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Chimney repair/liner

Fizz Member Posts: 538
Noticed upper part of chimney parging coming off, and cracks along length of chimney, called contractor and he came today.  He said because we converted to gas the chimey terra cotta lining is deteriorating as is mortar.  He suggests a 6" stainless steel liner(t361, with titanium and transferable lt warranty),top plate and rain cap, along with custom fit snout to boiler/hot water heater piping.  He also noted height of chimney not up to code(I know this), and wants to add 5 block extension to brick/parged chimney which is 100 yrs old. Will draft of gas steam boiler be affected, he claims venting will be improved.


  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    With the increased

    capability of the lined chimney your draft should be fine if not somewhat improved. Natural draft is created by temperature difference in the flue and the height of the flue, so improving both should make it much better.
  • icesailor
    icesailor Member Posts: 7,265
    Draft: Part 2:

    There's a second more important part to draft.

    Flowing air has less pressure than static air. Air outside is almost always moving and air inside is static with higher pressure. Heated air flows to colder air.

    Heat flows to cold, dampness flows to dryness, high pressure flows to low pressure. In a vacuum, pressurized air is always trying to get into the vacuum to equalize the pressure.

    The higher and colder the wind outside, the lower the pressure. The pressure inside the building will be higher. Why you leave the windows open on the lee side in a high windstorm to help equalize the pressure. Pressure in a attic with a religious (holy) chimney, looses pressure to the attic (which has lower pressure than the rest of the house) as it is equalized. Holy chimney's above the roof flashings lose draft. Draft is the momentum and velocity of the gas inside.

    My Laser class sailboat goes through the water by bending air. Bending the air cause it to accelerate. The more air you bend, the faster you go. My iceboat bends air so much that it will go 2 to 5 times the speed of the wind. 55+ MPH in 15 MPH winds. Rough flues cause turbulence which slows down the velocity of the flowing air. Hot air want to get to cold air. Its the physics of flowing air that count.

    Like HVAC systems with the supply's and returns on the floor running on AC. The hot air stays on the ceiling and the cold AC air comes up through the floor and goes right back down as cold air.

    Winning sailboat racing strategy when racing in light air on a lake: There's almost always wind by and under the trees on the shore because the sun heats the dark trees which heat the air, which cools more air, and it drops down to the water. Sometimes enough to get you moving. 30' from shore, there's no wind.
  • Fizz
    Fizz Member Posts: 538
    Made my

    decision much easier. Thanks!