Building Heat Shield – Compliance with CSA B365

Building a Heat Shield is a necessity when your current wood burning appliance does not comply with required clearance to combustible materials,  usually at the rear of your appliance.  This article will clearly identify the construction, materials and clearances you will need to reduce your distance to combustible walls.

The main clearances shown are;  heat shield spacing from wall 7/8 inch,  shield must extend 18 inches from side of appliance, and shield must extend 20 inches above appliance. Ember pad must extend 8 inches to side and rear of appliance and 18 inches in front of opening door.

Note:  This heat shield is designed for appliance protection.  Flue pipes may require their own heat shield if distance to combustibles does not comply.

Note:  Depending on the appliance heat protection for floor maybe required.  ( according to manfactures requirements or height of stove if uncertified )

The picture to the right shows the basic dimensions required when installing a heat shield.  The types of materials are listed in chart from CSA B365 and must be adhered to.

Heat Shield Materials

The material used to build your Heat Shield must comply to CSA B365 to be in compliance.  The materials listed are 29 gauge sheet metal,  Ceramic  Tiles  or  similar  non-combustible  material,  Ceramic  Tiles  on  29  gauge  sheet  metal,  brick  and  brick with 29 gauge sheet metal backing.  Clearance reduction ranges from 50 to 67%.

Building a Heat Shield Rules

Shield Construction Rules

Minimum space between shield and combustibles: 21 mm (7/8 in.).
Minimum clearance along the bottom of shield: 25 mm (1 in.).
Maximum clearance along the bottom of shield: 75 mm (3 in.).
Minimum clearance along the top of shield at ceiling: 75 mm (3 in.).
Shield extension beyond each side of appliance: 450 mm (18 in.).
Shield extension above appliance: 500 mm (20 in.).
Edge clearance for ceiling shields: 75 mm (3 in.).
Adhesives used in shield construction must not ignite or lose adhesive qualities at temperatures likely to be encountered.
Mounting hardware must allow full vertical ventilation.
Mounting hardware must not be located closer than 200 mm (8 in.) from the vertical center line of the appliance.
Mounting hardware which extends from the shield surface into combustibles may be used only at the lateral extremities of the shield.

How a Heat Shield Works

The design of the heat shield permits air to flow between the shield and the combustible surface allowing any heat to dissipate before coming into contact with wall.  A properly constructed heat shield can be used to safely reduce minimum clearances between walls and wood burning appliance. The shield is required to extend at least 500 mm (20 in.) above the top of the appliance and 450 mm (18 in.) beyond each edge of the appliance. Commercial shields are also available for the reduction of minimum clearances but the must be rated by an approved Testing Laboratory. These shields are subjected to a series of tests to determine how effectively they can reduce clearances. They are certified and carry a label which confirms that they have met the tests and provides information on clearance reduction details.

Ember Pad Requirements

Ember Pads have to be designed to protect the combustible floor from live embers that might fall from the stove during fire tending or ash removal. The floor pad must be made of a durable, noncombustible material, such as sheet metal, grouted ceramic tile, or mortared brick. Floor pads must normally extend not less than 450 mm (18 in.) in front of the loading door and 200 mm (8 in.) beyond the other sides and back. Floor pads must not be installed on carpet unless the pad is structurally supported so that it does not move or distort.

Heat Protection for Floor

A Listed Wood Burning Appliance installation instructions will detail the construction required to protect the floor from excessive heat. 

Vermont Casting Defiant Wood Stove – Floor Protection Example

Floor Protection: The Defiant does not require R value floor protection. The minimum floor protector material is 20 gauge
sheet metal. Other floor protector materials that can be used include: Type I hearth pads, ceramic tile, stone, brick, etc.
Protection requirements vary somewhat between the Untied States and Canada.: The Defiant does not require R value floor protection. The minimum floor protector material is 20 gauge
sheet metal. Other floor protector materials that can be used include: Type I hearth pads, ceramic tile, stone, brick, etc.
Protection requirements vary somewhat between the Untied States and Canada.

Floor pad size

The floor pad protects flooring from hot embers that might fall from the appliance during fuel loading or servicing. The pad should extend at least 200 mm (8 in.) beyond the sides and rear and 450 mm (18 in.) in front of the loading door. The floor pad must be a continuous, non-combustible surface. The floor pad must not rest on the carpet unless it is strong enough to resist bending or cracking. The best floor pads are laid on the sub-floor so that their finished level is flush to the floor, so there is no edge to trip on.

Un-Certified Wood Burning Appliances

Any wood burning appliance that does not have a listing Label idendifying Testing Laboratory and Installation Requirements is considered an Un-Certfied Wood Burning Appliance.  This appliance is then required to comply with installation instructions of CSA B365, which is the Authority Having Juristiction.  The strictest requirement is the distance to combustible products which is a minimum of 48 inches from every side of the wood burning appliance.

Even if your wood burning appliance meets all the requirements of CSA B365 there is no guarantee that your Insurance Company will insure your home with an Un-Certified Wood Burning Appliance installed.  It is recommended you contact your insurance company prior to installing unit or buying a home with one installed.

More information about Installing Wood Stoves, Fireplaces or Pellet Stoves is available by contacting the Wasaga Beach Home Inspector.