Published on June 1st, 2013 | by Henri


Chimney liner improves wood-stove efficiency

Q.    I’m having a wood-burning stove inserted in my fireplace. My dilemma is whether to have the flue relined. The contractor that is installing it says relining will make the stove more efficient. Is this true or are they trying to get another $700 from me? My house was built in 1940. The fireplace and chimney were built with the house at the same time. I’m only suspicious because the first place I went to gave the reline story with a different take, saying that since the house was old the lining is probably cracked, making it possible for carbon monoxide to leak into the house. The stove does include a 5-foot liner going into the flue. Should I go with the 5 feet or go the extra 25 feet?

A.    The stove will be more efficient with a stainless steel liner of the proper diameter all the way to the top of the chimney because the gases will remain warmer as long as the installers pour compatible insulation between the new liner and the existing flue.

When combustion gases rise in an existing chimney with a larger cross section than needed, they get “lazy” and cool fast, depositing creosote on the flue walls. That can lead to serious problems including potential chimney fires. There is also a problem with back-drafting – cold air running down the chimney walls affecting the draft negatively.

The other firm that mentioned the possibility of cracked flue liners is also correct.

You should also make it a practice to use ACS (Anti-Creo-Soot — a catalytic spray formula that changes creosote into a fine brown ash). Use it every day following instructions on the bottle. You can spray it on your firewood while it is stacked outside; the water vehicle will evaporate but the active ingredients are still there. To activate the catalytic action, you will need to start the day with a small but hot fire for about 45 minutes. You should be able to buy ACS from the stove dealer or any chimney sweep.

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