What does a chimney cap actually do?
A chimney cap is the screened, covered lid on top of your flue, and it earns its keep three ways: it keeps rain out of the chimney, it blocks birds, squirrels, and leaves from nesting inside, and it screens sparks from landing on the roof. On WNC's tree-heavy lots it also helps break up the wind that causes downdrafts.
The three core jobs
Rain is the quiet one. Water pouring straight down an open flue rusts the damper, soaks the masonry, and freezes and cracks the brick over our mountain winters. A cap sheds it.
The screen sides keep animals out — an open flue is prime real estate for birds and squirrels, and a nest is both a fire hazard and a draft blocker. And on a wood-burning chimney, that same screen is a spark arrestor, catching embers before they reach a dry roof or the dry leaves around it.
Extra value in the mountains
WNC's ridges, valleys, and tall trees make for swirling, gusty wind, and wind blowing across an open flue can shove air back down the chimney — a downdraft that pushes smoke into the room. A good cap, and in stubborn cases a specialized draft-improving cap, helps steady that.
We see downdraft complaints most in homes tucked against a hillside or under heavy tree cover, common enough around here.
A small part that fails quietly
Caps are cheap insurance that people forget until something goes wrong — a rusted-through cap, a screen packed with a nest, a cap that blew off in a storm. Any of those undoes the protection.
When we inspect a chimney we check the cap along with the crown, liner, and damper, and replace it if it's shot. If yours is missing or you're hearing critters up there, call (828) 545-0525.
How we can help
Related questions
- What is a flue?
- What is a chimney liner and what does it do?
- What is a chimney chase and a chase cover?
- What is a chimney crown, and how is it different from a chimney cap or chase cover?
- How does chimney draft work — why does smoke go up the chimney?
- What is a direct vent gas fireplace and how does it work?
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