Winterwarm fireplace insert or system, Requirements for the existing masonry fireplace, Requirements of your existing masonry chimney – Vermont Casting WinterWarm Fireplace Insert or System User Manual
Page 17: Minimum fireplace dimensions

17
WinterWarm Fireplace Insert or System
2000941
Section III: Preparing a Masonry Chimney
Installing the WinterWarm into a masonry fireplace is an 
effective way to add an efficient heater to your home.
Requirements for the
Existing Masonry Fireplace
The WinterWarm Fireplace Insert is listed only for 
installation within a properly built masonry or heat 
circulating, masonry-type fireplace that is constructed in 
accordance with the requirements of recognized build-
ing codes. A heat-circulating masonry-type fireplace 
must conform to building code standards for masonry 
fireplaces, and must consist of a factory-built metal 
firebox with air circulation pathways that are surrounded 
by masonry materials.
NOTE: The WinterWarm is not listed for use in 
“zero-clearance” prefabricated fireplaces, except 
when used as part of the Vermont Castings’ Winter-
Warm Fireplace system, including the WinterWarm 
Fireplace Energy Cabinet, item #2110 (referred to on 
the WinterWarm safety label as Fireplace Cabinet 
Model 1283). 
The fireplace and chimney must be clean and structur-
ally sound. Have it inspected by a qualified professional 
chimney sweep, a mason, or your Vermont Castings’ 
Authorized Dealer before the WinterWarm is installed. 
Any deterioration (cracks, loose mortar or loose bricks) 
must be repaired.
The fireplace should not be modified to install the Win-
terWarm without first checking with your local building 
inspector or fire marshal. Do not remove bricks or mor-
tar that may jeopardize the compliance of the fireplace 
with local building codes.
Requirements of your
Existing Masonry Chimney
Your fireplace chimney must be well-constructed and 
must meet minimum code requirements. The chimney 
flue should have a code-approved liner made of mason-
ry or pre-cast refractory tiles, straight or flexible stain-
less steel pipe, or a poured-in-place liner. An unlined 
chimney must be relined professionally. Chimney height 
should be no less than 15’ (4.6m) above the hearth and 
no more than 35’ (10.7m).
The chimney must have a nominal flue size of 8” x 8” 
(203 x 203mm) or larger, with a maximum size of 12” 
x 12” (305 x 305mm). Some chimneys originally de-
signed for fireplace use may perform differently when 
used to vent an air-controlled appliance such as your 
WinterWarm. A chimney on an outside wall with a large 
flue, for example, may not heat up enough to sustain 
an adequate draft. Such a flue can often be improved if 
it is relined to reduce its size and/or insulated to keep it 
warmer. 
The chimney should extend at least 3’ (914mm) above 
the highest point where it passes through a roof, and at 
least 2’ (610mm) higher than any portion of a building 
within 10’ (3m). (Fig. 18)
Existing masonry fireplace chimneys, especially older 
ones, may have one or more openings used at an 
earlier time to connect stoves in different rooms to the 
fireplace chimney. These openings must be sealed with 
masonry to the thickness of the chimney wall. Unused 
openings sealed with pie plates or wallpaper are a haz-
ard. In the event of a chimney fire, flames and smoke 
may be forced out of these unused openings.
Do not connect your WinterWarm fireplace insert to 
a chimney flue serving another appliance.
Minimum Fireplace Dimensions
The WinterWarm Fireplace Insert will fit most masonry 
fireplaces. To confirm that it will fit yours, measure the 
lintel depth, plus the height, width, and depth of your 
fireplace and your hearth. Compare them to the mea-
surements in the accompanying chart. If you choose to 
install a new hearth over an existing fireplace hearth, 
be sure to take its thickness into consideration when 
measuring both front and back height of the fireplace.
2' Min.
2' Min.
3'
Min.
0 To 10'
3'
Min.
0 To 10'
AC617
RLTSKC8
2/11/98
Reference
Point
AC617
Fig. 18 The 2’3’10’ rule for chimneys.
