As winter approaches, thoughts turn to a warm fire and, naturally, to thoughts of how to help the open fireplace produce more heat while using less wood. Provided you have a MASONRY FIREPLACE, this can easily be achieved by installing a wood stove insert or wood burning hearth stove. The fireplace flue provides the venting – saving the cost of building a new chimney – but will require a chimney liner that meets the need of the new wood burning model.
WOOD INSERTS are models made to insert into the fireplace opening. Provided your fireplace is large enough to accommodate it, this installation will provide a cleaner look and likely require the least alterations to the hearth or mantel as part of the project. The fireplace flue (properly modified as described later in this article) is used to vent the wood insert.
HEARTH STOVES are freestanding models that fit onto the hearth in front of the fireplace opening – or just partially inside of it – while venting into the (properly modified) fireplace chimney.
Installing a Wood Burning Insert or Hearth Stove Will Normally Require the Chimney to be Relined as Part of the Project
Simply stated, the venting system is of paramount importance to how a wood burning appliance operates. The required vent size on a wood burning stove will be specified by the manufacturer, but most new stoves today use a 6″ round vent.
Just sliding a wood stove insert into a fireplace results in the stove having poor draft (hard to light and hard to keep burning), resulting in a dirty burning fire that creates excessive creosote because that big chimney contains a lot of cold air that makes it difficult for smoke to rise through. This installation would not be allowed. CREOSOTE is simply wood smoke that has cooled down and becomes solid and creates a fire hazard that requires sweeping the chimney. Left unchecked, a chimney fire can cause chimney explosions and dangerous house fires. Today’s new wood stoves, when properly installed using good venting practices, are designed for optimum safety, providing long burn times while producing less smoke, yet they simply cannot provide good results when they’re not installed following exact venting requirements of the stove manufacturer and fire safety codes.
A standard fireplace – also considered a wood burning appliance – that has an opening of 36″ wide x 30″ tall needs a much larger chimney area than a wood stove with an opening of perhaps 20″ wide x 15″ tall.
The AREA of the chimney should be 1/10th the size of the opening for a square or rectangle flue (though severe rectangles should be larger), or 1/12th the size of the opening for a round chimney flue.
As an example, our open fireplace example is 36″ x 30″ = 1080 sq. inches, and the chimney would need to be at least 10″ x 11″. Most commonly we find this fireplace will have a flue tile measuring or 12″ x 12″ (interior dimension roughly 11 x 11), a standard size that’s readily available at the brick yard.
11″ x 11″ = 121 Square Inches
The area of a 6″ circle (the size of the vent on the wood stove) is 28.26″
This means the 12″ x 12″ chimney tile liner is MORE THAN 4 TIMES THE SIZE REQUIRED BY THE WOOD STOVE, therefore relining the flue to down size it is required.
Today’s new wood stoves are pretty finicky burners. Catalytic converters and other clean burning technologies demand strict adherence to venting requirements. The venting, along with close adherence to combustible clearances, really is a job best handled by a pro.
The best alternative for lining your fireplace chimney to accommodate a wood stove is a stainless steel chimney liner. Stainless steel is designed to withstand higher temperatures than those experienced in a chimney fire, providing an extra layer of safety. The stainless steel liner extends all the way from the flue outlet on the wood stove to the top of the chimney, providing a seamless passageway for smoke to rise and exit quickly to the atmosphere. High-tech wood stoves, installed with the appropriate size liner, will burn the wood more completely, efficiently extracting the available btu’s in the wood and transferring that heat into your home. You’ll enjoy using much less wood; a wood stove will hold about 1/4 as much or less wood than the open fireplace, yet burn for 6 to 10 hours or more. Combustion technology reduces smoke output for cleaner air. Used regularly, you may enjoy heating cost savings of many hundreds of dollars each winter.
Please call BLUE SKY CHIMNEY SWEEPS to discuss and plan your new wood stove installation.