from Brad in Fox Point, WI:
#668
How much energy is wasted with an unused fireplace with the damper closed? Would it be beneficial to fill it with insulation for winter months?
It depends on how well the damper seals.
It depends on how well the damper seals. If the closed damper is a tight fit, little energy is wasted.
Should you decide to “fill it with insulation for the winter months”, please be advised that it’s not recommended to seal the flue completely from the top and the bottom as it can potentially cause condensation. You can, however, tightly stuff some fiberglass insulation into the flue from the bottom and this will suffice. Make sure the top has a high-quality stainless steel or copper chimney cap installed to keep rain and animals out of the flue. As a precaution, it is recommended to provide some sort of “notification” to a future owner that the flue is blocked in the event they don’t see the insulation in the flue and attempt to start a fire.
There are also commercial products such as chimney balloons that are available to temporarily seal chimneys.
Published Tuesday, January 19, 2010