Flue
Definition
A flue is an enclosed, internal passageway within a chimney or a specialized pipe designed to safely convey smoke, exhaust gases, and other by-products of combustion from a fireplace, furnace, or boiler to the outside atmosphere. Functioning primarily through the stack effect or buoyancy, it creates a draft that pulls oxygen into the heat source to feed combustion while protecting inhabitants from harmful pollutants like carbon monoxide. Historically integrated into masonry structures as a hollow void, modern flues often utilize protective clay, metal, or ceramic liners to improve thermal efficiency, prevent heat transfer to adjacent combustibles, and ensure the structural integrity of the building.
Structural & construction notes
Common flue types include traditional masonry or brick chimneys (Class 1), prefabricated metal systems (Class 2), and shallow pre-cast concrete or clay block flues. Other specialized options include balanced flues for direct exterior venting, flueless systems with catalytic converters, and various liners made from stainless steel, clay tiles, or cast-in-place concrete. Common materials include stainless steel, aluminum, clay tile, and concrete. High-durability options like stainless steel and concrete involve higher initial costs but offer superior heat resistance and longevity, whereas more affordable materials like aluminum or clay provide lower upfront investment but may have shorter lifespans or higher risks of cracking over time.
Frequently Asked Questions
An educational reference. Project-specific design requires professional guidance.