NFPA-Approved Wall Protection Systems for Wood Stoves
The National Fire Protection Agency develops standards for the safe installation of wood stoves. The agency works with manufacturers and independent testing laboratories, such as Underwriters Laboratory, to develop universal installation systems, recommendations and guidelines, which meet the majority of state and local building codes nationwide. However, you must always check and confirm that your stove installation meets ordinances in effect where you reside, especially with regard to installing and using asbestos-based materials.
Radiant and Circulating Stoves
NFPA guidelines for wall protection systems are based on two types of wood-burning stoves -- circulating stoves and radiant stoves. A circulating stove is one that circulates warm air through a room with a fan. These stoves have a double-walled inner combustion chambers constructed of cast iron or firebrick-lined welded steel, and a lightweight sheet metal shell surrounds the combustion chamber. Most new-model wood-burning stoves are circulating stoves. Radiant stoves may or may not have a lined combustion chamber and do not incorporate a fan to circulate warm air. Heat is transferred as radiant energy, emitted from the stove’s interior and exterior surfaces. An old-fashioned potbelly stove is an example of a radiant wood-burning stove.
Radiant Stove With Asbestos Millboard
The NFPA wall clearance systems for radiant stoves are based on using one-quarter-inch millboard with asbestos. If you nail the millboard directly to a wall, the rear panel of the stove should be 36 inches away. However, if you leave a one-inch spacing between the millboard, and then install an interior wall behind the millboard, such as one made of cement board or gypsum, the back of the stove can be placed as close as 18 inches.
Circulating Stove With Millboard
Because circulating stoves are often newer and more efficient, NFPA wall system guidelines are less restrictive than those for radiant stoves. The NFPA recommendation is 12 inches from the back of the stove to the wall if you nail one-quarter-inch millboard directly to the wall, and if you allow for a one-inch clearance between the millboard and a cement board or gypsum wall, the recommended clearance is only six inches.
Radiant Stove With 28-Gauge Sheet Metal
The NFPA has three wall clearance system recommendations for using 28-gauge sheet metal attached to millboard. If you attach the sheet metal on top of one-quarter-inch millboard and nail it directly to the wall, the recommended clearance is 18 inches. When you leave a one-inch-space between the millboard and sheet metal combination and install a back wall made of cement board or gypsum, you only need 12 inches of clearance and you can use millboard that is either one-quarter inch or one-eighth inch thick.
Circulating Stove With Sheet Metal
NFPA wall clearance system requirements are the lowest when you combine asbestos millboard and 28-gauge sheet metal and have a circulating stove. The recommended clearance is only six inches if you nail the millboard and sheet metal directly to the wall, and drops to only four inches if there is one-inch spacing between the millboard and sheet metal and a back wall made of cement board or gypsum.
- Purdue University Cooperative Extension: Residential Wood Stove Installation; Daniel Cassens and Suzanne Badenhop
- University of Missouri Extension; Wood Stoves and Their Installation; David E. Baker; October 1993
- Hearth; Wood Stove Clearances; April 2004
- National Ag Safety Database; Wood Stove Installation and Operation; Ronald C. Jester; October 1991
- NFPA: Overview
- Hearth: How to Ensure Safe Stove Clearances to Combustibles; Ken Rajesky