Lindon · Utah County
Stopping Chimney Smells and Drafts in Lindon
Every July we take calls from people whose fireplace smells, and every one of them assumes it needs sweeping. Sweeping helps a little. The reason the smell is in the room is something else entirely.
Why an unused fireplace smells in summer
Two things combine. The first is direction of flow. In winter, warm indoor air rises and the chimney pulls upward. In summer, with the air conditioning running and the house cooler inside than out, that reverses. The column of air in the chimney is now heavier than the air in the room, so it sinks, and it brings the smell of everything on the flue walls down with it. Add an extractor fan and the house pulls even harder in the same direction.
The second is humidity. Creosote and old soot are hygroscopic, and damp air moving across them releases far more odor than dry air does. That is why the smell arrives with weather rather than with use.
Cleaning removes some of the source. It does not change the airflow, and the airflow is the mechanism. What actually fixes it is closing the top of the flue.
The top-sealing damper
The original cast-iron damper in the throat of a fireplace was never a seal. It is a metal plate on a frame, it sits inches above the firebox, and after decades of heat it warps and rusts and closes even less well than it did new. Everything in the flue above it is still connected to your room. The worst of them in Lindon are in the older farm houses, where that plate has had many decades of heat cycling to warp it out of shape.
A top-sealing damper puts a lid with a silicone gasket at the top of the chimney, held closed by spring tension and opened by a cable that runs down to a handle in the firebox. Closed, the whole flue is outside the building. That stops the summer odor, stops the winter draft you can feel across the hearth, keeps the masonry dry, and closes the flue to birds and squirrels at the same time.
Caps and waterproofing, in that order
A stainless cap with a screen keeps rain out of the liner and wildlife out of the shaft, and rain in the flue is where tile cracking and rusted dampers start. On masonry that is otherwise sound, a vapor-permeable repellent then keeps the wall from soaking up driven rain while still letting it dry outward. Never a glossy film-forming sealer, which traps moisture inside and takes the brick faces off at the next hard freeze.
Questions
Caps & Dampers in Lindon — common questions
Will sweeping the chimney get rid of the smell?
It reduces it, sometimes noticeably, but it rarely solves it on its own. The smell is coming into the room because air is flowing down the flue. Close the top of the flue with a sealing damper and the path disappears.
Can I just shut the damper I already have?
Try the incense test. Hold a lit stick under the closed damper and watch the smoke. If it climbs, air is passing, and a throat damper that leaks in summer leaks all winter too.
Is a top-sealing damper hard to operate?
No. A cable runs down the flue to a handle inside the firebox, and it takes a moment to open before lighting a fire. The one habit to build is remembering to open it, and the handle is designed to be obvious for that reason.
Does capping a chimney cause moisture problems inside it?
A properly built cap is open at the sides and only covers the flue from above, so the chimney still breathes. What causes moisture problems is a solid seal at the top of a damp masonry stack, which is not what a cap or a gasketed damper does.
Also in Lindon
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Chimney Sweep Inspection Chimney Repair Fireplace Repair Installation Gas Fireplace Dryer Vents All Lindon services
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