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Should My Chimney Be Relined AND Insulated?

Should My Chimney Be Relined and Insulated?

Definitely. You should have a stainless steel liner and it should be insulated. Here's why.

The National Fire Protection Agency NFPA 211 in summary states that: Masonry Chimney Flues must be lined, whether that's with Fire Brick or Clay Tiles, and they must not be cracked or have open gaps between the tiles. If there are any of these defects, then a stainless steel liner is required and sized properly.

There are a number of reasons when stainless liners are required.

  1. Your chimney may not have any clay tiles. Older homes, typically before the 1940's, were built when clay tiles did not exist.
  2. If the clay tiles are cracked, damaged, or missing. This is very common.
  3. If you are installing a heating appliance, stove, insert, furnace, or water heater.

Insulating the stainless liner is very beneficial, and in some cases, required by building code. IF certain building code requirements have not been met, as listed below, insulation would be required for solid fuels (wood, pellets, coal, etc).

NFPA 211 Residential Code states that a Minimum Air Space Clearance (Air Gap) is required.

NFPA 211 Code RESIDENTIAL Minimum Air Space Clearances - Air Gap:

  • Interior Chimney 2" from the Chimney to combustible materials (Brick Chimney located inside the house)
  • Exterior Chimney 1" from Chimney to combustible materials (Brick Chimney located on the outside of the house)
  • This Air Space Shall not be filled

What this means, is if you have an interior chimney, located on the inside of your house, there needs to be a 2" air gap clearance between the outer brick of the chimney and any combustible materials. This would usually be visible from inside the attic area. For an exterior chimney, the requirement is 1" air gap. Again, usually visible from inside the attic. Often times, determining if your chimney was originally built to code is very difficult and therefore, chimney insulation should be used for solid fuels.


In summary, it's beneficial to insulate your new stainless steel liner for improved appliance performance. It's typically required to insulate your new stainless steel liner for solid fuels, according to UL 1777, if your chimney is non-code conforming.

If you are required to insulate your liner, or just want the added benefits and performance, you will want to measure the flue tile dimensions. Depending on the flue tile dimensions, it may require the removal of the clay tiles in order to fit the insulation blanket around the stainless liner. There are tools available, for rental or purchase, or contact a Certified Chimney Sweep.

Rockford's chimney insulation blanket helps prevent creosote build-up for solid fuels and reduce condensation for gas/oil fuels. Insulating your new stainless steel liner will help the flue gases stay warmer and also improves the performance of the appliance. Rated up 2100 degrees.

Interior Chimney with 2" Air Gap Exterior Chimney with 2" Air Gap
2in. air gap 1in. air gap