Lloyd Walker
Colorado State University Cooperative Extension
- Adding
a wood stove to a house must be undertaken properly
to ensure a safe installation.
- Install
a stove with adequate clearance from any combustible
surfaces, including floors, walls or furniture.
- Any
chimney must have adequate capacity, the correct
height, proper location, proper clearance from combustibles
and proper mechanical support to be safe.
- When
an efficient airtight stove is selected and installed
with a proper chimney, the efficiency and safety
of the stove operation is largely dependent on the
skill of the operator.
- The
type of wood also can affect stove operation.
- A
wood stove requires regular maintenance: proper
cleaning of the chimney to remove creosote deposits,
regular inspection of the installation, and handling
of ashes.
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Many
homeowners concerned about rising home heating costs purchase
wood stoves to reduce heating bills. Adding a wood stove to
a house must be undertaken properly to ensure a safe installation.
A wood stove is unlike any other device presently in a modern
home.
A wood
stove regularly has surface temperatures over 400 degrees
F. The interior stove temperatures are over 1,000 degrees
F, and if a chimney fire occurs, temperatures over 2,000 degrees
F are possible. Obviously, a device that can achieve such
high temperatures must be treated with respect, and installed,
operated and maintained properly to ensure the device does
not pose any hazard in the home.
Table
1. Minimum clearances from combustible walls and ceilings. |
|
Stove
type |
Type
of protection |
Radiant |
Circulating |
Stovepipe |
None |
36" |
12" |
18" |
1/4"
Noncombustible board spaced out 1" |
18" |
6" |
12" |
28
gauge sheet metal, spaced out 1" |
12" |
4" |
9" |
28
gauge sheet metal on 1/8" noncombustible board, spaced
out 1" |
12" |
4" |
9" |
Once a location
for a stove is established, prepare the area properly to ensure
there is adequate clearance from any combustible surfaces. Combustible
surfaces include floors, furniture, and walls of plaster, drywall
or paneling. The proper distance from these combustible surfaces
is determined by consulting three sources. If the stove is "listed,"
which means it was safety tested by an independent testing lab,
there will be manufacturer's recommendations for clearance from
combustibles.
If a
stove is not listed, follow the National Fire Protection Association
recommendations (see Table 1) for clearance from combustibles.
However, either of these recommendations are superseded by
local building codes. Check with the local building inspector
to find out what clearance standards are enforced in your
area.
From
Table 1, the distance to unprotected surfaces, especially
for radiant stoves, is quite large--36 inches. Thus, most
stove installations have some type of non-combustible wall
protection behind the stove to allow for installation closer
to the wall without presenting a safety hazard (see Figure
1). Asbestos millboard, while it is an acceptable type of
protection, is not recommended because of the health hazard
from asbestos fibers. If asbestos is used, paint with a high
temperature enamel o lock in the fibers.
A most important item in wall protection is the 1-inch spacing
necessary between the protecting material and the wall. The
1-inch spacing is necessary to ensure air circulation between
the protection and the wall so that the wall is not subject
to high temperatures. The spacers used to attach the sheet
metal to the wall also must be non-combustible. (Do not use
wood furring strips.)
Another
method to achieve the same type of protection is using brick
or masonry with a 1-inch air space between the brick or masonry
and the wall. However, the weight of such a wall may cause
structural problems in the house. Protection on the wall behind
the stove must extend far enough on either side of the stove
so that the distance measured from the stove body to the combustible
part of the wall is at least 36 inches.
Floor
protection is the other critical area to considered with stove
installation. The National Fire Protection Association's recommendation
for extent and type of protection of combustible floors under
stoves are given in Table 2. If the stove is listed, install
it according to the manufacturer's instructions. Check local
building codes for specifics regarding type of floor protection
and acceptable clearances. Cover floor protection materials
with noncombustible materials such as brick, stone or tile
to improve appearance.
With the stove properly installed, connect the stove to the
chimney. For this connection, use a heavy gauge stove pipe--generally
24 gauge for most installations--and follow manufacturer's
recommendations. The connecting stove pipe must be as short
as possible. Secure all joints with sheet metal screws and
connect the pipe with the crimped end pointing downward to
contain creosote (see Figure 2). It is important to observe
the 18-inch clearance from combustible surfaces. To reduce
clearances, dd wall protection using the same materials and
techniques recommended for the stove installation (see Table
1).
Choose
the type of chimney with safety in mind. A masonry chimney
is acceptable but may be expensive and difficult to build.
An existing fireplace chimney can be used for a wood stove.
The simplest type of chimney to add to a house is a factory-built
metal chimney (see Figure 3). When choosing a factory-built
chimney, choose a chimney that is listed (tested by an independent
lab).
The innermost lining of the chimney should be stainless steel
to withstand high temperatures and corrosive environment.
Install only a class A, all-fuel, or solid-fuel chimney for
a wood stove installation.
There
are three common types of listed factory-built metal chimneys;
all are equally safe when installed in accordance with instructions
and properly maintained. The three types are: 1) the air cooled
thermo-syphon chimney, 2) solid pack insulated chimney and,
3) air insulated chimney.
Wood
stoves function more efficiently with less maintenance problems
when using a solid pack or air insulated chimney. The thermo-syphon
chimney is designed principally for use with fireplaces and
can present problems in wood stove operation due to the cool
temperatures maintained on the innermost lining, which will
accelerate creosote formation and require more frequent cleaning.
Any
chimney must have adequate capacity, correct height, proper
location, proper clearance from combustibles and proper mechanical
support to be a safe installation. The diameter of the chimney
must meet manufacturer's recommendations to provide adequate
capacity for the stove. The chimney must be high enough to
ensure efficient functioning of the stove (see Figure 4).
The
most desirable location for a chimney is in the center of
the house where most of the chimney is inside of the building.
By exposing a minimum amount of chimney to the outside, creosote
problems are minimized. A chimney located primarily on the
outside of the house operates with cooler surface temperatures
and tends to have creosote deposits more frequently and requires
more periodic maintenance. A safe chimney installation requires
at least a 2-inch minimum clearance from combustibles. A chimney
that projects more than 4 feet above the roof should have
some kind of mechanical support by wires, brackets, etc.,
to ensure that it will not be damaged by high winds.
If an
old and long-unused masonry chimney is brought back into service
for use with a wood stove, carefully inspect it to ensure
that it is still safe to operate. If it does not have a tile
lining, add stainless steel stovepipe the entire length of
the chimney. Check with the building inspector or fire department
for inspection of such an installation.
Once
the stove is installed but before it is used, a local building
inspector or fire department representative should inspect
the installation. It is important to notify your insurance
company about the installation to be sure your homeowner's
policy will cover a wood stove installation.
There
are several safety recommendations to follow after installing
a wood stove:
- install
a 10-pound ABC fire extinguisher, and a smoke detector in
the home.
- familiarize
house occupants with fire evacuation procedures. Adding
a wood stove to a home will change the fire evacuation routes
and these must be well understood by all occupants.
- Regularly
inspect the entire installation. Inspect it carefully and
frequently during the first few months of operation to be
sure that everything operates properly and familiarize yourself
with its operating and maintenance characteristics.
- Clean
the chimney at least once a year.
It is
extremely important to follow all of the installation procedures
outlined in this fact sheet when installing a wood stove.
The most efficient wood stove is not going to save any money
if the end result is a house fire. Since the wood stove is
a potentially dangerous device, treat it with respect and
show proper adherence to installation procedures.
When
an efficient, airtight stove is selected and installed with
a proper chimney, the efficiency and safety of the stove operation
largely depends on the skill of the operator. The first consideration
in operating a stove efficiently is properly preparing the
wood for use in the stove. Thoroughly air dry the wood to
ensure a moisture content of about 20 percent so that the
maximum amount of energy is extracted from the wood.
Green
wood does not burn well and the amount of energy available
in green wood is 60 percent less than the amount of energy
available in dry wood. Season green wood at least six months.
Protect the wood from rain or snow with a cover so it does
not absorb moisture.
The
type of wood used also affects stove operation. Regulate stove
operation by the size and type of wood used. Use hardwood
(which is not in abundance in Colorado, the only exception
being gambel oak), if available, for overnight burns since
its higher density provides a longer duration burn. Use small
split wood for fire starting and quick heating, often needed
in the morning. Use larger round or split pieces when the
stove is regularly attended.
Proper
operation of a stove improves efficiency and reduces creosote
problems. A small hot fire is the most efficient way to burn
wood. Add small amounts of wood at a time to the stove and
operate the draft controls in at least a half-open position.
However, with overnight burns, load the firebox with wood
and restrict the draft for a long duration burn. This type
of burn produces more creosote. When loading the firebox for
an overnight burn, set the draft controls wide open for the
first 20 minutes to establish a hot fire and restrict the
draft.
When
firing the stove upon awakening in the morning, open the draft
wide open with a small hot fire to help dissipate creosote
that may have developed from the overnight burn. Make every
attempt to operate the stove using a small hot fire whenever
it is regularly attended.
The
use of a chimney temperature gauge helps assess the operating
mode of the stove. This device shows temperature of the burning
gases exiting the stove. Install in the chimney connector
approximately 3 feet from the exit of the stove. It can be
a useful device to help monitor the operation of the stove
and retard the production of creosote.
When
using a wood stove, be sensitive to the operating characteristics.
Regulate the amount of wood and the amount of air provided
to the stove to achieve comfort levels in the house. Since
a stove does not respond automatically, anticipate its performance
in order to have uniform heat production.
An essential
part of operational procedures is to know what to do in an
emergency situation caused by a chimney fire. A chimney fire
occurs when buildup of creosote in the chimney is ignited
and burns quickly and hot. A chimney fire is not difficult
to detect. It involves flames and sparks shooting out the
top of the chimney, a roaring sound similar to a jet engine,
the stovepipe glowing red hot and vibration or throbbing of
the stovepipe. It generally has a short duration but is intensely
hot and has the potential to do serious damage to the chimney
and, in some cases, extreme damage to the house.
The
best reaction to a chimney fire is to shut off the oxygen
to the stove, alert occupants in the house, call the fire
department, and make careful observation of the chimney, attic
and outside of the house for fire. When a chimney fire is
extinguished, carefully inspect the chimney for damage. Inspect
the area around the chimney for any smoldering fires that
may have started due to the intense heat, and before using
the stove again be sure that nothing is damaged that would
compromise the safety of the chimney. A chimney fire can be
avoided with periodic chimney cleaning and avoiding extremely
hot fires (which can occur when burning trash, Christmas wrapping
paper, etc.). When a stove begins to glow, it is usually the
result of being over-fired. This can damage the stove and
has potential to start a chimney fire.
Use
of a wood stove requires regular attention to a few maintenance
procedures--proper cleaning of the chimney to remove creosote
deposits, and regular inspection of the installation and handling
of ashes. Creosote is an inevitable by-product of burning
wood. Periodically clean out the deposits formed on the chimney
walls to ensure good performance of the stove and reduce any
safety hazards created by the creosote deposits. Clean chimneys
at least once a year. A more specific rule to follow is to
clean the chimney whenever there is a 1/4 inch or more creosote
buildup on the chimney walls. Chimneys can be cleaned by a
homeowner, using a stiff wire brush designed for the purpose,
or by a professional chimney sweep. Cleaning a chimney can
be a messy task because of the creosote deposits that are
scraped out of the chimney. Take care to prevent dust and
creosote from settling in the house. Wear a face mask when
cleaning a chimney to avoid inhaling the creosote particles.
Check
the stove installation at least once a year to be sure that
there is no hazard created by the stove and that clearances
from combustible surfaces are maintained. It is important
to check the stove pipe used in the chimney connection. Stove
pipe is subjected to high temperatures and will corrode in
time. It must be checked periodically and replaced when it
appears to be corroding beyond safe limits.
Dispose
of ash properly. Carry ashes out in a non-combustible container
such as a metal bucket, and do not leave them in contact with
combustible surfaces. Charcoal buried in ash may smoulder
for days. When placed into an improper container such as a
cardboard box, it can easily cause a disastrous house fire.
Dispose of ash immediately after cleaning the stove by spreading
it on flower beds, gardens or compost piles.
Table
2. Floor protection for stove installations. |
Height
of stove bottom from floor |
Protection
needed |
18
inches or more |
24
gauge layer of sheet metal |
6
to 18 inches |
24
gauge layer of sheet metal over 1/4-inch layer of non-combustible
board |
6
inches or less |
4
inches of hollow masonry laid to provide air circulation
through the masonry layer covered by a sheet of 24-gauge
sheet metal |
Extent
of protection is:
18 inches beyond any side with a firebox opening (door)
12 inches beyond all sides with no openings |
The innermost lining of the chimney should be stainless steel
to withstand high temperatures and corrosive environment.
Install only a class A, all-fuel, or solid-fuel chimney for
a wood stove installation.
There
are three common types of listed factory-built metal chimneys;
all are equally safe when installed in accordance with instructions
and properly maintained. The three types are: 1) the air
cooled thermo-syphon chimney, 2) solid pack insulated chimney
and, 3) air insulated chimney.
Wood
stoves function more efficiently with less maintenance problems
when using a solid pack or air insulated chimney. The thermo-syphon
chimney is designed principally for use with fireplaces
and can present problems in wood stove operation due to
the cool temperatures maintained on the innermost lining,
which will accelerate creosote formation and require more
frequent cleaning.
Any
chimney must have adequate capacity, correct height, proper
location, proper clearance from combustibles and proper
mechanical support to be a safe installation. The diameter
of the chimney must meet manufacturer's recommendations
to provide adequate capacity for the stove. The chimney
must be high enough to ensure efficient functioning of the
stove (see Figure 4).
The
most desirable location for a chimney is in the center of
the house where most of the chimney is inside of the building.
By exposing a minimum amount of chimney to the outside,
creosote problems are minimized. A chimney located primarily
on the outside of the house operates with cooler surface
temperatures and tends to have creosote deposits more frequently
and requires more periodic maintenance. A safe chimney installation
requires at least a 2-inch minimum clearance from combustibles.
A chimney that projects more than 4 feet above the roof should
have some kind of mechanical support by wires, brackets,
etc., to ensure that it will not be damaged by high winds.
If
an old and long-unused masonry chimney is brought back into
service for use with a wood stove, carefully inspect it
to ensure that it is still safe to operate. If it does not
have a tile lining, add stainless steel stovepipe the entire
length of the chimney. Check with the building inspector
or fire department for inspection of such an installation.
Once
the stove is installed but before it is used, a local building
inspector or fire department representative should inspect
the installation. It is important to notify your insurance
company about the installation to be sure your homeowner's
policy will cover a wood stove installation.
There
are several safety recommendations to follow after installing
a wood stove:
- install
a 10-pound ABC fire extinguisher, and a smoke detector
in the home.
- familiarize
house occupants with fire evacuation procedures. Adding
a wood stove to a home will change the fire evacuation
routes and these must be well understood by all occupants.
- Regularly
inspect the entire installation. Inspect it carefully
and frequently during the first few months of operation
to be sure that everything operates properly and familiarize
yourself with its operating and maintenance characteristics.
- Clean
the chimney at least once a year.
It
is extremely important to follow all of the installation
procedures outlined in this fact sheet when installing a
wood stove. The most efficient wood stove is not going to
save any money if the end result is a house fire. Since
the wood stove is a potentially dangerous device, treat
it with respect and show proper adherence to installation
procedures.
Operation
When
an efficient, airtight stove is selected and installed with
a proper chimney, the efficiency and safety of the stove
operation largely depends on the skill of the operator.
The first consideration in operating a stove efficiently
is properly preparing the wood for use in the stove. Thoroughly
air dry the wood to ensure a moisture content of about 20
percent so that the maximum amount of energy is extracted
from the wood.
Green
wood does not burn well and the amount of energy available
in green wood is 60 percent less than the amount of energy
available in dry wood. Season green wood at least six months.
Protect the wood from rain or snow with a cover so it does
not absorb moisture.
The
type of wood used also affects stove operation. Regulate
stove operation by the size and type of wood used. Use hardwood
(which is not in abundance in Colorado, the only exception
being gambel oak), if available, for overnight burns since
its higher density provides a longer duration burn. Use
small split wood for fire starting and quick heating, often
needed in the morning. Use larger round or split pieces
when the stove is regularly attended.
Proper
operation of a stove improves efficiency and reduces creosote
problems. A small hot fire is the most efficient way to
burn wood. Add small amounts of wood at a time to the stove
and operate the draft controls in at least a half-open position.
However, with overnight burns, load the firebox with wood
and restrict the draft for a long duration burn. This type
of burn produces more creosote. When loading the firebox
for an overnight burn, set the draft controls wide open
for the first 20 m nutes to establish a hot fire and restrict
the draft.
When
firing the stove upon awakening in the morning, open the
draft wide open with a small hot fire to help dissipate
creosote that may have developed from the overnight burn.
Make every attempt to operate the stove using a small hot
fire whenever it is regularly attended.
The
use of a chimney temperature gauge helps assess the operating
mode of the stove. This device shows temperature of the
burning gases exiting the stove. Install in the chimney
connector approximately 3 feet from the exit of the stove.
It can be a useful device to help monitor the operation
of the stove and retard the production of creosote.
When
using a wood stove, be sensitive to the operating characteristics.
Regulate the amount of wood and the amount of air provided
to the stove to achieve comfort levels in the house. Since
a stove does not respond automatically, anticipate its performance
in order to have uniform heat production.
An
essential part of operational procedures is to know what
to do in an emergency situation caused by a chimney fire.
A chimney fire occurs when buildup of creosote in the chimney
is ignited and burns quickly and hot. A chimney fire is
not difficult to detect. It involves flames and sparks shooting
out the top of the chimney, a roaring sound similar to a
jet engine, the stovepipe glowing red hot and vibration
or throbbing of the stovepipe. It generally has a short
duration but is intensely hot and has the potential to do
serious damage to the chimney and, in some cases, extreme
damage to the house.
The
best reaction to a chimney fire is to shut off the oxygen
to the stove, alert occupants in the house, call the fire
department, and make careful observation of the chimney,
attic and outside of the house for fire. When a chimney
fire is extinguished, carefully inspect the chimney for
damage. Inspect the area around the chimney for any smoldering
fires that may have started due to the intense heat, and
before using the stove again be sure that nothing is damaged
that would compromise the sa ety of the chimney. A chimney
fire can be avoided with periodic chimney cleaning and avoiding
extremely hot fires (which can occur when burning trash,
Christmas wrapping paper, etc.). When a stove begins to
glow, it is usually the result of being over-fired. This
can damage the stove and has potential to start a chimney
fire.
Maintenance
Use
of a wood stove requires regular attention to a few maintenance
procedures--proper cleaning of the chimney to remove creosote
deposits, and regular inspection of the installation and
handling of ashes. Creosote is an inevitable by-product
of burning wood. Periodically clean out the deposits formed
on the chimney walls to ensure good performance of the stove
and reduce any safety hazards created by the creosote deposits.
Clean chimneys at least once a year. A more specific rule
to follow is to clean the chimney whenever there is a 1/4
inch or more creosote buildup on the chimney walls. Chimneys
can be cleaned by a homeowner, using a stiff wire brush
designed for the purpose, or by a professional chimney sweep.
Cleaning a chimney can be a messy task because of the creosote
deposits that are scraped out of the chimney. Take care
to prevent dust and creosote from settling in the house.
Wear a face mask when cleaning a chimney to avoid inhaling
the creosote particles.
Check
the stove installation at least once a year to be sure that
there is no hazard created by the stove and that clearances
from combustible surfaces are maintained. It is important
to check the stove pipe used in the chimney connection.
Stove pipe is subjected to high temperatures and will corrode
in time. It must be checked periodically and replaced when
it appears to be corroding beyond safe limits.
Dispose
of ash properly. Carry ashes out in a non-combustible container
such as a metal bucket, and do not leave them in contact
with combustible surfaces. Charcoal buried in ash may smoulder
for days. When placed into an improper container such as
a cardboard box, it can easily cause a disastrous house
fire. Dispose of ash immediately after cleaning the stove
by spreading it on flower beds, gardens or compost piles.
Service in Action 10.614, Cooperative Extension, Colorado
State University. Published August 1981. Revised July 1993.
Copyright 1993. For more information, contact your county
Cooperative Extension office.
Colorado State University Cooperative Extension specialist
and research associate, agricultural and chemical engineering.
Disclaimer
and Reproduction Information: Information in NASD does not
represent NIOSH policy. Information included in NASD appears
by permission of the author and/or copyright holder. More
NASD Review: 04/2002
Service
in Action 10.614, Cooperative Extension, Colorado State
University. Published August 1981. Revised July 1993. Copyright
1993. For more information, contact your county Cooperative
Extension office.
Colorado
State University Cooperative Extension specialist and research
associate, agricultural and chemical engineering.
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