Should the damper be kept closed during the off-season?
Yes — on a wood fireplace or vented gas logs, close the damper in the off-season so you're not letting cooled or heated indoor air escape up the chimney and damp outside air, bugs, and animals down it. The one hard exception: if a gas pilot stays lit, the damper must stay open so combustion gases vent. Direct-vent and ventless units don't have a damper at all.
It's an open window you forgot about
An open damper is a hole in your house. All summer it lets your air-conditioned air slip up the flue and pulls humid mountain air, pollen, and the occasional squirrel back down — one reason rarely-used fireboxes get damp and rusty. Closing it in the off-season stops that draft both directions and keeps the firebox drier and cleaner.
Come winter it's the reverse: an open damper on an idle fireplace is like cracking a window in January, so it stays closed until you're actually burning.
The safety line you don't cross
Here's the rule that overrides everything: never close a damper over a lit pilot. If you leave your gas pilot burning through the summer, that flame produces combustion byproducts that have to vent, and a closed damper traps them.
Units built to run a standing pilot with the damper closed have a permanent damper clamp that holds it slightly open for exactly this reason — that clamp is required, not optional. If you want the damper fully closed in the off-season, shut the pilot off first.
A better long-term fix
A traditional throat damper — the metal flap just above the firebox — seals poorly even when closed, because it warps over the years and the gap lets air right by. If you're tired of the drafts, downdrafts, and critters that come with WNC's ridgelines and tall trees, a top-sealing damper at the chimney crown closes with a rubber gasket and seals far tighter, and a proper chimney cap keeps rain and animals out year-round.
We can look at what your chimney has and what would seal it best. Call (828) 545-0525.
Related questions
- How do I keep dust and debris out of my fireplace during the months it is not used?
- How do I get my fireplace ready for fall and winter?
- How do I shut down my gas fireplace for the summer?
- Why does my fireplace smell like burning dust the first time I light it each fall?
- How do I winterize an outdoor gas fireplace?
- How often should a gas fireplace be serviced?
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