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Hi John, All Codes are written for safety and as yet I've never found one Code written that was wasteful. The most important part of the fireplace is the chimmeny. The thimble(roof or sidewall penetration fitting) is very important as this keeps your building from catching fire. Flue temperatures do reach 3000 degrees plus on a regular basis and it's very common on a wood stove to draw "fire" all the way upto the rain cap. A thimble is made to where there is the main flue pipe, then 1" larger there is another pipe over the main flue pipe thus making a double wall thimble. A triple wall thimble would be another pipe installed over the double wall at 1" larger dia. This creates a 1/2" HEAT insulating air space around each pipe to cool the flue pipe sidewall temperature to a point that it will not catch the surrounding flamables on fire as the flue penetrates the roof or sidewall. This air gap is the "only way" to prevent the heat flow below a safe point. The reason code spec's either double wall or tripple wall pipe on the outside of the structure is so trees, bushes, etc., will not catch fire by touching the flue sidewall. It doesn't not matter how thick your flue pipe is as it will heat almost to the same temperature as the inside flue temp. Now when you use your 6", 1/4" single wall pipe for a flue it will have to be supported because of the excessive weight. The stand-off supports will also have to be fire rated or they will transfer heat just like the single wall flue and create another fire hazzard. Most Codes call for a double wall flue from the roof thimble to the rain cap. Mobilhome code is always triplewall. The inside flue from the stove discharge to the thimble is the only place where "some" codes will allow singlewall flue pipe. The curent code trend is to require double wall flue here. Please give it alot of thought before you try and short change the wood stove install codes as it's your familys life your risking to save a few bucks. T_Bone
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