The quick answer is yes, a pellet stove does need a chimney pipe or chimney liner to properly vent the exhaust gases and smoke. Pellet stoves burn fuel inefficiently compared to gas or oil systems, producing more air pollution and creosote buildup. Proper venting through a chimney or direct vent pipe is required to safely remove this exhaust from the home.
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Overview of Pellet Stoves
Pellet stoves are a type of wood-burning stove that burns compressed wood or biomass pellets for heat. The pellets are fed into a burn pot using an electric auger system. As the pellets burn, a blower fan circulates air over the fire to distribute warm air into the room through vents.
Compared to a wood stove or fireplace, pellet stoves offer these advantages:
- Burn pellets with consistent size, shape, moisture and energy content
- Automated feeding of fuel, no manual loading of wood required
- Thermostatically controlled combustion for consistent heat output
- Less air pollution and particulate emissions than wood stoves
However, pellet stoves have some downsides as well:
- Require electricity to power the auger, fans, and control systems
- More maintenance than gas or oil furnaces – weekly cleaning of burn pot and venting system
- Pellet storage bins required
- Higher raw fuel costs than wood stove
Overall, pellet stoves offer a convenient method of zone heating using a renewable biomass fuel source. Proper installation and maintenance is required to operate them safely and efficiently.
Do Pellet Stoves Require a Chimney?
Yes, pellet stoves must be connected to a chimney or approved venting system to exhaust the smoke and gases from combustion. This is required for several important safety and performance reasons:
- Prevent smoke, carbon monoxide (CO), and creosote buildup indoors
- Properly draft exhaust to maintain ideal burn conditions
- Extract moisture and condensation from combustion
- Adhere to building code safety standards for solid fuel appliances
Pellet stoves are not permitted to vent exhaust gases directly into the home. The exhaust must be vented outside through chimney pipe, double-wall stove pipe, or direct vent kits.
Venting Requirements
The exact venting requirements depend on the type of pellet stove and installation location. Here are some general guidelines:
- Freestanding stoves usually require 3″ or 4″ (minimum) approved chimney liner or stove pipe
- Inserts installed into existing masonry fireplaces use the fireplace chimney
- Venting must maintain proper draft – at least .08 w.c. (water column inches)
- Use UL-listed pellet vent pipe sections or adapters (stainless steel)
- Follow manufacturer’s instructions for allowable vent configurations and connector types
- Terminate the vent above roofline and away from windows or foot traffic
The chimney or venting system must provide adequate draft to properly exhaust the stove while also allowing sufficient air intake. Insufficient draft will cause poor combustion, smoke spillage or backdrafting.
Vent Installation Options
There are several options for installing the necessary venting when installing a pellet stove:
Direct Vent
A direct vent system uses a dedicated exhaust pipe and fresh air intake piped directly through the wall behind the stove. The sealed vent pipes run horizontal until exiting the home. Direct vents can terminate just above ground level.
Pros:
- Does not require a chimney
- Short, straight venting
- Lower cost than a chimney
Cons:
- Must accommodate exterior wall penetration
- May be difficult to route through finished spaces
- Visible vent termination outside home
Chimney Liner
A stainless steel flexible chimney liner can be installed inside an existing masonry chimney. Adapters connect the stove vent to the liner running up through the chimney.
Pros:
- Uses existing chimney with minimal alteration
- Straight, vertical venting promotes draft
- Hidden venting within chimney
Cons:
- Chimney may need repairs or repointing
- Limited chimney access for inspection or cleaning
- Diameter must match stove outlet size
Vent Through Chimney
Stove vent sections can be connected together and run vertically through the open chimney flue. Adapters are used transition from the stove collar to the chimney crown.
Pros:
- Straight, vertical venting
- Uses existing flue
- Lower cost than re-lining
Cons:
- May need block-off plate below vent
- Creosote can accumulate in unused flue
- Access needed for periodic cleaning
Exterior Stove Pipe
Doubled-walled or insulated stove pipe sections can be used to vent the stove horizontally until turned vertically to rise above the roofline. Supports, adapters and a cap are required.
Pros:
- Does not require chimney
- Uses standard pellet vent materials
- Can avoid roof penetrations with sufficient vertical rise
Cons:
- May require long vent run to roof
- Exposed vent pipes on exterior
- Elbows reduce draft efficiency
Chimney Liner Size
The chimney liner or venting pipe must be the proper diameter to create adequate draft. Pellet stove vents are typically 3″ or 4″ diameter. Some factors to consider for size:
- Stove manufacturer’s specified pipe diameter
- Long or horizontal vent runs require larger diameter
- Higher BTU stoves may require 4″ over 3″
- Elevation impacts draft – larger diameter at high elevations
The liner size should never be smaller than the stove outlet diameter. Oversizing the liner 1″ larger is generally recommended for optimal draft.
Minimum Recommended Chimney Liner Size for Pellet Stoves:
| Pellet Stove BTUs | Minimum Liner Size |
|---|---|
| Less than 40,000 BTU/hr | 3 inches |
| 40,000 – 60,000 BTU/hr | 3 or 4 inches |
| Over 60,000 BTU/hr | 4 inches |
When in doubt, choose the larger diameter liner for the stove’s BTU rating. The additional cost of the 4″ liner is low compared to the benefits of proper draft.
Chimney Installation Codes
Chimney and pellet stove installations must comply with local building codes. Key requirements include:
- Chimney liner and connectors must have proper clearance to combustibles
- Follow rise, run, termination requirements based on type of vent
- Maintain air space around liner inside chimney flue
- Properly attach and support liner
- Seal openings with ceramic wool or refractory cement
- Install rain cap and spark arrestor at termination
A qualified chimney professional or certified installer should perform or oversee the installation. Homeowners who self-install should have the work inspected by the local building department to ensure code compliance.
Conclusion
Pellet stoves provide an efficient way to heat with wood fuel. However, they must be connected to a proper venting system to remove smoke, fumes, and moisture from combustion. Vents also enable the correct draft through the burn pot for good combustion.
Chimney liners and direct vent kits specific to pellet stoves must be used. Proper sizing, installation and termination are critical to avoid health hazards from dangerous exhaust gases or creosote buildup in stoves and vents. Adhering to manufacturers instructions and local building codes ensures pellet stoves operate safely and at peak efficiency.