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Direct Connect

A direct connect is when an insert or a woodstove is installed into a masonry fireplace without a full liner. Instead it will have a short length of stainless liner (often an oval or rectangular shape) extending just to the bottom of the flue (the terra cotta tiles).While building code allows for a direct connect, the NFI does not allow them and Wooden Sun does not install them, for the following reasons:

  • The appliance will not draft as well because the flue is so much bigger than the flue collar (see the flue size FAQ on our “more information” page).
  • The appliance will take a lot longer to start up and begin drafting properly because heating up a larger flue takes significantly longer than heating up a stainless liner wrapped in an insulation blanket (see our post on drafting issues for more information on the physics of your chimney).
  • Because of the drafting issues, the appliance will never be as efficient, meaning that it will take more wood to heat the same amount of space.
  • These types of installations can be dangerous and are more prone to chimney fires.
    • Direct connects produce a lot more creosote because the flue gases cool down so much more, forming glazed creosote (also called third degree creosote) which can only be removed with a rotary sweep. Third degree creosote catches fire relatively easily, and burns very hot, very fast.
    • Unless the direct connect is completely removed (a big job requiring moving the appliance and taking apart the direct connect), the area where the direct connect goes into the flue cannot be reached to clean–a lot of creosote forms in these spaces and if it is not swept properly the creosote buildup is significant. This can catch fire and be the beginning of a major structural fire.
  • Fully lined chimneys are much safer if a chimney fire were to occur. With terra cotta tiles only, it is possible for the chimney fire to spread through voids in the mortar or cracks in the flue tiles. A full liner is a chimney system within a chimney system–the fire can be contained by the stainless liner and insulation, with the added back up of the terra cotta and masonry chimney.
  • In summary, direct connects are the height of “penny wise and pound foolish.” While they are initially a cheaper installation, in just a few years the full liner will have paid for itself in increased efficiency and decreased cleaning costs, not to mention dramatically improved safety.
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