What's the best way to insulate an unused fireplace and chimney?

Asked by Jim Simmons
Reston, VA

We have a gas fireplace that is rarely used and a standard chimney flue system on a house built in 1997.



Without having more detail on the type of construction and location of the chimney, it is difficult to answer your question with the best possible solution. However, I’ll try.

If your gas fireplace flue is located in a framed or masonry chimney on the exterior of the home, it is probably not insulated.

However, the interior wall abutting the chimney should be. A possible solution is to install on the exterior of the chimney a “nail sheet.”

  • A nail sheet is constructed of ½” plywood with rigid insulation varying in thickness from ½” to 12”. It has an R-value of 4.
  • This sheet then can be covered with a variety of finishes, from vinyl siding to masonry, allowing you to blend it in with the existing aesthetics of your home.


For more information:

Read Harold Remlinger's Q&A "We need to seal our fireplace since there is a constant cold draft coming in, and lot of heat escape. How to seal it?"

Tagged In: insulation, fireplace

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