exhaust vent joint connections must be properly sealed according to manufacturer specifications to ensure proper ventilation.
Installation Costs: Direct Vent Fireplace With vs. Without Chimney
Installing a direct vent gas fireplace without a chimney is generally less expensive than installing one using an existing chimney. Here is a cost comparison:
| System | Average Installed Cost (Parts + Labor) |
|---|---|
| Direct Vent with Roof Venting | $2,500 – $5,000 |
| Direct Vent Using Existing Chimney | $3,000 – $6,000 |
As you can see, using roof or side wall venting is generally $500 – $1,000 cheaper than routing vents through an existing chimney. The primary costs savings is less labor for chimney routing and termination.
However, for masonry chimneys especially, chimney inspection and re-lining will add $1,000 – $2,000 or more to the costs if required. This can make chimney venting more expensive overall.
Conclusion
In summary, direct vent gas fireplaces eliminate the need for chimney venting in most standard installations. Direct venting allows routing through exterior side walls or the roof to bring in combustion air and expel exhaust gases without using a chimney. While a chimney can still be used with a direct vent fireplace if desired, it is not required in most cases. By avoiding the need for a chimney entirely, direct vent offers more flexibility in installation location and can reduce overall costs as well.