Are You Converting from Oil to Gas Heat? Then You'll Need a Chimney Liner

Chimney liners protect the flue from the acidic condensate produced by burning natural gas, as the condensate can corrode the chimney's interior masonry. In addition to protecting the masonry, the liner prevents the chimney from overheating and keeps toxic gas from infiltrating the building.

There are several types of chimney liners, each characterized by its material and how it is installed or applied.

Thick-gauge (10-gauge or heavier) stainless steel is the most common type and can be used in flues of all heights and diameters. Because stainless steel liners can weigh several thousand pounds, they need to be braced at intervals, and the existing building structure may require reinforcement.

Light-gauge (24-gauge or lighter) stainless steel factory-designed chimney liners are typically fastened together with predesigned collars, straps, ties and supports. They require engineered supports at frequent intervals, which can make them impractical for relining chimneys with difficult-to-access interiors.

Ceramic flue sealant, which is sprayed onto the interior of the masonry chimney. The spray, a ceramic compound with a consistency equivalent to unformed concrete, hardens to form an impenetrable surface that improves the chimney's resistance to extreme heat and may greatly reduce the need for structural reinforcement.

Your chimney may also need an extension or an offset.

Special Inspections

Special inspections take place at various points in the construction process and are conducted by a special inspection agency registered with the New York City Department of Buildings (DOB). All new and altered chimneys require special inspections to verify that the work complies with the approved construction documents and that the chimney has proper clearance from adjacent combustible structures. If the construction work involves masonry wall, steel-bolting, steel-welding, anchors or masonry erection, special inspections will be needed for those items as well.

DOB Inspections

In addition to special inspections on the chimney and liner, the oil-to-gas conversion work itself must undergo inspections by the DOB to ensure it meets code. The DOB's plumbing division inspects the gas piping and gas meter room, and the boiler division the boiler, burner, and related equipment.

Your building cannot begin burning gas until all of the work is completed and passes DOB inspection. Even then, because of the backlog of buildings being converted from oil to gas, it can take several months for Con Edison to run the gas line to the building and provide a gas meter for installation. Until then, the heating plant must continue to run on oil, so condo and co-op boards should plan accordingly.

Stephen Varone and Peter Varsalona are principals at Rand Engineering & Architecture.

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