We are thinking of installing a woodstove that can burn with its doors open. This will be in a new addition, so we can build whatever kind of chimney we want. Should we build a masonry chimney with a flue liner or use a prefabricated chimney that meets the Type HT requirements? Our builder likes to build masonry chimneys and seems to think they are less of a fire hazard, but the woodstove manufacturer recommends the metal prefabs saying they draw better.
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>>Our builder likes to build masonry chimneys and seems to think they are less of a fire hazard, but the woodstove manufacturer recommends the metal prefabs saying they draw better.
My understanding is that the old masonry chimneys and flue liners are accepted only through "courtesy" and they aren't as good or safe as the metal prefabs (when properly rated and installed.)
Let us take a look from your view since its your cash .
Metal prefabs with three liners offer less creosote build up since the flue is in fact insulated. Unburned violates ignite at 650 degrees for complete consumption. So in therory the metal chimney would infact burn cleaner.
Some people like me use the chimney for heat it self. Ihave a three flue masonary chimney in a A frame thats showing about 24 ft high in the living room open to ceiling to bottom of rafters. The surface of that massive chimney puts out as much or more than the insert in the fireplace! There are a lot of folks that swear by heat transfer.
If built right a masonary chimney will hold up to years of service where the metal if used a lot wont . I would check warranty specs for years of service.
Occasional users like the cost differnce and rightly so, but a metal prefab is still a serious option for serious wood burners from the cleaner operation stand point. Depending on the type of heater you choose whether it be an open fire place to a stove or insert, there are differences in clean burning stoves . Most all open fireplaces have complete combustion but rob the house of preconditioned heat and can actually raise utility bills .
Most prefabs are a hidden affair with style and can be incased behind drywall or if you prefer you can lay a masonary front with a mantle . There are many options.
The masonary chimney will transfer heat evenly and slowly.to a lessor heat degree that can be handled to be next to wood framing allowing some clearances. But to also keep in mind that chimney is not actually insulated at all and has to be "warmed " up" making it a cooler chimney for condensation of creosotes.
The match off may be that the metal chimney paired with the right stove and dry wood will never have to be cleaned. On the other hand the wrong combimation may have to be cleaned every year . Over all it should be noted that there are more problems with masonary chimneys paired with wood stoves making yearly cleaning of a flue necesary. Cresote is not all that bad a thing as long as its kept to a maintenence schedule that is religious. Especially is a masonary chimney that is used for heat transfer is paying its way for that cleaning . My stove is rated for 64,000 btu making it a big stove . Im quite sure the chimney will match it after a 24 hour burn. So at peak I may expect somewhere in the category 128,000 btu in peak demand but those numbers are only to sell stoves and it has a greater bearing on the wood , the draft chosen and the size load that is being used. It would be impossible to expect those numbers through a full burn and should only be expected as peak times. However chimney heat transfer is even through out the burn.
Tim
Edited 10/28/2005 2:28 pm by Mooney