We often get insulation questions here at Lindemann Chimney Supply. Why is it so important to insulate a chimney liner? Is insulation an option or is it required as part of the listing? Of course it depends on how the product was listed and also the fuel that’s being vented through the liner.
For solid-fuels insulation is always needed to pass the UL tests. No liner has been listed without it. In the case of solid fuels, high temperature tests are done and the liner must be able to contain the heat. This prevents heat transfer that might otherwise ignite combustible materials that are next to the chimney structure.Using the right type of insulation with the brand of liner you’ve chosen is also crucial to the listing. You can’t mix and match liners and insulation. The installation instructions must be followed for the UL Listing.
In addition to preventing heat transfer, insulating for a solid fuel liner also increases the performance of the appliance and the venting system. Poorly working stoves have been known to draft very strongly after the correct size insulated liner is installed.
For gas and oil applications the most important reason to insulate the liner is performance based. Flue gasses for oil and gas are much lower than solid fuels. As a result, they can cool much quicker resulting in a more sluggish draft as well as more condensation and flue gas deposits inside the flue.
For every cubic foot of gas burned approximately two cubic feet of water vapor is produced. If this travels up a cold masonry flue, the flue gases will likely cool and deposit flue gas condensate inside the chimney.This can lead to a damaged chimney, white mineral salts on the chimney exterior, moisture damage in plaster, drywall and even peeling wallpaper.
So always build insulation into your bid. You will have a satisfied customer as well as following the recommendations of the chimney liner manufacturer. And keep in mind that when it comes to solid fuels, an uninsulated chimney liner is an unlisted one.