Cast Iron Stove Installation

In recent years, wood stove manufacturers have recognized
the demand for close clearances and provided heat shields and/or cabinets
for solid fuel appliances. Listing also often includes close clearance
chimney connector options. The listed clearances for these appliances
are usually acceptable without further protection of nearby combustibles.
Some installations, however, call for reduction of listed
clearances. This may be done, provided that an approved clearance reduction
system is installed to reduce the heat transferred to combustible material.
Listed clearance reduction systems may be used in accordance with the
manufacturer's specifications. Site-constructed systems may also be
used for clearance reduction.
Site-Contructed clearance reduction systems
The primary source of clearance reduction methods, other
than from the appliance manufacture, is the National Fireplace Institute.
Most site-constructed clearance reduction systems utilize minimum 24
gauge sheet metal (e.g., galvanized steel, aluminum, copper, brass),
1/2 inch thick noncombustible insulation board, or 4 inch (nominal)
thick masonry.
The most effective clearance reduction systems are spaced
out at least 1 inch from the combustible surface. The 1 inch space provides
free air circulation. It is essential that there be openings at the
top, bottom, and/or sides of these clearance reduction systems (see
illustration) so warmer air can exit at the top, pulling in cooler air
at the bottom. It is this circulation of cooler room air into the air
space that makes these shields effective. Methods of ventilating the
clearance protection system with masonry and with sheet metal or noncombustible
insulation board are shown in the illustration.
There are a number of methods for mounting the wall protection.
With sheet metal or noncombustible insulation board, noncombustible
spacers may be used to maintain the 1 inch air space. With masonry wall,
metal wall ties are used to anchor the brick to the wall. The spacers
or wall ties should not be placed directly behind the appliance (or
chimney connector) in order to avoid excessive heat transmission through
the metal to the combustible surface. The excess mortar behind the brick
must be carefully removed to maintain the air space; alternately, laying
the brick against a piece of sheet metal that has been installed with
the proper air space prevents this problem. Typical ventilated clearance
reduction systems utilizing masonry and sheet metal are shown.
Masonry or other noncombustible products attached directly
to a combustible wall transfer more heat to combustibles and therefore
do not provide as much protection from heat buildup as when air space
is utilized. Consequently, the clearance reduction is less for unventilated
systems.