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.