Limestone: replacing a rusted throat damper with a top-sealing damper
A 1970s Limestone ranch with a fireplace that leaked cold air all winter. The old cast-iron damper was the problem, and the fix went on top of the chimney.
The complaint
The homeowner could feel cold air pouring out of the fireplace on windy days with the damper closed, and the family room was always the coldest in the house. The fireplace was original to the 1970s ranch off Tower Road. The throat damper, the cast-iron plate above the firebox, was warped from fifty years of heat and rusted along one edge where water from an uncapped flue had sat on it. Closed, it left a gap you could slide a hand through.
Why throat dampers fail
Cast iron warps with repeated heating, and the frame the plate seats against fills with grit and rust. Even a new throat damper does not seal tightly; it was never designed to. It is a metal plate resting on a metal frame with no gasket. An open flue is a hole in the top of the house, and a leaky damper is a smaller hole that runs all winter. Heated air rises out of it, cold air falls in, and the fireplace becomes an energy cost even when it is not lit.
The top-sealing damper
A top-sealing damper mounts on top of the flue tile. Its lid closes against a silicone gasket, operated by a stainless cable that drops down the flue to a handle in the firebox. Closed, it seals far better than any throat damper, keeps out rain, animals and cold air, and doubles as the cap. Open, it lifts fully clear of the flue. We removed the old warped plate so it could not interfere, installed the top damper, and the family room stopped being the cold room. The one fireplace we will not put one on is a fireplace with a vented gas log set, which requires the damper to be fixed open by code. This one burns wood, so it was the right call.
If this sounds like your house: we handle dampers, caps and crowns across Kankakee County, and our Limestone page covers what we usually find there. Call (815) 449-4264, 7am to 9pm, any day.
Quick questions
Does a top-sealing damper replace the cap?
Yes. It seals the flue and keeps out rain and animals, so a separate cap is not needed.
Can I install one on a fireplace with gas logs?
Not with vented gas logs; the damper must stay open. Wood-burning fireplaces are the right fit.
How do I open and close it?
A stainless cable with a handle mounted in the firebox. Pull to open, release to close.
Does it help with the campfire smell in summer?
Yes. A sealed flue stops humid air from pulling the creosote smell down into the room.
Published October 4, 2026 · By Jacob Dove, Friendship Chimney Sweep, Bourbonnais IL